Q. When is the best time to take my supplements?

A. The short answer: Whenever you can make it a habit to take your supplements will end up being the best time for you. Dietary supplements that sit forgotten on your counter can't help you, so choose a convenient time and stick with it.

If you're aiming for an optimal experience, though, the answer gets a tad longer and more involved.

Unless the label says otherwise, most supplements are better taken with food, typically at breakfast or dinner. This improves absorption and minimizes stomach irritation. In particular, taking B-complex vitamins with food will help to prevent queasiness; and calcium absorption improves when taken after a meal.

Only a few supplements are best taken on an empty stomach. One is iron (although the small amount of iron in a multi-vitamin/mineral is fine to take with food). Probiotics are another, but check your label, because a few varieties can be taken with meals. Proteolytic, or digestive, enzymes (such as bromelain or protease) fight inflammation best when taken on an empty stomach. (But take with meals if using them as a digestive aid.)

Keep in mind that alcohol interferes with the absorption of many nutrients, so it's best to take your supplements at a meal that won't include alcohol. And if you're using iron supplements, avoid taking them with coffee or tea, which can interfere with absorption.

This Q&A was written by Victoria Dolby Toews, MPH, author of the The Soy Sensation (McGraw-Hill, 2002) and The Green Tea Book (Avery, 1998).