Vitamin D, commonly referred to as the "sunshine vitamin," plays an important role in your health. It is the only vitamin that can be made by the human body from sunshine. Research is suggesting a strong link between vitamin D status and basic cognitive function, mood and overall mental health. The recommended adequate intake (AI) level for the active form of vitamin D (vitamin D3 or cholecalciferol) is 5 micrograms (mcg) for adults aged 31 to 50 years. After the age of 50, the AI increases to 10 mcg.
Vitamin D: How it is Made
Vitamin D is unique because it is made by the body when the skin is exposed to ultraviolet rays from the sun. When this happens, a cholesterol-like compound is converted to a vitamin D precursor and then to vitamin D3, (or cholecalciferol). Vitamin D3 is activated by enzymes from the liver and the kidney. When activated, vitamin D functions as a hormone. Just 15 minutes under the sun (for most people, without sunscreen), three times per week makes enough vitamin D. It can be stored for several months in the body.
Vitamin D deficiency, or hypovitaminosis D, is common in Americans, especially those who live in colder, northern climates, as well as the elderly population. This is because our ability to produce the vitamin declines with age. Although the AI is expressed in mcg, most vitamin D supplements are expressed in International Units (IU). One IU = 0.025 mcg cholecalciferol.
In its active form, cholecalciferol travels through the bloodstream, targeting certain organs, such as the brain, affecting what that organ does. Vitamin D is essential for regulating cell growth, increasing calcium and phosphorus absorption, maintaining immune system integrity and cardiovascular health. It may play a role in cancer prevention. Vitamin D helps to maintain blood calcium levels high for building bone and teeth, muscle contraction, and the transmission of nerve impulses.
In regards to mental health and cognition, Vitamin D appears to activate receptors on neurons in parts of the brain responsible for behavior regulation. It stimulates the release of important brain chemicals and protects the brain by acting as a buffering antioxidant. Vitamin D also works as an anti-inflammatory agent against vascular injury.
Vitamin D and Depression
For many years, exposure to sunlight has been associated with a more positive mood, particularly in those with mild to moderate depression. Is it the sunshine, or is it the active cholecalciferol circulating in the bloodstream (made by the body) that affects the brain. More and more, experts are saying it is the latter.
A European study examined the relationship between serum 25-hydroxyvitamin D levels (blood levels of vitamin D) and depression in 400 overweight subjects and the effect of vitamin D supplementation on depressive symptoms. They were divided and given supplemental vitamin D weekly (or a placebo) for 1 year. Subjects with lower serum vitamin D levels scored higher (more depressive traits) on the Beck Depression Inventory (BDI) scale than those with higher serum vitamin D levels. The group given supplemental vitamin D showed a significant improvement in BDI scores in 1 year. Other studies have shown similar results but more research is needed to draw conclusions.
Vitamin D and Cognitive Performance
Vitamin D has been increasingly associated with cognition and mental illness, especially in the elderly population. Hypovitaminosis D is prevalent among older adults. Several studies have looked into the link between blood vitamin D levels and basic cognitive function. A study published by the American Journal of Geriatric Psychiatry involved 80 participants (40 with Alzheimer's disease) and the objective was to examine the relationship among vitamin D status, cognitive performance, mood, and physical performance.
Not surprisingly, 58 percent of the participants had low levels vitamin D in the bloodstream. Even after adjusting for age, race, and gender vitamin D deficiency was associated with the presence of an active mood disorder. The vitamin D-deficient group performed significantly worse on two of the standard cognitive tests. The conclusions drawn from this study were that, in a cross-section of older adults, hypovitaminosis D was associated with low mood and impairment on two of four standard cognitive performance tests.
Food Sources and Supplementation
It has been estimated that as much as 75 percent of Americans may not be getting enough vitamin D for optimum health. Ironically, the more we find out about how important this vitamin is in cardiovascular, bone and mental health, in addition to its role in cancer prevention, the less we seem to be consuming (on average). This is due, at least in part, to American's attempt to avoid direct sunlight for fear of increasing the risk of developing skin cancer.
You could not consume enough vitamin D-rich foods to equal the amount your body can manufacture from just 10 minutes of sunlight exposure. Very good food sources of vitamin D include salmon, sardines, shrimp, milk, cod, and eggs. Those who do not go outdoors much should consider a 1,000 IU vitamin D supplement, daily (subject to approval by your physician).
- Journal of Internal Medicine; Effects of vitamin D supplementation on symptoms of depression in overweight and obese subjects: randomized double blind trial; R Jorde, M Sneve, Y Figenschau, J Svartberg J and K Waterloo; Dec 2008
- American Journal of Geriatric Psychiatry; Vitamin D deficiency is associated with low mood and worse cognitive performance in older adults; CH Wilkins, YI Sheline, CM Roe, SJ Birge and JC Morris; Dec 2006
- Nutrition for Foodservice and Culinary Professionals, 6th Ed.; KE Drummond and LM Brefere; 2007