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Winter 2024

What’s the Scoop? Questions and Answers About Dietary Supplements

Are any supplements such as vitamin C and zinc helpful for the common cold?

Woman with cold

Dietary supplements won’t prevent or treat illnesses such as the common cold. However, some supplements might help somewhat. For example, taking vitamin C supplements on a regular basis might decrease cold symptoms and reduce the number of days a cold will last. And zinc lozenges may speed recovery from the common cold if you take them for a few days at the start of a cold.

Learn more about these supplements and others in our fact sheet, Dietary Supplements for Immune Function and Infectious Diseases.


When is the best time of day to take supplements?

Supplement bottles and capsules

The time of day you take dietary supplements doesn’t usually matter––find a time that works for you. Some supplements can interfere with the absorption of medications. If you take any medications, ask your health care provider if you should take your supplements and medications at different times.

Many supplements, such as vitamin D and fish oil, are better absorbed with a meal. And in some cases, certain nutrient combinations can affect absorption. For example, taking an iron supplement with a beverage that contains vitamin C, such as orange juice, can increase iron absorption.
On the other hand, taking iron at the same time as calcium can hinder iron absorption.

We recommend talking with your health care provider and following the directions on product labels.

Have more questions about things to consider when taking dietary supplements? See our fact sheet, Dietary Supplements: What You Need to Know.

For more information about calcium, iron, vitamin C, vitamin D, fish oil, and other dietary supplements, see our Dietary Supplement Fact Sheets.

Habla español?

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Consulte nuestra información basada en la ciencia para ayudarle a tomar las mejores decisiones para su salud con respecto al uso de suplementos dietéticos.


Do you or someone you know prefer to get health information in Spanish? See our science-based dietary supplement information in Spanish.


Pills in shape of question Mark


Have more questions about dietary supplements?

Send your questions to ODS:



About ODS

The Office of Dietary Supplements (ODS) is part of the National Institutes of Health (NIH), the nation’s medical research agency—supporting scientific studies that turn discovery into health.

Contact Us

Office of Dietary Supplements
National Institutes of Health
6705 Rockledge Drive (Rockledge I)
Room 730, MSC 7991
Bethesda, MD 20817