When magnesium was taken orally along with calcium supplements, anxiety was decreased compared to placebo. Similarly, supplementation with magnesium and vitamin B6 was shown to reduce GAD in women
Selenium: In clinical trials people given daily oral supplementations of selenium, for 5 weeks reported less anxiety
Omega-3 fatty acids: dietary omega-3 fatty acids have been shown to improve mood and reduced the risk of anxiety
Vitamin C supplementation reduces anxiety by limiting the oxidative stress from metabolites and also by limiting cortisol (stress hormone).
Vitamin E also reduces anxiety and vitamin D reduces anxiety in people with fibromyalgia-associated anxiety.
Dietary deficiency in L-tryptophan, L-phenylalanine, or L-tyrosine leads to low serotonin synthesis due to the lack of availability of these building blocks and this dietary deficiency is associated with anxiety. L-lysine deficiency is known to increase the risk of anxiety in humans. In clinical trials, supplementation of the diet with the amino acid nutrient arginine reduces synthesis of the stress hormone, cortisol, in humans and may in this way be involved in the health of HPA-axis
Alramadhan, E., Hanna, M. S., Hanna, M. S., Goldstein, T. A., Avila, S. M., & Weeks, B. S. (2012). Dietary and botanical anxiolytics. Med Sci Monit, 18(4), RA40-48. doi:10.12659/msm.882608