Fermented Foods

By: Jeremy Partl, Registered Dietitian

Summertime is here. In 2020, the year of the coronavirus, things haven’t really looked the same. But, there’s no doubt that summer will still include our favorite foods and beverages. Who doesn’t like the sauerkraut on their hotdog or bratwurst, a nice yogurt and berry parfait, and the classic staple of a crisp, refreshing beer on a hot summer evening? These foods are here to stay, even in the midst of a pandemic.

One commonality between all these items is that they are considered fermented foods. Recently, Western societies have shown a renewed interest in fermented foods due to supposed health benefits. We have taken the traditional indigenous fermented foods, such as tepache, dahi, bhalle, papad, idli, and dosa, foods made in rural and tribal areas with historic knowledge and locally available raw materials, and started to turn fermentation into a global, industrial-sized production.

The goal of this article is to clear the picture on whether or not fermented foods are as beneficial for our health as suggested by their rising popularity.

What are Fermented Foods

Fermentation is a process that dates back thousands of years, playing major roles in food preservation (alongside drying and salting), food quality modification, and culinary enjoyment (owing to the distinct flavors, aromas, and textures of fermented foods).^[1] Fermentation is the process of turning complex organic substances into simpler compounds through microorganisms, including bacteria (e.g., Lactobacillus, Streptococcus, Enterococcus, Lactococcus, and Bifidobacterium) and molds (e.g., Aspergillus oryzae, Aspergillus sojae, Penicillium roqueforti and Penicillium chrysogenum), and yeasts (e.g., Saccharomyces cerevisiae, Candida krusei , and Candida humilis).

There are many products around the world that are a result of fermentation, either occurring naturally or through a starter culture. Each of these foods has different bacterial and yeast species present, which create unique flavors and textures.

Below are some of the most common fermented products that you may be familiar with:

These foods are some of the most familiar to westernized societies. However, there are also many other traditional fermented foods that have been consumed and passed down for generations.

Western consumers in countries like the United States have come to appreciate fermented food products in part for their unique tastes and the representation of different cultures. In addition, there has been an increasing demand for fermented food products for their supposed health benefits, which I will explore below.

Health Benefits

Despite their highly proclaimed benefits, research on the health benefits of fermented foods is still relatively new and not that solid in human models. Early research on fermented foods has suggested that they can be beneficial, potentially reducing the incidence and duration of respiratory infections, bringing improvements to bone, liver, body mass, and blood pressure indices, preventing digestive problems, and even improving skin health.^[2], ^[3]

Whether research will continue to show health benefits, the mechanisms for improved health from fermented foods—to the extent that such benefits are causal—come from the living organisms they contain. Here are some of the ways that fermented foods potentially positively impact human health.

Production of the “Biotics”

One of the most intriguing concepts related to the growing interest in fermented food products is the facilitation of healthy gut microbiota—sometimes called gut flora. With regard to the “biotics,” we are primarily talking about the production of probiotics and prebiotics. Putting it simply, probiotics are the “beneficial bacteria” that are present in the gut microflora. Probiotics are fed by prebiotics, which are non-digestible food ingredients that stimulate the growth or activity of one or a limited number of the bacterial species residing in the colon. This relationship is referred to as synbiotic, in which probiotics and prebiotics are used in combination to improve the viability of probiotic bacteria while conferring the benefits of both the live microorganism and prebiotics.^[4]

One of the ways that the production of the “biotics” is helpful is through the “gut-brain axis,” which is essentially the connection between the microflora in our GI tract and our brain. Because the gut microbiome is responsible for the production of a wide array of neurotransmitters- like dopamine, serotonin, and norepinephrine- consumption of fermented foods has been found useful in improving mood and cognitive function while reducing symptoms of depression and anxiety. ^[5], ^[6], ^[7]

Additionally, the gut microbiota can ferment soluble dietary fiber and βeta-glucans into Short Chain Fatty Acids, such as butyrate, propionate, and acetate. These are important to the normal function of the human body in terms of regulation and the metabolism of glucose and lipids, promoting mineral absorption, and reducing the prevalence of inflammatory diseases and anti-oxidative functions. ^[8], ^[9]

Increased Digestibility, Accessibility, and Enrichment of Nutrients

Fermentation can make digestion of food much easier on the body by pretty much “pre-digesting” the compounds found in foods. Practically, this can help to reduce cooking times. It can also allow nutrients to be digested and absorbed better.

Through enzymatic degradation, fermentation works to soften tissues and cell walls to loosen and break down the proteins and carbohydrates found in our foods. As a result, fermentation can make foods easier to digest, increase the nutritional value of foods, and actually enhance our bodies to extract nutrients (through increased absorption or by removing unwanted substances) without deteriorating the food quality (as compared to thermal, chemical and mechanical processes).^[10]

This is particularly important for individuals who struggle with lactose-intolerance or who might have a gluten-intolerance. Products like yogurt, cheese, and sourdough bread have been shown to be better tolerated in individuals who struggle with these issues because the respective sugars and proteins (lactose and gluten) are already digested, and their content is lowered. While individual responses are different, sometimes people with these issues could potentially enjoy fermented dairy and grain products with fewer or no symptoms.^[11], ^[12]

Fermentation can help to enrich the nutrient content of foods, including macro- and micro-nutrients like essential amino acids, fatty acids, vitamins, and minerals. Some examples of how this can play out:

• After fermentation, the amino acid profile of kefir contained higher contents of lysine, proline, cysteine, isoleucine, phenylalanine, and arginine.^[13]
• Certain Bifidobacteriaand Lactobacilli strains can produce isomers of Conjugated Linoleic Acid (CLA) in fermented milk and derived dairy products, promoting the well-backed ability to enhance health in a variety of ways.^[14]
• The profile of carbohydrates can undergo dynamic changes during fermentation. For example, the content of total dietary fiber and the proportion of insoluble and soluble fibers in fermented legumes can be modified, the content of certain sugars that have high colonic fermentability may increase, and low calorie sweetness like xylitol can be produced via fermentation. ^[15], ^[16], ^[17]
• Fermented foods generally contain significantly higher amounts of vitamins and minerals than their raw counterparts. In addition, their bioavailability for utilization is actually enhanced a well. For example, fermented dairy foods have high amounts of calcium, chloride, sodium, phosphorus, potassium, and zinc naturally, but these minerals may be enriched and/or have increased availability due to fermentation.

Adding to these changes, fermentation does a good job of removing unwanted substances to help increase micronutrient uptake. There are naturally occurring “anti-nutrients” like enzyme inhibitors, glucosinolates, lectins, tannins, polyphenols, phytic acid and saponins that are present in plants that can harm our bodies by impairing the intake, digestion, absorption or utilization of other foods and nutrients. However, the fermentation process works to reduce the amount of these unwanted substances.

For example, the presence of phytate in the human diet has a negative effect on mineral uptake. However, fermenting corn for 14 days was found to reduce the phytic acid content while simultaneously increasing the extraction of calcium, phosphorus, iron, and manganese. ^[18]

Antioxidant Activity

In general, fermentation increases the antioxidant activity of foods by producing different compounds that are created by various raw materials, fermenting agents, and processing conditions. Take, for example, the origin of the milk: milk fat content and fermenting microorganism strains can release bioactive peptides following the digestion of milk proteins and subsequently increase the antioxidant activity of fermented dairy products. ^[19] Antioxidants like phenolic compounds, vitamin C, carotenoids, and other compounds are protective against oxidative damage that can lead to the onset and development of most age- and diet-related chronic diseases.^[20] In addition, the fermentation of grain-based foods, fruits, and vegetables can increase the antioxidant activity via the production of greater amounts of phenolic compounds, GABA, and bioactive peptides. ^[21]

Anti-Diabetic Properties

Small amounts of research have elucidated a slight anti-diabetic potential with the consumption of fermented foods. ^[22]

The mechanisms may be related to changes in the gut microbiome, phenolic content, antioxidants, and GABA, as well as changes in the starch matrix. Specifically, lactic acid deriving from the fermentation sourdough reduces the starch bioavailability, and consequently, the glycemic index of grain-based products. In addition, acetic acid and propionic acid can slow gastric emptying.^[23], ^[24]

Anti-Hypertensive Properties

An increase in the prevalence of hypertension has increasingly pushed the food industry toward the development of innovative food products with reduced sodium content.

One unique intervention found that sourdough fermentation had the ability to mask decreased salt content (thanks to the production of flavoring free amino acids) and enrich products with functional anti-hypertensive compounds. ^[25]

In addition, studies have shown that fermented milks can have a blood pressure-lowering effect through the inhibition of the Angiotensin-Converting Enzyme. ^[26]

Conclusion

While the science and research on the effects of fermentation on human health are still early, there is plenty of mechanistic rationale to include fermented foods into your diet. And, there is little downside; there does not seem to be much harm in including fermented foods into your diet.

You don’t necessarily have to go out of your way and purchase a $10 Kombucha drink from the store, but it would be good to include fermented foods like yogurt, cheese, pickled vegetables, etc. into a well-varied diet.

References

^[1] Xiang, H., Sun-Waterhouse, D., Waterhouse, G. I., Cui, C., & Ruan, Z. (2019). Fermentation-enabled wellness foods: A fresh perspective. Food Science and Human Wellness, 8(3), 203-243.

^[2] Mota de Carvalho, N., Costa, E. M., Silva, S., Pimentel, L., Fernandes, T. H., & Pintado, M. E. (2018). Fermented foods and beverages in human diet and their influence on gut microbiota and health. Fermentation, 4(4), 90.

^[3] Chilton, S. N., Burton, J. P., & Reid, G. (2015). Inclusion of fermented foods in food guides around the world. Nutrients, 7(1), 390-404.

^[4] Xiang, H., Sun-Waterhouse, D., Waterhouse, G. I., Cui, C., & Ruan, Z. (2019). Fermentation-enabled wellness foods: A fresh perspective. Food Science and Human Wellness, 8(3), 203-243.

^[5] Melini, F., Melini, V., Luziatelli, F., Ficca, A. G., & Ruzzi, M. (2019). Health-promoting components in fermented foods: An up-to-date systematic review. Nutrients, 11(5), 1189.

^[6] Mota de Carvalho, N., Costa, E. M., Silva, S., Pimentel, L., Fernandes, T. H., & Pintado, M. E. (2018). Fermented foods and beverages in human diet and their influence on gut microbiota and health. Fermentation, 4(4), 90.

^[7] Kim, B., Hong, V. M., Yang, J., Hyun, H., Im, J. J., Hwang, J., … & Kim, J. E. (2016). A review of fermented foods with beneficial effects on brain and cognitive function. Preventive nutrition and food science, 21(4), 297.

^[8] Mota de Carvalho, N., Costa, E. M., Silva, S., Pimentel, L., Fernandes, T. H., & Pintado, M. E. (2018). Fermented foods and beverages in human diet and their influence on gut microbiota and health. Fermentation, 4(4), 90.

^[9] Zhao, X., Jiang, Z., Yang, F., Wang, Y., Gao, X., Wang, Y., … & Zhu, Y. (2016). Sensitive and simplified detection of antibiotic influence on the dynamic and versatile changes of fecal short-chain fatty acids. PloS one, 11(12).

^[10] Xiang, H., Sun-Waterhouse, D., Waterhouse, G. I., Cui, C., & Ruan, Z. (2019). Fermentation-enabled wellness foods: A fresh perspective. Food Science and Human Wellness, 8(3), 203-243.

^[11] Poutanen, K., Flander, L., & Katina, K. (2009). Sourdough and cereal fermentation in a nutritional perspective. Food microbiology, 26(7), 693-699.

^[12] Solomons, N. W. (2002). Fermentation, fermented foods and lactose intolerance. European journal of clinical nutrition, 56(4), S50-S55.

^[13] Menestrina, F., Grisales, J. O., & Castells, C. B. (2016). Chiral analysis of derivatized amino acids from kefir by gas chromatography. Microchemical journal, 128, 267-273.

^[14] Johnson, M. E., & Steele, J. L. (2013). Fermented dairy products. In Food Microbiology (pp. 825-839). American Society of Microbiology.

^[15] Nair, N. U., & Zhao, H. (2010). Selective reduction of xylose to xylitol from a mixture of hemicellulosic sugars. Metabolic engineering, 12(5), 462-468.

^[16] Frias, J., Penas, E., & Martinez-Villaluenga, C. (2017). Fermented pulses in nutrition and health promotion. In Fermented Foods in Health and Disease Prevention (pp. 385-416). Academic Press.

^[17] Nishiwaki, M., Kora, N., & Matsumoto, N. (2017). Ingesting a small amount of beer reduces arterial stiffness in healthy humans. Physiological reports, 5(15), e13381.

^[18] Sokrab, A. M., Ahmed, I. A. M., & Babiker, E. E. (2014). Effect of fermentation on antinutrients, and total and extractable minerals of high and low phytate corn genotypes. Journal of food science and technology, 51(10), 2608-2615.

^[19] Fardet, A., & Rock, E. (2018). In vitro and in vivo antioxidant potential of milks, yoghurts, fermented milks and cheeses: a narrative review of evidence. Nutrition research reviews, 31(1), 52-70.

^[20] Fardet, A., & Rock, E. (2018). In vitro and in vivo antioxidant potential of milks, yoghurts, fermented milks and cheeses: a narrative review of evidence. Nutrition research reviews, 31(1), 52-70.

^[21] Melini, F., Melini, V., Luziatelli, F., Ficca, A. G., & Ruzzi, M. (2019). Health-promoting components in fermented foods: An up-to-date systematic review. Nutrients, 11(5), 1189.

^[22] Sivamaruthi, B. S., Kesika, P., Prasanth, M. I., & Chaiyasut, C. (2018). A mini review on antidiabetic properties of fermented foods. Nutrients, 10(12), 1973.

^[23] Liljeberg, H. G., Lönner, C. H., & Björck, I. M. (1995). Sourdough fermentation or addition of organic acids or corresponding salts to bread improves nutritional properties of starch in healthy humans. The Journal of nutrition, 125(6), 1503-1511.

^[24] Liljeberg, H., & Björck, I. (1998). Delayed gastric emptying rate may explain improved glycaemia in healthy subjects to a starchy meal with added vinegar. European journal of clinical nutrition, 52(5), 368-371.

^[25] Peñas, E., Diana, M., Frías, J., Quílez, J., & Martínez-Villaluenga, C. (2015). A multistrategic approach in the development of sourdough bread targeted towards blood pressure reduction. Plant foods for human nutrition, 70(1), 97-103.

^[26] Jauhiainen, T., & Korpela, R. (2007). Milk peptides and blood pressure. the Journal of Nutrition, 137(3), 825S-829S.