At the end of winter, our exposure to sunlight has been at an all-year low so our need for added Vitamin D is at an all-year high.
John Scott explains why and how we can best built up our Vitamin D status.

A recent study showed that children and adolescents with low vitamin D levels had increased sensitivity to 11 out of 17 allergens that were tested, including both environmental and food allergens. So, for anyone with an allergic child, increasing their vitamin D level would seem to be a wise step, but how much should they take?

Another new study has shown that we need a significantly higher intake of vitamin D than was previously realised in order to achieve a blood serum level that is capable of preventing or markedly reducing several major diseases.

The researchers found that adults need a daily intake of between 4,000 and 8,000 IU of vitamin D to maintain blood levels of the vitamin's metabolites in the range needed to reduce by about half the risk of a number of diseases including breast cancer, colon cancer, multiple sclerosis and type 1 diabetes.

This latest study has confirmed what had been predicted by previous investigations: that much higher amounts are needed than the 400 IU per day of vitamin D that was required to defeat rickets in the 20th century, and also much higher than the current recommended daily allowance (RDA) of 600 IU, set only recently for the US by the Institute of Medicine (IOM).

Many of the scientists who are actively working with vitamin D now believe that a blood serum level of 40-60 ng/ml (100-150 nmol/L) is the appropriate target concentration of vitamin D and, in December of last year, a US National Academy of Sciences Institute of Medicine committee identified 4,000 IU per day of vitamin D as being safe for everyday use by adults and children of nine years and older, with 1,000-3,000 IU per day for infants and children up to age eight.

The Vitamin D Council recommends a slightly higher blood serum level of 50-80 ng/ml (125–200 nmol/L) and has set the minimum at 50 ng/ml (125 nmol/L) because it has been shown that the average person only begins to store vitamin D at 40 ng/ml (100 nmol/L) whereas, at 50 ng/ml (125 nmol/L), virtually everyone begins to store it for future use. That is, at levels below 50 ng/ml (125 nmol/L), the body uses up vitamin D as fast as it is made or consumed.

In order to establish one's vitamin D level, one needs to have this checked by means of a 25-hydroxyvitamin D blood test the most accurate measure of the amount of vitamin D in the body. The ideal time of year to have this test is in March, because this is when the blood level of this vitamin is at its lowest following the winter.

The level established by the test provides a baseline from which to calculate how much vitamin D will be required to reach at least the minimum of 50 ng/ml (125 nmol/L). Every 1,000 IU that is consumed or made by exposing the skin to the sun will raise the blood level a further 7-10 ng/ml.

Those who live in a warm climate and can spend 10-15 minutes each day moving around in the sun between 11.00 am and 1.00 pm, with 40% of their body exposed, and without sunscreen, will, if they have Caucasian skin, produce approximately 5,000 IU vitamin D in response to that 10-15 minutes exposure. (Those with dark skin need up to six times longer.) However, those who live in a cooler climate, or are confined indoors, will need to take a supplement, which should be the D3 form of the vitamin (cholecalciferol, obtained from sheep's wool), as this is the type that is made naturally by the skin. The plant-based alternative, vitamin D2, is best avoided, as this is not easily metabolized by the body.

The importance of having one's blood level measured was brought home to me recently when I had my own vitamin D status checked after a gap of 2 years, during which time I had taken 5,000 IU of vitamin D3 daily. Given this level of intake, I had expected to be well over the Vitamin D Council's minimum acceptable level but, in fact, I scored only 43.27 ng/ml (108 nmol/L).

My GP was actually happy with this result, saying that it was well within the normal range but he, like the vast majority of medics, is clearly unaware that the body does not reliably begin to store vitamin D in fat and muscle tissue until the level gets above 50 ng/ml (125 nmol/L).

Anyone who is not able to get their vitamin D level checked immediately, but who wants to begin supplementation right away, could begin with the Vitamin D Council's recommended daily adult dose of 5,000 IU. Alternatively, a dose that is more accurately tailored to one's weight can be achieved by taking 1,000 IU per day for every 25 pounds of body weight. Had I used this calculation, I would have been taking at least 6,000 IU per day, which would have given me a minimum blood level of 50 ng/ml (125 nmol/L).

As there are other factors besides weight that influence one's need for vitamin D - age, gender, and skin colour, for example - getting tested and basing one's intake on the result of the test is undoubtedly the best course.

For those people who are more used to thinking in terms of the official RDAs for vitamins, and who may be concerned about the risk of toxicity from taking doses of vitamin D that are considerably higher than the RDA, there is reassurance in the IOM Committee Report, mentioned above. This considered 10,000 IU per day to be the lowest dose that could be associated with any risk. And many researchers go much further than this to state that there is no likelihood of any toxicity below a blood level of 200 ng/ml (500 nmol/L), which gives a very large margin of safety with all the doses quoted above.

In order to get the best value from vitamin D supplements, it is important to ensure an adequate supply of this nutrient's co-factors: magnesium, (the most important co-factor), vitamin A (although this should not exceed 6,000 IU per day, at which point it begins to compete with, and reduce the uptake of vitamin D), vitamin K2,zinc, and boron.

Obtaining an adequate supply of all the co-factors will particularly help anyone who has difficulty tolerating supplemental vitamin D. Additionally, there are intriguing reports that those with impaired tolerance for this nutrient who become users of helminthic therapy, find that their tolerance increases after treatment. One individual who was unable to tolerate vitamin D found that, after inoculating with hookworm and whipworm, he could take 10,000 IU of vitamin D per day without any problem. Someone else, found that they were able to tolerate 2,000 IU per day while hosting helminths, after previously experiencing an exacerbation of their auto-immune problems with a dose of only 400 IU.

Not only is vitamin D tolerated more readily by people using helminthic therapy, but these two agents appear to be complementary in addressing allergic and autoimmune diseases, with considerable evidence showing the importance of vitamin D for both allergic hypersensitivity and autoimmunity.

The science on vitamin D is now unequivocal, with literally hundreds of studies having shown the benefits of ensuring an optimal vitamin D intake, and researchers have uncovered up to 2,000 different genes - roughly one-sixth of the human genome - that are regulated by this nutrient.

Manufacturers are already starting to seek commercial advantage from this knowledge by introducing new vitamin D-enriched food products, but some of these, including the High Vitamin D loaf, use the less effective D2 form of the vitamin, and the amounts that are being added to foods are woefully inadequate and not to be relied upon to provide anything close to an optimum intake.

As is almost always the case with new health research, governments and their medical advisers are dragging their feet over making this information available to the general public so, once again, it's up to individuals to look out for themselves. And, to help those who want more detail about all of this, here is an excellent video that explains the above issues in greater detail.

Fortunately, vitamin D is relatively cheap, so there is no reason why everyone should not be able to take the recommended amount, and gain the significant benefits to their health that will result.

First published March 2011

Click here for more articles

Click here for LINKS to manufacturers of nutrition and food supplements.

Back to top