Vitamin D and Bone Health

Monday, 22 February 2010 12:31

Research indicates that a sufficient blood level of this hormone is associated with fewer deaths from heart disease; breast, colon, and prostate cancer; hypertension, and the autoimmune conditions multiple sclerosis and type 1 diabetes. (Science tidbit: vitamin D is considered a hormone, because it can be manufactured in our bodies and it reaches our intestine via the blood stream to signal an increase in the absorption of calcium and phosphorus.)

An understanding of the role of vitamin D and concern over what appears to be a nationwide deficiency epidemic is increasing. In 2008, The American Journal of Clinical Nutrition reported the results of a study that looked at the vitamin D status of the U.S. population from 1988-1994 compared with 2000-2004. Overall, the researchers concluded that average blood levels of vitamin D had declined significantly from the earlier period—possibly related to changes in body mass, lower milk consumption, and the use of sunscreen.

With concern over their patients’ nutritional status growing, more doctors are testing blood levels of vitamin D (25-hydroxyvitamin D) levels and prescribing supplements reports Tara Parker-Pope in a New York Times blog. She notes that one testing company logged a 50% increase in orders for tests in the fourth quarter of 2009 over the same quarter a year earlier. And in 2008, consumers bought $235 million worth of vitamin D supplements, a more than 500% increase over 2001 sales.

Though the excitement over the positive health benefits of vitamin D seems warranted, some authorities have suggested that caution is in order. They point to the relatively few randomized clinical studies that have been performed and to the little that is known about optimal dosage levels. The issue of cause-and-effect has also raised its head. That is, healthy people typically have good levels of vitamin D—a positive correlation—but there are likely to be other contributors, such as outdoor exercise and non-smoking, to their good health.

American Bone Health believes that the evidence, both from formal studies and clinical observations, supports the role of vitamin D in promoting good bone health.

We support supplementation simply because it is very difficult, if not impossible, to get enough vitamin D from diet alone. As Ms. Pope points out in her blog, a person must drink a quart of milk a day to meet the current RDA of the vitamin, which is generally considered too low.

Clearly, more research is needed, and American Bone Health is eagerly awaiting the results of a five-year nationwide clinical trial that has just kicked off. In the meantime, we’re recommending that adults supplement their diets with 1,000 to 2,000 IU of vitamin D daily.