Taking the supplement with a meal containing fat may boost absorption by 32% compared to when taken with a fat-free meal, according to findings published in the Journal of the Academy of Nutrition and Dietetics.
However, the type of fat in the meal did seem to influence absorption, with the ratio of monounsatured fats (MUFAs) to polyunsaturated fats (PUFAs) not affecting vitamin D absorption.
“This finding improves our understanding of how the composition of a meal taken in conjunction with vitamin D impacts its absorption,” said first author Bess Dawson-Hughes, MD, a senior scientist at the USDA Human Nutrition Research Center on Aging at Tufts University.
“This study provides rationale for recommending that vitamin D supplements be taken with a meal containing fat. It may also influence the design of future studies of vitamin D absorption.”
Vitamin D is a fat-soluble nutrient and, while it may seem logical that consuming it with a fat-containing meal would be beneficial, there is a lack of conclusive evidence that this is the case, said the researchers.
The Sunshine Vitamin
Vitamin D refers to two biologically inactive precursors - D3, also known as cholecalciferol, and D2, also known as ergocalciferol. Both D3 and D2 precursors are transformed in the liver and kidneys into 25- hydroxyvitamin D (25(OH)D), the non-active 'storage' form, and 1,25-dihydroxyvitamin D (1,25(OH)2D).
While our bodies do manufacture vitamin D on exposure to sunshine, the levels in some northern countries are so weak during the winter months that our body makes no vitamin D at all, meaning that dietary supplements and fortified foods are seen by many as the best way to boost intakes of vitamin D.
According to the 2014 CRN Consumer Survey on Dietary Supplements, vitamin D is the second leading category among supplement users after multivitamins.
Dr Dawson-Hughes and her co-workers recruited 50 healthy older men and women to participate in their one-day study. The volunteers were divided into three groups: The first group consumed a fat-free meal, and the second and third groups consumed meals with 30% of calories as fat. The two fat-containing meals differed by the ratio of MUFAs to PUFAs, with the second group having a low ratio (1:4) and third group having a high ratio (4:1) of MUFA to PUFA. All of the volunteers took a single 50,000 IU vitamin D-3 supplement (in powder form) with their meal.
Results showed that the maximum plasma level of vitamin D3 was 32% higher in the fat-containing meal groups, compared with the fat-free meal group. “Absorption at 10 and 14 hours was also greater, by means of 40% and 25%, respectively,” wrote the researchers.
However, contrary to their expectations, the MUFA:PUFA ratio did not affect vitamin D absorption, they said.
“This study provides the rationale for recommending that vitamin D supplements be taken with a meal containing fat,” they concluded.
Ditte Arltoft, PhD and global nutritional science lead for Caltrate at Pfizer Consumer Healthcare, welcomed the study’s findings, noting that it helps better understand vitamin D absorption.
“For consumers, it is understood that the absorption of both calcium and vitamin D is enhanced when taken with food,” said Dr Arltoft. “This latest vitamin D analysis shows that absorption can be significantly increased when supplementation is taken with a meal containing the amount of fat generally recommended in a daily diet.”
The study was funded by Pfizer and the USDA Human Nutrition Research Center on Aging at Tufts University.
Source: Journal of the Academy of Nutrition and Dietetics
Published online ahead of print, doi:
“Dietary Fat Increases Vitamin D-3 Absorption”
Authors: B. Dawson-Hughes, S.S. Harris, A.H. Lichtenstein, G. Dolnikowski, N.J. Palermo, H. Rasmussen