Welcome to your home on the web for optimum nutrition: nutrition information and nutritional products recommended by a licensed physician and certified nutritionist.

James McNabb, M.D., C.N.S.

Vitamin D:
The Right Dosage for This Miracle Drug

Intake from food

Vitamin D really is in a class by itself among the vitamins, since humans do manufacture it under exposure to the sun. We can also get small amounts from eggs, milk, butter, and cold-water fish. Cod liver oil contains the greatest amount that we usually can get from our diet. Dietary intakes range around 200 IU daily under good conditions.

Production from UV exposure to skin

When our skin is exposed to the UV of the sun, it converts 7 dehydrocholesterol to a precursor form of Vitamin D called cholecalciferol. This precursor is then sent to the liver where it is converted to (25)hydroxy Vitamin D3. This is the form that is present in serum. It is finally sent to the kidney where it is transformed by the action of Parathyroid hormone into its final active form, calcitriol. This final form is 1000 times more potent than the (25)hydroxy Vitamin D3.

Twenty minutes of midday sun at mid latitudes in summer in light skinned people will produce 10,000 IU of D3. Spring and fall exposure will require somewhat more time. Dark skinned people will require twice the exposure under identical conditions. We do not want the skin to turn red as that indicates that damage is occurring and it is not necessary. The problem arises in the northern latitudes during the months from November to March when the sun is too weak to produce any amount of Vitamin D.
It is during these months that Vitamin D is truly a vitamin.

 
There is an additional problem in months and climates when sun exposure is available. We have been conditioned to think that any exposure to sun is harmful. We are told to avoid any exposure by using hats, long-sleeved clothing, and sunscreen to any exposed skin. While this may keep the skin free of wrinkling and skin cancers, it completely prevents the skin from manufacturing Vitamin D. While we may have had beautiful skin of late, we are running dangerously low on Vitamin D. Dr. Holick (J Nutrition, 2005) believes that hypovitaminosis D is reaching epidemic levels.
My recommendation is that when possible, we expose our skin to sunshine without sun block for 20 minutes as often as possible, twice as long if you are dark complected. I recommend protecting the face and eyes at the same time. Vitamin D can be stored in the body for up to 12 weeks, carrying us partially into the winter months. Each exposure will produce approximately 10,000 IU of Vitamin D.

Protection from deficiency vs. excess

As you can see from the above discussion, there is a tremendous discrepancy between the 200 IU we can get in our diet, and the 10,000 IU that our skin can make with UV exposure. Because we can make so much, yet have so little in our diet, our bodies have developed ways to deal with excess much better than with deficiencies. Additionally, since Vitamin D comes from such distinct sources of diet and skin production, scientists have had a very difficult time trying to establish both upper and lower limits.
 

Deficiency conditions

Rickets and osteomalacia

The classic deficiency state for Vitamin D has been rickets in children and osteomalacia is adults. It was for this reason that milk has been fortified since the 50’s with 400 IU of Vitamin D2 (a weak plant-based form of Vitamin D). Fortunately, this weak form of Vitamin D is effective in preventing these conditions. It is not strong enough to influence cancer rates. The earliest recommendations on Vitamin D intake were the amount needed to prevent these bone conditions.

Cancer

Dr. Garland (Am J Pub Health, 2006) has published a paper with maps of the USA showing the incidence of both colon and breast cancer increasing by a factor of 2 as you proceed north. With latitude being such a strong factor, it is impossible to avoid the conclusion that Vitamin D is involved.

Autoimmune diseases

Investigators into muscular sclerosis have known for a long time that the incidence of MS also rises as you go north, with the incidence in Canada almost 4 times what it is in the southern US. Within Canada, there is a gradient from a low in Nova Scotia to higher rates in the Canadian Rockies. Nova Scotians may not get more sun than their mountain neighbors, but they do eat more fresh fish, which have more Vitamin D.

Fibromyalgia

The symptomotology of fibromyalgia is widespread pain lasting 3 months or more, muscle tenderness and pain with firm touch. The symptoms of Vitamin D deficiency are tenderness, bone and muscle pain, and cramps. The similarity of these symptoms has led some researchers such as Dr. Holick to conclude that, in many cases, fibromyalgia may be simply Vitamin D deficiency.

How much Vitamin D is necessary?

In comparison to the 10,000 IU that our skin can make in 20 minutes, the current RDA of 200 IU seems rather paltry. Most scientists investigating Vitamin D are recommending at least 1000 IU daily. Dr. Heaney is recommending 4000 IU. The Vitamin D Council believes the RDA should be set at 3000 IU daily. The current RDA is based on the prevention of rickets, and has not considered that to fulfill its other functions, higher levels of Vitamin D are required.

Toxic levels

If the body can make 10000 IU daily, it would seem logical that the toxic level of Vitamin D should be above this level. Indeed, a number of studies have indicated that it takes 50000 IU daily to reach toxic levels. Yet the National Academy of Sciences has set the tolerable upper limit for (TUL) Vitamin D at 2000 IU daily, implying that serious health risks will occur beyond this level.

Dietary recommendations

This has always been the tricky aspect, because there are a number of variables involved. Here they are: season, latitude, skin color, age, use of sunscreen, sun exposure, life style (indoor or outdoor). Therefore, if you are an elderly black living in a northern climate, I would suggest at least 4000 IU daily. You would probably be safe up to 10000 IU daily. Alternately, a lighter skinned individual living in the South who sunbathes regularly might not need any extra supplemental Vitamin D in the summertime, and perhaps only 1000 or 2000 IU per day in
the winter.

The right form of the right vitamin

The Vitamin D that has fortified milk for the last half-century is Vitamin D2, a weak form derived from plants. While it does prevent rickets, it is not what the body produces. It seems that we have used the wrong form of Vitamin D for lo, these many decades. Cholecalciferol is the form that skin manufactures and should be the form we buy as a supplement. There are two pill sizes, a 400 IU and a 2000 IU.

Financial considerations

Dr. Cedrick Garland, a leading researcher in Vitamin D, estimates that around 50 to 60,000 persons die annually and prematurely from cancer due to inadequate Vitamin D levels. He estimates that correcting these low levels could save our medical system 46 to 65 billion dollars, or approximately 13.5 billion dollars annually. These estimates do not address the annual cost of hip replacement surgery and rehabilitation due to osteoporosis in the elderly.

Conclusion

We are learning in the last several years that Vitamin D has been much underrated as a vitamin, and that we need, as a nation, to recommend moderate doses of sunshine in order to produce our own supply, as well as to increase the RDA of Vitamin D from its current 400 to 600 IU daily, to over 4000 IU daily, especially to elderly blacks living in the northern tier of states. I am sure this will happen in the next few years. In the meantime, to maintain stronger bones, prevent cancer, and to reduce autoimmune diseases, be more aggressive in raising your levels of this important vitamin.
 

Disclaimer:
This site and its services are for consumer educational use only. Nothing contained in this site is or should be considered, or used as a substitute for, medical advice, diagnosis or treatment. We advise users to always seek the advice of a physician or other qualified health care provider with any questions regarding personal health or medical conditions. Never disregard, avoid or delay in obtaining medical advice from your doctor or other qualified health care provider because of something you have read on this site. If you have or suspect that you have a medical problem or condition, please contact a qualified health care professional immediately.

Optimum Nutrition: Nutrition Information and Nutritional Products from Physician-Nutrition.com