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Fermented foods have been getting a lot of attention recently. While fermentation has long been used to make food, new research into the gut’s microbiome has highlighted the potential its health benefits.
In a recent Instagram post, Professor Tim Spector, co-founder of personalized nutrition program Zoe, suggested eating a small amount of fermented foods everyday for gut health. He suggested trying to find ways to eat more of the 4 Ks – kefir, kombucha, kimchi, and (sauer)kraut.
So how do fermented foods benefit your health? And are some better than others? Here we dig into the science behind the fermented food trend.
What are fermented foods?
Fermentation involves breaking down sugars and starches in food using microorganisms like yeast and bacteria. These microbes transform the sugars and starches into lactic acid or alcohol. This helps to preserve food, as lactic acid stops the growth of other microbes that rot the food.
As a result of this process, fermented foods contain “good” bacteria called probiotics. These help to support healthy bacteria that already live inside our guts. “The probiotics in fermented foods multiply and grow via the fermentation process,” Lena Bakovic, Registered Dietitian at Top Nutrition Coaching tells Plant Based News. “Probiotics may be of particular benefit for people who already live with digestive issues such as irritable bowel syndrome (IBS).”
Among fermented foods, the 4 Ks are becoming increasingly popular across the globe. Kombucha is a fermented tea drink that can come in many flavors. Kimchi is a Korean condiment made of spicy fermented cabbage. Sauerkraut is another fermented cabbage dish from Germany. It’s a good alternative to kimchi for people who don’t like spicy food.
Kefir is a fermented milk drink made by adding kefir grains to milk. It can be made using sugar water or plant-based milk instead of dairy milk. Ideally the plant-based milk will have enough calories and about 3.5g sugar per 100ml for the microbes to feed on.
Tempeh and miso are both fermented soybean foods. Tempeh is a great protein-rich alternative to meat in many dishes. Miso is usually found as a paste that can be added to sauces and soups.
What is the gut microbiome?
Researchers are beginning to understand just how important the gut is to our overall health. The composition of the microorganisms in the gut is key to this. There are approximately 100 trillion microorganisms in the gastrointestinal tract. There are so many that scientists say this microbiome should basically be considered an additional organ. Most of the microorganisms are bacteria, but some are viruses, fungi, and protozoa (single-celled organisms).
What we eat plays a big role in what microorganisms we have in our guts. Greater diversity of microorganisms is thought to indicate better gut health, making it more resilient to other environmental influences. The health of the gut microbiome has been linked to the health of the immune system, metabolic functions, and even mental health.
Are some fermented foods healthier than others?
In his Instagram post, Spector says “there doesn’t seem to be much difference between” the 4 Ks in terms of the number of bacteria species in each. So when choosing which fermented foods to try, he says, “my advice is this: enjoy the ones you like!”
In a large-scale study of the effects of probiotics on gut health, researchers found that homemade fermented foods are better than many store bought ones for levels of good bacteria. Store bought sauerkraut, kimchi, and soft cheese had none of the good bacteria the researchers were looking for. This is because they would have been pasteurized to make them keep longer and safe to eat. This kills off good bacteria in the process.
The store bought kefir and kombucha, on the other hand, did contain good bacteria, as they were likely not pasteurized. Homemade fermented foods had a diversity of bacteria and in higher levels. But the researchers warn that homemade foods can contain harmful bacteria as well as good, particularly if they aren’t produced or stored properly.
Another caveat, says Bakovic, is to introduce fermented foods into the diet slowly. “If the introduction is a completely new approach for someone, adding in too many at once may produce digestive upset such as bloating or perhaps even gas from the sudden increase of probiotics,” she says. “For these reasons, a gradual introduction is recommended and then once tolerance established, including a variety of fermented food products will provide the most benefit due to the varying strains of probiotics.”
What other foods improve gut health?
Spector’s research with the American Gut Project revealed that the wider the variety of plants you eat, the better your gut health.
The research found that people who ate around 30 different plants a week had far more microbial diversity in their gut than people who ate just 10 types of plants a week. The plants can include not just vegetables, but fruit, nuts, seeds, and grains, as well as herbs and spices.
