Vitamin D, known sometimes as the sunshine nutrient, has been the bright star in a number of studies about good health. Countless media reports and scientific research have built a bastion of public health knowledge on its benefits, but vitamin D may also combat some frighteningly prominent chronic diseases. Earlier this month, the British Medical Journal published two major reviews linking vitamin D deficiency to higher death rates from cancer and cardiovascular diseases.
The two studies published in the BMJ employed gold standard scientific research methods to assess the benefits, if any, of daily vitamin D intake. Researchers from the United States and Europe conducted meta-analyses, which involved combing through a number of different studies and randomized control trials to identify patterns in study results, and included data on more than a million people.
The studies found some alarming links between low levels of vitamin D and higher death risk. Adults with lower levels of the vitamin D in their bodies were 35 percent more likely to die from heart disease, 14 percent more likely to die from cancer, and suffered a greater overall risk of death.
When researchers looked at supplement use, they found that middle-aged and older adults who took vitamin D3 — a form of the vitamin found in fish and dairy products and produced in response to sunlight — were 11 percent less likely to die from any number of causes, as compared to middle-aged and older adults who did not.
For a nutrient that has received so much scientific and public attention, a majority of people in Western cultures are not getting enough. In the United States and Europe, more than two-thirds of the population is not getting enough vitamin D. Authors of the first of the two new studies calculated that approximately 13 percent of all deaths in the United States, and nine percent in Europe, could be associated with vitamin D deficiency.
“We are talking about a large part of the population being affected by this,” said Dr. Oscar H. Franco, a professor of preventive medicine at Erasmus Medical Center in the Netherlands and an author of the first study.
Although it seems clear that vitamin D is important for health, getting a healthy level of vitamin D may not be as easy as just going outside, eating dairy or swallowing a few supplements. Unlike most vitamins, D can be produced by the body when exposed to sunlight and it does not take much either. The result is that vitamin D ultimately is not a vitamin at all but rather a hormone, and the only “vitamin” a body can produce on its own. It is no surprise that there may be a number of factors that affect its presence in the body, including diet, exercise, and metabolism.
The Vitamin D Council states that the best way to absorb the sunshine nutrient into the body is (safe) exposure to sunlight as well as supplements, the latter being especially beneficial for adults over 50 years old. The authors of the second study published in the BMJ found that this may not be the case, concluding that there was no “highly convincing” evidence that vitamin D supplements affected the health outcomes they examined. They also found evidence that it may play less of a role in bone health than previously thought. However, like the first study, the authors also concluded that there was “suggestive evidence” that high vitamin D levels could be a protective factor against illnesses like diabetes, stroke, and hypertension.
Blood levels of vitamin D paint an accurate picture about overall health, but there is still the question of whether low levels are a cause of disease or simply a sign of poor health behaviors like a sedentary lifestyle, smoking and unhealthy diet. Obesity and smoking are associated with lower blood levels of the vitamin, as is a diet in high-fat, processed foods. Another new study conducted by Fred Hutchinson Cancer Research Center found that healthy levels of vitamin D may be associated with weight loss, but it is not clear if other factors are involved.
The implications of vitamin D deficiency point to higher death risk from cancer and other chronic disease, but a lot of research lies in the future to determine whether or not it is causal. Although more light needs to be shed on the specific effects of the sunshine nutrient, Dr. Franco has advice that is important for maintaining a healthy lifestyle in general.
“The most important factors in obtaining vitamin D are going out and doing some exercise and following a healthy diet,” he said.
By Erica Salcuni