Vitamins A, D, E and K are fat-soluble and are better absorbed when taken with a meal that contains fat, as are fish oil and CoQ10 (although special formulations of CoQ10 are available which make it water soluble). The key compound in Boswellia serrata extracts (sold as a single-ingredient supplement or in combination with ingredients such as glucosamine and chondroitin in supplements for joint health) is also fat soluble and absorption may be enhanced by taking with fatty foods.
Certain other supplements are best taken with food because it can help to reduce potential side effects. For example, taking magnesium with food can reduce the occurrence of diarrhea and taking iron or SAMe with food can reduce the chance of stomach upset, although food is not needed for their absorption. Preliminary evidence suggests that taking green tea extract with a meal may reduce the chance of potential liver toxicity.
To find out whether a specific supplement is best taken with food, see the What to Consider When Using section in each product review >>
Also see the CL Answer about which types of vitamins should be taken together or separately.