Vitamin D is an important nutrient that keeps your bones strong and helps your body absorb calcium. You should be able to get most of the vitamin D you need from 10-30 minutes of daily sun exposure with no sunscreen protection, as your skin makes vitamin D from cholesterol when it is exposed to UV rays. Even though your body can make its own vitamin D, deficiency rates in the US are rising for a variety of reasons. Those with darker skin or who spend a lot of time indoors may be required to supplement vitamin D to maintain normal levels. A vitamin D deficiency can be determined via a simple blood test ordered by your doctor. If you have a deficiency, your doctor may recommend a supplement or give you a prescription for a high dose of the vitamin. But, if you do need a supplement, what type of vitamin D should you take, and where exactly should the vitamin D come from?
In most commercial supplements, vitamin D is found in either the D2 (ergocalciferol) form or D3 (cholecalciferol). D2 is made from yeast or other plants. Vitamin D2 is generally used to fortify milk and other food products, but this may not be the ideal form of vitamin D for humans. Many experts believe that D2 is not well absorbed or utilized because it is from plants and not the type of vitamin D our bodies are used to dealing with. Vitamin D3 is the exact form of vitamin D found in the body, and it is the type the sun induces our bodies to make. D3 is therefore better absorbed and is the preferred form for supplementation. If you are a vegetarian or vegan, you should know that D3 is derived from animals, so it is unfortunately not considered a vegan supplement. If you are concerned about vitamin D coming from an animal source, you will have to opt for a supplement containing D2.
Vitamin D3 is derived from two places, either fish oil or sheep’s lanolin. Lanolin is a waxy substance that is secreted by glands found in a sheep’s skin. Lanolin helps protect skin against rain or other environmental factors. In order to remove the lanolin from wool, the wool is rolled or squeezed, pushing out a yellowish waxy substance. This wax can then be used as a precursor to the production of vitamin D3. It is also used to soften baseball gloves, produce lip balm, and to make a whole variety of beauty products. In order to make vitamin D3, the lanolin must be purified which results in a substance called 7-dehydrocholesterol, the same precursor of vitamin D found in our skin. Then this substance is converted to D3 via exposure to ultraviolet rays, similar to what happens when our skin is exposed to the sun. The final product is extremely concentrated D3 and must be blended with other materials in order to achieve the proper dosage for human consumption. The lanolin-based vitamin D will usually be in powder or tablet form, as it is dried before being made into a supplement.
Vitamin D from fish oil comes from the skin of fatty fish such as salmon and tuna which naturally contain vitamin D. It may also be produced from cod liver oil, which is extremely high in vitamin D, containing 1360 IU per 1 tablespoon serving, far greater than the RDA of vitamin D (600 IU for most adults). Fish naturally store vitamin D in in their liver and fatty tissues. Fish do not make the vitamin themselves but actually get the vitamin from the plankton they eat. Certain fish oil may be very high in vitamin A, a fat soluble vitamin, making it important to read the label to avoid vitamin A toxicity. The RDA for vitamin A is 700-900 mcg/day.
The other danger in vitamin D from fish oil is its mercury content. Mercury, a naturally occurring metal, is also released into the air by pollution. Once in the water, bacteria transform mercury into soluble, toxic methylmercury, which fish absorb. When we eat fish high in methylmercury, or consume the vitamin D in fish oil derived from these fish, the toxin accumulates in the bloodstream and can endanger the nervous systems of babies and young children as well as the cardiovascular and neurological systems of adults. Nearly all fish contain trace amounts of methylmercury. Vitamin D derived from sheep lanolin contain no such mercury risk.
So which form of vitamin D is best? If you are not a vegetarian or vegan, choose a supplement containing vitamin D3 (cholecalciferol). According to the Vitamin D Council, vitamin D from either lanolin or fish is effective in helping to raise vitamin D levels in the blood. Too much vitamin A can be dangerous for those that are pregnant, and too much mercury can be dangerous for everyone, so vitamin D made from sheep lanolin is probably your safest bet. But, remember the ideal way to get vitamin D is from the sun. So, in addition to a supplement, try to get outside for 10-30 minutes per day for the best source of D!
