Vitamin D and Sunshine: an essential vitamin! Protects against cancer, heart and bone disease
(By Dr Sarah Myhill and Craig Robinson)
Stylistic note: Use of the first person singular refers to me, Dr Sarah Myhill. One can assume that the medicine and biochemistry are mine, as edited by Craig Robinson, and that any classical and mathematical references and quotes or historical and linguistic notes are Craig’s!
Western cultures have become almost phobic about any exposure of unprotected skin to sunshine with the well-recognised association between skin cancer and exposure to sunshine. Indeed the US Environmental Protection Agency is currently advising that ultraviolet light, and therefore sunlight, is so dangerous that we should "protect ourselves against ultraviolet light whenever we can see our shadow".
But a certain amount of sun exposure is essential for normal good health in order to produce vitamin D - and partly as a result of current recommendations, we are seeing declining levels of vitamin D and the problems that go with it.
Human beings evolved over hundreds of thousands of years in equatorial areas and were daily exposed to sunshine. Dark skins evolved to protect against sun damage. However, as hominids migrated north, those races which retained their dark skins were unable to make sufficient vitamin D in the skin and did not survive. Only those hominids with paler skins survived. Thus the further away from the Equator, the paler the skin became. Races in polar areas survived because they were able to get an alternative source of vitamin D from fish and seafood.
There is an interesting inverse correlation between sunshine exposure, vitamin D levels, and incidence of disease as one moves away from the Equator. Even correcting for other factors such as diet, there is strong evidence to show that vitamin D protects against osteoarthritis, osteoporosis, bone fractures (vitamin D strengthens the muscles thereby improving balance, movement and preventing falls), cancer, hypertension, hypercholesterolaemia, diabetes, heart disease, multiple sclerosis and vulnerability to infections. Multiple sclerosis is a particularly interesting example of a possible vitamin D deficiency disease. Indeed mice bred for susceptibility to multiple sclerosis can be completely protected against development of this disease by feeding them high doses of vitamin D.
For people living in equatorial areas, blood levels of 25 (OH) D) usually exceed 100nmol/l and often 200nmol/l. Since we evolved in hot climates, this is probably what is physiologically desirable. However, normal ranges in laboratories are still stated at around 40 to 100nmol/l. This almost certainly represents sub-optimal levels - it may be enough to prevent rickets and osteomalacia, but is not sufficient for optimal health.
For a pale skinned Caucasian, whole body sunlight exposure barely sufficient to trigger tanning (the so called minimum melanogenesis dose) is as little as 15 minutes and is equivalent to the consumption of 10,000i.u. of vitamin D. If this is compared to the US recommended dietary allowance now standing at 200i.u. (which is the amount in a teaspoon of cod liver oil), one can readily see that the best source of vitamin D is sunshine.
It is extremely difficult to get blood levels up to an optimum level on diet alone. Furthermore, dark-skinned individuals need very much more sunshine exposure in order to achieve the same blood levels of vitamin D. As people get older their requirements also increase - however, typically they spend less time in the sunshine and are much more prone to vitamin D deficiency and the problems that go with it.
In a study in which groups of elderly people started to take calcium and vitamin D, the occurrence of fractures is reduced by a third in the first year even though bone density is not increased sufficiently to account for the fewer fractures. What is not yet common knowledge is that vitamin D improves muscle strength and balance and it is thought that this is what reduces the occurrence of falls leading to fractures.
How to get more vitamin D
It is impossible for people living in Britain to get adequate vitamin D levels through full spectrum light. To receive sufficient vit D, you need to get the equivalent of at least 15 minutes per day whole body exposure to sunshine, probably more depending on the colour of your skin, to trigger tanning, but not burning of the skin. How likely is that? So what do you need to do to optimise your vitamin D levels?
- If you are taking my Mineral Mix at your full correct daily dose (up to max 5 g a day), then you will be getting 4000 - 5000 i.u. of vitamin D3 a day. You do not need to take any other Vitamin D supplement, but sunshine on your skin whenever you can get it will be a welcome bonus! If you are not taking the Mineral Mix, you need to add 5000 i.u. vitamin D3 to your nutritional regime.
- Lack of sunshine in the UK is an excellent excuse to book a holiday in a sunny climate during the winter! In order to get an equivalent dose through eating fish, one would have to consume 25 teaspoonfuls of cod liver oil or its equivalent. Eskimos and Inuit Indians probably achieve this easily with their diet, but I cannot see myself persuading my teenage daughters to do this. A foreign holiday sounds much more attractive, or keep taking your 5,000 iu daily.
Vitamin D supplements
In choosing a good vitamin D supplement, one needs to know a little of the biochemistry. Vitamin D2, ergocalciferol is made from yeast and is about a quarter as potent as vitamin D3. In order for D3 to be activated it needs to be twice hydroxylated in the liver and the kidney - bear in mind that anybody with liver or kidney problems may have a requirement for the active twice hydroxylated vitamin D (calcitriol) rather than D3.
In studies where vitamin D3 is supplemented at 10,000i.u. daily there have been no cases of hypercalcaemia. 5,000i.u. daily seems a reasonable dose for the winter months, higher amounts where there is pathology such as osteoporosis.
People will be delighted to hear that sunshine is good for them - the overwhelming majority feel much better for sitting out in the sunshine. If the skin goes red then they are having too much exposure - they need just sufficient to promote mild tanning.
People with dark skins need much more than people with fair skins, but again they can judge this from the degree to which their skin darkens with exposure to sunshine. Redness means inflammation due to skin damage and should be avoided. It's the old story - with any substance from water to sunshine, there is potential to underdose and overdose - it's all about getting the balance right!
"THE CLINICAL IMPORTANCE OF VITAMIN D (CHOLECALCIFEROL): A PARADIGM SHIFT WITH IMPLICATIONS FOR ALL HEALTHCARE PROVIDERS" by Vasquez et al. - gives the science behind vitamin D.
Home kit for 25-hydroxy vit D levels
- Please see Vitamin D Home Test Kit
The Vitamin D Laboratory at the City Hospital in Birmingham offers a "direct to the public service for serum 25-hydroxy Vitamin D based on dried blood spots". They send a home kit with detailed instructions, which makes it a very convenient way to check the levels. All the details on the page Vitamin D test.
Blood Spot Test Kit Order Line - Tel: +44 (0)121 507 4278
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