Innovative Nutraceutical Approaches to Counteract the Signs of Aging
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The following chapter regards the benefits related to the daily consumption of a nutraceutical liquid beauty supplements in the fight against skin aging. Aging is a complex biological phenomenon, caused by several factors which are genetically and environmentally determined. In the skin, aging induces a gradual decrease in the levels of collagen and elastin, which are the main proteins responsible for maintaining skin firmness and elasticity. As a consequence of aging, skin becomes more rigid and loses its ability to keep shape, and wrinkles and fine lines form. Following a healthy nutritional lifestyle can restore the homeostasis of macro- and micronutrients and support the physiology of cells and tissues in the skin. To this end, nutraceuticals offer formulations that increasingly represent a valid tool in the fight against skin aging. In this context, the consumption of hydrolyzed collagen-based beauty supplements can benefit the skin by restoring the natural production of collagen, hyaluronic acid and elastin. Blends of collagen peptides and multiple active ingredients can make them easily digestible, absorbed, and widely distributed in the human body. Importantly, they have been shown to restore skin hydration and elasticity and to reduce fine lines and wrinkles.
KeywordsSkin aging Hydrolyzed collagen Hyaluronic acid GOLD COLLAGEN® Antioxidants Nutraceutical Nutritional supplement Functional food Fine lines Wrinkles Skin hydration Skin elasticity
Skin aging is characterized by a gradual structural deterioration due to intrinsic genetic factors, which may be accelerated by extrinsic aging factors such as chronic sun exposure (photoaging) [1, 2] or by lifestyle factors such as smoking, alcohol, stress, and lack of sleep [3, 4].
Skin constitutes an effective environmental interface providing protection for human body homeostasis, and as such it is also exposed to several environmental toxic insults (UV rays and chemical factors), which can lead to the production of reactive oxygen species (ROS). These molecules are known to be involved in the pathogenesis of a number of skin disorders and some types of cutaneous malignancy  and are also believed to lead to aging. In fact, in 1956, Denham Harman first proposed that the oxygen-free radicals, endogenously formed from normal metabolic processes, could cause aging [6, 7] (although this theory does not exclude other aging mechanisms such as cell senescence, telomere shortening, and genomic instability).
Skin is capable of counteracting the action of these molecules through efficient antioxidant defense mechanisms. Unfortunately, these processes weaken with time and can be overwhelmed by increased ROS production. One approach to prevent or treat these ROS-mediated disorders is based on the administration of different antioxidants .
There has been some controversy on the link between aging and ROS production. Several in vivo studies have in fact shown that inhibition of antioxidants expression leads on one side to increased oxidative damage, but on the other side does not lead to the expected signs of accelerated aging nor to a reduced lifespan. This suggests how the aging process may be triggered by many factors other than ROS production [8, 9].
Many functional foods (food containing additives which provide extra nutritional value), also known as nutraceuticals, which are able to counteract oxidative stress and ROS-mediated disorders,  have recently come into the market in many countries. For example, a study has shown that collagen peptides, as a dietary supplement, are beneficial in suppressing UVB-induced skin damage and photoaging . Another study, conducted in hairless Sod1−/− double mutant mice, showed that co-treatment with collagen peptides and vitamin C corrected age-related skin thinning by attenuating oxidative damage . Also, dietary intake of astaxanthin (a powerful antioxidant) combined with collagen hydrolysate can improve elasticity and barrier integrity in photo-aged human facial skin . In addition, GOLD COLLAGEN® nutraceutical products have been shown to have beneficial effects on skin properties such as hydration, elasticity, and reduction of fine lines and wrinkles [13, 14, 15], making them a valid tool in the fight against skin aging .
Skin Structure and Function
Skin covers the whole human body and represents the principal barrier to the external environment . Skin has many more roles other than guarding the underlying muscles, bones, ligaments, and internal organs. For example, skin plays a key role in immunity by protecting the body against pathogens (Langerhans cells in the skin are part of the adaptive immune system). Moreover, skin prevents excessive water loss, it has a role in insulation, temperature regulation, sensation, synthesis of vitamin D, excretion, and absorption.
In the epidermis, melanocytes produce melanin and are responsible for skin pigmentation (skin color) and absorb some of the potentially dangerous UV rays present in sunlight. DNA repair enzymes help reverse UV damage in the skin, such that people lacking the genes coding for these enzymes suffer higher rates of skin cancer.
Skin is directly exposed to periodical changes in light and temperature, as it forms an interface between the external environment and the body. Many physiological processes are characterized by periodic daily fluctuations such as changes in skin temperature, sebum production, pH, and transepidermal water loss . Also cell division is associated with specific times of the day and exhibits a circadian periodicity . Epidermal cell proliferation is in fact regulated by a circadian clock, and this could serve as a mechanism for protecting against UV-induced DNA damage by minimizing DNA replication during exposure to the sun UV rays .
The extracellular matrix of connective tissues is formed by different protein families involved in providing structural integrity and several other physiological functions. In the dermis, one of the principal proteins of the ECM is collagen, an insoluble fibrous protein which, together with elastin and hyaluronic acid, is the main component of skin and has a key role in providing integrity and elasticity to this organ.
Collagen is mostly found in fibrous tissues, such as tendons and ligaments, and it is also abundant in the cornea, cartilage, bones, blood vessels, the gut, and intervertebral disks.
Collagen protein is composed of three polypeptide chains named α-chains, which form a triple helix . Based on their structure and three-dimensional organization, they can be grouped into fibril-forming collagens, fibril-associated collagens (FACIT), network-forming collagens, anchoring fibrils, transmembrane collagens (MACIT), basement membrane collagens, and others with unique functions. 28 triple helical proteins have been named as collagens [22, 23].
Type I: dermis, tendon, ligaments, and bone
Type II: cartilage, vitreous body, and nucleus pulposus
Type III: skin, vessel wall, and reticular fibers of most tissues (lungs, liver, spleen)
Type IV: forms the basal lamina and the epithelium-secreted layer of the basement membranes
Type V: lung, cornea, hair, and fetal membranes
A collagen fibril is composed of multiple triple helices and multiple fibrils form a collagen fiber. Collagen fibrils are made of different collagen types: collagen I and III in the skin and collagen II and III in cartilage . Type I collagen is the most abundant in the human body: it forms more than 90 % of bone organic mass, and it is the major collagen present in tendons, ligaments, cornea, and many interstitial connective tissues. It is also the main component of human skin (80 %) with collagen type III making up the remainder of skin collagen (15 %) [23, 24].
Together collagen fibers form a dense network throughout the dermis that confers structural integrity to the skin and also provides structural support to the epidermis.
In the connective tissues, collagen is mainly produced by fibroblasts . In the dermis, fibroblasts are the main cells responsible for producing and organizing the collagen matrix. The activation of fibroblasts results in an increase in the production of collagen. Also myofibroblasts  and numerous epithelial cells make certain types of collagens in other tissues .
Studies have shown that collagen synthesis varies at different stages of life. The relative proportion of the types of collagen in skin also changes with age. Young skin is composed of 80 % type I collagen and about 15 % collagen type III. With age, the ability to replenish collagen naturally decreases by about 1 % per year .
The elasticity of many tissues depends on the presence of elastic fibers which are composed by elastin and microfibrils. Elastin is a very important protein for arteries and helps in the pressure wave propagation for blood flow. Elastin is also very important for the lungs, elastic ligaments, and skin. The principal characteristic of elastic fibers is that they stretch rapidly under a load and return quickly to their original form once the load is removed.
Elastin contains many cross-linking sites . Thus, elastic fibers are freely mobile with respect to one another, except at points of cross-linking. The major cross-links in elastin are two polyfunctional amino acids, desmosine and isodesmosine, which account for both the elasticity and insolubility of elastic fibers. These fibers are mainly composed of an amorphous component, which is extensively cross-linked elastin, and a fibrillar component, which are primarily the microfibrils, such as fibrillin. Fibroblasts produce multiple tropoelastin molecules, which covalently bind together with cross-links to form the final elastin protein.
Another essential ECM protein is hyaluronic acid (HA). This molecule is found mainly in soft connective tissues, in particular skin and joints. HA is formed by alternating units of glucuronic acid and N-acetylglucosamine.
In the skin HA is synthesized by fibroblasts, keratinocytes, and other cells . HA is found not only in the dermis but also in the epidermal intercellular spaces. HA has a high molecular weight (10–104 KDa), and this represents a key factor in influencing its physical-chemical properties, such as viscosity, elasticity, and the ability to retain water. In fact, HA is essential for tissue hydration, lubrication, and the production of collagen in the dermis.
Though HA is known to play a structural role in connective tissue, its overall turnover rate appears to be surprisingly quick. Studies have shown that HA has a turnover rate of 0.5 to a few (2–3) days [29, 30].
It has been shown that HA is absorbed and distributed to organs and joints after a single oral administration . In vitro studies have shown that collagen peptides can stimulate not only dermal fibroblasts proliferation but also synthesis of hyaluronic acid .
HA has been widely used as an antiaging cosmetic ingredient. Its beneficial effects on skin are controlled by varying its molecular size. For example, lower-molecular-weight HA was shown not only to lead to a significant reduction of wrinkle depth  but also to penetrate the skin better and to influence the expression of many genes involved in keratinocyte differentiation and in the formation of intercellular tight junction complexes, which are reduced in aged skin .
Aging is the process of becoming older and in humans it refers to a psychological and physical processes. In particular, aging of the skin is a complex biological phenomenon which affects several of its constituents and hence its appearance, and for this reason it can have a big social impact.
There are two primary skin-aging mechanisms, intrinsic and extrinsic [3, 4]. Both intrinsic and extrinsic aging (discussed later on) act simultaneously and are associated with phenotypic changes such as wrinkle formation.
In aged skin, collagen fibers become thicker and much shorter, resulting in a loss of collagen type I, which alters the ratio of collagen types . The density of collagen and elastin in the dermis declines, and as a consequence, skin support and elasticity degrade and skin becomes thinner and more rigid. Reduced collagen can reflect two different underlying mechanisms: cellular fibroblast aging and a lower level of fibroblast cell stimulation. Hence, there is a destruction of existing collagen and a failure to replace damaged collagen with newly synthesized material . Moreover, it has been shown that in the presence of damaged collagen fibers, fibroblasts have a reduced proliferative capacity and synthesize less collagen [37, 38, 39].
The aging process results also in the loss of hyaluronic acid. This reduces the moisture, suppleness, and elasticity of the skin. The diminished elasticity of the skin reduces its ability to retain its shape, and therefore, it will not conform as closely to the contours of the face. The skin appears looser and sags, lines and furrows emerge to enable movement. Gravity then pulls on the skin, all leading to sagging eyelids and bags under the eyes and jowls.
Cumulative endogenous damage due to the formation of ROS which affects cellular constituents such as membranes, enzymes, and DNA.
Decreased sex hormone levels (estrogen, testosterone, dehydroepiandrosterone) and other hormones (i.e., melatonin, insulin).
Shortening of telomere length. It has been reported, for example, that in fibroblasts of quiescent skin, more than 30 % of telomere length is lost during adulthood .
Decreased levels of cytokines and their receptors with consequent loss of several skin functions.
Several changes occur in skin layers: there is a decreased number of melanocytes and Langerhans cells in the epidermis, alteration in the epidermal-dermal junction (with a consequent reduction of exchange of nutrients between the two), loss of dermal volume, decrease in blood supply, and reduced tyrosinase activity (which is linked to melanin production) .
All these changes lead to the formation of wrinkles and fine lines, which are exacerbated by gravitational forces and the loss of subcutaneous fat.
Chronic sun exposure (UV radiation is the most important factor for skin aging). It damages DNA in keratinocytes and melanocytes and induces the production of proteolytic enzymes, such as collagen-degrading enzymes. It is also responsible for the formation of thymidine dimers (“UV fingerprints”), which lead to an accumulation of DNA mutations. Clinically UV radiation leads to the formation of actinic keratosis, solar elastosis, lentigines, and carcinomas .
High alcohol intake
Extrinsically aged skin is characterized by the degradation and the alteration of collagen fibers and the accumulation of disorganized elastin proteins throughout the dermis, a process known as elastosis (Fig. 2). Metalloproteinases can be induced by UVA and UVB , and their proteolytic activity results in the degradation of collagen and elastin fibers. For example, metalloproteinases were found to be induced in cells obtained from old versus young subjects , and many other studies show their upregulation in photodamaged skin [44, 45, 46, 47]. As a consequence, the collagen density decreases each year with a faster rate in photo-exposed skin . In fact, aged fibroblasts synthesize lower levels of collagen, both in vitro and in vivo, compared to young adult fibroblasts , and photo-aged dermis contains disorganized collagen fibers and accumulated abnormal elastin [46, 48].
Another important aging phenomenon that takes place, especially in tissues very rich in proteins, is the production of advanced glycation end products (AGEs). These molecules form because of a chemical reaction between glucose and the free amino groups in proteins, and they remain in the tissue as they cannot be degraded normally by enzymes .
Clinical manifestations of extrinsic aging include leathery appearance, increased wrinkle formation, reduced recoil capacity, increased fragility of the skin, and altered color pigmentation (age spots).
The skin has two photo-protective mechanisms: the melanin in the lower layer of the epidermis and the urocanic barrier of the stratum corneum which absorbs a good amount of UV rays.
In addition, a very important role is played by antioxidants, which help counteract ROS damage. Antioxidants are naturally occurring in the skin and include superoxide dismutase, catalase, alpha-tocopherol, ascorbic acid, ubiquinone, and glutathione. A proper diet, rich in vitamins and antioxidants (e.g., coenzyme Q10 and alpha-lipoic acid), can help protect from oxidative damage .
Interestingly, alteration in diet can change the way skin functions as evidenced by the effects of dietary deprivation on skin health. For example, essential fatty acid deficiency  or the accumulation of abnormal fatty acids  results in the so-called skin scaling and poor barrier function.
Thus, it is important to have a correct nutritional approach, maintaining a balanced diet and a good supply of food supplements to restore the homeostasis of cells and tissues in the human body.
The Use of Hydrolyzed Collagen as a Nutraceutical
Hydrolyzed collagen is becoming an increasingly popular nutraceutical. It is produced from native collagen, and it consists of small collagen peptides with low molecular weight (0.3–8 KDa). It is formed through a process of hydrolysis which involves breaking down the molecular bonds between individual collagen strands using a combination of heat, acids, alkalis, or enzymes. Hydrolyzed collagen is widely used in cosmetics as a moisturizer, for example, in creams. The main advantage of using small collagen peptides, compared to native collagen, is that they are highly digestible, easily absorbed, and distributed in the human body. In literature there are numerous clinical trials that have been performed showing the efficacy and benefits of collagen peptides on skin properties (such as hydration, elasticity, and reduction of wrinkles). A reduction in skin collagen levels, which comes with age, can lead to a reduced mechanical tension on fibroblasts with a consequent loss in matrix production and stimulation instead of matrix-degrading enzymes . In this context, hydrolyzed collagen supplementation has a dual mechanism: (1) collagen peptides and free amino acids are used as building blocks for the formation of new collagen and elastin fibers; (2) the collagen peptides bind to fibroblasts receptors and stimulate the production of new collagen, elastin, and hyaluronic acid.
When administered orally, hydrolyzed collagen reaches the small intestine and then it is absorbed into the bloodstream. The collagen peptides are distributed in the human body and to the dermis through the circulatory system.
The bioavailability of hydrolyzed collagen was demonstrated first in mice by a study published in 1999. In this study the authors showed that when orally administered 14C-labeled hydrolyzed collagen was digested, more than 90 % was absorbed within the first 12 h from the intake. In fact, radioactivity in skin peaked 12 h after the administration of 14C-labeled hydrolyzed collagen, and in contrast to plasma, the radioactivity levels remained high up to 96 h . In a more recent study (published in 2005), the authors found that hydrolyzed collagen from porcine skin, chicken feet, and cartilage, ingested by healthy human volunteers after 12 h of fasting, was absorbed in the blood as small peptides. In fact, hydroxyproline-containing peptides were found to be increased in the plasma, reaching a peak level after 2 h and then decreasing to half of the maximum level after 4 h from the oral ingestion. The authors also identified a small peptide proline-hydroxyproline (Pro-Hyp) in the blood, which was present only after intake of hydrolyzed collagen .
The safety of collagen peptides and gelatin (from which hydrolyzed collagen is prepared) is widely recognized. The Food and Drug Administration (FDA) has classified gelatin as a safe substance. In addition, based on international research results, both the World Health Organization (WHO) and the European Commission for Health and Consumer Protection have confirmed that hydrolyzed collagen is safe. There may be only rarely minor side effects, such as nausea, flatulence, or dyspepsia.
The distribution of collagen peptides to the skin was demonstrated in a study in which 14C-labeled proline or 14C-labeled collagen peptides were administered to Wistar rats. After ingestion of the collagen peptides, radioactivity was measured in the different tissues until 14 days. The results showed that the radioactivity remained at high levels in the skin up to 14 days. This indicates the ability of collagen peptides to reach the dermis in the skin and stay there for prolonged periods .
Several in vitro and in vivo studies have demonstrated the efficacy of collagen peptides on skin health.
An in vitro study example is given by the work of Chen and coworkers . These authors studied the effect of different concentrations of hydrolyzed collagen from fish on fibroblasts and keratinocytes. In particular, they investigated cell proliferation, collagen production, and mRNA type I collagen expression. The authors found that an optimal concentration of collagen ranging between 48 and 97 μg/mL resulted in 191% increase in the percentage of fibroblast cell proliferation. Also the highest keratinocytes proliferation was achieved with a collagen concentration between 0.76 and 1.53 μg/mL, and this induced an increase of 242% in proliferation percentage. They also reported an increase in the expression of collagen I mRNA in fibroblasts.
In addition to these studies, Ohara et al.  further demonstrated that collagen peptides can stimulate not only the proliferation of dermal fibroblasts but also the synthesis of hyaluronic acid. In this study eight different collagen-derived peptides containing Hyp were analyzed, and a positive effect on proliferation was observed for Ala-Hyp, Ala-Hyp-Gly, and Pro-Hyp. The same eight peptides were also used to evaluate their effect on hyaluronic acid synthesis, and the results were consistent with the proliferation study. In both studies, Pro-Hyp showed highest efficacy in proliferation and hyaluronic acid synthesis.
Examples of in vivo studies are those by Matsumoto et al. . This research group carried out a preclinical trial in which they showed that daily ingestion of collagen peptides improved skin hydration in female volunteers after supplementation with fish collagen peptides for 6 weeks. This study was followed by a double-blind placebo-controlled study by the same research group . Healthy female volunteers aged 25–45 ingested 2.5, 5, and 10 g of fish collagen peptide, and the results were compared to a placebo group. Stratum corneum hydration was measured at baseline and after 4 weeks. When all subjects were included in the analysis no significant difference between the treated groups (2.5/5/10 g) and the placebo was observed. However, when only subjects older than 30 years were considered, there was a significant difference between the treated group (5 and 10 g) and the placebo.
Koyama et al.  demonstrated that women ingesting 5 or 10 g of pig skin collagen had an improvement of their skin condition already after 3 weeks and at the end of the treatment after 7 weeks. Furthermore, in a double-blind, placebo-controlled study, Proksch and colleagues investigated the effects of collagen hydrolysate on skin biophysical parameters such as skin elasticity , skin moisture, transepidermal water loss, and skin roughness. Sixty-nine women (35–55 years old) were randomized to receive collagen hydrolysate (2.5 g or 5.0 g) or placebo once daily for 8 weeks. At the end of the study, skin elasticity in both collagen hydrolysate dosage groups showed a statistically significant improvement in comparison to placebo . Results from several clinical trials, showing the efficacy of liquid hydrolyzed collagen -based dietary supplements, such as PURE GOLD COLLAGEN®, in reducing wrinkles and nasolabial fold depth and increasing skin hydration and elasticity, have been published recently [13, 14, 15].
A study involving 265 volunteers was carried out independently by 40 dermatologists across 5 different countries: USA, UAE, Greece, Czech Republic, and Spain. The subjects were given a standardized daily dose of PURE GOLD COLLAGEN® for 20 days before and 40 days after a cosmetic procedure. The outcome of the study showed that there was a significant increase in collagen density and skin firmness along with a significant reduction in skin dryness, wrinkles, and depth of nasolabial folds .
A double-blind, randomized, placebo-controlled study including 108 healthy volunteer subjects was performed by an independent Clinical Research Organization to assess the efficacy of PURE GOLD COLLAGEN® on skin condition. Volunteers consumed the products daily for 12 weeks. The effect on the skin was investigated and a significant improvement in wrinkles (19 % reduction compared to placebo) was achieved, primarily a decrease in the surface area and the mean length of wrinkles .
Another recent 12 weeks double-blind, randomized, placebo-controlled clinical trial was conducted on 18 female healthy subjects (between the ages of 45 and 64) to assess whether the oral consumption of PURE GOLD COLLAGEN® could improve certain specific skin properties of postmenopausal women such as depth of facial wrinkles, skin elasticity, and hydration. The results showed that the combination of specific ingredients such as hydrolyzed collagen, hyaluronic acid, and essential vitamins and minerals present in the nutritional drink acts to significantly reduce the depth of facial wrinkles within 9 weeks and increase skin elasticity (between week 9 and week 12) as well as skin hydration (after 6 weeks) .
Thus, on the basis of the significant amount of data now present in the literature, hydrolyzed collagen can be considered an important nutraceutical weapon in the everyday fight against skin aging.
GOLD COLLAGEN® Products: An Overview
Nutraceuticals containing collagen peptides together with vitamins and minerals are innovative liquid, nutritional food supplements. These dietary supplements help promote healthy skin, fight the early signs of aging, such as fine lines and wrinkles and promote healthy looking hair and nails. Examples of these innovative nutricosmeceuticals are the GOLD COLLAGEN® products, conceived and created by MINERVA Research Labs (http://www.gold-collagen.com).
Collaborative studies which are analyzing the mechanisms of action, safety, and efficacy of hydrolyzed collagen-based supplements, such as GOLD COLLAGEN® products, involving research and academic institutes in the UK, Europe, and USA, are currently ongoing.
Non-collagen Anti-aging Ingredients (Table 1)
Summary of Results Obtained with PURE GOLD COLLAGEN®
Ingredients present in nutraceutical supplements: properties, benefits, and approved claims
Borage oil is the richest known source (24 %) of gamma-linolenic acid (GLA), an essential fatty acid. GLA is converted, via a sequence of biochemical steps, into prostaglandin 1 (PG1), a key molecule for maintaining healthy skin. PG1 exhibits a potent anti-inflammatory effect on the skin and is very effective in regulating water loss and protecting the skin from injury and damage 
Borage oil/evening primrose oil
Evening primrose oil is often used in combination with borage oil for skin benefit. It contains very high levels of GLA
Both glucosamine and its derivative N-acetylglucosamine are substrate precursors for the biosynthesis of polymers such as glycosaminoglycans (e.g., hyaluronic acid) and for the production of proteoglycans
Because of its ability to stimulate hyaluronic acid synthesis, N-acetylglucosamine has been shown to accelerate wound healing, improve skin hydration, and decrease wrinkles 
Vitamin A consists of a group of unsaturated nutritional organic compounds that includes retinol, retinal, retinoic acid, and several provitamin A carotenoids, among which beta-carotene is the most important. Vitamin A has multiple functions such as vision, gene transcription, immune function, embryonic development and reproduction, bone metabolism, hematopoiesis, skin and cellular health, and antioxidant activity. This vitamin can be obtained from foods of animal origin such as organ meats, fish oil, and dairy products and from plant-origin foods.
Aging may reduce the efficiency of the conversion of provitamin A carotenoids to their active form .
Retinoids are well known as antiaging agents. For many years this vitamin has been used for the prevention and treatment of photoaging. Retinyl palmitate (vitamin A ester) has been used in skin creams, where it is broken down to retinol and metabolized to retinoic acid, which has potent biological activity. Retinoic acid, in fact, appears to maintain normal skin health by switching on genes and differentiating keratinocytes (immature skin cells) into mature epidermal cells . This suggests that retinoids also play a role in the prevention of aging, because of their inhibitory effects on metalloproteinases expression (which degrade collagen) .
Vitamin A contributes to the maintenance of normal skin and vision and to normal iron metabolism
Vitamin B3, also known as niacin, is a hydrophilic endogenous substance which can have antipruritic, antimicrobial, vasoactive, photo-protective, sebostatic, and lightening effect depending on its concentration. Niacin deficiency was described some centuries ago as it was responsible for pellagra (one of the most devastating nutritional diseases) characterized by extreme weakness and crusty skin. Vitamin B3 can be found in meats, cereals and grain products, and vegetables.
Vitamin B3 is a well-tolerated and safe substance often used in cosmetics. It has been shown to protect from inflammatory dermatoses and photoaging 
Vitamin B3 contributes to the maintenance of normal skin and to the reduction of tiredness and fatigue
Vitamin B6 is a water-soluble vitamin that is naturally present in many foods, and it is a cofactor in many cell reactions (primarily in the metabolism of amino acids but also carbohydrates and lipids). Vitamin B6 plays a role in cognitive development through the biosynthesis of neurotransmitters and in maintaining normal levels of homocysteine, an amino acid in the blood. Vitamin B6 affects all aspects of metabolic function and cellular homeostasis, and it is a vitamin widely distributed in foods of plant and animal origin
Vitamin B6 contributes to normal energy-yielding metabolism and to the reduction of tiredness and fatigue
Vitamin B12 is involved in:
Nervous system maintenance
Formation of blood
Cell metabolism (DNA synthesis and regulation, fatty acid metabolism and amino acid metabolism).
Humans obtain vitamin B12 from products of animal origin including meats, fish, shellfish, dairy products, and eggs. Altered vitamin B12 levels are associated with dermatological manifestations such as hyperpigmentation, hair and nail changes, vitiligo, atopic dermatitis, and acne .
Vitamin B12 contributes to a normal function of the immune system
Vitamin C (L-ascorbic acid) is a powerful antioxidant and a common enzymatic cofactor in mammals used in the synthesis of collagen. It is a powerful reducing agent capable of rapidly scavenging a number of reactive oxygen species (ROS). It is therefore involved into the development and maintenance of several biological systems: immune system, blood vessels, bones, gums and teeth, cell metabolism, nervous system, and skin condition. Low intakes of fresh fruits and vegetables increase the risk of scurvy (characterized by fatigue, skin spots, and bloody gums). Dietary vitamin C can aid with iron absorption. Vitamin C is widely used in cosmetic products to improve several skin parameters such as wrinkles [73, 74, 75]
Vitamin C contributes to normal collagen formation and the normal function of bones, cartilage, and skin
Vitamin D is responsible for enhancing intestinal absorption of calcium, iron, magnesium, phosphate, and zinc. The intake of Vitamin D can be through the diet, but mainly the body can synthesize it in the skin, from cholesterol, and with sun exposure. Sunlight exposure is the primary source of vitamin D for the majority of people. In the skin, vitamin D is produced in the two innermost layers, the stratum basale and stratum spinosum of the epidermis. One of the most important roles of vitamin D is to maintain skeletal calcium balance by promoting calcium absorption in the intestine, promoting bone resorption by increasing osteoclast number, maintaining calcium and phosphate levels for bone formation, and allowing proper functioning of parathyroid hormone to maintain serum calcium levels. Also other physiological systems respond to vitamin D such as the cardiovascular system, the immune system, muscle, pancreas, metabolic homeostasis, and the brain. Vitamin D reduces DNA damage, inflammation, and photo-carcinogenesis caused by UV rays, and it is very often recommended as a supplement, especially during childhood and pregnancy [76, 77]
Vitamin D contributes to normal absorption of calcium and phosphorous and maintenance of normal bones, normal muscle function, teeth, and the immune system
Vitamin E (or tocopherol) is a fat-soluble compound and has many biological functions: enzymatic activity, gene expression, neurological function and antioxidant function (which is the most important). It neutralizes reactive oxygen species, and as such, it protects cells and tissues from free radical damage; this is the reason why it is often used in antiaging skin creams. Vitamin E often works together with vitamin C, as the latter can help to activate vitamin E. Vitamin E works in lipid environment and halts lipid peroxidation in lipoproteins and membranes. The richest sources of vitamin E are plant oils, such as soya, corn, and olive oil. This vitamin works as a soothing and anti-inflammatory agent. In fact, vitamin E has been shown to protect the skin from chemical-induced irritation  and has been shown to have photo-protective effects against skin UV photodamage 
Vitamin E contributes to the protection of cell constituents from oxidative damage
Zinc is a trace element which has a role in catalytic, structural, and regulatory reactions. It serves as structural ions in transcription factors, and it stabilizes the tertiary structure of many proteins. Zinc is stored and transferred in metallothioneins. It is important in helping the body to make new cells, process food, and heal wounds. It also has antioxidant effects and is pivotal for the body’s resistance to infection and for tissue repair. Classic signs of zinc deficiency include reduced growth, diarrhea, skin and eye lesions, neuropsychiatric changes, and alopecia .
The food plants that contain the most zinc are wheat (germ and bran) and various seeds (sesame, poppy, alfalfa, celery, mustard). Zinc is also found in beans, nuts, almonds, whole grains, pumpkin seeds, sunflower seeds, and blackcurrant
Zinc contributes to the maintenance of normal skin, hair, and nails
Copper is a transition metal that is vital for all eukaryotic organisms. It is involved in important biochemical reactions including cellular respiration, antioxidant defense, detoxification, blood clotting, melanin production, and connective tissue formation. Copper is part of several enzymes and proteins that are essential for an adequate use of iron by the body. Copper is required for the formation of hemoglobin, red blood cells, and bones. It also helps with the formation of collagen and elastin, making them available for wound healing. Copper is useful to maintain joint and nerve health. Copper deficiency may lead to anemia, neutropenia, hypopigmentation, and abnormalities in the skeletal, cardiovascular, and immune system. Copper is present in many common foods, including legumes (beans), grains, and nuts
Copper contributes to normal skin and hair pigmentation and protects cell constituents from oxidative damage
Biotin, also known as vitamin H, is a water-soluble B vitamin. It is an essential coenzyme for several important enzymes, and it is necessary for cell growth, energy production, and maintenance of adequate blood sugar levels. Biotin helps in the production of fatty acids and the metabolism of amino acids. It is sometimes used as part of weight reduction efforts. Proper fat production is critical for the health of the skin because fatty acids protect skin cells against damage and water loss. Biotin is often recommended as a dietary supplement for strengthening hair and nails, and it is found in many cosmetic and health products for hair and skin. Biotin deficiency may lead to developmental delay in children and to skin and hair disorders. Food rich in biotin include egg yolk, liver, and some vegetables
Biotin contributes to the maintenance of normal skin and hair
Bioperine® is an extract derived from black pepper, Piper nigrum. Piperine is what gives peppers their spicy taste. This extract is marketed as a nutritional supplement, and it is believed to enhance cell bioavailability and so to increase the absorption of a variety of nutrients [81, 82]
Black pepper extract is clinically proven to increase bioavailability by 60 %
Glucosamine is a derivative of cellular glucose metabolism. It is also a component of glycosaminoglycans and proteoglycans of the cartilage matrix, covering the ends of bones, and hyaluronic acid which is a part of the synovial fluid within the joints. The primary source of exogenous glucosamine is the exoskeleton of shellfish. It exists in primarily two formulations, glucosamine hydrochloride and glucosamine sulfate. Glucosamine hydrochloride lacks the sulfate group and has 99 % purity. Glucosamine is readily absorbed from the gastrointestinal tract with oral administration, rapidly undergoes metabolism via the liver, and is eliminated through feces and urine. Because glucosamine is a part of the cartilage matrix in joint tissues, it has been theorized for many years that its administration could affect symptomatic relief for osteoarthritis
L-Carnitine is a naturally occurring compound, synthesized in the body from the essential amino acids lysine and methionine. L-carnitine is mainly found in the skeletal muscle, where it is required for the transport of fatty acids from the cytosol into the mitochondria for the beta-oxidation process. For its properties in increasing oxidative metabolism of fatty acids and muscle glycogen, supplementation of carnitine could have a potential role in muscular performance enhancement, in mental function increase and may be considered as a fat burner in weight loss diets (although all these properties need further scientific investigation)
Although the results present in literature related to the role of L-carnitine to improve energy performance are controversial, some studies have shown that this compound can positively impact the muscle recovery process after exercise, therefore allowing a more active lifestyle [86, 87]
Chondroitin sulfate is a sulfated glycosaminoglycan. It is usually found attached to proteins as part of a proteoglycan. Chondroitin sulfate is an important structural component of cartilage and provides much of its resistance to compression. Along with glucosamine, chondroitin sulfate has become a widely used dietary supplement for the treatment of osteoarthritis
Chondroitin sulfate and glucosamine sulfate have been shown to exert beneficial effects on the metabolism of in vitro models of cells derived from synovial joints: chondrocytes, synoviocytes, and cells from subchondral bone, all of which are involved in osteoarthritis. They increase type II collagen and proteoglycan synthesis in human articular chondrocytes and are also able to reduce the production of some pro-inflammatory mediators and proteases, to reduce cellular death process, and to improve the anabolic/catabolic balance of the extracellular cartilage matrix .
See glucosamine hydrochloride above for other references
Resveratrol is an antioxidant polyphenol found in the skin of red grapes and in other fruits. It has several benefits: cardiovascular system (via increased nitric oxide production, downregulation of vasoactive peptides, lowered levels of oxidized low-density lipoprotein, and cyclooxygenase inhibition), Alzheimer’s disease (by breakdown of beta-amyloid and direct effects on neural tissues), phytohormonal actions, anticancer properties (via modulation of signal transduction, which translates into anti-initiation, anti-promotion, and anti-progression effects), and antimicrobial effects 
A study showed that resveratrol helped to increase the rate of skin fibroblast proliferation and inhibited collagenase activity . In fact, resveratrol is used also for skin care formulations against a wide range of cutaneous disorders including skin aging and skin cancers .
Also, resveratrol is responsible for epidermal homeostasis and has therefore potential cosmetic and/or dermatological applications 
The fruit of Euterpe oleracea, commonly known as acai berry, has been shown to exhibit significantly high antioxidant activity in vitro, especially as a scavenger for superoxide and peroxyl radicals, and it has therefore health benefits
Together with licorice, green tea, arbutin, soy, turmeric, and pomegranate, acai berry exhibits strong antioxidant properties, and it is among those plants and compounds found to be most beneficial to treat skin hyperpigmentation 
It is a natural compound often used in cosmetic dermatology 
Coenzyme Q10 (CoQ10) is an antioxidant, and it is a vitamin-like substance found throughout the body, especially in the heart, liver, kidney, and pancreas. It is present in most eukaryotic cells, primarily in the mitochondria. This molecule can exist in a completely oxidized form and a completely reduced form, and this enables it to perform its functions as an antioxidant . Besides endogenous synthesis, CoQ10 is also supplied to the organism by various foods (present in small amounts in meat and seafood)
CoQ10 positively influences the age-affected cellular metabolism and helps to counteract signs of aging at the cellular level. As a consequence to topical application, CoQ10 is beneficial for human skin as it rapidly improves mitochondrial function in skin in vivo .
Moreover, CoQ10 has been shown to promote proliferation of fibroblasts, increase collagen expression, and reduce UVR-induced matrix metalloproteinases. It also increased elastin production, and it was shown to have depigmentation properties 
Pomegranate is rich of polyphenols and has therefore antioxidant properties which have been shown to have health-promoting effects . In fact, the oil of pomegranate contains ellagic acid, which is a natural phenol antioxidant and it is found in many fruits and is believed to have anticancer properties
Pomegranate is considered part of the botanic ingredients used in the prevention of skin aging . Moreover, it was shown that ellagic acid, of which pomegranate is rich, prevented collagen destruction and inflammatory responses caused by UVB. Therefore, its dietary supplementation may be a promising treatment strategy to reduce skin wrinkling and inflammation (which come with photoaging) 
Lycopene is known to be one of the most effective antioxidants in the carotenoids family, with excellent stability and bioavailability. Its powerful antioxidant activity is effective in maintaining the strength, thickness, and fluidity of cellular membranes which form the cell external layer. Strong and healthy cellular membranes are of pivotal importance in the prevention from many diseases. Moreover, lycopene acts as an antioxidant preventing free radicals from disrupting the balance of new bone formation and bone loss that naturally occurs with age 
Carotenoids are widely used in the cosmetic industry as skin care products .
Moreover, it has been shown that β-carotene and lycopene are able to modulate skin properties when ingested as supplements or as dietary products. While they cannot be compared with sunscreen, there is evidence that they protect the skin against sunburn (solar erythema) by increasing the basal defense against UV light-mediated damage 
Carnosine is an endogenous free radical scavenger. It is concentrated in muscles when they are working, and it is also found in the heart, brain, and many other parts of the body. Carnosine is used to prevent aging and to prevent or treat complications of diabetes such as nerve damage, eye disorders (cataracts), and kidney problems
The latest research has indicated that apart from the function of protecting cells from oxidation-induced stress damage, carnosine is able to extend the lifespan of cultured cells, rejuvenate senescent cells, and maintain cellular homeostasis . Thus, carnosine-containing products can be used in preparations to reduce skin wrinkles [104, 105]
One of these studies  was an open-label multicenter study conducted by 40 dermatologists who worked independently in different countries (namely, the UK, USA, UAE, Greece, and the Czech Republic). The study involved 265 healthy volunteer subjects, ingesting one bottle (50 ml) of the dietary supplement daily for 60 days. Subjects had a skin assessment before, during, and at the end of the treatment.
Preliminary Results Obtained with GOLD COLLAGEN® FORTE
An independent double-blind, randomized, placebo-controlled clinical trial was performed to investigate the effects of GOLD COLLAGEN® FORTE on skin elasticity in subjects who underwent a cosmetic treatment (fillers and Botox in the face) and subjects who did not while using this nutraceutical supplement.
Subjects participating in the trial were divided into two groups: 30 volunteer subjects (28 females and 2 males, between 40 and 60 years old) who consumed GOLD COLLAGEN® FORTE daily and other 30 volunteer subjects (27 females and 3 males, between 40 and 60 years old) who consumed placebo. Subjects drank one bottle (50 ml) of product daily over a period of 90 days.
DermaLab SkinLab USB elasticity module was used to measure skin elasticity on each subject forearm at baseline (day 0) and at the end of the treatment at day 90.
A self-assessment questionnaire including questions related to skin, hair, nails, joints, mood, and photoaging conditions and questions regarding the subjects’ opinion about the product was filled by each subject. The questionnaire comprised of two parts: the first section was completed by the subjects at baseline (day 0), while the second section was completed at the end of the trial (day 90).
To evaluate the efficacy of the product on skin, histological examination was performed in two subjects who took the product for 90 consecutive days. Histological exam was performed staining the sections with hematoxylin and eosin (E-E) for the assessment of skin structures and, in particular, of collagen and elastin fibers.
Increase in skin elasticity after 90 days of treatment, Fig. 6.Interestingly, the overall increase in skin elasticity in the subjects taking GOLD COLLAGEN® FORTE (from 8.42 to 9.17 mm) was statistically significant (p < 0.05, T-test), and an increase in skin elasticity was observed singularly both in subjects who underwent a cosmetic treatment and subjects who did not. Moreover, no significant change in skin elasticity was observed in the placebo group, both in subjects who underwent or did not undergo a cosmetic treatment. The increase in skin elasticity suggests that this functional food supplement, containing collagen peptides among other active ingredients, has an effect in restoring the correct levels of extracellular matrix proteins such as elastin. In fact, hydrolyzed collagen has a dual action mechanism in the dermis: (1) collagen peptides and free amino acids provide building blocks for the formation of collagen and elastin fibers; (2) hydrolyzed collagen binds to receptors present on the membrane of fibroblasts and stimulates the production of new collagen, elastin, and hyaluronic acid.
Reduction in solar elastosis and in hyperkeratosis, Fig. 7.
Histological sections of healthy skin (by hematoxylin-eosin staining) relative to two female subjects before and after 90 days of treatment with GOLD COLLAGEN® FORTE revealed a reduction in epidermal hyperkeratosis and of solar elastosis in the dermis.
Self-assessment questionnaire outcome.
The subjects’ perception of GOLD COLLAGEN® FORTE versus placebo on skin, hair, nails, joints, and mood and their feedback about the product were further investigated. Results from the self-assessment questionnaires showed that the perception of the overall skin, hair, nails, and joints condition was dramatically improved after 90 days of treatment. Importantly, these improvements were not observed in the subjects taking placebo.Together with other cosmetic treatments or taken alone, daily consumption of a liquid hydrolyzed collagen-based nutritional supplement , such as GOLD COLLAGEN® FORTE, led to significant benefits in terms of efficacy and patient compliance, suggesting that hydrolyzed collagen can help counteract signs of aging and boost the effect of cosmetic treatments (Fig.6 and Fig.7).
Preliminary Results Obtained with ACTIVE GOLD COLLAGEN®
An in-house clinical trial has been carried out to evaluate the effect of the systemic treatment with a hydrolyzed collagen-based nutraceutical supplement, such as ACTIVE GOLD COLLAGEN®, on collagen density, skin elasticity, and body composition in healthy and active volunteer subjects.
The study was conducted in 20 male volunteer subjects aged 20–60 years. Each subject was administered 1 × 50 ml daily dosage for a maximum of 14 weeks.
Increase in skin elasticity, Fig. 8.
An increase in skin elasticity was observed at 7 and 14 weeks in the subjects who were taking ACTIVE GOLD COLLAGEN® with a statistically significant improvement detected at week 14 (65% increase).
Increase in collagen density, Fig. 9.
The same subjects were also measured for collagen density in the ventral forearm. In 55% of the subjects, a constant statistically significant increase was observed in the collagen density over 14 weeks.
This study supports published literature demonstrating increased collagen production in the skin as a result of an oral treatment with collagen peptides .
Improvement in body composition and fitness level, Fig. 10.
Body fat, muscle mass, bone density, and hydration were measured in the 20 subjects who took part in this study using Ozeri Touch II Digital Scale, a multifunction scale that provides profile-driven measurements for these parameters. A decrease in weight and body fat was detected over the 14-week treatment with ACTIVE GOLD COLLAGEN®, together with an improvement in hydration, muscle mass, and bone density (Fig. 10).
As shown in Table 2, the resting heart rate can vary according to the fitness level and with age: the fitter a person is, generally the lower the resting heart rate. This is due to the heart getting bigger and stronger with exercise and getting more efficient at pumping blood around the body – so at rest more blood can be pumped around with each beat, and therefore, less beats per minute are required. In 55 % of the subjects, a 9 % reduction in the resting heart rate (from 71 to 64 on average) was noticed after 5 weeks (Fig. 10). According to Table 2, this means that those subjects moved from an average level (highlighted in yellow) to a good level (highlighted in cyan) of fitness, improving their performances.These results suggest that daily oral consumption of a dietary supplement containing collagen peptides, vitamins, and minerals, in this case ACTIVE GOLD COLLAGEN®, does lead to a detectable improvement in skin properties, such as elasticity and collagen density. Moreover, the active ingredients present in this liquid supplement have a positive effect on the level of fitness, muscle mass, bone density and decrease body fat and resting heart rate ( Fig. 8, Fig. 9, Fig. 10 and Table 2).Table 2
Chart relating resting heart rate and fitness level.
Resting heart rate for men
Innovation in Liquid Hydrolyzed Collagen-Based Supplementation
The novelty of nutraceutical supplements (sometimes referred to as nutricosmeceuticals) for skin care, such as GOLD COLLAGEN® products, is based on their orally ingestible formulation and the use of the highest-quality hydrolyzed collagen together with a specific blend of active ingredients that can be easily absorbed and distributed, by the bloodstream, throughout the whole body.
Many topical collagen-containing products such as creams, lotions, and serums are unable to reach the dermis to boost the production of skin collagen. This is because collagen has a large molecular size and cannot penetrate the skin surface (epidermis). A daily oral intake of a product containing hydrolyzed collagen is therefore more effective, as collagen peptides are able to reach the dermis from the inside, with no need to penetrate the epidermis. Liquid nutritional supplements are easier to swallow than a pill and work from within, in the dermis, to nourish and rejuvenate your skin.
Proven Benefits of GOLD COLLAGEN® Products
Several independent clinical trials have shown visible and significant benefits on skin, hair, and nails after daily intake of GOLD COLLAGEN® nutricosmeceutical supplements. The subjects taking these hydrolyzed collagen-based drinks also perceived an improvement in their mood and energy levels. Additional clinical trials and explorative research projects are currently in progress to further investigate the benefits and mechanisms of action of these supplements.
Nutricosmeceutical products represent an innovative and powerful tool in the fight against skin aging. It is important to underline how the interaction between the ensemble of all the ingredients present in these liquid supplements, such as GOLD COLLAGEN® products, gives these nutricosmeceuticals the ability to have a multipurpose action so to benefit not only the skin but also other structures of the connective tissue such as hair and nails, to boost the body’s energy and to contribute to the person’s general well-being. Although aging is in fact an irreversible biological process, which is mostly visible on skin, it involves the whole body leading to a slow and progressive deterioration of all human tissues, particularly cartilage in the joints. In this context, nutricosmeceutical supplements containing collagen peptides and other active ingredients, such as vitamins, minerals, and antioxidants, might appear to represent a powerful tool to slow down the aging process.
We would like to thank Dr. Martin Godfrey for his time and expertise in critically reviewing the manuscript. We would also like to thank all the dermatologists who collected the data, in particular Professor Andrea Corbo.
- 12.Yoon HS, Cho HH, Cho S, Lee SR, Shin MH, Chung JH. Supplementating with dietary astaxanthin combined with collagen hydrolysate improves facial elasticity and decreases matrix metalloproteinase-1 and -12 expression: a comparative study with placebo. J Med Food. 2014;17:810–6.PubMedCrossRefGoogle Scholar
- 14.Borumand M, Sibilla S. A study to assess the effect on wrinkles of a nutritional supplement containing high dosage of hydrolysed collagen. Cosmeceuticals 2014;2014:93–96.Google Scholar
- 15.Borumand M, Sibilla S. Effects of a nutritional supplement containing collagen peptides on skin elasticity, hydration and wrinkles. J Med Nutr Nutraceuticals 2015;4:47–53.Google Scholar
- 16.Freinkel RK, Woodley DT. The biology of the skin. Pantheon Publishing, USA (New York) and UK (London), 2001.Google Scholar
- 20.Geyfman M, Kumar V, Liu Q, Ruiz R, Gordon W, Espitia F, Cam E, Millar SE, Smyth P, Ihler A, Takahashi JS, Andersen B. Brain and muscle Arnt-like protein-1 (BMAL1) controls circadian cell proliferation and susceptibility to UVB-induced DNA damage in the epidermis. Proc Natl Acad Sci U S A. 2012;109:11758–63.PubMedPubMedCentralCrossRefGoogle Scholar
- 34.Farwick M, Gauglitz G, Pavicic T, Kohler T, Wegmann M, Schwach-Abdellaoui K, Malle B, Tarabin V, Schmitz G, Korting HC. Fifty-kDa hyaluronic acid upregulates some epidermal genes without changing TNF-alpha expression in reconstituted epidermis. Skin Pharmacol Physiol. 2011;24:210–7.PubMedCrossRefGoogle Scholar
- 37.Varani J, Spearman D, Perone P, Fligiel SE, Datta SC, Wang ZQ, Shao Y, Kang S, Fisher GJ, Voorhees JJ. Inhibition of type I procollagen synthesis by damaged collagen in photoaged skin and by collagenase-degraded collagen in vitro. Am J Pathol. 2001;158:931–42.PubMedPubMedCentralCrossRefGoogle Scholar
- 44.Quan T, Little E, Quan H, Qin Z, Voorhees JJ, Fisher GJ. Elevated matrix metalloproteinases and collagen fragmentation in photodamaged human skin: impact of altered extracellular matrix microenvironment on dermal fibroblast function. J Invest Dermatol. 2013;133:1362–6.PubMedPubMedCentralCrossRefGoogle Scholar
- 50.Perricone N. The wrinkle cure: unlock the power of cosmeceuticals for supple, youthful skin. New York: Warner books; 2001.Google Scholar
- 57.Chen RH, Hsu C, Chung MY, Tsai WL, Liu CH. Effect of different concentrations of collagen, ceramides, n-acetyl glucosamine, or their mixture on enhancing the proliferation of keratinocytes, fibroblasts and the secretion of collagen and/or the expression of mRNA of type i collagen. J Food Drug Anal. 2008;16:66–74.Google Scholar
- 58.Matsumoto H, Ohara H, Ito K, Nakamura Y, Takahashi S. Clinical effect of fish type I collagen hydrolysate on skin properties. ITE Lett. 2006;7:386–390.Google Scholar
- 60.Koyama Y. Effect of collagen peptide on the skin. Shokuhinto Kaihatsu. 2009;44:10–12.Google Scholar
- 80.Aggett PJ. Severe zinc deficiency. In: Colin F. Mills (ed.) Zinc in human biology. International Life Sciences Institute, Springer, London, 1989:259–79.Google Scholar
- 81.Umesh K Patil, Amrit Singh, Anup K Chakraborty. Role of piperine as a bioavailability enhancer. Int J Recent Adv Pharm Res. 2011;4:16–23.Google Scholar
- 84.Sawitzke AD, Shi H, Finco MF, Dunlop DD, Bingham 3rd CO, Harris CL, Singer NG, Bradley JD, Silver D, Jackson CG, Lane NE, Oddis CV, Wolfe F, Lisse J, Furst DE, Reda DJ, Moskowitz RW, Williams HJ, Clegg DO. The effect of glucosamine and/or chondroitin sulfate on the progression of knee osteoarthritis: a report from the glucosamine/chondroitin arthritis intervention trial. Arthritis Rheum. 2008;58:3183–91.PubMedPubMedCentralCrossRefGoogle Scholar
- 85.Clegg DO, Reda DJ, Harris CL, Klein MA, O’Dell JR, Hooper MM, Bradley JD, Bingham 3rd CO, Weisman MH, Jackson CG, Lane NE, Cush JJ, Moreland LW, Schumacher Jr HR, Oddis CV, Wolfe F, Molitor JA, Yocum DE, Schnitzer TJ, Furst DE, Sawitzke AD, Shi H, Brandt KD, Moskowitz RW, Williams HJ. Glucosamine, chondroitin sulfate, and the two in combination for painful knee osteoarthritis. N Engl J Med. 2006;354:795–808.PubMedCrossRefGoogle Scholar
- 97.Mertens-Talcott SU, Jilma-Stohlawetz P, Rios J, Hingorani L, Derendorf H. Absorption, metabolism, and antioxidant effects of pomegranate (Punica granatum l.) polyphenols after ingestion of a standardized extract in healthy human volunteers. J Agric Food Chem. 2006;54:8956–61.PubMedCrossRefGoogle Scholar
- 100.Rao LG, Krishnadev N, Banasikowska K, Rao AV. Lycopene I – effect on osteoclasts: lycopene inhibits basal and parathyroid hormone-stimulated osteoclast formation and mineral resorption mediated by reactive oxygen species in rat bone marrow cultures. J Med Food. 2003;6:69–78.PubMedCrossRefGoogle Scholar
- 103.Wang AM, Ma C, Xie ZH, Shen F. Use of carnosine as a natural anti-senescence drug for human beings. Biochemistry (Mosc). 2000;65:869–71.Google Scholar
- 104.Babizhayev MA, Deyev AI, Savel’yeva EL, Lankin VZ, Yegorov YE. Skin beautification with oral non-hydrolized versions of carnosine and carcinine: effective therapeutic management and cosmetic skincare solutions against oxidative glycation and free-radical production as a causal mechanism of diabetic complications and skin aging. J Dermatolog Treat. 2012;23:345–84.PubMedCrossRefGoogle Scholar