Flu Busters: Can Fermented Foods Keep You Healthy?

Fermented foods are known for their numerous health benefits, such as aiding digestion, lowering the risk of developing diabetes, maintaining mental health, and helping to maintain a healthy body weight. But did you know that they can also help fight the flu? It makes sense when you consider that around 70 to 80 percent of your immune system is located in your gut. By consuming fermented foods rich in beneficial bacteria, you can keep your immune cells functioning optimally.

One specific healthy bacterium in fermented foods that may protect you from the flu’s worst effects is lactic acid.

Lactic Acid: A Flu-Fighting Weapon

A study conducted at Georgia State University (GSU) found that lactic acid reduces the severity of the flu in mice. Prior research had already proven lactic acid’s ability to combat bacteria and viruses. It has been shown to provide protection against Streptococcus pneumoniae (which can cause pneumonia), colds, and the flu. The GSU researchers aimed to add to the supporting evidence for lactic acid’s effectiveness in fighting pathogens.

In the study, mice were treated with a type of lactic acid called Lactobacillus casei DK128 and then infected with a strain of the influenza A virus. The mice that received this lactic acid bacteria displayed a significant level of protection against the flu. They had more immune cells to clear harmful debris from their lungs and nasal passages. Furthermore, they produced more virus-fighting antibodies to combat the replicating virus. These antibodies also developed immunity to other strains of the influenza virus, resulting in reduced inflammation and lower levels of inflammation-producing proteins called cytokines.

Ultimately, the mice treated with lactic acid had 18 times fewer influenza viruses in their lungs than untreated mice, making them less likely to lose weight or die as a result of the virus.

Sources of Flu-Fighting Lactic Acid

If you want to try using lactic acid to help your body fight off the flu, it’s easy to find in various healthy, tasty, and safe fermented foods. You should incorporate these foods into your diet to promote good health, regardless of the time of year. Some sources of lactic acid include:

  • Yogurt
  • Kefir
  • Sauerkraut
  • Tempeh
  • Pickled vegetables
  • Sourdough bread
  • Miso
  • Red wine
  • Kombucha

In addition to fermented foods, exercise is another source of lactic acid. So, staying active during flu season can also help boost your immune system.

A Word of Caution

It’s important to note that consuming too much lactic acid can potentially lead to a dangerous and sometimes fatal condition called lactic acidosis. This condition has been observed in people who have overexercised. However, the chances of developing lactic acidosis from eating fermented foods are minimal unless you consume excessive amounts daily.

Instead of overindulging in fermented foods at every meal, make a point to eat or drink something fermented each day. This could be a bowl of yogurt for breakfast, a serving of sauerkraut with lunch, or a kombucha as a mid-afternoon snack. By doing so, you’ll be promoting good health and keeping the flu at bay.


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  • J. Jung, et al. “Heat-killed Lactobacillus casei confers broad protection against influenza A virus primary infection and develops heterosubtypic immunity against future secondary infection.” — Scientific Reports, 2017.
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