The hypothesis that some children with attention-deficit hyperactivity disorder (ADHD) may show sensitivity or allergic reactions to various food items has led to the development of the the few-foods (or oligoantigenic)diet. The rationale of the diet is to eliminate certain foods from the diet in order to exclude potential allergens contained either naturally in food or in artificial ingredients with allergenic properties. The oligoantigenic diet attempts to identify individual foods to which a person might be sensitive. First, ADHD symptoms are monitored while multiple foods are excluded from the diet. Subsequently, if symptoms remit, foods are re-introduced, while observing the individual for the return of symptoms. An advantage of the oligoantigenic diet is that it can be tailored to the individual. A growing body of evidence suggests that behavioral symptoms of subgroups of children with ADHD may benefit from the elimination of certain foods. The effect sizes of an oligoantigenic diet regarding improvement of ADHD symptoms have been found to be medium to large. Available evidence suggests that the investigation of the role of food hypersensitivities in ADHD is a promising avenue worthy of further exploration. Further large-scale, randomized controlled studies including assessment of long-term outcome are therefore warranted.

The Nutri-Score is a 5-color front-of-pack nutrition label designed to provide consumers with an easily understandable guideline to the healthiness of food products. The impact that the Nutri-Score may have on consumers’ choices is unclear since different experimental paradigms have found vastly different effect sizes. In the present study, we have investigated how student participants change a hypothetical personal 1-day-dietary plan after a learning phase during which they learn about the Nutri-Scores of the available food items. Participants were instructed to compose a healthy diet plan in order that the question of whether the Nutri-Score would improve their ability to compose a healthy dietary plan could be investigated, independent of the question of whether they would apply this knowledge in their ordinary lives. We found a substantial (Cohen’s d = 0.86) positive impact on nutritional quality (as measured by the Nutrient Profiling System score of the Food Standards Agency) and a medium-sized (Cohen’s d = 0.43) reduction of energy content. Energy content reduction was larger for participants who had initially composed plans with higher energy content. The results suggest that the Nutri-Score has the potential to guide consumers to healthier food choices. It remains unclear, however, whether this potential will be reflected in real-life dietary choices.

Available evidence suggests that the consumption of edible insects may not only contribute protein and other valuable nutrients to the human diet but may also provide health benefits through various insect-derived peptides and bioactive compounds. Most studies of potential anti-obesity effects of edible insects have been conducted in vitro. The available in vivo evidence stems mainly from rodent models. Anti-obesity effects of various edible insect species, such as Tenebrio molitor, Hermetia illucens, and Acheta domesticus, have been suggested, and the findings of studies in mice models suggest the presence of bioactive compounds in edible insects with a potential efficacy in weight control. The mechanisms suggested to underlie the lipid-lowering and anti-obesity effects of edible insect extracts include the inhibition of pathways related to lipid metabolism, downregulation of genes involved in the metabolism of adipose tissue, effects on gut microbiota and increased satiety following consumption of insect-derived food products. However, any claims of health benefits of insect-derived compounds need to be sufficiently established, and trials in humans are a prerequisite. With respect to anti-obesity (and other health) effects, no such compound identified in insects has thus far been tested in humans. Further studies of the effects of bioactive compounds contained in edible insects on human health are therefore needed in order to validate the potential of edible insects as a novel measure in combatting obesity and promoting health in general.

Given its increasing global prevalence, Alzheimer's disease (AD) has become a major public health challenge worldwide. The symptomatic treatments available for AD have shown no significant efficacy, and no disease-modifying interventions are capable of slowing the progression of the disorder. The potential of lifestyle-related factors, including diet, is increasingly recognized as an important consideration in the primary prevention of AD. Numerous mechanisms potentially underlying neuroprotective effects of bioactive components contained in tea, such as (–)-epigallocatechin-3-gallate, as well as their preventive efficacy against AD, have been elucidated in preclinical studies. However, in contrast to the abundance of mechanistic findings in animals, clinical results demonstrating efficacy in humans are scarce. While epidemiological studies have provided some evidence indicating that green tea consumption is associated with a reduced risk of age-related cognitive decline and AD, a causal relationship cannot be established on the basis of these observations. The clinical evidence regarding preventive or therapeutic effects of green tea and its bioactive components is unsatisfactory. A role of green tea in the prevention of AD cannot be recommended until well-designed, randomized, placebo-controlled clinical trials using standardized formulations confirm the purported beneficial effects of green tea.

The available evidence, which derives from studies investigating mechanistic effects of tea, research on animal models as well as epidemiological studies and intervention trials in humans, suggests that compounds contained in tea may have the potential to aid in the prevention of depression or in its treatment as an addition to established therapies. A wide range of potentially antidepressive biological activities of tea components have been reported. However, the mechanisms of tea phytochemicals possibly capable of decreasing the risk of depressive symptoms are complex, multifaceted and not well understood. Potent pharmacological effects on circumscribed neurobiological systems may be produced not by individual tea components but rather by the synergistic action of various compounds on multiple pathophysiological mechanisms involved in depression. While epidemiological studies have generally demonstrated beneficial effects of tea consumption on mood and depressive symptoms, cross-sectional studies are unable to prove a cause-effect relationship. If positive effects on mood could be firmly established, tea drinking could support mental health. However, the moderate antidepressive effects observed in healthy people are not necessarily indicative of possible clinical effects in major depressive disorder. Randomized controlled intervention studies are needed to establish a causal relationship between bioactive compounds in tea and depression.

The findings of various epidemiological studies, interventions using randomized controlled trials and mechanistic experiments have suggested a protective role of tea and its bioactive components in cardiovascular health. The potential of tea in the prevention of cardiovascular diseases (CVDs) has therefore attracted increasing research interest. Polyphenols, in particular flavonoids, found in both green and black tea, have been suggested to play a primary role in the reduction of CVD risk. While promising results regarding the effects of tea on blood pressure and other CVD-related biomarkers have been found in preclinical experiments, the effects demonstrated in human studies are modest and less satisfactory. This discrepancy may be explained, at least in part, by different research strategies used in human and animal research. However, since tea is globally one of the most commonly consumed beverages, even small beneficial effects in humans may shift the population distribution of CVD risk, with major implications for public health. However, research conducted to date does not yield sufficiently robust evidence to allow a recommendation as to an optimal level of tea consumption as an element of health policies seeking to prevent hypertension and improve cardiovascular health.

Vitamin D has increasingly been associated with the pathophysiology of mental illness and has been suggested to have beneficial effects on depression in adults. Epidemiological studies concerning vitamin D and depression have found inconsistent results and many have significant methodological limitations. The available evidence suggests that depressed individuals show reduced vitamin D concentrations compared to controls without depression. Despite the available findings suggesting that hypovitaminosis D elevates the risk of depressive mood, the evidence of observational and interventional studies is insufficient to establish causality between low vitamin D levels and the occurrence of depression. The question of whether vitamin D sufficiency has protective efficacy against incident depression or recurrence requires future investigation. In order to examine the therapeutic efficacy of vitamin D, further well-designed, large-scale, long-term intervention trials of vitamin D supplementation in people of different age groups with depressive symptoms, diagnosed depression, postpartum depression or other depressive disorders are warranted. In short, current evidence cannot definitively establish whether vitamin D deficiency is a risk factor in the development of depression or whether vitamin D is effective in the treatment of depression.

Autism spectrum disorder (ASD) is a set of heterogeneous neurodevelopmental conditions, characterized by early-onset difficulties in social communication as well as repetitive and unusually restricted behaviors and interests. The treatment of ASD is based primarily on psychoeducational and behavioral interventions. Since the effectiveness of available treatments for ASD is limited, many families search for alternative therapies, such as the gluten-free and casein-free (GFCF) diet. Despite the popularity of the GFCF diet as a supplementary treatment in children with ASD, several rigorous evaluations have failed to confirm its effectiveness. The majority of the available studies examining the efficacy of the GFCF diet are seriously flawed and allow no firm conclusions. The available evidence regarding the effectiveness of the GFCF diet in the treatment of childhood ASD is very weak and cannot be considered promising. The GFCF diet should be used only if an allergy or intolerance to nutritional gluten or casein has been established. The identification of a hypothetical diet-related ASD phenotype may help in selecting children who could benefit from a GFCF dietary intervention. An important consideration is that potentially ineffective therapies may imply considerable opportunity costs, with other possibly more effective treatment approaches remaining unutilized.

The hypothesis that omega-3 fatty acids may play a role in preventing and treating depression is based on correlative associations between fish consumption, omega-3 fatty acid intake and the prevalence of major depressive disorder. Reduced omega-3 fatty acid erythrocyte levels have been found in individuals with depressive disorders. These observational findings are unable to establish a causal relationship between omega-3 fatty acids and depression. The results of randomized controlled trials of omega-3 fatty acids for depressive disorders are inconclusive and also fail to prove causation. The therapeutic efficacy of omega-3 fatty acids appears to be moderate at best but is more likely to be minimal or non-existent. Potential long-term adverse effects of omega-3 fatty acid supplementation should be considered. Large-scale, well-controlled clinical trials are required to establish potential anti-depressive effects of omega-3 fatty acids. Such studies need to consider baseline values of omega-3 fatty acids and symptom severity, the dosage and types of the fatty acids used, the duration of supplementation and the concomitant use of medication. Conclusive evidence of the efficacy of omega-3 fatty acids in depression is currently lacking. The recommendation of potentially ineffective therapies may have considerable opportunity costs, with other possibly more useful treatments remaining unutilized.

Entomophagy (consumption of insects) is an issue of global nutritional and environmental interest. The nutritional value of insects appears to be high, since they are rich in protein and fat and provide a range of vitamins and minerals. Edible insects contain similar amounts of protein to conventional meat and higher levels of polyunsaturated fatty acids. Due to their high content of protein, micronutrients and fiber, insects could become a valuable alternative to food derived from other animals. The findings of various in vitro and in vivo animal studies suggest beneficial effects of entomophagy with respect to cardiovascular, gastrointestinal and non-communicable diseases as well as immune functions and carcinogenesis. Edible insects appear to be a promising and insufficiently explored source of macronutrients, micronutrients and food bioactives. In the course of time, some edible insects may meet the criteria of functional food ingredients. However, there is a significant lack of research investigating health outcomes in humans. The available evidence in humans, derived from randomized controlled trials, suggests a role of edible insects in the promotion of mineral status and the modulation of gut microbiota, with some prebiotic effects. High-quality clinical studies assessing efficacy, oral intake safety and allergy risk are needed.