Vitamin D is an essential nutrient that your body can produce from exposure to UV rays in sunlight. It is also found naturally in some foods, and vitamin D is fortified in other food products such as milk. Vitamin D is one of the fat-soluble vitamins and there are two different types: D2 and D3. Your body synthesizes vitamin D3 from the sun, but both forms are found in supplements and food.
Functions of Vitamin D
Vitamin D plays many different roles in your body. One function of vitamin D is that it helps your body absorb calcium from your diet. This is one reason why vitamin D is added to dairy products. Women need to make sure they have enough vitamin D throughout their lifetimes in order to decrease the risk of osteoporosis. Vitamin D is also needed to keep the correct level of phosphorus and calcium in your blood. While there is quite a bit of confusing research about vitamin D, the Institute of Medicine reports that there is not enough research to support the claims that vitamin D is beneficial in other ways.
Vitamin D2 vs. Vitamin D3
To add further controversy and debate, there are two different forms of vitamin D. Vitamin D2, also known as ergocalciferol, is generated by plants and commercially made by exposing yeast to UV light. Your skin synthesizes vitamin D3, also known as cholecalciferol, when it is exposed to light. Vitamin D3 is also found in cod liver oil and is commercially produced by irradiating lanolin, which is a fatty substance found on sheep's wool. There has been much debate about whether vitamin D2 is as effective as vitamin D3. A review by Houghton and Vieth argued that while vitamin D2 can prevent rickets in children, it should not be used to fortify the food supply.
On the other hand, the NIH has concluded that more research needs to be done in order to differentiate between the two forms of vitamin D. While the research has yet to come to a conclusive answer regarding vitamin D, you should always strive to include vitamin D, whether in the form of sun exposure or food, in your daily routine.
Recommended Intake
The Institute of Medicine makes recommendations for your dietary intake of vitamins and minerals. The IOM recommends 600 IUs of vitamin D per day for adults ages 19 to 70. Older adults ages 71 and over should strive for 800 IUs daily. If you are pregnant or lactating, you should speak with your doctor about your specific recommendation. You may also see the amount of vitamin D listed in mcg, or micrograms. One microgram of vitamin D is equal to 40 IUs.
Food Sources
Your body can make all the vitamin D it needs just by exposing your skin to sun. But if you frequently wear sunscreen or do not spend much time outdoors, you will need to find food sources to fulfill your daily vitamin D recommendation. Foods such as fatty fish, including tuna, mackerel and salmon, are good sources of vitamin D. It is also found in fortified dairy products and mushrooms that have been exposed to UV light.
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