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Vitamin D Info

Did you know?

1) Vitamin D was originally confused with Vitamin A?

2) It’s the only vitamin that can be manufactured by the body?

3) Synthetic versions are made with irradiated fungus or animal fat and do not supply the whole vitamin?

If any of this surprised you, read on!


The earliest records of Vitamin D are all about the formerly common disease called rickets, a childhood bone disease. Dr. Daniel Whistler and Professor Francis Glisson both published papers on the disease but the real breakthrough didn’t come in until 1919.

Sir Edward Mellanby was working with dogs raised without exposure to sunlight or ultraviolet light earlier in this year when he proved that the bone disease was caused by the absence of some trace component in the diet, Vitamin D.

In the early 1930’s, the vitamin was chemically characterised into three separate parts, vitamins D1 – D3 and the most common supplement form (cod liver oil – D3) was identified in 1936. There are now 10 different known types of the vitamin.

It is the only vitamin that can be produced in the body itself, with the addition of sunlight.

What does Vitamin D do?

The major function of this vitamin is to maintain the levels of calcium and phosphorus in the blood.

It helps in the absorption of calcium, helping to form and maintain strong bones.

Is synthetic Vitamin D the same as a natural one?

No, the synthetic versions are made from ergosterol (a waxy plant or fungus extract) irradiated with ultraviolet light, while the whole version appears naturally in cod liver oil and milk, among other things.

Some synthetic versions are also made from irradiated animal fat or lanolin, which only supplies a fraction of the total vitamin.

Go for a whole food source, preferably a fatty food fish source.

Click here to see our recommendations for natural sources of Vitamin D

How much do I need?

According to the standard RDA’s, you need approximately 400 IU’s per day, however, some researchers are claiming this to be ridiculously low.

The 1989 US nutrition guidelines said that taking more than 5 times the RDA would be harmful and cited a 1963 expert committee report, which itself referred back to a 1938 report in which infant bone growth was retarded at that level.

Ok, but does that apply to adult nutrition?

The only two studies I have found so far include a 1987 council report for the AMA that cited two reports, one with no evidence to support it and another (published 1948) which showed that people given 150,000 – 600,000 IU’s per day showed some ill effects. No kidding.

Besides, I doubt the RDA findings anyway, please see our RDA page for more information.
Please read this to see why we think this isn't your best guide

What are the best food sources?

Fatty fish and fish oils, although the best source is probably exposure to sunlight if you have the opportunity!

Other Food Sources

Fish liver oils

For every 5% of your skin exposed, approximately 435 IU is generated per day. This is decreased if you are dark skinned or shower immediately after being exposed to the sun (apparently the oil on your skin needs to remain intact for while after exposure).

What if I have a deficiency?

In children, a deficiency can result in rickets, which results in skeletal deformities.

In adults, it manifests as ostemalacia, a condition characterised by weak muscles and bones.

Back to More Facts About Vitamins from Vitamin D Info