How much vitamin D should I take?

Everyone's situation is either a lot, or at least a little, different. How much vitamin D you need varies with age, body weight, percent of body fat, latitude, skin coloration, season of the year, use of sunblock, individual variation in sun exposure, and—probably—how ill you are. As a general rule, old people need more than young people, big people need more that little people, fat people need more than skinny people, northern people need more than southern people, dark-skinned people need more than fair skinned people, winter people need more than summer people, sunblock lovers need more than sunblock haters, sun-phobes need more than sun worshipers, and ill people may need more than well people.

Regular readers should understand the reasons behind all these statements except for the last one. However, don't feel bad, no one understands it. Vitamin D is used by the body—metabolically cleared—both to maintain wellness and to treat disease. If you get an infection, how much vitamin D does your body use up fighting the infection? Nobody knows. If you have cancer, how much vitamin D does your body use up fighting the cancer? Nobody knows. If you have heart disease, how much vitamin D does your body use up fighting the heart disease? Nobody knows. If you are a child with autism, how much vitamin D does your brain need to turn on the genes that autism has turned off? Nobody knows. If you are an athlete, how much vitamin D does your body use up making you stronger and quicker? Nobody knows, etc.

This is what I'd do. If you live in Florida and sunbathe once a week, year around, do nothing. If you use suntan parlors once a week, do nothing. However, if you have little UVB exposure, my advice is as follows. Well children under the age of two should take 1,000 IU per day, over the age of two, 2,000 IU per day. Well adults and adolescent between 80 pounds and 130 pounds should start with 3,000 IU per day, over 130 pounds but less than 170 pounds, 4,000 IU per day and over 170 pounds, 5,000 IU per day. Two months later have your doctor order your first 25-hydroxy-vitamin D blood test. Yes, start the vitamin D before you have the blood test. Then adjust your dose so your 25(OH)D level is between 50 and 70 ng/ml, summer and winter. These are conservative dosage recommendations. Most people who avoid the sun—and virtually all dark-skinned people—will have to increase their dose once they find their blood level is still low, even after two months of the above dosage, especially in the winter.

One more thing. Everyone has different vitamin D machinery. For example, regular run-of-the-mill rickets does not require much vitamin D to be cured. However, two other forms of rickets, both rare, one caused by a defective vitamin D receptor and the other by a malfunction of the enzyme that activates vitamin D, requires either much more vitamin D or activated vitamin D (calcitriol) itself. It seems likely that there is as much variation in the amount and functionality of the enzyme that activates vitamin D as there is in the vitamin D receptor. Furthermore, there are probably tissue variations as well. That is, one vitamin D deficient child gets rickets, another autism, another asthma, and yet another type 1 diabetes because functionality of the vitamin D machinery is genetically variable both between children and within children's tissues. Therefore, some people, who have genetically determined decreased functionality of the machinery in different tissues, will need more vitamin D. How much more, we do not know. However, should you have a child with autism, they will usually need more than a normal child to overcome their genetic defects. None of what I say in this paragraph is proven, it is theoretical.

Drisdol is a prescription of 50,000 IU tablets of ergocalciferol or D2. Ergocalciferol is not vitamin D but it is similar. It is made by irradiating ergosterol, which is found in many living things, such as yeast. D2 is not normally found in humans and most studies show it does not raise 25(OH)D levels as well as human vitamin D (cholecalciferol or D3) does. However, Drisdol is a lot better than nothing. The best thing to do, if you are vitamin D deficient (and human) is to take human vitamin D—cholecalciferol vitamin D3.

Cod liver oil contains toxic amounts of vitamin A. Vitamin A antagonizes the action of vitamin D. Stay tuned to the press. In several months you will see a clear warning by numerous experts not to take vitamin A or cod liver oil.

Read the full newsletter for more details.

Source: The Vitamin D Newsletter July 2008 - Vitamin D Council - John Jacob Cannell MD, Executive Director