Science News By Nathan Seppa, Web edition: April 8, 2013
Vitamin D seems to be living up to high expectations.
A spate of 2013 studies has found that the vitamin may yield benefits in groups ranging from pregnant women to members of the military to kids in a dentist chair.
Six recent reports offer a sampling of the evidence:
- An analysis of 24 clinical trials in children finds that kids getting vitamin D supplements had a 47 percent reduced risk of dental caries, researchers report in Nutrition Reviews.
- A study of 242 healthy adults getting daily calcium supplements shows that those who also took modest vitamin D supplements of 800 IU per day saw their blood pressure decrease. Their top blood pressure number fell by 10 points on average after a year and their bottom BP number fell by four points. Writing in Nutritional Influences on Bone Health, the researchers also report that the vitamin D folks saw their heart rate decline from 74 to 70 beats per minute. The calcium-only group saw no improvement on average.
- A 28-year study in which Danish scientists monitored the health of nearly 10,000 people finds that those who developed a tobacco-related cancer during that time had vitamin D levels at the study outset of 14.8 nanograms per milliliter of blood on average, compared with 16.4 ng/ml on average for everyone else. That report shows up in Clinical Chemistry.
- BMJ reports in a review of 31 studies that pregnant women with vitamin D levels of less than 30 ng/ml had an increased risk of developing a complication such as preeclampsia or gestational diabetes.
- Low vitamin D levels may hamper metabolism in blacks. A study in Nutrition Research finds that adult blacks averaged vitamin D of only 14.6 6 ng/ml compared with 25.6 ng/ml on average in whites. Blacks were also more likely to have insulin resistance, a condition in which cells fail to use the hormone insulin efficiently to process glucose. But when researchers compared groups with similar vitamin D levels, the differences in insulin resistance disappeared. That suggests that the higher burden of insulin resistance in blacks is at least in part the result of low vitamin D, they conclude.
- Very low vitamin D might be linked to suicide risk. An analysis of military service members finds that people who committed suicide appear to have similar vitamin D levels on average compared with those who don’t. But a closer look finds that people with the very lowest levels, less than 15 ng/ml, were roughly twice as likely to commit suicide as people with vitamin D ranging from 17 to 41 ng/ml. That study appears in PLoS One.
If well-stocked bins in pharmacies are any indication, news of vitamin D’s benefits is reaching the mainstream. Public health leaders have responded unevenly to such data, however. In 2010, the Institute of Medicine, the health arm of the National Academy of Sciences, which is charged with advising the government and the public on health matters, declared that 20 ng/ml was the minimum blood concentration of vitamin D for bone safety. The IOM also bumped up the daily recommended intake, but only slightly to 600 to 800 IU for most adults (1/1/11, p.14; 7/16/11, p. 22).
The Endocrine Society, the oldest and largest group devoted to hormone research, cited ample research in upping the ante several months later and calling for vitamin D intake levels two to three times higher than IOM’s.
Not all vitamin D studies show a benefit. It’s also difficult to randomly assigned people to get specific amounts of a vitamin that can be obtained from sun exposure. Can the benefits of vitamin D be oversold? Possibly. But one thing is clear: So far, 2013 is shaping up to be a very good year for the sunshine vitamin.
Citations
- S. Afzal et al. Low plasma 25-hydroyvitamin D and risk of tobacco-related cancer. Clinical Chemistry. Volume 59, 2013, in press. doi: 10.1373/clinchem.2012.201939.
- F. Aghajafari et al. Association between maternal serum 25-hydroyvitamin D level and pregnancy and neonatal outcomes: systematic review and meta-analysis of observational studies. BMJ. Volume 346, 2013.
- P. Hujoel et al. Vitamin D and dental caries in controlled clinical trials: systematic review and meta-analysis. Nutrition Reviews. Volume 71, 2013, p. 88. doi: 10.1111/j.1753-4887.2012.00544.x.
- M. Pfeifer. Effects of vitamin D and calcium supplementation on heart rate and blood pressure in community-dwelling older individuals. Nutritional Influences on Bone Health. 2013, p. 343. doi: 10.1007/978-1-4471-2769-7_33.
- J. Umhau et al. Low vitamin D status and suicide: A case-control study of military service members. PLoS One. Volume 8, 2013.
- S. Williams et al. Association of racial disparities in the prevalence of insulin resistance with racial disparities in vitamin D levels: National Health and Nutrition Examination Survey (2001-2006). Nutrition Research. In press, 2013.
Suggested Reading
N. Seppa. The power of D. Science News. Volume 180, July 16, 2011, p. 22.
N. Seppa. Vitamin D targets increased. Science News. Volume 179, Jan. 1, 2011, p. 14.