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Vitamin D has long been recognized as vital to bone health because the body needs the vitamin to absorb calcium. But research has suggested that it may be good for a lot more than just bones. Ample intake of vitamin D may help fend off a wide range of conditions, including colon cancer, diabetes, and physical weakness in old age.

Meanwhile, another batch of studies has found that many people, especially as they grow older, have low levels of vitamin D in their blood. Our skin has an amazing ability to produce vitamin D when it’s exposed to sunlight, but with age, the skin becomes less productive. The problem is made worse by older people spending more time indoors.

Other factors that contribute to low vitamin D levels include living in the upper latitudes, where winters are long, and having darker skin. Rickets is the classic children’s disease caused by vitamin D deficiency. It has re-emerged as a problem in some African American communities. Because of the evidence for shortfalls and the possibility of added benefits, some experts think the recommendations for vitamin D are set way too low. The vitamin D3 enthusiasts say adults should be getting at least 5-6,000 IU (International Units) a day.

 Up the D3 limit

The committees of experts convened by the Institute of Medicine to set daily nutrition requirements also calculate an upper limit (the technical term is Tolerable Upper Intake Level). It’s the too-much-of-a-good-thing level at which a normally healthful nutrient becomes possibly toxic. The upper limit for vitamin D is 2,000IU per day. Some of the same experts who think we should have a lot more vitamin D in our diets are saying that upper limit needs to be increased because, at its current level, it may be scaring people off so they don’t get the vitamin D they need.

An article published in the January 2007 American Journal of Clinical Nutrition reviewed dozens of vitamin D toxicity studies, including some that involved volunteers taking a whopping 100,000IU a day. The authors concluded that the upper limit for daily intake of vitamin D could safely be set at 10,000 IU.

A group of 15 nutrition experts cited the study in an editorial in the March 2007 issue of the same journal that called for an overhaul of vitamin D guidelines, although they stopped short of recommending definite amounts. The experts — who include Dr. Walter C. Willett, chair of the Harvard School of Public Health’s nutrition department — noted that 400IU doesn’t increase the amount of vitamin D circulating in the blood very much. Depending on how much a person started out with, they said a daily intake of about 2,000IU — is necessary before blood levels get high enough for vitamin D to have its full disease-fighting effects.

Current Vitamin D Guidelines

Age 19-50       200iu

Age 51-70       400iu

Age 71+          600iu

I believe these to be far too low, as some experts recommend 2,000iu-10,000iu daily