A new recommendation to increase the RDA for vitamin D by the Institute of Medicine (note not the USFDA or the NIH) from 200 IU to 600 IU daily was published recently. Keep in mind that the US RDA formally is 400 IU daily, so the IOM has leapfrogged them by going from a lower to a higher recommendation. This is in line with what many physicians have been recommending for some time, and seems to me to be reasonable. Still it is not without controversy. Some experts recommend much more, some less. As those of you following DrPullen.com have seen, vitamin D deficiency is really common, and Vitamin D deficiency is implicated in far more than Rickets. Vitamin D deficency has been associated with cognitive function, depression and calcium metabolism disorders. As you may know vitamin D can be produced in the body, but requires sun exposure for efficient productin, and especially in the northren climates is often deficient or in the low normal ranges in many people. Many experts have been recommending supplemental vitamin D to assure levels of vitamin D that are highter than the low normal ranges.
Medscape has a very nice though very detailed article outlining the controversy and difficulty of studying Vitamin D levels, deficiency, and ideal RDA in humans. For a brief but very detailed discussion see:
How much vitamin D is enough? Over the past decade, rickets has re-emerged as a noticeable public health issue in some areas (Lanham-New et al, 2010) and many physicians have been ordering lab values of blood vitamin D levels on their patients and prescribing large doses of the vitamin for the patients whose levels seemed low: <20-30 ng/ml. However, the accuracy of serum vitamin D assessments, the need for the vitamin D supplementation, and efficacy of the supplements have not been clear. Now, the Institute of Medicine recommends tripling the daily intake for most children and adults to 600 IU per day, up from 200 IU/day (Institute of Medicine, 2011). This recommendation is not without controversy. read more
In this week’s issue of the Annals of Internal Medicine (unfortunately you need a subscription to see the article) Dr. Andrew Gray MD, and Mark Bolland PhD write an interesting editorial called Vitamin D: A Place in the Sun. In it they discuss the current flood of claims for health benefits of vitamin D. When analyzing a finding such as the link between Vitamin D levels and a disease state, one of the most difficult aspects is to control for “confounding variables.” The definition of a confounding variable in The Free Dictionary online is, “interference by a third variable so as to distort the association being studied between two other variables, because of a strong relationship with both of the other variables.” Low vitamin D levels are associated with such potential confounding variables as obesity, sedentary lifestyle, and lack of sunlight exposure. These conditions and others are potentially associated with depression, diabetes, and many of the other conditions for which low vitamin D levels has been suggested as a risk factor Hence the concern about confounding variables not accounted for in the association of these conditions with vitamin D. This is elegantly stated in these authors middle paragraph of their editorial:
“Although some evidence from preclinical studies suggests thatcomponents of the vitamin D system might impact favorably onsome diseases,4 it seems intuitively unlikely that a singlehormone could play a substantial role in preventing or amelioratingthe diverse range of diseases that have been linked to low levelsof vitamin D. A more plausible and prosaic explanation for thefindings of the observational vitamin D studies is the presenceof common confounders. Vitamin D levels are directly relatedto sunlight exposure and physical activity, and inversely relatedto adiposity.5-6 It is likely that less healthy individuals,who are more likely to subsequently experience morbid events,will be heavier, less active, and more sunlight-deprived thanhealthier ones and therefore have lower levels of 25(OH)D. Thisnotion is supported by previous studies7and by the study ofLlewellyn et al,2 in which several indices of poor health weremore commonly observed at baseline in those with lower levelsof vitamin D. Thus, low vitamin D levels may simply be a markerfor lower health status rather than a cause of it. Healthinessis difficult to measure and adjust for, as illustrated by thedisparate results of observational studies and randomized controlledtrials (RCTs) of postmenopausal hormone therapy and cardiovasculardisease or antioxidant treatment and cardiovascular diseaseand cancer.8-11 We should therefore treat the data from observationalstudies of vitamin D with caution.”
Although low vitamin D levels are associated with multiple conditions it will be interesting to see if supplementation of vitamin D lowers the risk of these conditions or whether only improving the confounding conditions, like more exercise, lower levels of obesity, more sunlight, etc. works to prevent the medical conditions. It will sure be nice if just taking those nice small, easy to swallow yellow capsules works, but as for me I remain skeptical.
Imagine a treatment that could build bones, strengthen the immune system and lower the risks of illnesses like diabetes, heart and kidney disease, high blood pressure and cancer.
Some research suggests that such a wonder treatment already exists. It’s vitamin D,
The latest edition of the British Medical Journal reports a study showing a very statistically significant (p<0.001 for you statisticians) inverse correlation between levels of vitamin D and the risk of developing colorectal cancer. People were looked at in 5 subsets, highest to lowest vitamin D levels. Those in the highest 1/5 of vitamin D levels had a 40% lower chance of developing colorectal cancer than those in the lowest 1/5 group. No proof yet that increasing vitamin D levels can prevent colorectal cancer, but one more positive thing about having good high levels of Vitamin D. See my prior post on vitamin D. This was also reported in MedPage Today for a more detailed explanation, or the original report in BMJ.
In the 1950’s vitamin D was added to most milk products and many bread products to address a nationwide concern of vitamin D associated rickets. At the time this seemed to prevent rickets, the concern at that time. Now we are seeing vitamin D deficiency problems again. This is a problem with multiple causes:
-Less skin exposure, more time indoors, more use of sun screen. (The natural precursor of the active form of vitamin D requires sunlight exposure in the skin to change into its active form)
-Concern that many more medical problems may possibly related to low levels of Vitamin D. (Multiple sclerosis, depression, fatigue, osteoporosis, fibromyalgia, … there is much debate about most of these concerns)
-The optimal level of vitamin D is being questioned, is 20mcg/dl OK, should it be 40, 50. or even higher for optimal levels?
