Fans of kimchi, sauerkraut, and kombucha got good news recently, as one European study seemed to show a reduced risk in mortality rates from COVID-19 associated with the regular consumption of fermented vegetables.
The study (which is a preprint of new medical research and has yet to be peer reviewed) compared COVID-19 death rates in different European countries, correlating this data with traditional fermented food consumption in those countries. Researchers found that countries in the Balkans and Scandinavia that traditionally consume a high proportion of fermented foods – specifically fermented vegetables – had lower COVID-19 death rates than countries like France, the UK, and Italy where these vegetables are less frequently consumed. Risk of mortality dropped 35.4 percent for every gram per day increase in the average national consumption of fermented vegetables.
“If the hypothesis is proved, COVID-19 will be the first infectious disease epidemic whose biological mechanisms are proved to be associated with a loss of nature,” writes the team, which concludes that moving away from fermented foods may have “drastically changed” the human microbiome, facilitating the spread and severity of COVID-19.
Experts not linked to the study caution against jumping to conclusions following these preliminary results, which are currently undergoing peer review.
“I think that the connection between fermented food and low mortality rates is just pure coincidence,” says Dr. Giuseppe Aragona, General Practitioner & Family Doctor at Prescription Doctor. “While some foods can help to support the immune system, this cannot stop it from affecting you entirely, or defeat it better.”
Lisa Young, PhD, RDN, nutritionist, author of Finally Full, Finally Slim, and adjunct professor of nutrition at NYU, notes specifically that this study is “shows an association as opposed to a causation."
“I can’t say that it’s a poor study," she says. "However, it set out to show a correlation or association as opposed to cause and effect.”
This study is further complicated as it compares the average diet with mortality rates rather than the diets of the individual people who contracted the virus.
“What if the people who died hated fermented vegetables and just didn't eat them?” says Dr. Nicole Avena, PhD, nutrition and health expert. “As a whole, some countries might consume these foods more than others, but the researchers don't assess individual patients, so we know very little about the impact of diet on the disease based off of this correlative assessment. While the findings are interesting and preliminary, more research is needed before anyone should even begin to think that specific foods can have an impact on death rate from a viral respiratory infection.”
Alicia Galvin R.D., a Resident Dietitian for Sovereign Laboratories, agrees, noting that the study also neglected to explore other risk factors such as exercise rates and obesity rates.
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“I don’t think we can say that if people just consume fermented foods that their risk of having adverse outcomes from COVID will go down. It has to be more of a comprehensive approach than that,” she says. “But what we do know is that the obesity rates of other countries like China are much lower than that of the United States. What we do know is that inflammation and obesity are huge factors in the mortality rate with COVID. So nutrition and overall diet quality does make an impact.”
She also notes that fermented foods can help manage oxidative stress and inflammation, which could theoretically reduce the severity of symptoms, a hypothesis echoed by Dr. Naveen Gupta, M.B.B.S, BSc and co-founder of website The Lifestyle Cure.
"Research indicates a link between alteration in the microbiome and changes in inflammation, immune response and development of lung diseases,” she says. “A less diverse gut microbiome has also been found in the elderly (which COVID has been particularly biased towards) as well many chronic diseases that are risk factors for COVID."
This is echoed by Serena Poon, CN, CHC, CHN, a leading chef, nutritionist and reiki master.
"There are a lot of unknowns around COVID-19 and its symptoms, but based on the quality research conducted on fermented foods over the years, like this systematic review published in 2019, eating fermented foods to optimize health during this time would be safe to say," she says. "I would caution against thinking that anything in your diet would make you completely immune to this virus. The goal is to keep the immune system healthy, balanced and optimal."
Dr. Julia Skinner, founder and director of Root Kitchens, says it "seems to be a promising study at the forefront of what I'm sure will be a deeply explored topic in the years to come."
Whether or not fermented foods are shown to actually reduce the risk of mortality as linked to COVID-19, they’re certainly good to include in your diet.
“A healthy gut keeps the digestive process working smoothly which prevents free radical and toxin build up in the body known to lead to many acute and chronic illnesses,” says Trista Best, a Registered Dietitian at Balance One Supplements. “It is also thought that probiotics secrete substances that trigger the immune system to react more strongly, thereby preventing pathogens from being able to take root and cause illness. All these, and more, make gut health an underrated tool in the overall protection against COVID and other illnesses.”
To add more fermented vegetables to your diet, consider these ten easy home ferments, embrace your own home-fermented kombucha, and pair homemade sauerkraut with your favorite salads, sandwiches and more.
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Please note, when making changes to your health care routine please get professional advice from your primary care physician. The above conversation is for discussion purposes only and is not medical advice. There isn’t a dietary supplement on the market that can cure, treat, or prevent COVID-19 or any disease. It is important to understand that with the ongoing pandemic, there is no one supplement, diet, or lifestyle changes, other than what’s recommended by the CDC including social distancing, hand washing, and hygiene practices, that can prevent you from being infected with the COVID-19 virus. There is no current research that supports the use of dietary supplements to protect you from the COVID-19 virus infection.