Life Extension Magazine®

Peeled onions that are rich in sulfur for immune boosting

Superfoods: Onions

Onions provide sulfur and important antiviral and immune-boosting properties. Their compounds support heart health and bone density and may reduce the risk of certain cancers.

Scientifically reviewed by: Holli Ryan, RD, LD/N, in August 2023. Written by: Laurie Mathena.

Chopped onions are notorious for making your eyes water. But their health benefits are nothing to cry over.

A member of the allium family of vegetables (which also includes garlic and leeks), onions have important antiviral and immune-boosting properties.

They are a good source of sulfur, which is important for detoxification and protein synthesis.

Onions also contain compounds that help support heart health, reduce the risk of certain cancers, and can even improve bone density.

Heart Health

Studies have shown that onions improve numerous factors associated with heart health.

Red onions in particular contain anthocyanins, which give them their deep red color. People who consume high amounts of anthocyanins have a lower risk of heart attacks.1

Onions also contain small amounts of a beneficial flavonoid called quercetin.

Animal studies have indicated that consuming onions can reduce heart disease risk factors like inflammation,2 high triglycerides,3 and blood clot formation.4

Cancer Prevention

A meta-analysis that included 16 studies and more than 13,000 people showed that compared to those with the lowest intake, people with the highest intake of onions had a reduced risk of colorectal cancer.5

Another meta-analysis showed that people who consumed the most allium vegetables (like onions and garlic) were less likely to be diagnosed with stomach cancer, compared to those with the lowest intake.6

This cancer protection is likely due to onions’ sulfur-containing compounds (which have been shown to decrease the growth and spread of tumors in test tube studies7) and flavonoids like quercetin8 and fisetin9 (which may inhibit tumor growth).

Boost Bone Density

Consuming onions could possibly help prevent osteoporosis by decreasing bone loss and boosting bone mineral density.

In one study of perimenopausal and postmenopausal women, those who ate onions at least once a day had greater bone density than those who only ate them once a month or less. And compared to women who never ate onions, those who ate them most frequently decreased their risk of bone fracture.10


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  3. Plant Foods Hum Nutr. 2006 Dec;61(4):179-85.
  4. Food Chem Toxicol. 2013 Jul;57:99-105.
  5. Mol Nutr Food Res. 2014 Sep;58(9):1907-14.
  6. Mol Nutr Food Res. 2015 Jan;59(1):171-9.
  7. Mol Nutr Food Res. 2016 Nov;60(11):2467-80.
  8. Oncol Rep. 2017 Aug;38(2):819-28.
  9. Exp Ther Med. 2018 Mar;15(3):2667-73.
  10. Menopause. 2009 Jul-Aug;16(4):756-9.