Vitamin D is essential for many functions in the human body. It is a fat-soluble vitamin that can be obtained from sun exposure and certain foods, including beef liver, egg yolks, fortified dairy and non-dairy products, and the flesh of fatty fish such as salmon, tuna, and trout. Vitamin D is well-known for its role in support of musculoskeletal health, a healthy immune response, and cellular health. It has also been studied for its potential role in support of a healthy mood. 

The potential biochemical link between depression and vitamin D has been postulated in the literature. Studies indicate that certain brain areas associated with depression have vitamin D receptors. Gene polymorphisms related to vitamin D receptors have also been connected to depression in older adults. Vitamin D is believed to interact with certain hormones and inflammation pathways related to depression.

A randomized, controlled clinical trial published in the Journal of the American Medical Association (JAMA) by Okereke and colleagues explored the potential mood-supportive impact of long-term supplementation with vitamin D3, also known as cholecalciferol. Cholecalciferol is the predominant version of vitamin D found in nature. This study involved over 18,000 adults 50 years of age and older who did not report clinically relevant depressive symptoms or depression at baseline.

Study participants were randomized to either a placebo group or a treatment arm consisting of 2,000 IU (50 mcg) of vitamin D plus fish oil daily. The authors reported no significant differences between the placebo and treatment groups at the end of the study. However, post hoc analysis included some subgroup analyses that comparatively favored the vitamin D3 group in a nonsignificant manner. These included women, participants between 50 and 74 years of age, and individuals who reported lower levels of physical activity. The authors of the study published in JAMA do note that the individuals included in the study did not exhibit nutritional deficiencies in vitamin D. 

In contrast, a meta-analysis was conducted regarding serum vitamin D levels and depression in older adults by Li and colleagues published in the American Journal of Geriatric Psychiatry that reported a dose-dependent relationship. In this publication, six prospective studies were pooled analyzing data from more than 16,000 older adults. The study results indicated that serum vitamin D concentrations were associated with the risk of developing depression in this population. 

Other studies have also indicated vitamin D may play a role in helping to support a normal mood. A cohort study by Wu and colleagues involving more than 8,000 older adults compared calcium supplementation with calcium plus vitamin D supplementation. Study results indicated that calcium plus vitamin D may be associated with a decreased risk of depression as compared to calcium supplementation alone. 

Cohesion among these studies regarding the link between vitamin D and the risk of depression may be lacking; however, the studies by both Li and Wu suggest a relationship. Vitamin D supports musculoskeletal health, immune function, and cellular health. Although further studies need to be conducted before clear conclusions can be made, vitamin D may also play a role in the support of a healthy mood.

By Colleen Ambrose, ND, MAT