The Importance Of Vitamin D3 In Humans

Vitamin D, commonly referred to as the sunshine vitamin, plays an important role in health. It is the only vitamin that can be made by the human body from sunshine. Vitamin D3 (cholecalciferol) is the active form of the vitamin in the body. The recommended adequate intake (AI) level for the vitamin D3 is five micrograms (mcg) or 200 International Units (IU) for adults aged 31 to 50 years. After the age of 50, the AI increases to 400 IU or 10 mcg. This nutrient is vital for the immune system, strong bones, cancer prevention and mental health.

Function

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. Vitamin D3 is the most metabolically active form of vitamin D. When activated, vitamin D functions as a hormone. Just 15 minutes under the sun (for most people, without sunscreen), three times a week makes enough vitamin D. It can be stored for several months in the body.

Healthy Immune System

Vitamin D3 helps regulate immune system activity by preventing excessive or prolonged inflammatory responses. Your immune system cells, specifically your active T-cells, have vitamin D3 receptors. Many diseases and health conditions are characterized by chronic or acute inflammation, such as diabetes, irritable bowel syndrome, and autoimmune diseases such as multiple sclerosis and rheumatoid arthritis. When vitamin D3 is in short supply, T-cells recruit other immune cells to help drive the inflammatory process. When vitamin D3 levels are plentiful, the body switches on a vitamin-D-mediated system that can help decrease or even shut down inflammation.

Strong Bones

The major minerals calcium and phosphorus are essential for building and maintaining strong, hard bones. Vitamin D3, in conjunction with the parathyroid hormone (PTH), plays an important role in ensuring optimum calcium and phosphorus levels in the blood and bones. For example, if vitamin D levels are chronically low, the parathyroid gland becomes overactive, resulting in hyperparathyroidism. In response, blood levels of phosphorus drop. Without enough phosphorus, bone can't be properly mineralized, and new bone cells absorb too much water and swell, causing bone pain (a condition known as osteomalacia).

Cancer Prevention

Epidemiologic studies support the hypothesis that individuals with lower serum vitamin D levels have a higher risk of developing several types of cancer. One of the most persuasive studies was conducted by Giovannucci et al. (in the Annals of Epidemiology). This study reported that among more than 40,000 individuals in the Health Professionals Study, those with the highest circulating levels of 25(OH) cholecalciferol (active vitamin D3 in the bloodstream) have a significantly lower incidence of cancers of the head/neck, esophagus, pancreas, as well as a reduced risk of developing acute leukemia (by 30 to 50 percent).

Mental Health and Cognitive Function

Vitamin D has been increasingly associated with cognition and mental health, especially in the elderly population. Several studies have studied 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. 58 percent of the participants had low vitamin D3 levels 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.