Garlic (Allium sativum) is a plant related to onions, leeks, and chives. Fresh garlic is commonly used to add flavor to foods. It also has a long history of use for a broad range of purported health benefits: from a natural antiseptic to cancer prevention. As a dietary supplement, garlic is commonly promoted for cardiovascular health and to reduce blood pressure and cholesterol. It’s also marketed to support or boost the immune system, act as a “cold blaster,” and offer support for the “cold and flu season.”

There isn't enough evidence to show whether garlic as a dietary supplement can support or boost immune health.

Garlic’s health benefits supposedly come from a sulfur compound called allicin (also responsible for garlic’s odor and pungent taste). This compound is present in fresh, raw garlic, but the heat of cooking removes the allicin. Due to the strong odor and taste of raw garlic, garlic supplements might seem an appealing alternative to eating raw garlic.

Dietary supplement products sometimes list garlic as “standardized” to a specific allicin content, as an “aged garlic extract” (a process that removes the garlic odor), or as an amount equivalent to a fresh garlic bulb. The way in which garlic supplements are formulated varies, and questions remain regarding the actual health benefits of garlic in supplement form.

Can garlic supplements support or boost your immune health?

Very little research has been done to show that healthy individuals taking garlic dietary supplements throughout the cold and flu season experience fewer cold episodes or flu symptoms. Evidence is lacking to show whether you are at any less risk of getting sick during the winter months if you take such supplements on a daily basis. What would be considered an effective amount for any specific health benefit is currently unknown.

Can garlic supplements negatively affect your health and performance?

In general, dietary supplement products with garlic in amounts comparable to what you might consume in foods (up to 1–2 cloves a day) appear to be well tolerated by healthy adults. Common adverse effects (to either raw garlic or as a dietary supplement) include stomachache, body odor, bad breathe, and nausea. There is some concern of possible increased risk of bleeding or allergic reactions. Garlic also might interact with certain medications (such as blood thinners), as well as other plant-based supplements, so talk with a healthcare professional before you take a garlic supplement.

The bottom line

There is insufficient evidence to support claims for garlic as a dietary supplement to support or boost immune health. Always speak with a healthcare practitioner before you use any dietary supplement, and always look for third-party seals on products. And remember, no dietary supplement can be legally marketed to diagnose, treat, cure or prevent any disease or health condition, including flu, colds, and COVID-19 (such as the “cold blaster” mentioned above). However, adding a bit of garlic to your meals is always a healthy option.

The information in this article is only related to the use of garlic as a single dietary supplement ingredient by healthy individuals looking to support immune health and does not represent the evidence for garlic in combination with other ingredients. Unfortunately, little or no evidence is available regarding the various combinations of ingredients found in such products.

 

Updated 1 December 2022

References

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Crawford, C., Brown, L. L., Costello, R. B., & Deuster, P. A. (2022). Select dietary supplement ingredients for preserving and protecting the immune system in healthy individuals: A systematic review. Nutrients, 14(21), article 4604. doi:10.3390/nu14214604

Josling, P. (2001). Preventing the common cold with a garlic supplement: A double-blind, placebo-controlled survey. Advances in Therapy, 18(4), 189–193. doi:10.1007/bf02850113

Lissiman, E., Bhasale, A. L., & Cohen, M. (2014). Garlic for the common cold. Cochrane Database of Systematic Reviews(Issue 11), article CD006206. doi:10.1002/14651858.CD006206.pub4

Nantz, M. P., Rowe, C. A., Muller, C. E., Creasy, R. A., Stanilka, J. M., & Percival, S. S. (2012). Supplementation with aged garlic extract improves both NK and γδ-T cell function and reduces the severity of cold and flu symptoms: A randomized, double-blind, placebo-controlled nutrition intervention. Clinical Nutrition, 31(3), 337–344. doi:10.1016/j.clnu.2011.11.019

Percival, S. S. (2016). Aged garlic extract modifies human immunity. The Journal of Nutrition, 146(2), 433S–436S. doi:10.3945/jn.115.210427