Maternal Fish Consumption and Prevention of Low Birth Weight in the Developing World
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- Mohanty, B.P., Ganguly, S., Karunakaran, D. et al. Natl. Acad. Sci. Lett. (2012) 35: 433. doi:10.1007/s40009-012-0073-3
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Low birth weight (LBW) is characterized by less than 2,500 g of body weight at birth. It represents about 15.5 % of total births worldwide and is a major cause of neonatal death. Most notably, 95.6 % of all LBW infants are born in the developing countries. It is primarily resulted from either preterm birth (before 37 weeks of gestation) or intrauterine growth restriction (IUGR). Infants with LBW are about 20 times at higher risk of neonatal mortality and are believed to be more susceptible to cardiovascular complications, inhibition of growth and cognitive development and chronic diseases later in life. Despite its high incidence worldwide and clinical implications, there is still no clear understanding of its causes and consequently, no specific treatments exist. Maternal nutrition before and during pregnancy plays a major role in determining the pregnancy outcome and health of the new born. Fish is a cheap source of quality animal proteins and micronutrients, and fish oil is rich in omega-3 polyunsaturated fatty acids (PUFAs), EPA and DHA. Although the beneficial effects of fish oil on human health is known since 1930s, its protective effects against various pregnancy complications, including IUGR and LBW, have been increasingly recognized during the last two decades. Despite the poor outcome of clinical trials on therapeutic use of fish oil for various pregnancy complications in Western countries, our preliminary epidemiological findings, and numerous observational and experimental studies in developing countries highlight the beneficial effects of fish consumption on pregnancy outcome, particularly in reducing the incidence of LBW. The present paper summarizes various evidences on effects of maternal fish consumption on birth weight, growth and development of infants and young children in the developing world, and emphasizes future research for better understanding of the effects of maternal fish consumption on pregnancy outcome in low socioeconomic settings.
KeywordsLBWIUGRPUFAsEPADHAFOADPreeclampsiaMicronutrient deficiencyFish consumption
Intrauterine growth restriction (IUGR) is also a major problem in developing countries. It refers to the poor growth of a baby while in the mother’s womb during pregnancy . The causes can be many, but most often involve poor maternal nutrition or lack of adequate oxygen supply to the fetus. Specifically, IUGR means birth weight less than 2,500 g and gestational age greater than 37 weeks; and birth weight less than 2 standard deviations below the mean value for gestational age. IUGR is also one of the adverse fetal outcomes associated with preeclampsia which is a pregnancy-specific disorder characterized by hypertension and excess protein excretion in the urine . The physiopathology of preeclampsia is still unclear, but an imbalance between reactive oxygen species (ROS) and antioxidants appears to be an important contributory factor . The long-term sequel of IUGR include small permanent deficits in weight and length, mild neurocognitive deficits and increased risk of hypertension, coronary heart disease and diabetes in adult life .
Higher Fish Consumption Is Associated with Low Risk of Low Birth Weight (LBW)
In a prospective cohort study of 8,729 pregnant women in Denmark, low dietary fish intake was “strong” risk factor for preterm delivery and low birth weight (the incidence of preterm delivery was 7.1 % for women who never ate fish compared with 1.9 % for women who ate fish at least once per week) [13, 14]. Utero environment controls prenatal development and also sets off structural and functional mechanism that will have a prolonged effect in entire lifespan. New facts in human describing the importance of the womb environment for the long term health of offspring is increasingly understood now and studies have shown that diet taken by the mother in late pregnancy can alter the stress response in future progeny and eventually will lead to cardiovascular and other stress related diseases in adulthood . Scientists from the University of Cambridge have sited an increase risk of type 2 diabetes in old age which also leads to heart disease and cancer, in children born to mother with unhealthy maternal diet during pregnancy. The gene Hnf4a, which has been linked to type II diabetes, is controlled by maternal diet through epigenetic modification to DNA. It also plays an important role in pancreatic development and insulin secretion . Chronic maternal consumption of high fat diet with fetal hepatic apoptosis suggests that a potentially pathological maternal fatty acid milieu is replicated in the developing fetal circulation in the non human primates . Health experts in a maternity hospital in Motherwell, Scotland have recommended eating one pound of red meat daily during pregnancy. Compared with offspring of mothers who had reported eaten not more than 13 meat/fish portions per week, the average cortisol concentration were raised by 22 and 46 % in offspring of those reporting 14–16 % and at least 17 portions per week, respectively. Diets with low carbohydrate or high protein have been associated with an increased risk of kidney problems and metabolic ketoacidosis, another potential prenatal stressor. The onset of ketoacidosis starts when carbohydrate intake is restricted and simultaneously body turns to alternative energy sources like fat, acids (beta-hydroxybutyrate, acetoacetone and acetone) known as ketones in the blood. When the level of beta-hydroxybutyrate (by-product of ketoacidosis) rises during gestation period, it can inhibit psychological behavioral and scholarly development in offspring’s . Malnutrition during this crucial period is certainly not due to poverty and lack of family resources alone, but due to lack of knowledge and not giving priority to young child feeding also . Previous studies have shown the association of anemia, low socio economic status and pregnancy weight gain with low birth weight [20, 21].
Health Benefits of Eating Fish
Fish has been an important part of the diet of human in almost all the countries in the world. Fish is one of the cheapest sources of animal proteins and availability and affordability is better for fish in comparison to other source of animal protein. Fish serves as a health-food for the affluent world owing to the fish oils which are rich in polyunsaturated fatty acids (PUFAs); especially the ω-3 PUFAs, EPA and DHA, at the same time, it is a health-food for the people in the other extreme of the nutrition scale owing to its proteins, oils, vitamins and minerals . Under nutrition, malnutrition and starvation and resultant mortality have remained the major problems in underdeveloped and developing countries. ‘Marasmus’ (chronic deficiency of calories) and ‘Kwashiorkor’ (chronic protein deficiency), the two forms of child under nutrition, often occurring together, are world health problems. In this context, fish, being one of the cheapest sources of quality animal protein, is playing a big role which can still play a bigger role in preventing the protein-calorie malnutrition .
Nutrient profiling of fishes show that fishes are superior nutrients and a number of health benefits are believed to be associated with regular fish consumption. Fish, especially saltwater fish, is high in ω-3 fatty acids, which are heart-friendly, and a regular diet of fish is strongly recommended by the nutritionists. This is conjectured to be one of the major causes of reduced risk of cardiovascular diseases in Eskimos . It has been suggested that the longer lifespan of Japanese and Nordic populations may be partially due to their higher consumption of fish and seafood. The new USDA ‘Dietary Guidelines’ are clear about the benefits of seafood and point out that Americans eat only 44 % of the target amount of seafood for optimal health. Moreover, there is convincing evidence of beneficial health outcomes from fish consumption for reduction in risk of cardiac death and improved neurodevelopment in infants and young children when fish is consumed by the mother before and during pregnancy. A recent report of WHO mirrors the ‘Dietary Guidelines’ conclusion that the, “benefits of consuming seafood far outweigh the risk; even for pregnant women” . Fishes are also good for the skin. Nutritionists recommended that fish be eaten at least 2–3 times a week. Massive studies to evaluate the health benefits of eating fish are being taken up globally.
The health benefits of eating fish are being increasingly understood now. In the recent past, a $20-million US Government sponsored probe has been launched to examine whether fish oils and vitamin D can help prevent heart disease, cancer and a range of other illness. Oily fish is claimed to help prevent a range of other health problems from mental illness to blindness. Excessive consumption of red meat is the real killer and if people are eating fish which is quite harmless in itself, it means they are not eating meat. Therefore, their health is bound to benefit. Similarly, there are on-going Government of India-sponsored projects, running under ICAR and ICMR, which aim at nutrient profiling of important food-fishes from the Indian waters and also to study the health benefits of eating fish [25, 26].
LBW is Less Prevalent in Marine Fish Eating Population
It has already been reported that marine fishes are rich in ω-3 PUFAs specially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), an important component of neural and retinal membranes which accumulates rapidly in the brain and retina during the later part of gestation and early postnatal life [27, 28]. The effect of pregnancy on maternal ω-3 fatty acid status is likely to be dependent on pre pregnancy ω-3 fatty acid status and intake during pregnancy. Eating seafood, which is rich in long chain ω-3 fatty acids, may increase birth weight in two ways: it may prolong the duration of pregnancy by interfering with the prostaglandins involved in the process of parturition and it may increase the fetal growth rate by raising the ratio of biologically active prostacyclins to thromboxanes and reducing blood viscosity, thereby facilitating placental blood flow [29–31]. Maternal ω-3 fatty acid intakes might have significant effects on several pregnancy outcomes as well as on subsequent infant visual function and neuro developmental status. Studies, both observational and interventional, assessing the influence of ω-3 fatty acids during pregnancy or the early postpartum period on duration of gestation and infant size at birth, preeclampsia, depression, and infant visual function and neurodevelopment have been reported. Marine food products ingested in pregnancy increase the baby’s size at birth, and also that the dose–response relationship has a saturation level. Therefore, the fishermen community eating marine fish regularly may have a lower chance of low birth weight incidences. Moreover the relationship of maternal health and nutrition with low birth weight has been previously documented. In Kerala, where there is some evidence of child morbidity, the use of health services is also very high. Indeed, the success of Kerala in past health initiatives is often attributed, at least in part, to female literacy and education, and this force can be used to address health issues of adolescent girls and women of reproductive age in Kerala not only to combat child malnutrition, but for women’s own health, well-being and productivity [32, 33].
Undernourished women and those having low body weight (<40 kg) must take energy supplements to improve pregnancy outcomes. Since, maternal weight prior to conception and pregnancy weight gain are potential strategies to improve birth weight, personalized diet will help to minimize incidences of low birth weight.
Micronutrient supplementation is extremely important during pregnancy as it can substantially reduce maternal anemia, mortality rate, birth defects, preterm delivery and also improve breast milk quality. Fish is a cheap source of quality animal proteins. Moreover, as the small indigenous fishes (SIFs) are micronutrient rich especially in calcium, iron, phosphorous, zinc and vitamins like A, D, E [26, 34], they serves as a natural supplement for protein and micronutrients and protect against protein-calorie malnutrition and micronutrient deficiencies. Therefore, fish consumption, both large fishes and SIFs, before and during pregnancy must be encouraged.
Marine fishes are rich in omega 3 PUFAs, especially EPA and DHA. The estuarine/migratory fishes like Tenualosa ilisha are also a rich source of ω-3 PUFAs . Oily fish helps to prevent a range of health problems like childhood asthma and Attention Deficit Hyperactivity Disorder (ADHD) in pediatric population . PUFAs are also important structural constituents of the highly specialized membrane lipids of the brain and the central nervous system, critical for normal growth and development. So pregnant women need to include marine fishes and other omega-3 PUFA rich fishes like hilsa, at least 2/3 servings per week, to meet the EPA + DHA requirement.
Maternal seafood consumption is essential for optimum neural development of the child as seafood is a predominant source of omega-3 fatty acids. Lower omega-3 fatty acid intakes in pregnancy predicts lower verbal IQ, increased risk of suboptimum outcomes for prosocial behavior, fine motor, communication, and social development scores. Therefore, pregnant women are advised to have seafood intakes of more than 340 g per week so as to ensure proper neuronal development of the child .
According to the National Institutes of Health, USA there is scientific evidence that fish oil lowers high triglycerides (which are the fats that are linked to high cholesterol) and it can also lower blood pressure. Pregnant women with low levels of omega-3 fatty acids were 7.6 times more likely to have preeclampsia (high blood pressure during pregnancy), compared with women who had high levels of omega-3 fatty acids in their system . Therefore, pregnant women are recommended to consume omega 3 PUFA rich diets.
Fish oil is beneficial in protecting against premature birth. Eating fish, or taking fish oil supplements, will increase DHA in diet and possibly stop early contractions from taking place. The reason behind this is the presence of DHA which is known to suppress the formation of prostaglandins, the hormones that cause uterus to contract in a normal labor. Women who are at risk for delivering early, like women who are pregnant with twins or conceived with in vitro fertilization, must take fish oil supplements .
Fish is a rich source of quality animal proteins. As, unlike other sources of animal proteins, fishes are available in large varieties and they also come in different price ranges, fish is affordable by a common man for meeting the protein requirement of the family. Therefore, fish consumption, in plenty, before and during pregnancy must be encouraged for all types of consumers.
This work was supported by the Indian Council of Agricultural Research under Outreach Activity on ‘Nutrient Profiling and Evaluation of fish as a Dietary Component’. SG is thankful to ICAR for the financial support. The authors are thankful to Dr S. Ayyappan, Secretary, DARE & Director General, ICAR and Dr B. Meenakumari, DDG (Fisheries) for the encouragement and support.