The issue is of particular interest in the Pacific Northwest, where many people have comparatively low vitamin D levels. Dr. Jeffrey Duchin, health officer for Public Health - Seattle & King County, cautioned the new analysis lumps a lot of different types of people together.
One of the most contentious questions in nutrition science over the past decade has been whether older adults should be taking supplemental vitamin D and calcium. As the world’s population ages and broken bones and fractures become even more of a public-health concern, with huge social and economic consequences, researchers have been trying to make sense of conflicting studies on the association between supplements and fracture risk.
A study published in the Journal of the American Medical Association (JAMA), conducted by Jia-Guo Zhao of Tianjin Hospital in China, was focused on older adults who live in the general community and did not include those in nursing homes, hospitals and other facilities.
The conclusion was clear: Vitamin D and calcium supplements do not seem to be warranted to prevent bone breaks or hip fractures in those adults. Such supplements had no clear benefit regardless of dose, the gender of the patient, history of fractures or the amount of calcium in the diet.
The U.S. Preventive Services Task Force (USPSTF), an influential federal advisory body, has raised questions about these supplements since 2013, when it issued recommendations saying evidence to support the benefit of the supplements in older adults without osteoporosis or vitamin D deficiency was “insufficient.”
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Marion Nestle, a professor emerita of food sciences and nutrition at New York University, wrote in an opinion piece at that time that the USPSTF’s statement should caution clinicians “to think carefully before advising calcium and vitamin D supplementation for healthy individuals.”
She said this week that bone health involves many different aspects of eating and activity. “Bone preservation throughout life requires eating healthfully, engaging in weight-bearing activity, avoiding excessive alcohol and not smoking — good advice for everyone,” Nestle said.
Dr. Jeffrey Duchin, health officer for Public Health – Seattle & King County, cautioned that the new analysis lumps a lot of different types of people together. “It’s important for people to understand … that they should not necessarily draw conclusions about their individual needs and requirements from this study,” he said.
“While it’s probably right that most people should not routinely be taking vitamin D and calcium, there are some situations where it’s appropriate.”
People currently taking supplements at their doctor’s suggestion shouldn’t stop without discussing it, Duchin added.
But generally, it’s preferable to rely on a healthful diet, exercise and exposure to sunlight to ensure bone health, he said.
People who live in northern latitudes, like the Pacific Northwest, often have lower vitamin D levels than those who live in sunnier climates, but it’s not clear if those lower levels cause health problems, Duchin said.
“There’s a lot of chatter about vitamin D and all sorts of conditions, from infections to cancer, and there’s just not a lot of good quality evidence to help us understand exactly whether or not vitamin D supplements make a difference in health outcomes.”
Vitamin D is not a vitamin but a hormone that is produced in reaction to sunlight and seems to have many different roles in the body related to bones, cancer, heart disease, diabetes, immune function and reproductive health.
Calcium and vitamin D have been known to be important to bone maintenance for a long time, and the best way to get the daily recommended doses are the natural way.
For calcium, that means eating dairy products like milk, cheese, yogurt or calcium-rich leafy greens. For vitamin D, that means getting some sun exposure. Only a few foods contain vitamin D, and they include fatty fish like salmon.
Daniel Fabricant, president of the Natural Products Association, which represents manufacturers and retailers of dietary supplements, said the study draws its conclusions with “too broad of a brush.” He said it focuses on the healthiest segment of the population by looking at people who are able to live at home.
“There is a lot missing,” Fabricant said. “People with prior breaks or family incidence of osteoporosis may still need vitamin D.”
The issue is many Americans don’t get enough calcium or vitamin D — which is why the debate over supplements has become so important. In 2010, the Institute of Medicine (IOM) released recommendations tripling the daily intake of vitamin D for most people to 600 IU per day and raising the calcium intake to 1,000 milligrams.
While that report has few explicit mentions of supplements, the use of supplements seems assumed, and it includes a lot of discussion about the importance of setting and following upper limits for intake of vitamin D and calcium.
“As North Americans take more supplements and eat more of foods that have been fortified with vitamin D and calcium, it becomes more likely that people consume high amounts of these nutrients,” the group wrote, warning of the possibility of kidney and tissue damage from overconsumption.
Fabricant also said the new study contained limited information on the dosages involved. “Maybe the average dose was on the lower end of dose response curve,” he said. “While it’s a nice exercise of mathematics, it doesn’t get at the actual issue which is what are optimal levels for people who need the supplements.”
The new study did not look at the benefits or risks of vitamin D supplements on other conditions, but previous studies have suggested they can lower risks for diabetes and certain cancers. However, an April 2017 study in JAMA Cardiology found high monthly doses of vitamin D supplements did not seem to do much to help with cardiovascular disease.
Dr. Anne McTiernan, an expert on diet and cancer at the Fred Hutchinson Cancer Research Center, said she’s still convinced that people with low levels of vitamin D can benefit from supplements.
She and others have found that people with the highest blood levels of vitamin D have about a third lower risk of colorectal cancer. Direct cause and effect hasn’t been proved, but clinical trials have found that vitamin D can lower some cancer risk factors, including inflammation and DNA damage.
McTiernan, author of “Starved: A Nutrition Doctor’s Journey from Empty to Full,” pointed out that the studies included in the new JAMA analysis involved standard doses of vitamin D. But her own research has found that the same dose can lead to different blood levels in different people.