Dietary fat increases vitamin D-3 absorption

By David Douglas

NEW YORK (Reuters Health) - Vitamin D-3 absorption from a dietary supplement can be significantly improved by taking it with a meal that contains fat, according to Boston-based researchers.

As Dr. Bess Dawson-Hughes told Reuters Health by email, "There is widespread vitamin D insufficiency and many people are advised to take a supplement. Improving absorption of supplemental vitamin D represents one step toward reducing the insufficiency."

Plasma 25-hydroxyvitamin D response to supplementation with vitamin D is known to vary widely, but absorption differences based on diet composition is poorly understood, Dr. Dawson-Hughes of Tufts University School of Medicine and colleagues note in the Journal of the Academy of Nutrition And Dietetics, online November 17.

To test the hypothesis that absorption of vitamin D-3 is greater when the supplement is taken with a meal containing fat, the team studied 50 men and women aged at least 50 years. They also examined whether absorption would be greater when the fat in the meal had a higher monounsaturated-to-polyunsaturated fatty acid ratio (MUFA:PUFA).

In a one-day study, after a 12-hour fast, the subjects were randomly assigned to one of three breakfast types: a fat-free meal, a meal with 30% of calories as fat with a low (1:4) MUFA:PUFA ratio and one with a high (4:1) ratio. They also took a 50,000 IU vitamin D-3 tablet.

They then went on to receive a boxed lunch and dinner of a similar composition to the breakfast test meal and they agreed to eat nothing else during the study.

Vitamin D-3 levels were examined before and up to 14 hours after taking the tablet. The mean peak (12-hour) plasma vitamin D-3 level after the dose was 32% higher in those taking the fat-containing meal (p=0.003).

Low and high MUFA and PUFA ratios had no significant effect on absorption, however.

The researchers say a limitation of the study was that it involved a single 50,000 IU dose, and further work is required to determine whether with smaller and repeated dosing, absorption is similarly influenced by meal content.

Nevertheless, the team concludes, "This study provides the rationale for recommending that vitamin D supplements be taken with a meal containing fat."

Commenting on the paper by telephone, Dr. Jonathon L. Maguire of the University of Toronto, who has conducted related research, said the findings were interesting.

"There's been much debate about variability in absorption of vitamin D supplements," he told Reuters Health. "This study may supply part of the explanation."


J Acad Nutr Diet 2014.

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