Your patients are drinking onion water: Here’s why

By Anastasia Climan, RDN, CD-N | Fact-checked by Jessica Wrubel
Published March 28, 2023

Key Takeaways

  • People are drinking onion water to fight off colds and viruses.

  • Onions help support a healthy immune system, but onion water is likely to fall short of these promises.

  • Clinicians should ask patients about home remedies and discuss topics like food safety to identify potential hazards.

Onion water is the latest “home remedy” to hit social media, and some TikTokers swear by its ability to prevent and cure respiratory infections.

They advise their audience to make onion water by slicing raw onions, placing them in a jar of filtered water, and letting them soak overnight in the fridge. Drinking the infused water is said to clear congestion and kick the immune system into high gear. But is a cure for the common cold really that simple?

Although onions are undoubtedly healthy, there’s no proof that onion water has curative benefits. Like many fads, the hype surrounding onion water is a case of good science turned on its head. Unfortunately, patients who look to social media every time they get sick could delay effective treatments or even put their health at risk.

Here’s what you should know about the latest trend your patients may be using and how to redirect them on a better path.

How do onions boost the immune system?

The theory behind drinking onion water is based on onion’s natural anti-inflammatory and antimicrobial effects. Along with ginger, garlic, and turmeric, onions are known to fight off inflammation, oxidation, and harmful bacteria and viruses.[]

Onion’s hallmark stinkiness is caused by organosulfur compounds, including quercetin and allicin. These powerful antioxidants inhibit viral replication and reduce oxidant markers in the lungs, making them particularly effective against respiratory illnesses.

Onions are also a good source of the prebiotic fiber inulin. Inulin feeds healthy gut bacteria that serve an important role in the immune system.[] Although the science is still young, promoting beneficial strains of microflora in the gut by eating a diet rich in prebiotics is associated with stronger natural defenses against harmful pathogens. Health benefits may also extend beyond the immune system to metabolism and disease prevention.

Unless an individual is allergic to onions, most people would stand to benefit from eating them more often. Onions fit perfectly into an anti-inflammatory dietary pattern that’s increasingly recommended for overall health.

Is onion water effective?

Onion water videos on TikTok instruct users to drink the infused water and discard the actual onion. However, onion’s health-promoting properties are either fat-soluble or found within its fibrous layers. By discarding the onion, there’s a good chance you’re also tossing potential health benefits in the trash.

For example, both quercetin and allicin are fat-soluble and unlikely to dissolve in water.[][] To extract these compounds from onions, fat (like olive oil) would be a more effective choice than water.

In addition, to take advantage of the immune-boosting benefits of onions, patients must eat raw onions or, better yet, sautee onions in healthy fat and incorporate them into meals. Eating whole onion ensures the consumption of beneficial compounds and pre-biotic fibers that won’t fully make their way into onion water.

Is it safe to drink onion water?

Water infused with onion is likely harmless, especially if the onions are thoroughly cleaned, and the mixture is kept in the refrigerator for a limited time.

However, depending on how your patients prepare onion water, it can easily become a vehicle for food poisoning. After all, onions grow underground and easily trap dirt and bacteria that spread when the layers are sliced. Placing onions in water may encourage bacteria to grow, including those associated with foodborne illnesses, like E. coli

To safely prepare any type of infused water, it’s essential to have clean hands and use a vegetable brush to remove remaining debris and soil. If the cutting board or utensils aren’t properly sanitized, pathogens may be introduced when chopping.[] 

Perhaps one of the most crucial factors is timing the drinking. People should drink infused water within 4 hours if they don’t plan on letting it sit. When solids are left in the water, they should be filtered out within 24 hours, and the refrigerated liquid should be discarded after 3 days.

Immunocompromised patients, young children, and older adults must be particularly cautious to avoid food poisoning. Discussing home remedies with your patients and their caretakers can help you identify potential causes for concern and act as a gateway into conversations about food safety.

What this means for you

Drinking onion water is far from a miracle cure, but this trend brings attention to the beneficial properties of allium vegetables. Clinicians can encourage patients to eat more onions while advising on effective and safe food preparation methods.

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