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Is Vitamin D Overrated? Another Study Casts Doubt on Benefits

Health logo Health 8/4/2022 Korin Miller

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For years, Vitamin D has been viewed as a helpful supplement to address everything from mood disorders to heart disease prevention. The popular supplement has also long been used to reduce the risk of bone fractures in older adults. 

New research however, suggests that taking Vitamin D may not be as useful for some of these ailments as it was initially thought to be.

The study, published in The New England Journal of Medicine, suggests it may be time to abandon the Vitamin D craze after researchers found that the supplement did not have an impact on reducing bone fractures in older adults. And—in another blow—the same study points out that taking the supplement didn't decrease a person's risk of developing heart disease, cancer, or memory loss.

"The data related to whether Vitamin D supplementation can prevent fractures has been inconsistent," Sylvia Christakos, PhD, a professor at Rutgers New Jersey Medical School, told Health. Christakos said the latest findings clearly indicate that giving Vitamin D supplements to people who are already getting enough of this nutrient, did not ultimately lower the patient's risk of fracture. 

"More is not better," Christakos said.

Despite the new findings, experts say there's still a role for Vitamin D in some cases. Here's a closer look at the latest insights and recommendations regarding Vitamin D supplements.

RELATED: Is It Possible To Take Too Many Vitamins?

Vitamin D and Fracture Prevention

The use of Vitamin D to address bone health has been widely recommended since at least 2011, when the National Academy of Medicine advised 600 to 800 international units (IU) daily for the general public. The recommendation at that point stemmed from research indicating the supplement might support calcium absorption, which could inhibit bone deterioration.

The newly published clinical trial, however, which was focused on determining whether added Vitamin D would preventatively improve bone health, appears to undermine such recommendations. The clinical trial results found 1,991 fractures in 1,551 study participants and discovered that there wasn't a significant difference in risk between study participants who took Vitamin D and those who did not.

To arrive at these findings researchers engaged 25,871 study participants— men 50 or older and women 55 or older. Slightly more than half of the participants were women, and the median age was about 67. Additionally, the majority of study participants entered the trial with sufficient Vitamin D levels. Just just 2.4% had what was considered to be a severe deficiency.

As part of the study, participants were asked to take either 2,000 international units of Vitamin D each day or a placebo and then were tracked for about five years. Incident fractures were reported by participants on an annual questionnaire.

The conclusion of all the research? "Vitamin D3 supplementation did not result in a significantly lower risk of fractures than placebo among generally healthy midlife and older adults," according to the study. 

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Why is Vitamin D Important, In General?

Vitamin D promotes calcium absorption in your gut, helps keep your bones healthy and prevents them from becoming thin, brittle, or misshapen, according to the National Institutes of Health (NIH). The supplement also helps prevent muscle cramps and spasms and can reduce inflammation.

Most people get their Vitamin D from sunlight, but you can also get it from the flesh of fatty fish, beef liver, egg yolks, and cheese, the NIH says. Fortified foods also provide significant amounts of Vitamin D in American diets. Most of the U.S. milk supply is fortified with this supplement.

According to the NIH, the recommended daily allowance of Vitamin D varies by age. For those 70 and under the recommendation is 600 international units. Those over 70 should be getting about 800 IUs.

The NIH also points out that people can develop Vitamin D deficiency when usual intakes are lower over time than the recommended levels, or when exposure to sunlight is limited. Those who have milk allergy or are lactose intolerant and those who consume vegetarian or vegan diets may also experience lower levels of Vitamin D.

When deficiencies develop in children, it can cause conditions such as rickets, a disease characterized by a failure of bone tissue to become properly mineralized, resulting in soft bones and skeletal deformities, according to the NIH. Meanwhile, in adults and adolescents, inadequate Vitamin D can cause a condition known as osteomalacia—which involves existing bone being incompletely or defectively mineralized, resulting in weak bones.

For which conditions is vitamin D Still necessary?

Experts stress that the latest study results do not mean individuals should completely cease taking Vitamin D. 

Most of the participants in the recent clinical trial were healthy— they didn't have a history of cancer or heart disease. And most of them also had good Vitamin D levels at the start, Sina Gallo, PhD, RD, associate professor of nutritional sciences at University of Georgia, told Health.

"This may explain their null findings as individuals with lower Vitamin D status may benefit most from supplementation," Gallo said. "It is well established that Vitamin D promotes calcium absorption and assists to maintain blood calcium concentrations hence, assisting in the mineralization of bone."

The study "does not say that Vitamin D is not involved in this role," Gallo continued, "only that a daily Vitamin D supplement of 2,000 IU alone —not with a calcium supplement—does not reduce fracture risk in healthy middle age and older adults." 

It could simply be that the amount of Vitamin D wasn't correct or that other nutrients, such as calcium, need to be taken with Vitamin D in order to have an impact on bone health, Gallo pointed out.

Jennifer Beck, MD, associate clinical professor in the Department of Orthopaedic Surgery at the David Geffen School of Medicine at UCLA, said the study does not influence her opinion on Vitamin D, adding that research has shown Vitamin D has many benefits.

"The question at this time is not 'if Vitamin D is helpful'—the more appropriate question is 'in what population is Vitamin D helpful?'" Dr. Beck said. "We have at least two studies in [the] pediatric population stating that there's increased fracture risk and fracture severity in patients with low Vitamin D. So, although I applaud the authors for their efforts, this study is a case of don't throw out the baby with the bath water." 

The study results should not undermine the need for Vitamin D assessment and replenishment in high risk populations, Dr. Beck added. 

It's also important to consider the fact that Vitamin D doesn't work alone in your body. "I like to always remind people that many nutrients in our bodies work synergistically and placing too much importance on any one will probably disappoint us," Liz Weinandy, RD, a registered dietitian at The Ohio State University Wexner Medical Center, told Health.

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