By Dr Odette Vos

Fermented foods have in recent years, taken social media and the food industry by storm. They have been linked to gut health and improving the gut microbiome, a relatively new and growing topic in the medical field itself.

I have enjoyed experimenting with milk kefir, fermented vegetables, kombucha mixes and adding this to a whole food plant-based diet. But is there truth to this claimed significant health benefits of fermented foods, and how best can we incorporate this into our nutritional education for patients?

What are fermented foods?

Fermented foods are foods that have undergone a natural process of fermentation, where microorganisms like bacteria and yeasts convert sugars and starches into alcohol or organic acids such as lactic acid and acetic acid. This process has been used for millennia to preserve food and enhance its nutritional profile and flavour. There are six primary food fermentation processes, of which lactic acid fermentation from sugars are the most common.

Some popular examples include:

• Yogurt: Created by fermenting milk with specific bacterial cultures.
• Sauerkraut: Finely shredded cabbage fermented by lactic acid bacteria.
• Kimchi: A spicy Korean dish made from fermented vegetables, usually cabbage and radishes.
• Kombucha: A fermented tea drink
• Kefir: A tangy, yogurt-like drink made by fermenting milk with kefir grains. This can also be used to make a water kefir.
• Miso: A fermented soybean paste used in Japanese cooking.
• Sourdough: Sourdough bread is a bread made by the fermentation of dough using a wild lactobacillaceae and yeast starter.

The current evidence behind fermented foods:

The science behind fermented foods is in their ability to produce natural probiotics, antioxidants and other bioactive substrates. These are live microorganisms and phytochemicals that can provide health benefits when consumed in adequate amounts. In a recent up-to-date Systematic Review, Melini et al., (2019) demonstrates the growing body of evidence behind chemical and bioactive substrates produced by certain fermented foods that may explain these health benefits.

1. Improved Digestion

One of the most well-known benefits of fermented foods is their positive impact on digestion. This can be explained by the probiotic activity in fermented milks and certain vegetables and fruit as well as the improved digestibility of proteins. The probiotics found in these foods help break down food more efficiently and improve nutrient absorption. They can alleviate symptoms of digestive disorders such as irritable bowel syndrome (IBS), lactose intolerance, bloating, and constipation.

2. Enhanced Nutrient Absorption

Fermentation can increase the bioavailability of nutrients, making it easier for the body to absorb vitamins and minerals. For example, the fermentation process in foods like miso and sauerkraut enhances the absorption of B vitamins, vitamin K, and certain minerals like iron and zinc. Tempeh, a fermented soybean contains a considerable amount of Vitamin B12, particularly important in patients following predominantly plant-based diets.

3. Anti-hypertensive properties

Fermented milks and grains such as sourdough release ACE- inhibitory peptides that has been linked to improving hypertension. It is important to note that there is a difference between fermentation and pickling, as pickling uses large amounts of salt to preserve food and can thus have the opposite effect on blood pressure due to high salt intake.

4. Boosted Immune System and Anti-allergy potential

A healthy gut is closely linked to a robust immune system. Regular consumption of fermented foods such as fermented milks can enhance the gut barrier function, reduce inflammation, and promote the production of immune cells. Research suggests that probiotics can help prevent respiratory infections and other illnesses.

5. Mental Health Benefits

Emerging studies suggest a strong connection between gut health and mental well-being, often referred to as the “gut-brain axis.” The probiotics in fermented foods may help alleviate symptoms of anxiety and depression by influencing the production of neurotransmitters like serotonin and dopamine.

6. Weight Management and Glycaemic control

Fermented foods can also play a role in weight management. Probiotics may help regulate appetite, improve metabolism, and reduce body fat. Some studies indicate that certain strains of probiotics can assist in weight loss and help prevent obesity. Contrary to public belief, fermented grains, fruits and vegetables do not have high sugar content. Fermented grains such as sourdough bread is classified as a Low GI food, whilst Kombuchas convert most sugars into phenolic compounds that may be important in diabetics for improved glycaemic control.

How to Incorporate Fermented Foods into Your Diet, a doctor- patient discussion:

South Africa, along with a few other countries have included recommendations for consumption of fermented foods into their national dietary guidelines. There is no current evidence that suggests that fermented foods should be excluded in certain age groups, in fact ‘the South African Food-Based Dietary Guidelines (2012) recommend that children from ages 12 months and up have maas or yogurt every day’. (de Waal and van Niekerk., 2024)

We can encourage patients to incorporate simple and easy to come by fermented foods such as yoghurt and fermented vegetables, fruits and grains into their daily diet. Here are a few easy examples.

Breakfast: Start your day with a bowl of yogurt topped with fresh fruits and nuts. Alternatively, try overnight oats made with milk kefir for a tangy twist.

Lunch: Add sauerkraut or kimchi to salads, sandwiches using sourdough bread, or grain bowls for an extra crunch and flavour kick.

Snacks: Choose fermented snacks like pickles or kefir smoothies. They make for a healthy, gut-friendly option between meals.

Dinner: Experiment with miso soup or use fermented sauces like soy sauce or fish sauce to enhance your dishes.

Conclusion:

Fermented foods are a tasty and nutritious addition to any diet. Despite strong emerging evidence of its various health benefits, it is important that we know of the different fermenting processes and what to advise patients. Fermented foods have potential short- and long-term effects on the gut microbiome and as the research in this field grows, we will have a better understanding of the processes by which it influences a healthy gut. We should encourage  patients to incorporating fermented foods into their meals, bearing in mind that not all fermented foods have the same benefits and those commercially produced may have other added ingredients. Experimenting with fermentation at home should also involve food safety as contamination may lead to unwanted bacterial and yeast growths. Fermented foods certainly provide food for thought, so why not take a journey into the world of fermentation and discover the delicious possibilities for yourself?

References:

1. Melini F, Melini V, Luziatelli F, Ficca AG, Ruzzi M. Health-Promoting Components in Fermented Foods: An Up-to-Date Systematic Review. Nutrients. 2019;11(5):1189. doi:https://doi.org/10.3390/nu11051189
2. de Waal P, van Niekerk E. FERMENTED FOODS AND ALLERGY PROTECTION: LESSONS FROM RURAL COMMUNITIES. Current Allergy and Clinical Immunology. 2024;37(2):74-80. Accessed October 21, 2024. https://journals.co.za/doi/pdf/10.10520/ejc-caci-v37-n2-a5
3. Leeuwendaal NK, Stanton C, O’Toole PW, Beresford TP. Fermented Foods, Health and the Gut Microbiome. Nutrients. 2022;14(7):1527. https://pubmed.ncbi.nlm.nih.gov/35406140/