In summary, a wide range of topics are offered in adult education centers in Germany. We did not find substantial differences between offers in the western and eastern parts of Germany. This is remarkable, as in contrast to the development in the Federal Republic of Germany (FRG), medical services from non-medical practitioners as well as CAM were not wanted in the German Democratic Republic (GDR) . Thus, until 1989, distribution of CAM was rare in the GDR. Within the past 30 years, this difference seems to have vanished in part. This rapid development points to a high demand for information on this specific content.
Courses offered by adult education centers in the category CAM are mostly based on topics of alternative medicine and Far Eastern healing arts. Instead, courses related to evidence-based complementary medicine and phytotherapy are rarely offered. In the category of nutrition, courses relating to the basics of healthy nutrition are seldom offered. In contrast, courses on special forms of diet prevail. A substantial portion of these courses represents controversial and non-evidence-based types of diet. Often, we found offers for alkaline fasting and traditional nutrition forms from traditional Chinese medicine or ayurveda.
While most of the courses were led by non-medical practitioners, courses led by healthcare professionals such as physicians, physiotherapists, or psychologists were rare. Frequently, special knowledge in CAM or nutrition was claimed by the course instructors. The lack of statues in training of NMPs and the diversity of offers on the market for additional specialist knowledge cast strong doubt regarding whether this is a qualifying further education. In fact, an analysis of the NMPs’ schools in has shown that the content taught by these schools is not scientific or evidence based .
Similar problems can also be found in the field of nutritional therapy. In Germany, several terms describing nutritional therapists, e.g., “nutritionist,” are not subject to any legal protection, which is why they can be used by everyone without further requirements. In addition to certified degrees, for example certified by the German Nutrition Society, there is also a variety of offers for private or institute-internal degrees . Certified degrees in nutritional counseling or therapy could rarely be found in our study.
Highly problematic is that this lack of qualification might not be recognized by the participants of the courses who most probably rely on the selection criteria of the institutions. Due to the growing popularity, around 2.5 million participants per year enroll in health courses in adult education centers in Germany . In fact, these courses receive a high level of acceptance by health insurance funds, mostly cost-covered and actively promoted by them .
Our analysis of course offers of German adult education centers with respect to CAM showed a thematic focus on mind and body practices, including mainly procedures from a Far Eastern cultural background such as tai chi, qigong, and yoga. Mind and body practices use the mutual influence of body, psyche, and behavior on health. The focus of this concept is to improve health resources and strengthen self-efficacy. Recent studies could describe positive effects for only a few indications such as coronary heart disease, arterial hypertension, and chronic lower back pain [12,13,14]. Despite a great public and media interest, an advantage of CAM over physical activity or sports and a relevant clinical impact have not been shown so far. Accordingly, it has been shown that the use of yoga interventions compared to sporting activity does not offer any advantages in terms of tumor-associated fatigue .
In fact, also for other methods offered, scientific evidence is missing, although individual health-promoting effects are sometimes described. This applies, for example, to the use of reflexology in cancer care or treatment of multiple sclerosis [16, 17]. The same is true for the use of massage therapy in supportive care for cancer patients  or reducing symptoms of fibromyalgia .
This also applies to most other TCM methods. While for acupuncture and acupressure many studies have been published, data are heterogenous [20,21,22,23]. In addition, relaxation techniques may reduce anxiety and depression of cancer patients and increase patients’ quality of life [24, 25].
As, most probably, the scientific evidence is scarcely discussed in the courses, non-evidence-based knowledge may strongly impact the medical understanding of larger parts of the population, which could encourage an improper use of CAM and diet methods.
Moreover, these methods gain impact as they impress patients by their ease of use and the allegedly missing side effects. Moreover, TCM is a good example of CAM methods not lacking side effects. Besides reports of hepato- and nephrotoxicity, some herbal or dietary supplements are mixed with pesticides or drugs like corticosteroids. These interactions with conventional therapy have to be co considered [26,27,28]. CAM methods should not be recommended for every user without considering the individual medical condition and circumstances. Potential side effects should also be discussed within the courses. Especially the uncritical use of medicinal plants and homeopathy can be associated with an increased health risk [29, 30].
The effectiveness of dieting is clinically well proven, especially in combination with exercise and behavioral therapy for overweight and obesity . The aim of dieting methods is to improve or stabilize health.
Overall, course offers mostly dealt with controversial diet procedures such as alkaline fasting, detox diets, and low-carb diets. Neither the influence of acid-forming foods on the acid–base balance, nor the existence of so called “slags” and consequent detox diets are evidence-based concepts and methods [32, 33]. Strong carbohydrate restrictions should also be viewed critically. Seidelmann et al. could show in their study that both a low carbohydrate intake (< 40% of energy) and a high carbohydrate intake (> 70% of energy) are associated with an increased risk of mortality . None of the diet methods mentioned are recommended by the German Nutrition Society for long-term weight loss. Long-term use of non-evidence-based dieting methods can be associated with health risks, as vital nutrients could be supplied in insufficient quantities. It should also be addressed that very strict diets with rigid eating behavior and low protein and calorie intake can increase the risk of eating disorders.
In addition to several findings, our analysis also had limitations. Interpretations were based on course descriptions which were published on the websites of adult education centers. We are aware that the course descriptions may not reflect all characteristics and details of the content conveyed. Within our analysis period there was still no description for some courses; for other health courses, descriptions were partly no longer available.
Geographically, the search radius of our analysis was limited to 80 km based on the ten largest German cities by population. Rural, less densely populated regions outside this search area could not be included. Therefore, courses with regard to CAM and nutrition could potentially differ.
Detailed information on the course instructors and their professional skills were also not regularly found. In a quarter of the cases, despite naming the course instructor, no information about his professional qualifications was given. In addition, the diversity of offers on the market for training and further education without any statutes on binding content made the comparison even more difficult.