With food or without?

Most supplements should be taken with food to reduce the chances they’ll upset your stomach and to stimulate digestion and improve absorption. For a select few, it really doesn’t matter if you take them on an empty stomach. So which ones should you pay attention to?

Iron, magnesium and fish oil supplements are the most common culprits for digestive upset when taken on an empty stomach, so have these with a meal or snack.

Fat-soluble vitamins A, D, E and K are better absorbed when you have them with a meal or snack that contains at least a teaspoon of fat, about 5 grams. The same goes for your multivitamin, which contains these vitamins. If you’re taking your multivitamin with breakfast, make sure you’re having some almond butter with your oatmeal or avocado with your eggs and toast.

For probiotics, preliminary research suggests taking them with a meal or 30 minutes before a meal rather than taking them after eating.

Hydration is also important, Blumberg says. “Fluid intake is especially important for the disintegration of the supplement tablet or capsule and for dissolution of water-soluble nutrients such as vitamin C and B vitamins,” he says. So be sure to wash down all supplements with a tall glass of water.

The main exception to the “take with food” rule for dietary supplements is with certain types of minerals. Only chelated mineral supplements can be taken without food, Levin says. Chelation occurs when a mineral has been bound to an acid, so it doesn’t rely on your stomach acid to break it down. Calcium citrate and magnesium glycinate are the main examples. (If this level of detail is overwhelming, take your supplements with food to cover your bases.)

Christy Brissette is a registered dietitian, nutrition writer, TV contributor and president of 80TwentyNutrition.com.