Veggie Blog

Plenty of people take a vitamin every morning without a thought about when or how. Timing and combinations can matter, though, and it is worth knowing which supplements work best with a meal and which should not be taken together. Here are the basics, along with a few popular ideas that are not quite right.

Should you take supplements with food?

For many, yes. Some vitamins are fat-soluble, meaning they dissolve in fat: A, D, E and K. The NIH Office of Dietary Supplements notes that the presence of fat in the gut enhances absorption of vitamin D, although some is absorbed even without it, so taking it with a meal that contains some fat, such as nuts, avocado, dairy or olive oil, makes sense. Taking a multivitamin with a meal is also easier on the stomach, and if a supplement upsets your stomach, taking it with food often helps. Read the label of each product, because the directions differ.

Which supplements should you take at different times?

Calcium and iron are the classic pair. Experts recommend taking calcium and iron supplements at different times, because calcium might interfere with iron absorption. Calcium from supplements is also absorbed best in doses of 500 mg or less, so if you need more than that, splitting it over the day works better than one big tablet. Our guide to taking calcium supplements safely explains how. High iron doses (45 mg a day or more) may also cause nausea and constipation, so more is not better. Vitamin C, on the other hand, helps your body absorb the type of iron found in plant foods, which is useful for vegetarians, so a glass of orange juice with an iron-rich meal is a good habit.

Does taking more help?

No. The ODS says that taking more than you need costs more and might also raise your risk of side effects. Fat-soluble vitamins can build up in the body, and even for water-soluble vitamin C, absorption falls to less than 50 percent at doses above 1 gram a day, with the rest passing out in urine. Check the “upper limit” for each nutrient, and remember to count what you get from fortified foods. Our posts on vitamin C and getting the right amount of vitamins give typical amounts.

Can supplements fix poor digestion?

Some people do have trouble absorbing nutrients. Vitamin B12, for example, needs a protein called intrinsic factor made in the stomach, and the NIH lists surgery on the digestive tract and long-term use of medicines such as metformin or proton pump inhibitors among the causes of deficiency. If you suspect that you do not absorb food well, do not diagnose yourself. See your doctor, who can test your blood. Eating a varied diet rich in whole foods is the best first step, and supplements fill specific gaps. They are not a replacement for finding and treating the cause of a digestive problem.

Do vegetarians need supplements?

Some do. Vegans and vegetarians have a higher risk of vitamin B12 deficiency, because the natural food sources of B12 are limited to animal foods. Fortified breakfast cereals and fortified nutritional yeast are good sources, and many people choose a supplement. The iron requirement is also 1.8 times higher for people who follow vegetarian diets, since the body absorbs less iron from plant foods. See vitamins and your health for more.

How do you choose a safe product?

The FDA does not determine whether dietary supplements are effective before they are marketed. Several independent organizations test products and let those that pass display a seal showing that the product was properly made and contains what the label says, although a seal does not guarantee that it is safe or effective. Tell your doctor and pharmacist about everything you take, because some supplements can increase the risk of bleeding or change your response to anesthesia before surgery. The ODS has a clear consumer guide, Dietary Supplements: What You Need To Know, and a detailed fact sheet on iron.