Q: Is it necessary to have some fat in a meal for the body to absorb fat-soluble nutrients such as vitamin D?
A: Probably at least a small amount of fat, though the research is not clear and many variables are involved. The key difference between fat-soluble vitamins (A, D, E, K) and water-soluble ones (C and the Bs) is that the former are stored in the liver and fatty tissues and are eliminated much more slowly than the latter, which need to be consumed more regularly.
Some studies have found that high-dose vitamin D supplements are better absorbed with a very high-fat meal than with a very low-fat meal, but some others have not found a difference in the vitamin’s absorption.
The evidence is somewhat clearer for beta carotene, a fat-soluble precursor to vitamin A. Studies have found, for instance, that beta carotene in a salad is much better absorbed when regular dressing is used instead of nonfat dressing, or when avocado is included.
Keep in mind, many factors affect the bioavailability of nutrients, notably other nutrients and compounds in the food or meal, what you ate earlier, whether the vitamin is in a food or a pill, and your body’s needs.
If you have a varied, nutritious diet, none of this should be a concern, unless you have a medical condition that affects nutrient absorption.
Originally published June 2012. Updated August 2019. This article first appeared in the UC Berkeley Wellness Letter.
Also see Nutrients: They’re Team Players.