Health Benefits of Fermented Foods

Written by: Julie Tang, MS, RDN, CNSC

For thousands of years, cultures around the world have used fermentation as a traditional preservation method to extend the shelf life of perishable foods. It was not only an effective way to prevent food from spoilage, but it contributed to a new and unique taste to the human palate. Since then, interest in fermented foods has grown rapidly. Current interest in fermented foods has less to do with food preservation and more to do with links to the health benefits that they provide. Today, our modern food culture reflects this interest in a large variety of consumer products from fermented foods to dietary supplements to beverages. Some of the most common fermented foods we see today are yogurt, kefir, cheese, kimchi, sauerkraut, pickles, and kombucha.

The Basics of Fermentation

Fermentation is an anaerobic process when microorganisms such as bacteria and yeast convert sugars into acids, alcohols, and carbon dioxide. The essential ingredients for fermentation are water, salt, and sugar. Water and salt combined create a solution called brine that kickstarts the fermentation process. Salt plays a pivotal role by preventing the growth of pathogenic microorganisms, controls the rate at which foods ferment, and adds flavor and nutrients. Sugar helps feed the good microbes as they start fermenting the food. The final product of fermentation typically results in a unique tart flavor that is unforgettable. Think of the tartness you may have experienced before when eating certain yogurts, pickles, sauerkraut, kimchi, or even cider and wine.

Understanding Bacteria

There are trillions of microorganisms in our body that make up the microbiome. Imagine the microbiome as a diverse community of live microorganisms that work together to keep us healthy. Within the microbiome, we have some good and some bad bacteria that naturally live inside us. Bad bacteria are what make us sick, while good bacteria are what helps us fight off bad bacteria and keeps us healthy.

In the 1900s, a Russian microbiologist, Elie Metchnikoff, discovered probiotics. Probiotics are a type of good live bacteria that keep our digestive system healthy. We now know that probiotics play various roles in our body, including promoting the health and maintenance of our digestive tract, supporting our immune function, and controlling inflammation.

With further scientific understanding, researchers learned that fermented foods contain probiotics. This was a significant discovery and paved the way for understanding the health benefits of fermented foods. By regularly incorporating fermented foods with probiotics into the diet, we are able to positively influence the population of healthy bacteria in our digestive system. It is believed that an imbalance in the gut microbiome contributes to a number of health problems, including gastrointestinal issues, as well as immune dysfunction and infections. An imbalance can be caused by medical conditions, emotional and physical stress, and the use of antibiotics, which could destroy the good bacteria along with the bad.

Not All Fermented Foods Contain Probiotics

It is important to note that not all fermented foods provide health benefits because some of them do not contain any probiotics. Be aware that the jars of pickles or sauerkraut that are sold off the shelf at the market are sometimes pickled using vinegar and did not go through the natural fermentation process using live organisms, which means they don’t contain probiotics. For foods to be classified as containing probiotics, they must have live bacteria that confer health benefits when consumed in adequate numbers. Be sure to look at the food label for “live and active cultures.” You may also look for the words “naturally fermented” on the label. When you open the jar, be sure to look for signs of bubbles in the liquid, which can indicate it contains live organisms. When handling fermented foods, it is important to practice basic food safety and buy from a trusted source.

Fermented foods that commonly contain probiotics are:

• Cheese (aged or made from raw, unpasteurized milk*)
• Yogurt
• Kefir
• Kimchi (made from fermented cabbage)
• Kombucha
• Miso (made from fermented soybeans)
• Natto
• Pickles
• Sauerkraut (refrigerated, not shelf-stable)
• Tempeh

*Certain groups of individuals are not recommended to eat raw, unpasteurized milk and milk products. Check with a provider if you’re not sure if you fall into that category.

Why Choose Fermented Foods?

Here are the five reasons to add them to your diet

1. They promote gut health

There is emerging scientific evidence of the human gut microbiota and its role in our health. The diversity of the gut microbiota is important, and we are able to increase diversity by including a variety of fermented foods that contain live active cultures. Consumption of foods with good bacteria has been linked to a reduction in gastrointestinal symptoms such as bloating, gas, diarrhea, and constipation (1)(4)(6)(7).

2. A natural boost to the immune system

A healthy gut is vital to keep our immune system strong, reduce infections, and fight chronic inflammation that may lead to certain chronic diseases such as diabetes, neurodegenerative disease and obesity. Research has suggested that healthy adults who were supplemented daily with vitamins plus minerals with probiotics had a shortened duration of common cold symptoms. Additional studies have shown an association between probiotics and reduced duration of illness in subjects with respiratory infectious conditions (9).

3. Restoring gut health after taking antibiotics

Antibiotics are medications that fight against illness-causing bacteria. In the process of treating bacterial infections, they can also kill off good bacteria. Sometimes the side effects of antibiotics affect the digestive system causing symptoms of nausea, loss of appetite and diarrhea. Eating fermented foods with probiotics may help reduce the severity of diarrhea and restore the good bacteria in our gut. In addition, eating foods high in fiber such as whole grains, fruits, vegetables, beans, lentils, and nuts can help promote the growth of good bacteria (8).

4. They often come with vitamins

Fermentation of food and beverages often alter the nutrient profile, including an increase in vitamins. Many fermented foods often provide Vitamin C, Vitamin B2 (riboflavin), Vitamin B9 (folate), Vitamin K, Vitamin B12 (pyridoxine), iron, and zinc (2)(6).

5. A possible role in mental health

The gut-brain system is known to have physical and chemical connections between our gut and brain. They are in constant communication by sending signals from the gut to the brain and vice versa. Emerging studies have shown an association between mental health and probiotics, in which probiotics found in fermented foods may help to reduce symptoms of anxiety and depression. There is increasing interest in microbiota and mental health and more studies are still needed to further understand the relationship (3)(5).

References

1. Chmielewska, A and Szajewska, H. Systematic review of randomised controlled trials: Probiotics for functional constipation. World J Gastroenterol. 2010 Jan 7; 16(1): 69–75.
2. Denter, J and Bisping, B. Formation of B-vitamins by Bacteria During the Soaking Process of Soybeans for Tempe Fermentation. Int J Food Microbiol. 1994 Apr;22(1):23-31.
3. Evrensel, A and Ceylan, M.E. The Gut-Brain Axis: The Missing Link in Depression. Clin Psychopharmacol Neurosci. 2015 Dec; 13(3): 239–244.
4. Guyonnet, D., Schlumberger, A., Mhamdi, L., Jakob, S. and Chassany, O. Fermented Milk Containing Bifidobacterium Lactis DN-173 010 Improves Gastrointestinal Well-Being and Digestive Symptoms in Women Reporting Minor Digestive Symptoms: A Randomised, Double-Blind, Parallel, Controlled Study. Br J Nutr. 2009 Dec;102(11):1654-62.
5. Luna, R.A. and Foster, J.A. Gut Brain Axis: Diet Microbiota Interactions and Implications for Modulation of Anxiety and Depression. Curr Opin Biotechnol. 2015 Apr;32:35-41.
6. Melini, F., Melini, V., Luziatelli, F., Ficca, A.G. and Ruzzi, M. Health-Promoting Components in Fermented Foods: An Up-to-Date Systematic Review. Nutrients. 2019 May; 11(5): 1189.
7. Ritchie, M.L and Romanuk, T.N. A Meta-Analysis of Probiotic Efficacy for Gastrointestinal Diseases. PLoS One. 2012;7(4):e34938.
8. Rodgers, B., Kirley, K. and Mounsey, A. Prescribing an antibiotic? Pair it with probiotics. J Fam Pract. 2013 Mar; 62(3): 148–150.
9. Wang, Y., Li, X., Ge, T., Xiao, Y., Liao, Y., Cui, Y., Zhang, Y., Ho, W., Yu, G. and Zhang, T. Probiotics for prevention and treatment of respiratory tract infections in children. Medicine (Baltimore). 2016 Aug; 95(31): e4509.