No evidence that red onion and Coca-Cola infusion cures the flu; drinking soda is linked to adverse health outcomes

Key takeaway

Scientific evidence shows that drinking sugar-sweetened beverages like Coca-Cola is associated with adverse health outcomes including cardiovascular diseases and type 2 diabetes. While onions do possess some nutritional benefits, there isn’t evidence that mixing them with Coca-Cola creates a remedy for the flu or its associated symptoms.

Reviewed content

Verdict:

Unsupported

Claim:

Drinking an infusion of red onion and Coca-Cola can cure the flu

Verdict detail

Inadequate support: There isn’t sufficient evidence to indicate that an infusion of red onions and Coca-Cola can cure the flu. On the contrary, drinking a caffeinated beverage like Coca-Cola may exacerbate dehydration caused by the flu.
Factually inaccurate: Scientific evidence shows that drinking sugar-sweetened beverages like soda is associated with cardiovascular disease and diseases that cause memory loss such as dementia and Alzheimer’s.

See our method of evaluation

Full Claim

“Mix Coca-Cola with onion and you will never use another remedy again [...] You can take it every night before going to sleep, and you can fight the flu quickly and effectively [...] Some studies claim that Coca-Cola can improve the memory and functioning of the heart.”

“Natural” flu remedies often attract widespread attention online, though scientific evidence for their effectiveness may be sparse. In one such example, a Facebook reel shared in late August 2024 claimed that an infusion of Coca-Cola and red onions could be used as a remedy for the flu. Variations of this claim previously appeared on Instagram and TikTok, where the posts racked up tens of thousands of interactions.

The reel also claimed that there are studies showing that Coca-Cola can improve memory and heart health.

As we will explain below, both of these claims are unsupported by scientific evidence.

Onions are often touted as a “natural cure” for various illnesses in viral social media posts

Science Feedback previously reviewed claims regarding the alleged health benefits of onions, including a claim that a natural remedy using onions could replace the flu shot and that placing raw onions on the feet can cure illnesses such as the common cold or flu.

As we explained in these previous claim reviews, eating onions as part of a balanced diet can have some health benefits. Onions contain the compound quercetin, which possesses antioxidative and anti-inflammatory properties. They’re also rich in nutrients like vitamin C, which help to support a healthy immune system. And as the reel itself accurately points out, onions are a source of potassium, which helps to maintain healthy cell function.

However, as we addressed in these earlier reviews, we found there is no scientific evidence proving that onions can cure or alleviate symptoms of diseases such as the flu.

The claim about the Coca-Cola and red onion infusion follows this trend about the alleged health benefits of onions. The reel stated that if you “take [the infusion] every night before going to sleep […] you can fight the flu quickly and effectively”.

To determine whether there was evidence for the efficacy of this specific infusion, we conducted a few different searches on PubMed, a repository of publications maintained by the U.S. National Library of Medicine. Our searches included combinations of the terms “onion”, “soda”, “Coca-Cola”, and “sugar-sweetened beverage” with “flu” and “influenza”. These searches yielded no results.

Further, it’s important to note that caffeinated beverages like Coca-Cola can have a dehydrating effect. Because dehydration is already a concern when someone is sick with the flu, medical centers such as the Cleveland Clinic recommend steering clear of such beverages in favor of hydrating with water, broths, herbal teas, and fruit juices.

Drinking sugar-sweetened beverages is associated with adverse health outcomes

The claim that Coca-Cola can “improve memory and functioning of the heart” is false. Indeed, scientific evidence has routinely shown that drinking sugar-sweetened beverages (SSBs) like soda has the opposite effect and is linked to numerous adverse health outcomes, including heart disease. According to the U.S. Centers for Disease Control and Prevention (CDC):

“Frequently drinking sugar-sweetened beverages is associated with weight gain, obesity, type 2 diabetes, heart disease, kidney diseases, non-alcoholic liver disease, tooth decay and cavities, and gout, a type of arthritis.”

This is further supported by evidence from numerous studies.

In one umbrella review evaluating SSB consumption of more than 22 million individuals, Lane et al. found “direct associations between greater sugar-sweetened beverage consumption and higher risks of adverse health outcomes” including cardiovascular disease, type 2 diabetes, and depression^[1].

Another umbrella review evaluating studies of tens of thousands of individuals found that SSBs were associated with a higher risk of cardiovascular disease^[2].

And a review of multiple studies found “strong evidence” for an association between SSB consumption and coronary heart disease, type 2 diabetes, and non-alcoholic fatty liver disease^[3].

Scientific evidence also indicates that SSBs don’t improve memory; rather, that these drinks may do the opposite.

In one study of nearly 4,000 individuals, Pase et al. found that those who consumed higher amounts of SSBs had smaller total brain volume, a marker of preclinical Alzheimer’s disease^[4]. And in a different study of nearly 3,000 individuals, Pase et al. found that a higher intake of artificially-sweetened beverages (such as diet sodas) was associated with a higher risk of stroke, all-cause dementia, and Alzheimer’s disease^[5]. While the correlation between SSBs and dementia doesn’t demonstrate a causal effect, it does suggest the improbability of Coca-Cola’s ability to improve memory.

Conclusion

Onions do have some health benefits, but we couldn’t find evidence to support the claim that red onions alone or infused with Coca-Cola can counteract the flu. Existing scientific evidence also directly contradicts the claim that a sugar-sweetened beverage like Coca-Cola improves heart health or memory.

REFERENCES

• 1 – Lane et al. (2024) Sugar-Sweetened Beverages and Adverse Human Health Outcomes: An Umbrella Review of Meta-Analyses of Observational Studies. Annual Review of Nutrition.  
• 2 – Diaz et al. (2023) Artificially Sweetened Beverages and Health Outcomes: An Umbrella Review. Advances in Nutrition.
• 3 – Malik and Hu. (2022). The role of sugar-sweetened beverages in the global epidemics of obesity and chronic diseases. Nature Reviews Endocrinology.
• 4 – Pase et al. (2017) Sugary beverage intake and preclinical Alzheimer’s disease in the community. Alzheimer’s & Dementia.
• 5 – Pase et al. (2017) Sugar- and Artificially Sweetened Beverages and the Risks of Incident Stroke and Dementia: A Prospective Cohort Study. Stroke.