Vitamin D is a fat-soluble vitamin that humans produce in the presence of UVB rays. During the 1930's, Professor A. Windaus at the University of Göttingen discovered that Vitamin D deficiency causes bone diseases, and recent research has linked low Vitamin D blood levels to breast, colon, prostrate and other cancers. Many studies are underway to closely examine Vitamin D's anticarcinogenic properties.
About Vitamin D
Vitamin D is one of the few nutrients that the body can self-produce. It occurs naturally in three forms: calciferol, ergocalciferol and cholecalciferol (Vitamin D1, D2 and D3, respectively). Foods such as fish, egg yolks and cod liver oil contain calciferol. Mushrooms, algae and other lower-level organisms contain ergocalciferol. The cholesterol in your skin makes cholecalciferol when it encounters solar rays, but Vitamin D3 is also added to milk and cereals. You can get Vitamin D by eating plenty of these foods, taking supplements or going outside in sunny weather.
Vitamin D's Role in the Body
The body needs Vitamin D to absorb calcium, which is why calcium supplements often come with Vitamin D. Without Vitamin D, the calcium you get from foods or supplements is useless. Vitamin D also helps maintain stable blood levels of calcium.
Besides that, Vitamin D regulates cell activity and growth, stabilizes immune function, reduces inflammation, strengthens muscles, and optimizes cardiovascular function. It often works in concert with calcium, but it can also work independently.
Vitamin D and Cancer
Studies have established an inverse relationship between Vitamin D blood levels and cancer, particularly reproductive cancer. For example, epidemiological studies have shown that men who live near the equator, where there is more sunlight, have lower prostate cancer rates. A 2008 study at the University of Toronto followed 512 women who had been diagnosed with breast cancer since 1996. The women with the lowest Vitamin D levels developed the most aggressive forms of breast cancer.
However, some studies have indicated that there is no relationship. Vitamin D may prevent cancer through its regulatory role in cell growth and activity. But these findings are not conclusive and further research is underway.
Why Deficiency is Common
Getting enough Vitamin D can be challenging. Very few foods naturally contain it. The foods that do have it, such as mushrooms or egg yolks, contain small amounts. Older people or those with metabolic disorders produce little Vitamin D. Moreover, if you live in a northern climate, the sun's rays are not powerful enough to produce Vitamin D from November to March. Additionally, the melanin in dark-hued people's skin blocks UV rays, which might explain why African-Americans have the lowest Vitamin D levels. Due to the risk of skin cancer, lighter-skinned people tend to wear sunscreen or avoid the sun altogether, which puts them at risk for deficiency.
Precautions
To maintain optimal health and possibly minimize cancer risk, doctors recommend getting 15 minutes of sun three times a week or taking a Vitamin D3 supplement. The sun is the most powerful source of Vitamin D, but those who are extremely fair-skinned should take supplements instead. Taking megadoses of Vitamin D can be toxic, and taking cod liver oil can also be toxic due to its high Vitamin A levels.
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