*3.7. Vitamins*

A large number of animal studies (*n* = 56) have investigated the effects of vitamins B, C, D, E, choline, and folic acid and reported primarily anxiolytic effects (Figure 10). Among the human observational studies, the majority of studies assessing vitamin C, vitamin E, and broad-spectrum micronutrients reported an association with less anxiety symptoms while the majority of the studies assessing levels or intake of B vitamins and folic acid reported no association with anxiety symptom severity. Additionally, five case reports reported improvement in anxiety symptoms following broad-spectrum micronutrient supplementation.

**Figure 10.** Studies assessing vitamins and anxiety. ■ Higher intake or levels associated with decreased anxiety. ■ No association between intake or levels and anxiety. ■ Higher intake or levels associated with increased anxiety.

> Among the human experimental studies, several studies reported improved anxiety symptoms following supplementation of vitamin C (*n* = 3) and broad-spectrum micronu

trients (*n* = 12); mixed findings were reported by studies assessing vitamin D, B vitamins, and folic acid. Two human experimental studies involved participants with anxiety disorders. These trials delivered vitamin D [41] and two different broad-spectrum vitamin and micronutrient formulas [42], one assessed at a low and high dose. Both studies reported a reduction in anxiety symptoms.

A number of studies were identified that delivered combination natural health products to human (*n* = 22) or animal (*n* = 11) participants. The formulas included combinations of vitamins (typically two or three) or combinations of fatty acids, vitamins, minerals, probiotics, and amino acids. Among the human studies, 16 of 22 reported a significant improvement in anxiety symptoms. Among the animal studies, eight of 11 reported a significant improvement. The remaining studies reported no change. Two human trials involved participant with anxiety disorders or elevated anxiety symptoms. One included individuals with GAD [43], one included individuals with high trait anxiety levels [44]. The former delivered a combination of three vitamins (A, C, and E) and reported an improvement. The latter delivered a combination of probiotics, B vitamins and proteins and did not find a reduction in anxiety symptoms; however, other self-reported and biological markers of stress improved.
