Answer:Although many supplements can be taken on an empty stomach, certain supplements should be taken with a meal (i.e., just before, while eating or immediately after eating) to improve absorption or to allow them to act on the food itself (such as some cholesterol-lowering supplements). For other supplements, it may be preferable to take them with a meal or snack to reduce side effects.
To improve absorption:
As explained in our Reviews of each, vitamins A, D, E and K are fat-soluble and are better-absorbed when taken with a meal that contains fat. The same is true of CoQ10, curcumin (from turmeric), CBD, and even fish oil. If you must take these without a meal, there are special formulations of CoQ10 and curcumin that can improve their absorption by making them more water-soluble. (For information about taking multivitamins or combinations that contain both fat-soluble and water-soluble ingredients, see our article about when to take a multivitamin).
The key compound in Boswellia serrata extracts, AKBA, is also fat-soluble, and absorption may be enhanced by taking it with a fatty meal. (AKBA is often sold in combination with ingredients such as glucosamine and chondroitin in supplements for joint health.)
It is best to take fat-soluble supplements with a meal that contains significant amounts of oils and/or fats, which for many people, tends to be lunch or dinner. There needs to be enough fat to stimulate the release of bile acids into the intestine, as these aid the absorption of fats and fat-soluble ingredients.
To reduce side effects or as needed for efficacy:
It may be preferable to take certain other supplements with food to reduce potential side effects, although food is not needed for their absorption and, in some cases, may slightly decrease absorption of the supplement (or the supplement may decrease absorption of nutrients in the food). Such supplements can be taken with whichever meal or snack is most convenient, as the fat content doesn't have a significant effect.
For example, taking magnesium with food can reduce the occurrence of diarrhea, and taking vitamin C, iron or SAMe with food can reduce the chance of stomach upset.
Keep in mind that there are vitamin C formulations and iron formulations that may be less likely to cause stomach upset. Be aware that taking iron with certain foods can decrease its absorption.
Beta-sitosterol (used to reduce symptoms of prostate enlargement) may be taken with food to reduce gastrointestinal side effects, but if you are taking beta-sitosterol to reduce cholesterol, it must be taken with food.
Although protein supplements do not have to be taken with food, consuming protein drinks with a meal (rather than between meals) after resistance exercise may help to increase muscle and reduce fat.
Preliminary evidence suggests that taking green tea extract (i.e., from a pill) with a meal may reduce the chance of potential liver toxicity. Be aware that green tea (as a beverage) may reduce the absorption of iron from iron-containing food and iron supplements. Similarly, iron from food or supplements may reduce the absorption the active constituent in green tea.
To find out whether a specific supplement is best taken with food, see the What to Consider When Using section in each product review >>