*3.3. Dietary Patterns*

Many studies were identified that assessed the impact of dietary patterns on anxiety symptoms severity or anxiety disorder prevalence including both animal models (*n* = 101) and human studies with observational (*n* = 102) and experimental (*n* = 84) designs. Dietary pattern studies evaluated the impact of combinations of foods or patterns of eating. Studies looked at both the types of foods that were consumed (Figure 5) and the quantity and timing of food consumption (Figure 6). Because studies may have defined specific dietary patterns differently, it is noted that significant heterogeneity exists within each category. In general, "Healthy" diet patterns were described as diets aligned with generally accepted principles of healthy eating. Many involved the calculation of a healthy eating score or index and were defined by higher intake of vegetables, fruit, whole grains, fish, legumes, and unprocessed meat. Diets or dietary patterns defined as "Unhealthy" or "Western" generally included higher intake of processed foods, sugar and sweetened foods, soft drinks, fried foods, processed meats, "junk food", and "fast food". In the animal studies, the "Western" or "Cafeteria" diet included a combination of high fat and high carbohydrate, in particular, high saturated fat and high refined carbohydrates. In many cases, the diet was designed to be highly palatable and to induce obesity [22,23].


**Figure 5.** Studies assessing the composition of dietary patterns. ■ Higher intake or levels associated with decreased anxiety. ■ No association between intake or levels and anxiety. ■ Higher intake or levels associated with increased anxiety.

**Figure 6.** Studies assessing the amount of food consumed or timing of eating. ■ Higher intake or levels associated with decreased anxiety. ■ No association between intake or levels and anxiety. ■ Higher intake or levels associated with increased anxiety.

The animal studies reported a mixture of anxiogenic and anxiolytic effects following administration of the "unhealthy", "cafeteria", or "Western" style eating patterns. Predominantly anxiolytic effects were seen following caloric restriction and fasting.

Observational studies showed an association between lower anxiety symptom severity or disorder prevalence and "healthy" diet patterns, the Mediterranean diet, traditional diets, the vegetarian diet, consumption of breakfast, anti-inflammatory diet patterns, and increased diet variety. Higher anxiety symptom severity or disorder prevalence was associated with "unhealthy" diet patterns, caloric restriction, and snacking. It is noted that among the observational studies assessing the relationship between vegetarianism and anxiety symptoms, two of the three studies that reported an increase in anxiety were prospective in design while all of the studies reporting an association between the diet pattern and less anxiety were cross-sectional in design. Two case reports described improvement in anxiety symptom severity following multimodal interventions with a dietary component. One involved the elimination of "inflammatory foods" in combination with exercise and psychological treatment [24]. The other delivered a vegan diet in combination with fruit and vegetable juice, nutritional supplements, exercise and stress management techniques [25].

Of the experimental studies delivering an intervention that promoted healthy eating behaviors, twenty reported a reduction in anxiety symptoms while sixteen did not

observe a significant effect. Only two of these trials recruited individuals with anxiety disorders [26,27]; the remaining studies recruited individuals with medical illnesses or healthy participants. One randomized controlled trial enrolled participants with moderate to severe anxiety disorders and assessed the impact of dietary counselling, in combination with a multivitamin and a herbal remedy, compared to a psychosocial intervention, and reported a significant improvement in anxiety symptoms with the combination intervention as compared to the psychosocial intervention [26]. Another study randomized individuals with anxiety and/or depressive disorders to either dietician consultations or an attention control intervention; significant improvement was seen in both treatment groups [27]. Nine of thirteen studies promoting caloric restriction reported an improvement in anxiety symptoms. While one of the studies recruited participants with elevated anxiety symptoms [28], all involved overweight and obese participants. A meta-analysis of studies delivering caloric restriction to adults with obesity did not find a significant reduction in anxiety symptoms [29] while a meta-analysis on the same topic that included child and adolescent populations did report a reduction in anxiety [30].
