Calcium and vitamin D3 are necessary for bone health. Vitamin D3 is a fat-soluble vitamin that is poorly soluble in aqueous environments like intestinal lumen. Therefore for it to be absorbed it needs to be solubilized by dietary fat and bile salt.
Some studies have shown that some types of dietary fat like PUFA (poly unsaturated fat which is high in corn and soybean oil) might decrease the vitamin D levels in the body. Therefore the researchers of this study decided to design a study to investigate the effect of different dietary fats on the vitamin D increase in the body after supplementation.
This study was done on participants over 65 years old, who are at higher risk of bone problems like osteoporosis, due to their age. The researchers excluded those with medical problems, medications related to bone metabolism and those with very low bone mass density. Also those with personal calcium or vitamin D3 supplement use, cod liver oil and dietary calcium>1500 mg/d were excluded.
This study was a part of a study in which participants were recruited into control or treatment groups randomly. Both the participants and the staff did not have information about the groups. A supplementation of 700 IU/d vitamin D3 and 500mg/d calcium was given to the participants. Their blood levels of 25(OH) D (the usual form of vitamin D measured in the blood to estimate body stores) was measured after 8 hours of fasting, once at baseline and again after 2 years. Their dietary fat and vitamin D3 intake was measured through a food frequency questionnaire (FFQ) at the 18-month visit.
They found that total fat intake was not associated with the change in blood vitamin D level. But higher MUFA (mono unsaturated fat which is high in olive oil) to PUFA ratio was associated to higher vitamin D level in the blood. Which means that the increase in MUFA rich oils (olive oil and canola oil) may improve the bioavailability (absorption) of vitamin D3 in the intestine.
A limitation for this study is that it is a retrospective analysis, and although their blood measurements were done twice (once at the beginning and once after 2 years), their dietary measurement, the FFQ, was done only throughout the study. Therefore, it is not clear if there were dietary changes over the 2-year period.
The increase in MUFA –rich oils can help to improve the uptake of vitamin D supplements, which may be especially important for the elderly who are at risk of osteoporosis.
The full article title is “Type of dietary fast is associated with the 25-hydroxyvitamind d3 increment in response to vitamin D supplementation.” Published on October 2011 in the Journal of Clinical endocrinology and Metabolism (96 (10) 0000-0000) The authors are S. Niramitmahapanya, s.S. Harris, B. Dawson-Hughes
Written by S. Sefidbakhtand N. Gekhtman, Dept. Nutritional Sciences, Rutgers University-NewBrunswick Edited by SA Shapses, PhD, RD