Effects of Vitamin D Supplementation on Cognitive and Emotional Functioning in Young Adults – A Randomised Controlled Trial

Randomized controlled trial in healthy young adults recruited from the University of Queensland in Australia. Participants were screened to exclude major psychiatric or neurological disorders and current vitamin D or calcium supplement use; the vitamin D arm included 63 randomized participants.

Vitamin D3 (cholecalciferol) was given as 5000 IU per capsule, taken orally once daily for 6 weeks, versus placebo. In the vitamin D arm, 63 participants were randomized.

Vitamin D supplementation increased 25OHD3 levels but did not improve cognitive or emotional functioning in healthy young adults. In the vitamin D arm, 25OHD3 rose from 76.2 to 98.0 nmol/L, with a significant baseline to follow-up change (F = 21.44; p < 0.001; d = 0.83), but there were no significant time by group effects for working memory (p = 0.30), response inhibition (p = 0.37), cognitive flexibility (p = 0.24), hallucination count (p = 0.88), depressive symptoms (p = 0.51), or anxiety and anger outcomes (p = 0.23 and p = 0.26). The authors concluded that supplementation does not confer these cognitive or emotional benefits in this population.

Short 6-week duration and a relatively small, healthy young adult sample from a single university limit generalizability. Baseline vitamin D status was already fairly adequate, which may have reduced the chance of detecting benefit, and the study does not support effects in this population despite biochemical repletion.