Sunshine in a Bottle: Continuing Debate over Vitamin D Supplements
Two large studies of almost a million people published in the April 2014 issue of the British Medical Journal suggest that while there is no doubt that vitamin D is essential for bone health and cell communication, there is no clear evidence that vitamin D is beneficial against other health problems and diseases.
Findings from one study suggested that blood levels of vitamin D might be markers of overall health, but could not answer the question of whether low levels of the vitamin cause disease or are just markers of a poor lifestyle that paves the way for disease. For example, such factors as an unhealthy diet, smoking, obesity, and lack of exercise can lower blood levels of the vitamin.
Beyond bone health? Vitamin D helps to absorb calcium and support bone health, and is a vital part of the immune system. But Dr. Oscar Franco, a professor of preventive medicine at Erasmus Medical Center in the Netherlands, an author of one of the studies, suggested vitamin D “has effects at the genetic level and affects cardiovascular and bone health.” He and his team found that adults with lower levels of vitamin D had a 35 percent increased risk of death from heart disease, a 14 percent risk of death from cancer, and overall, a greater mortality risk.
This risk may be caused by increased levels of inflammation and oxidative load, which pave the way for free radicals that can cause cell injury, including mutations, metabolic dysfunction, and cell aging, the researchers speculated.
In the meta-analysis, scientists analyzed 73 cohort studies of almost 900,000 participants and 22 randomized controlled studies comprising 31,000 participants. The second study found that an infant’s birth weight is linked to its mother’s vitamin D levels in late pregnancy, and also showed probable evidence for reduced caries in children, higher vitamin D levels in mothers at term, and lower PTH level in dialysis patients. Further, the team found no evidence that taking vitamin D supplements had any osteoporosis benefits, or even helped prevent falls, contrary to the public’s view of vitamin D benefits.
Vitamin D supplementation. The study found that supplementation with vitamin D3, known as cholecalciferol, reduced all-cause mortality by 11 percent, while supplementing with vitamin D2 (ergocalciferol) had no overall effect on mortality. About two-thirds of the population in the U.S. and Europe is deficient in vitamin D, researchers noted. Further, 13 percent of all deaths in the U.S. and nine percent in Europe can be attributed to low vitamin D levels (compared, in the U.S., to mortality risk of 20 percent from smoking, 11 percent from physical inactivity, and nine percent from alcohol).
Second team unconvinced. The second study, led by a team of researchers from Stanford and several European universities, said there was “suggestive,” but not “highly convincing” evidence that high levels of vitamin D protected against a number of diseases, including diabetes, stroke and hypertension. The team said they could not recommend widespread supplementation with the vitamin, based on the evidence to date.
Upended truths. Vitamin D has long been held as the gold standard against osteoporosis prevention and subsequent fracture from falls, but the study found no evidence to support this, and suggested that people refrain from taking vitamin D supplements pending further study, relying instead on sunlight and better diet to improve vitamin D levels.
Jury is still out. An accompanying editorial said that, while the “apparent degree of benefit from D3 “seems remarkable,” it warned it was premature to recommend widespread D3 supplementation “in patients without bone-disease-related conditions.” The authors recommended that clinicians “encourage better lifestyles in general, and target established risk factors in people at elevated risk.”
It’s a dialogue to be continued…but if your physician has recommended vitamin D supplementation to maintain bone density, generally at levels higher than 35 to 40 ng/ml for preventive health, continue with that regimen.
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