Study calculates optimal upper limit of vitamin D

CHEVY CHASE, Md. — Researchers claim to have calculated for the first time the upper safe limit of vitamin D levels of 36 nanograms per milliliter, above which the associated risk for cardiovascular events or death raises significantly, according to a recent study accepted for publication in The Endocrine Society’s Journal of Clinical Endocrinology & Metabolism.

“The unpredictable results from previous studies may be due to the misconception that ‘the higher [supplementation with vitamin D] the better,’” stated Yosef Dror of Hebrew University in Rehovot, Israel, and lead author of the study. “Although our study did not directly test the impact of vitamin D supplementation, we believe our results suggest it may be possible that only moderate supplementation within a narrow range of serum calcidiol (the main vitamin D fraction in the blood) will be associated with the most positive results.”

Researchers conducted a study of 422,000 people aged 45 years or older, who underwent vitamin D blood assays. They found for the first time that the safe range of vitamin D levels with respect to coronary morbidity lies between 20 to 36 ng/mL. Vitamin D levels below and above this range adjusted rates of increased mortality and morbidity significantly.

More than 60% of the tested population had insufficient blood levels of vitamin D. Half of these subjects had severely low vitamin D levels which was associated with a 1.5 times increased risk of acute coronary morbidity or mortality. And 3% of those tested had elevated vitamin D levels above 36 ng/mL, which was associated with a 1.13 times elevated risk of coronary morbidity or death.


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