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Low vitamin D in older adults: How much protects health?

Kathleen Blanchard's picture
How much vitamin D older adults need studied.

Researchers may have figured out how much vitamin D older adults really need for optimal health. In an observational study, investigators from University of Washington looked at vitamin D blood levels relative to risk of major medical events. They found when circulating levels of 25-hydroxy-vitamin D fell below 20 ng/milliliter or 50 nmol/liter, older adults were more prone to heart attack, hip fractures, cancer and even death.

Vitamin D and medical events vary with season

The findings, published in the Annals of Internal Medicine, showed adults over age 65 with vitamin D levels below 20ng/milliliter –measured in the blood stream as 25-hydroxy-vitamin D (25(OH)D), was associated with more medical problems. They also found levels varied with seasons, making it important to find ways to boost vitamin D levels in winter to keep older adults healthy.

"Sun exposure is tricky," de Boer explains in a media release, "because people have to protect themselves from skin cancer and other sun damage." Sunscreen blocks the UVB waves responsible for producing Vitamin D. Food sources for Vitamin D are milk, fortified juice and cereal and oily fish like salmon, mackerel, cod and herring.”

Additional studies are needed he says to see the impact of raising levels; de Boer suggests clinical trials to compare the health effects of boosting outdoor activity, diet or vitamin D supplements would lower health risks when the so called sunshine vitamin levels fall below 20 ng/milliliter or 50 nmol/liter.

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Vitamin D levels fell among the study participants in the winter and spring and are higher in summer and autumn.

The observational study was done because of controversy that exists over optimal levels of vitamin D. Several organizations have set guidelines, but there hasn’t been widespread agreement about how much of the vitamin is needed for disease prevention and bone health.

Dr. Ian de Boer, assistant professor of medicine in the Division of Nephrology and a member of the Kidney Research Institute said in a press release, that the study finding is in line with recommendations for optimal vitamin D from the national independent advisory group, the Institute of Medicine (IOM).

The take home message from the study is that vitamin D is essential for health and levels vary with seasons. The authors of the study concluded, “Season-specific targets for 25(OH)D blood concentration may be more appropriate than a static target when evaluating patients’ health risk." The finding suggests there is a link between lower vitamin D levels and risk of major medical events among older adults.

Annals of Internal Medicine
"Serum 25-Hydroxyvitamin D Concentration and Risk for Major Clinical Disease Events in a Community-Based Population of Older Adults: A Cohort Study"
Ian H. de Boer, et al
May 1, 2012

Image credit: Morguefile