The Truth About Vitamin D

Information about vitamin D has become more prevalent in the media in recent years. While it has long been known that vitamin D can prevent a condition called rickets or osteomalacia (soft bones), there is mounting evidence that it can help prevent certain types of cancer, improve our immunity, cardiovascular health and more. We can synthesize vitamin D in our skin when we expose our skin to ultraviolet light. However, exposure to ultraviolet light can cause skin cancer. Is there a way to avoid skin cancer and insure that we have adequate amounts of vitamin D?

What is Vitamin D?

Vitamin D is actually a group of fat soluble compounds which are responsible for enhancing phosphate and calcium absorption in our diets. Of these, the most important for humans are vitamin D3 or cholecalciferol and vitamin D2 or ergocalciferol. Both vitamin D3 and vitamin D2 can be ingested in adequate amounts in our diets. Vitamin D can also be synthesized in the skin when exposed to ultraviolet light, specifically ultraviolet B (UVB).


By the numbers: A single serving of wild salmon contains nearly 1000 IU of vitamin D, while a single serving of farmed salmon contains less than 300 IU.


Why Is Vitamin D Important?

Because it enhances our absorption of calcium, vitamin D is particularly important for us to maintain our bone density and bone health. Children who don’t get enough vitamin D can suffer from a condition called Rickets or osteomalacia, in which their bones actually bend under their weight causing them to eventually be bow-legged. More recent evidence suggests that vitamin D can help prevent certain types of cancers, particularly colorectal cancer.

How Do We Get Vitamin D?

Vitamin D is found naturally in fish such as sardines, mackerel, salmon, tuna and other fish liver oils. Much of the milk supply in the United States, as well as orange juice and cereals have vitamin D added to them. Vitamin D can also be taken as a supplement in tablet form. Sunlight in the form of ultraviolet B (UVB) causes a chemical reaction in our skin to synthesize vitamin D. However, UVB can cause sunburns, skin cancer and cause the skin to age prematurely. Tanning beds utilize ultraviolet A (UVA) light and therefore do not cause the skin to synthesize vitamin D. There is no difference in the vitamin D taken orally, or made by sunlight exposure and therefore to avoid skin cancer and premature skin aging it is best to ensure adequate daily intake.

How Much Vitamin D Do We Need?

There is some debate on the correct amount of vitamin D, but in 2010, the Institute of Medicine set a recommended daily allowance (RDA) of 600 international units (IU) for children and adults up to age 70, and 800 IU for adult over age 70. The upper safe limit of vitamin D was set at 4000 IU per day. These recommendations assume that no vitamin D is synthesized by sunlight exposure. There is no recommendation for the amount of sun exposure since studies have shown that even in sunny climates exposure to sunlight does not always synthesize adequate amounts of vitamin D.

It is clear that vitamin D is an important vitamin for our daily health.  Getting sun exposure is often advised since we can synthesize vitamin D from ultraviolet B exposure. Some believe that by going to tanning beds they are synthesizing vitamin D but most tanning beds use ultraviolet A light which does not synthesize vitamin D in our skin. It is best to eat a well balanced diet to include foods rich in vitamin D and take a supplement to ensure adequate levels of vitamin D, and avoid ultraviolet B exposure which can cause skin cancer and premature aging of the skin.