Original title: ‘An Apple a Day’?: Psychiatrists, Psychologists and Psychotherapists Report Poor Literacy for Nutritional Medicine: International Survey Spanning 52 Countries

Authors: Mörkl, Sabrina et al.

Quelle: https: //doi.org/10.3390/nu13030822

Note: This scientific study is freely accessible to everyone and has been translated into German by me. The emphasis is mine.

What was the study about?

A total of 1056 participants from 52 countries were surveyed via an online questionnaire:

  • 354 psychiatrists, 511 psychologists, 44 psychotherapists and 147 psychiatric specialists in training
  • On the quality of patient nutrition
  • For training / education on nutritional psychiatry
  • For further training after studying nutritional psychiatry
  • On the use of nutritional approaches in the treatment of patients


  • All participants were of the opinion that the quality of the diet of people with mental disorders is poorer than that of the general population.
  • The majority of psychiatrists (74.2%) and psychologists (66.3%) stated that they had no training in nutrition.
  • Nevertheless, many of them used nutritional approaches, with 58.6% recommending supplements and 43.8% recommending specific nutritional strategies to their patients.
  • Only 0.8% of participants rated their training as “very good” in terms of nutrition. Almost all (92.9%) stated that they would like to expand their knowledge on the subject of ‘nutritional psychiatry’.
  • There is an urgent need to integrate nutrition education into MHP training, ideally in collaboration with nutrition experts, to achieve good care in practice.

Summary in text form:

Nutrition-related interventions have positive effects on certain psychiatric disorder symptoms and common physical comorbidities. However, there are only a few studies that examine the nutritional competence of mental health professionals (MHP). This study aimed to evaluate the across 52 countries. The questionnaires were distributed via colleagues and professional associations. Data was collected on self-reported general nutritional knowledge, nutrition education, learning opportunities and tendency to recommend supplements or prescribe certain diets in clinical practice. A total of 1056 people took part in the study: 354 psychiatrists, 511 psychologists, 44 psychotherapists and 147 MHPs in training. All participants were of the opinion that the quality of nutrition of people with mental disorders is worse compared to the general population (p < 0.001). The majority of psychiatrists (74.2%) and psychologists (66.3%) stated that they had no training in nutrition. Nevertheless, many of them used nutritional approaches, with 58.6% recommending supplements and 43.8% recommending specific nutritional strategies to their patients. Only 0.8% of participants rated their training as “very good” in terms of nutrition. Almost all (92.9%) stated that they would like to expand their knowledge on the subject of ‘nutritional psychiatry’. There is an urgent need to integrate nutrition education into MHP training, ideally in collaboration with nutrition experts to achieve best practice care


  • People with psychiatric disorders often experience a reduced quality of life due to disability, comorbidity and stigmatization and have a lower life expectancy than the general population [1,2].
  • Psychiatric disorders contribute significantly to the global burden of disease and represent one of the most pressing challenges today [3].
  • Conventional treatment and management strategies for psychiatric disorders have suboptimal effectiveness and usually focus on trying to reduce symptomatology, which means that the disorders often persist and are not transient.
  • In addition, people living with psychiatric disorders have a life expectancy that is 15 years lower than the general population [4], which is mainly due to the high rates of cardiovascular disease, diabetes and metabolic syndrome [5].
  • Research into novel prevention and treatment strategies is essential to reduce the burden of disease associated with psychiatric disorder and common chronic disease comorbidities.
  • Nutritional psychiatry (NP ) is an emerging field with promising research indicating a role for supplemental nutritional approaches in the prevention and treatment of numerous neuropsychiatric disorders [6].
  • The idea that the availability of micro- and macronutrients is fundamental to the development and function of the brain is well known. More recently, dietary composition has been shown to play a crucial role in influencing the gut microbiota, neurotransmitters, neuropeptides and the immune system, all of which are involved in the pathogenesis of psychiatric disorders [7,8,9].
  • Poor diet is considered a modifiable risk factor for general mental health and certain mental disorders. For example, eating five portions of fruit and vegetables a day is associated with better general and mental health (increased optimism and self-efficacy as well as reduced psychological distress and depressive symptoms) [10].
  • This link between dietary intake and mental health was strengthened by a recent meta-analysis of 16 randomized controlled trials (RCTs; n = 45,826), which found that nutritional interventions significantly reduce depressive symptoms, especially when delivered by accredited nutrition professionals (e.g. dietitians or nutritionists) [11].
  • The effects of nutritional interventions are superior to behavioral therapy and a “social support group” in patients with depression [12,13]. Given the inadequacies of traditional prevention, treatment and management strategies in psychiatry when used alone, greater emphasis should be placed on complementary strategies such as nutritional psychiatry [14,15].
  • In addition, people with mental health problems often have an unhealthy lifestyle, including poor eating habits, disordered eating patterns and nutritional deficiencies [16,17]. This is partly the reason for the high rates of chronic disease and reduced life expectancy [2]. Therefore, lifestyle modification (including diet) should be included as a best practice measure to treat physical comorbidities in people with psychiatric disorders [18].
  • It is reassuring to note that the dietary recommendations and eating patterns that protect physical health are in line with those that are beneficial for mental health.
  • It is critical that mental health professionals (MHPs) have basic training and knowledge of nutrition so that they can provide initial nutritional counseling to patients and refer them to nutrition experts when needed. However, the training, knowledge and application of nutritional approaches by the main MHPs, psychologists and psychiatrists, remains unclear. European and US studies have examined current nutrition education in general medical curricula and found that nutritional medicine is either not taught or inadequately taught in medical education [19,20,21]; however, there are some recent developments to integrate nutrition into medical education (e.g. PAN-int.org). In addition, some universities have begun to offer certifications in nutritional psychology, but there are no official regulations or standards.
  • To our knowledge, there are few studies on the perception, training and awareness of psychiatrists, psychologists and psychotherapists in relation to nutritional literacy and interventions. A small study (n = 6) investigated the subjective opinion of psychotherapists on the topic of nutrition [22] and suggested that nutritional issues should be more strongly integrated into the field of psychotherapy. In a 1989 survey, 232 American psychologists indicated that they received no training in nutrition, but more than half of the respondents felt that nutrition and exercise should be a mandatory part of the graduate school curriculum [23]. More recent studies on this topic were not identified by the authors. Based on the existing curricula, a large educational gap in nutrition education is still foreseeable.

We therefore formulated the following hypotheses:

  • (1) MHPs worldwide have done little to no nutrition education and self-perceived nutrition literacy is low because nutrition approaches are not taught in MHP graduate or postgraduate courses,
  • (2) nutritional care is not integrated into routine clinical practice due to low nutritional literacy, and
  • (3) Nutritional interventions (i.e. diet or supplements) are not used in clinical practice.

The purpose of this study was to examine the level of nutrition education taught in university programs, self-perceived nutrition literacy, and the use of nutrition approaches (diet and/or supplements) in clinical practice.


The data was collected over a total period of 22 months (from December 2018 to September 2020). Participants who did not agree to the conditions (n = 22) and those who did not meet the inclusion criteria (n = 21) were excluded from the analysis. The remaining participants (n = 1056) were included in the data analysis. If someone practiced several professions (e.g. psychiatrist and psychotherapist), the main profession (psychiatrist) was counted. Figure 1 provides an overview of the flow of participants through the study.

3.1. Demographic data of the study participants

A final sample of 1056 participants, 354 psychiatrists, 511 psychologists, 147 psychiatry and psychology trainees and 44 psychotherapists, from 52 countries was included. The majority of participants were female (71.9%), and the average age was 39.9 (SD 10.0) years.

The majority of participants stated that they worked in a hospital (n = 450, 42.6 %), followed by private practices (n = 233, 22.1 %), outpatient psychiatric services (n = 178, 16.9 %), rehabilitation centers (n = 64, 6.1 %) and day clinics (n = 20, 1.9 %). A further 10% stated that they worked in establishments other than those mentioned above, and one participant did not specify where they worked.

Table 1 provides an overview of the country in which the participants work, grouped according to the country’s income level. Of those who indicated their country (n = 1047), most were based in high-income countries (n = 905, 86.4%), followed by upper-middle income countries (n = 121, 11.6%), lower-middle income countries (n = 20, 1.9%) and only 1 (0.1%) from a low-income country. By region, most participants were in Europe (31 countries, n = 866, 82.7%), followed by Asia (10 countries, n = 108, 10.3%), North America (3 countries, n = 34, 3.2%), Oceania (1 country: Australia, n = 19, 1.8%), South America (3 countries, n = 12, 1.1%) and Africa (4 countries, n = 8, 0.8%).

The participants specialized in general adult psychiatry or psychology (n = 467, 44.2 %), child and adolescent psychiatry or psychology (n = 151, 14.3 %), neuropsychiatry or psychology (n = 54, 5.1 %), psychosomatics (n = 49, 4.6 %), psychogeriatrics (n = 36, 3.4 %), addiction medicine (n = 22, 2.1 %) and forensic psychiatry or psychology (n = 15, 1.4 %). 72 (6.8%) participants stated that they had not specified their specialization, a further 154 (14.6%) stated that they had no specialization and 35 (3.4%) did not specify.

Table 2 provides an overview of the participants and comparisons of the main characteristics of psychiatrists, psychologists and psychotherapists.

Gender differed significantly across all groups (χ2 (6, N = 1054) = 100.0, p < 0.001). While about half of the psychiatrists were male, the psychologists and psychotherapists were predominantly female (Table 2). In addition, the groups differed significantly in terms of age (H (3) = 172.07, p < 0.001), with psychologists being slightly older than psychiatrists and psychotherapists (for both, p < 0.05). As expected, psychiatrists and psychologists were significantly older than those in training (p < 0.001). In addition, a significant difference in work experience was found between the groups (H (3) = 18.185, p < 0.001). There was a significant difference in the length of professional experience between participants in training and all other groups: Psychologists and participants in training (p < 0.001), Psychiatrists and participants in training (p = 0.012) and Psychotherapists and participants in training (p = 0.011).

In terms of year of postgraduate education, 304 (28.8%) participants had stated their current year of postgraduate education, 561 (53.2%) participants had completed their studies and 191 (18.2%) did not specify.

3.2. Nutrition-related training

Of the 511 psychologist participants, 51.1% (n = 261) responded to the question of whether they had received any nutrition training during their postgraduate studies: Of the responding psychologists, 173 (66.3%) reported not having attended any lectures, 59 (22.6%) reported some training during their psychology studies, 22 (8.4%) attended elective courses on this topic and 7 (2.7%) had compulsory courses (Austria n = 6 and Germany n = 1). Of the 354 psychiatry participants, 198 (55.9%) psychiatrists responded to the question of whether they had any special training in the nutritional care of patients during their psychiatric residency: 147 (74.2%) psychiatrists stated that they had not attended any lectures, 30 (15.2%) had training during their medical studies and 17 (8.6%) completed electives on this topic. A minority of participants (n = 4, 2.0%) had compulsory courses (Lithuania n = 1, Switzerland n = 1, UK n = 1 and USA n = 1).

While working as a psychiatrist or psychologist, 111 (10.5%) participants had attended special training in nutritional care. Regarding knowledge of courses teaching nutrition, 229 (21.7%) participants knew of courses teaching nutrition for the prevention and treatment of psychiatric disorders in their country or institution: 94 (41.1%) psychologists, 80 (34.9%) psychiatrists, 45 (19.7%) in training and 10 (4.4%) psychotherapists.

Almost all participants (92.9%) would be willing to expand their knowledge of “nutritional psychiatry”. The most popular learning channel was “congresses” (n = 650), followed by “specialist journals” (n = 495) and “interdisciplinary meetings” (n = 480). Participation in “Master’s degree programs” (n = 80) and “doctoral projects” (n = 59) was the least popular.

Perceived current knowledge in the field of “nutritional psychiatry” correlated positively with (i) participants’ perceived ability to improve their quality of work and participant outcomes through training in “nutritional psychiatry” (rs = 0.329, p < 0.001), (ii) the rating of the importance of “nutritional psychiatry” (rs = 0.393, p < 0.001) and (iii) the rating of the importance of nutritional discussions with patients (rs = 0.396, p < 0,001).

3.3. Treatment practices

238 (67.2%) psychiatrists, 335 (65.6%) psychologists and 29 (65.9%) psychotherapists reported using nutritional approaches to treat patients, with no significant differences between professional groups (χ2 (3, N = 1056) = 0.556, p = 0.906).

Nutritional approaches were most frequently used for the treatment of eating disorders (n = 436 responses) and affective disorders (n = 344 responses), followed by anxiety disorders (n = 208 responses), psychotic disorders (n = 130 responses) and obsessive-compulsive disorders (n = 58 responses). One third (n = 379 or 35.9%) of the participants stated that they had never used a nutritional approach for a psychiatric disorder. For the prevention of somatic comorbidities, 402 participants (38.1%) reported using nutritional interventions occasionally, while 212 (20.1%) reported never using such interventions and only 43 participants (4.1%) always included nutritional interventions.

Almost a quarter of the participating psychiatrists (n = 88; 24.9 %) stated that they occasionally took the individual nutritional status of patients into account when prescribing psychopharmacological therapy, 67 (18.9 %) stated that they did so most of the time, and 22 (6.2 %) stated that they always did so. Eighty-three (23.4%) reported never considering the nutritional status of patients when prescribing psychopharmacological medications and 62 participants (17.5%) almost never did.

The most frequently recommended lifestyle intervention was physical activity (n = 935), followed by dietary advice (n = 558) and cooking classes (n = 112), while 102 participants stated that they hardly ever recommended a lifestyle intervention. Most participants stated that they never (n = 498, 47.2 %) or almost never (n = 306, 29.0 %) test for food allergies, gluten sensitivity or food intolerances. There was no difference between the occupational groups (χ2 (12, N = 1009) = 8.058, p = 0.781) when testing for food allergies, gluten sensitivity or food intolerances.

Nutritional care in connection with mental disorders was considered “very important” by 121 (11.4%) of the participants (Likert scale 10/10). Discussion of nutrition in the clinical setting was rated as very important by 73 (6.91%) of the participants (Likert scale 10/10).

When asked to rate the nutritional status of the population of the countries, the most common rating was 5/10 (n = 199, 18.8 %); only 6 (0.6 %) rated the status as “very good” (Likert scale 10/10). When asked about the nutritional status of people with mental disorders in their country, the most common rating was 3/10 (n = 294, 27.8%); only 1 person (0.1%) rated the quality as “very good”. Importantly, participants rated the quality of nutrition of people with mental disorders (Mdn = 3.00) as significantly worse compared to the general population (Mdn = 5.00) in their country (U = 265739.00, p < 0.0001). The participants most frequently rated the quality of the food in the hospitals in their country of profession as 5/10 (n = 199, 18.8%). There was no significant difference between the qualification groups (H(3) = 1.841, p = 0.606).

Regarding regular check-ups for comorbid metabolic disorders, 314 (n = 29.7%) knew about regular check-ups at their workplace, while almost half of the participants did not know or gave no answer (n = 469; 44.4%) and 264 (25.0%) were unaware of regular check-ups. Interestingly, there was a significant difference between the occupations (χ2 (6, n = 1047) = 22.31, p = 0.001). After a Bonferroni correction for multiple testing, psychiatrists (p = 0.006) and psychologists (p = 0.006) as well as psychotherapists in their countries were significantly more informed about metabolic screening than those in training.

3.4. Recommendation of diets and dietary supplements by MHPs

Just under half (n = 462; 43.8 %) of the participants recommended a specific diet to their patients. Participants could check one or more boxes and had the choice between the following diets: Diet according to national guidelines, Mediterranean diet, vegetarian diet, vegan diet, ketogenic diet, low carb diet, glyx diet and/or other diets. The most frequently recommended diets were the Mediterranean diet (n = 210) and the diet according to national guidelines (n = 202), followed by the low-carbohydrate diet (n = 135) and others (n = 104). The Glyx diet (n = 15) and the vegan diet (n = 17) were the least recommended. Table 3 and Table 4 provide an overview of other diets that could be specified in a free text response field. When asked about the indications for recommending the diet (multiple answers were possible), most participants mentioned “metabolic comorbidities” (n = 421), followed by “prevention of obesity” (n = 387) and “obesity” (n = 330). In terms of psychiatric indications, “eating disorders” (n = 337) was in first place, followed by “symptoms of depression” (n = 282), “symptoms of anxiety” (n = 159) and ADHD (n = 140). There were no significant differences between male and female MHPs regarding the recommendation of a specific diet for patients (χ2 (2, N = 1034) = 3.246, p = 0.197). Almost half of the participants (n = 520, 49.2%) stated that they had already started a diet themselves and had maintained it for at least one month. There was no significant difference between occupational groups (χ2 (3, N = 1036) = 3.904, p = 0.272) and male and female MHPs (χ2 (2, N = 1033) = 1.016, p = 0.602).g.

Next, we asked all participants whether they recommend dietary supplements to their patients. A total of 619 (58.6%) participants stated that they would recommend dietary supplements: 64.5% of psychologists (n = 323), 57.2% of psychiatrists (n = 198), 54.5% of psychotherapists (n = 24) and 51.0% of psychologists and psychiatrists in training (n = 74). There was a significant difference between the occupations (χ2 (3, n = 1036) = 10.635, p = 0.014). Psychologists recommended more supplements than psychotherapists (χ2 (1, n = 397) = 8.571, p = 0.003), and the results were statistically significant after Bonferroni correction (p = 0.018). The higher rate of psychologists recommending supplements compared to psychiatrists (χ2 (1, n = 521) = 4.538, p = 0.033) was not statistically significant after Bonferroni correction for multiple testing (p = 0.198). There were no significant gender differences regarding the recommendation of dietary supplements (χ2 (2, N = 1033) = 3.758, p = 0.153).

We provided a list of commonly recommended mental health supplements that could be ticked if participants had ever recommended them to their patients (vitamin D, omega-3, vitamin A, vitamin E, selenium, zinc, magnesium, vitamin B6, vitamin B12, folic acid, iron, N-acetylcysteine). For this question, it was possible to check more than one box. The most frequently recommended supplement was vitamin D (n = 446), followed by vitamin B12 (n = 414), omega-3 (n = 364), folic acid (n = 319) and vitamin B6 (n = 314).

A further 164 participants (15.5%) said they would recommend supplements that were not listed in the survey or gave additional answers. Table 5 lists the additional food supplements recommended by the participants.

Most participants (n = 853, 79.1 %) stated that they took or had taken dietary supplements, while 206 participants (19.5 %) stated that they had never taken dietary supplements and 15 (1.4 %) gave no answer. There was no significant difference between occupations (χ2 (3, N = 1041) = 5.384, p = 0.146) or gender (χ2 (2, N = 1038) = 3.504, p = 0.173) in supplement use.

Table 6 lists the additional comments participants made in response to the question about recommended supplements.

  1. Discussion

In this international cross-sectional survey, we investigated subjective nutrition literacy, nutrition education and the use of nutrition interventions (such as diets and supplements) in 1056 MHPs from 52 countries. MHPs regard nutrition as an important pillar in the biopsychosocial care model. However, most MHPs reported having little or no nutrition expertise and no professional training in nutrition; yet nutrition approaches were recommended by half of the MHPs, and 60% of these recommendations were for the treatment of psychiatric disorders. It seems likely that these nutritional approaches are being recommended without an adequate knowledge base.

4.1. Education

MHPs’ limited nutrition discussion and education to patients may be due to inadequate training and subsequently low confidence in counseling patients [23]. Nutritional medicine is not adequately taught in medical schools, regardless of the future specialty; for example, only 40% of medical schools in the USA achieve the goal of teaching 25 hours of nutrition in the preclinical years [20,21]. This training gap seems to exist worldwide. An assessment of medical nutrition education in 15 European and six non-European countries concluded that “nutrition is insufficiently integrated into medical education, regardless of country, setting or year of medical training” [21]. This was also reflected in our results; more than two-thirds of psychiatrists and psychologists reported that they had no specific training in nutrition, with only a minority (2.68% of psychologists and 2.02% of psychiatrists) attending mandatory courses.

We hypothesized that psychiatrists might rate their knowledge of nutrition significantly higher compared to the other professional groups due to their medical training. However, there was no significant difference in nutritional competence between psychiatrists and the other professional groups. Importantly, therapists are more likely to promote healthy habits if they have sufficient knowledge and practice a healthy lifestyle themselves [107]. In addition, an American study found that 63% of mental health providers practiced poor dietary habits, even though they considered themselves role models for patients [108].

In conjunction with the current literature, our findings therefore emphasize the need to implement targeted nutrition education for MHP. Importantly, we suggest that undergraduate/graduate curricula include mandatory nutrition training, as the majority of MHPs do not appear to be willing to participate in postgraduate training. In addition, congresses, journal articles and interdisciplinary conferences could be possible tools to promote interest in the field of “nutritional psychiatry”, as these approaches were the most popular among the participants in this study.

The US Academy of Nutrition and Dietetics recommends that registered dietitians should play a significant role in the interprofessional education of medical students, residents and practicing physicians [109]. This interprofessional approach should also be applied to the training of MHPs, the majority of whom (90%) would like to expand their knowledge in the field of “nutritional psychiatry”. Based on our findings, the current practice of nutrition therapy in clinical psychiatry is untenable from an evidence-based medicine perspective, as MHPs recommend questionable diets and supplements despite having little to no training in nutrition therapy.

Some psychologists responded that they would refer their patients to doctors (e.g. one psychologist wrote: “I send my clients to a doctor when they ask me about nutrition”). Sending patients to a psychiatrist or a doctor in another specialty may not be the best advice, as nutrition does not appear to be a compulsory subject in medical curricula in many countries. Sending patients to a psychiatrist or a doctor in another specialty may not be the best advice, as nutrition does not appear to be a compulsory subject in medical curricula in many countries. In addition, the lack of reported referrals to dietitians appears to be a gap in collaborative care and likely to hinder the best patient outcomes.

4.2. Treatment practices

In our study, all professional groups used nutritional medicine approaches to treat psychiatric disorders despite a lack of nutritional medicine training, with eating disorders and affective disorders being the most prominent indications. In the case of somatic comorbidities, more than a third of the participants stated that they occasionally used nutritional interventions. This lack of training of MHPs could be the reason why nutritional interventions significantly reduced depressive symptoms in a meta-analysis, but only if they were carried out by accredited nutritionists (e.g. dietitians or nutritionists) [11].

As psychopharmacological medication can have serious consequences for the metabolism, nutritional approaches could be an ideal additional treatment. However, only 6.2% of psychiatrists in our survey stated that they always consider the nutritional status of patients when prescribing psychopharmacological therapy, and half of the participants were unaware of regular screening for metabolic disorders in psychiatric patients in their country. This is also reflected in studies on this topic: although metabolic syndrome is common in patients taking psychopharmacological medication, hardly any patients undergo regular metabolic screening [110,111].

In addition, physical health is neglected by most patients themselves and is associated with an increased prevalence of somatic diseases such as obesity, diabetes and cardiovascular disease, followed by a significant reduction in life expectancy of 10-20 years compared to the general population [112]. Importantly, our survey participants rated the quality of nutrition of people with mental disorders as significantly worse compared to the general population in their country.

Therefore, treatment practices need to be improved and include dietary recommendations for patients that complement other recommended lifestyle interventions such as physical activity.

4.3. Recommended diets and supplements by MHPs

Studies have shown that certain diets, such as the Mediterranean diet, are associated with a lower incidence of depression [113,114,115] and that diet is an important factor shaping the gut microbiome and its metabolites. Almost half of our survey participants (43.8%) said they would recommend special diets for patients with psychiatric disorders, with the Mediterranean diet being the most popular choice. A Mediterranean diet ensures adequate nutrient intake [116], combines the beneficial effects of individual nutrients and targets a variety of mechanisms, including anti-inflammatory, antioxidant, neurogenetic and microbiome and immune-modifying activities [117]. For example, the large European PREDIMED study showed a reduced risk of depression in people with type 2 diabetes who were randomized to a Mediterranean diet with nuts compared to a control group with a low-fat diet [118]. Conversely, a vegan diet was the diet least recommended by the study participants. In fact, a recent systematic review found that a vegan or vegetarian diet is associated with a higher risk of depression but lower levels of anxiety [119]. A striking finding of our study was the remarkable number of different additional diets for mental health recommended by the MHPs in a free-text response box (see Table 3). While there is evidence for the positive effects of some diets, others have not been sufficiently researched and their potentially harmful effects on patients cannot be completely ruled out on the basis of current evidence.

Even more participants recommended supplements instead of a special diet for patients with psychiatric disorders (58.6% vs. 43.8%). Recent study results suggest that untargeted supplementation of nutraceuticals (both single vitamins and multivitamins or minerals) may not be equivalent to recommending a properly balanced diet, such as the Mediterranean diet, which provides foods [86,120,121,122]. The most frequently recommended supplements in our survey were vitamin D, vitamin B12 and omega-3 fatty acids. Although there is some evidence to support the supplementation of these nutrients in psychiatric disorders [123,124,125,126], 164 (15.5%) participants reported recommending a range of additional supplements. In fact, nutraceuticals appear to be widely used in the treatment of psychiatric disorders. The market for nutraceuticals accounts for a quarter of the global pharmaceutical market, with growth potential in the coming years. Patients with psychiatric disorders often take dietary supplements [127,128], as around 40% of patients do not respond satisfactorily to antidepressant medication [129] and around 50% of psychiatric patients discontinue their psychopharmacological treatment prematurely due to side effects [130]. A significant proportion of patients do not achieve complete remission with modern therapies, reflecting our incomplete understanding of the complex etiology and pathophysiology of most psychiatric disorders [131]. We assume that MHPs recommend dietary supplements in an effort to improve a potentially unsatisfactory response of their patients to treatment or due to the frequent request of patients to find a suitable, “natural”, “complementary” or “alternative” treatment with an estimated lower incidence of side effects [132]. Therefore, there is an urgent need to complement the current treatment paradigm with safe and sustainable interventions. Without question, micronutrients are vital for neurotransmitter synthesis and the proper functioning of the nervous and immune systems. Several micronutrients such as selenium, zinc, iron, magnesium, vitamin B12 and folic acid have been found to be inversely associated with an increased risk of depression [7,8,9,133,134], and some nutraceuticals such as 5-hydroxytryptophan, omega-3 fatty acids or folic acid are used as complementary treatments in psychiatry [125,135,136].

However, the efficacy of most supplements for psychiatric indications has not been sufficiently researched and evidence-based recommendations are lacking for many [121]. While some supplements have been used in traditional systems of medicine for thousands of years, there is little high-quality evidence for most of the supplements recommended by MHPs for the treatment of psychiatric disorders (see Table 5). Some of these supplements may have mechanisms of action on the central nervous system and the gut-brain axis that have not yet been explored and further research is needed. In addition, long-term effects and side effects are unknown for most of the dietary supplements reported. In many countries, food supplements are regulated as foods and not as prescription drugs. In our survey, psychologists reported recommending dietary supplements significantly more than psychiatrists and psychotherapists, although the significant difference between psychologists and psychiatrists remained non-significant after correction for multiple comparisons. We suspect that psychologists recommend dietary supplements as an aid to therapy because in most countries they are not allowed by law to prescribe medication. Nevertheless, dietary supplements may contain ingredients that have potent biological effects that can interact with psychopharmacological medications [137,138]. Therefore, medical and nutritional education is required to avoid adverse effects for patients.

4.4. Strengths and limitations

Our present study has several strengths: as far as we know, this is the first and largest study on this topic to date. We have a relatively high number of participants, covering 52 countries worldwide from all income groups. However, some countries (such as Austria) had a very high number of participants, while the response rate in other countries was significantly lower, which makes direct comparisons between experts from different countries difficult. In addition, most of our survey participants (71.9%) were female – but this is not unexpected as MHPs are predominantly female [139,140]. In each case, there were no significant gender differences in terms of assessed knowledge of “nutritional psychiatry” or recommendations of specific diets or supplements for psychiatric disorders. Nevertheless, there could be a gender bias in the results, as women may have been more interested in participating in nutrition surveys, as women tend to have a greater interest in healthy eating and lifestyle [141]. As always with online surveys, the assessment of the participants’ nutritional knowledge is based on subjective self-perception. Some participants in the group of psychiatrists and psychologists in training stated that they had more than 40 years of professional experience, resulting in a mean professional experience of 13.9 years. This could be due to physicians having more than one specialty (e.g., one participant stated that he first specialized in internal medicine and then later in his career began training in psychiatry).

Another obvious limitation is the potential for ‘selection bias’, whereby those with an interest in nutrition are more likely to participate in such a survey. In addition, educational and professional standards vary greatly from country to country. In addition, culturally established approaches can be reflected in the use of nutraceutical therapies. Since the links received were not individualized, there could theoretically be duplicate participation in the study, but we consider it unlikely that this was the case to an extent that would have significantly affected the results (given the time required to complete the survey and the lack of additional benefit to the participant from completing it more than once). The survey was distributed primarily by e-mail to national and international colleagues, using a combined snowball system. Since participation by professional groups other than MHPs could not be definitively ruled out due to the anonymous, self-assessment nature of the survey, the questionnaire included a question on current medical qualifications. If a participant stated that they were not a psychiatrist, psychologist or psychotherapist, this data was excluded from the survey (as shown in Figure 1; n = 14 participants belonged to other professions and n = 5 did not state their profession). Finally, the technique of snowball sampling is often used in web surveys such as this one. The non-probabilistic nature of the sample excludes the generalizability of the results to the entire population of MHPs.

4.5. Implications for future research

Future research should focus on the effectiveness and efficacy of nutrition as part of the training curriculum for MHPs to sustainably integrate nutrition into the biopsychosocial treatment model and to avoid treatment failures and adverse health effects of supplement recommendations without evidence. Most of our study participants reported that the quality and outcome of their work could be improved by further training in “nutritional psychiatry”, and almost all MHPs would like to increase their nutritional competence.

In 2018, we were one of the first universities in Europe to launch a training program on nutritional medicine and mental health for medical students at the Medical University of Graz, Austria. We are currently investigating the impact of this training program in terms of creating awareness of the topic and the use of this knowledge in clinical practice.

  1. Conclusions

As a first step, this international survey aimed to raise awareness of the alarming lack of knowledge about nutritional medicine in MHPs, despite the rapidly developing evidence base for the use of complementary feeding therapies in the routine care of psychiatric patients. The improvement of current training curricula and the integration of suitable modules on nutritional psychiatry appear to be of crucial importance in view of the rising costs of psychiatric care.

Subsequently, patients should expect appropriate, evidence-based basic counseling at the beginning of treatment, with the option to refer to nutrition specialists (physicians with nutritional training, nutritionists, dieticians, dieticians) if needed. This collaborative process has the potential to improve outcomes in relation to mental disorder and common metabolic comorbidities [142].

Most importantly, the medical maxim “first, do no harm” should be followed by avoiding the recommendation of supplements or diets without sufficient scientific evidence and prior physical examination and laboratory testing (including screening for deficiencies). The next generation of MHPs should not only be able to treat patients with cutting-edge psychotherapy and psychopharmacology, but also interest their patients in body and brain care, nutrition, and the multifactorial cause and prevention of psychiatric disorders.

Supplementary materials

The following materials are available online at https://www.mdpi.com/2072-6643/13/3/822/s1, Supplementary File S1: Survey questions. Supplementary file S2: Answers to the survey.