Why Do We Need Vitamin D?

Vitamin D is a type of secosteroid, closely related to steroids, a type of hormone necessary for certain bodily processes. There are several different chemicals that all fall under the catchall name “vitamin D”, but the two main ones are vitamin D2, and vitamin D3. Each provide similar functions.

It is acquired primarily through sunlight exposure on the skin, and also through the diet. Primary dietary sources include fatty fishes like salmon and tuna, as well as fortified foods like milk and some breakfast cereal. The recommended daily allowance is 600 IU per day, although it is difficult to overdose on it.

Once in the bloodstream, vitamin D goes to the liver where it is converted to a prohormone called calcidiol. A prohormone is a precursor to hormones, which regulate chemical functions in the body. From here, the calcidiol goes to two different places: the kidneys, and the immune system.

Both transform the calcidiol into calcitriol, the active form of vitamin D which does the work. The immune system uses the calcitriol to fight microbial infections, and the kidneys use it to regulate calcium in the body. As a result, the most noticeable symptom from low vitamin D levels are weak bones from a disease called osteomalacia, or in children it manifests as a deformity called rickets.

There has been recent interest in vitamin D supplementation due to several studies that suggest it may reduce the risk of certain cancers (prostate and breast, mainly), and possibly even the risk of cardiovascular disease. However, these studies are still preliminary and no hard correlation between the two has been fully proven.

Your body requires vitamin D for bone health and possibly general health. You can acquire a suffient dose by making sure to get about 20 minutes of sunlight exposure several times per week, or you can choose an over the counter supplement of about 600 to 1000 IU. While it takes over 50,000 IU per day over several months to get toxic side effects, there is evidence that more than 4000 IU per day may cause serious health problems, so it’s best to keep it under that amount.