By Steven Reinberg
health day reporter
TUESDAY, Jan. 24, 2023 (HealthDay News) — Vitamin D is widely promoted for better health, but if you’re overweight, you might not reap the benefits.
In a new study, researchers found a 30-40% reduction in cancer, cancer death and autoimmune disease in people with a lower body mass index (BMI) who took vitamin D supplements, but only a small advantage in those with a higher BMI.
“Obese patients, despite the same amount of supplements, had a lower response,” said lead researcher Deirdre Tobias, assistant professor in the department of nutrition at the Harvard School of Public Health in Boston.
The threshold was a BMI of less than 25, which is considered a healthy weight, the study authors noted.
It’s unclear why being overweight or obese affects levels of the so-called “sunshine vitamin,” but low vitamin D absorption could be widespread, given that more than 40% of Americans are obese, according to the Centers for Disease Control and Prevention.
“It’s not clear if this is due to their body weight, per se, or perhaps some other factor related to an individual’s body weight. It may be due to adiposity itself. Having a lower body weight may result in a higher internal dose of vitamin D,” Tobias said. Adiposity is having too much fatty tissue in the body.
The next step in research is to try to determine what it is that weight affects vitamin D metabolism, she noted.
Tobias also said it was unclear whether overweight and obese people could counteract the diminished effect of vitamin D supplements by taking higher doses.
“It’s not the type of vitamin that you can take unlimited amounts of. You mostly excrete it in your urine if you take too much,” she said. “So taking a higher dose just to be on the safe side is not something this study suggests or would recommend.”
For the study, Tobias and his colleagues used data from the Vitamin D and Omega-3 Trial (VITAL), which randomly assigned nearly 26,000 older adults to either vitamin D supplements or a placebo. Although the trial showed little benefit from taking vitamin D supplements to prevent cancer, heart attacks or strokes, there appeared to be a correlation between body weight and the risk of cancer, death by cancer and autoimmune diseases.
The researchers decided to dig a little deeper into the data. They looked at around 16,500 participants who provided blood samples at the start of the trial and nearly 3,000 who gave follow-up blood samples two years later.
The researchers found that signs of vitamin D metabolism were seen in all participants, regardless of weight, but were much lower in overweight or obese people.
“Vitamin D has been shown to reduce the risk of osteoporosis and other chronic diseases,” said Emma Laing, director of dietetics at the University of Georgia and national spokesperson for the Academy of Nutrition and of dietetics.
Scientists have suggested a few ways that might make vitamin D supplementation less effective in people with larger bodies, Laing noted. “Because vitamin D is a fat-soluble vitamin, it is possible that people with higher levels of fatty tissue store more vitamin D in these tissues, so less is detectable in the blood. Another hypothesis is that fatty tissue suppresses the enzymes and receptors responsible for the effectiveness of vitamin D in the body,” she said.
Laing does not advise taking vitamin D supplements without first consulting your doctor, as supplements can have side effects. “Adverse events, ranging from less serious to life-threatening, can occur if you take more than the suggested dose, take a combination of supplements, or take a supplement that interacts negatively with your medications,” she said. declared.
Still, supplements are helpful in some cases, Laing noted.
Taking a vitamin D supplement may be appropriate if you cannot get the amount needed through your diet or if sun exposure is limited due to climate, skin color, or screen use. solar, she said.
“A supplement may be warranted if a person eliminates food groups from their diet, has a diagnosed vitamin or mineral deficiency, or takes medications that affect appetite or interfere with digestion and absorption of nutrients. “, said Laing. In these cases, it might be necessary to get vitamins and minerals from supplements, she suggested.
Additionally, when food choices are severely limited due to food allergies or intolerances, strict diets, or health conditions like celiac disease, supplementation is usually recommended to prevent vitamin and mineral deficiencies, explained Laing.
Additionally, people who have had weight loss surgery may need supplements. “Competitive athletes and people serving in the military are also among those who might need supplements if their physical performance demands make it difficult to meet their nutritional needs from food alone,” Laing said.
The report was published online on January 17 in JAMA network open.
To learn more about vitamin D, visit the US National Library of Medicine.
SOURCES: Deirdre Tobias, ScD, assistant professor, department of nutrition, Harvard School of Public Health, Boston; Emma Laing, PhD, RDN, Director, Dietetics, University of Georgia, Athens, National Spokesperson, Academy of Nutrition and Dietetics; Open JAMA NetworkJanuary 17, 2023, online