Yogurt is a fermented food, containing live cultures of specific bacteria. What are they? What role do they play? Let’s take a look at the fermentation and ferments’ effect on health.
What is fermentation?
Ferments are live agents, such as a bacteria or yeast, that causes fermentation, a process that has been used throughout history to preserve food, enhance the taste or the health benefits of food (1).
Many food products are the result of a fermentation carried out by bacteria and yeasts naturally found in the food or added. Cheese, yogurt, milk kefir, are dairy fermented foods (1-3).
A huge variety of fermented foods has been developed throughout history, including vegetables, cereals and breads, soybean products, fish products, and meats and we can distinguish:
- Fermented foods without live microorganisms at the time we eat/drink them: bread, wine, cocoa or coffee beans, for instance.
- Fermented foods with live microorganisms: sauerkraut, kimchi, kefir, yogurt, cheese, kombucha, or miso for example.
Consuming fermented food may also contribute to gut microbiota and its diversity, which is important for good health (5). The gut microbiome is composed of trillions of microorganisms that shelter in the gut and play a key role in maintaining the health of the host such as modulation of the immune system, helping to fight infections and even protecting against cancer.
The microbes in fermented food may help prevent infections by harmful bacteria in the gut by out-competing them in the gut environment.
Fermented foods consumption can exert changes to the gut microbiome in as little as 24 hours and help to minimise disruptions of gut microbiota balance
Focus on the specific ferments of yogurt
Yogurt is produced by the lactic fermentation of milk by two specific live bacteria. Lactobacillus Delbrueckii subsp. Bulgaricus and Streptococcus Thermophilus, which shall be viable, active and abundant in the product (4,7).
The fermentation process produces lactic acid by predigesting lactose into glucose and galactose resulting in the decrease of pH and the coagulation of milk casein proteins. This sets the milk into the gel-like signature texture of yogurt. Lactic acid fermentation also produces compounds such as carbon dioxide, peptides and amino acids which give yogurt its specific taste.
The decreased pH results in higher absorption of minerals such as calcium as it makes them more bioavailable.
Yogurt is also an interesting source of minerals for lactose intolerant people, as they are generally able to tolerate yogurt better than other dairy thanks to the pre-digestion of lactose, (5,6,8).
Fermentation in yogurt releases a wide range of metabolites such as:
- Hight amount of vitamin B
- Bioactive peptides which are antioxidants
- Exopolysaccharides (EPS) and Conjugated Linoleic Acid (CLA) which provide health benefits such as anti-inflammatory and immune system modulatory properties.
Ferments and probiotics: the same?
Probiotics are defined as: “Live microorganisms that, when administered in adequate amounts confer a health benefit on the host”.
A fermented food may be described as a “probiotic food” only if:
- It contains live microorganisms at the time it is eaten,
- Those microorganisms (bacterial or yeast strains) are well defined and have shown a health benefit in a scientific study, and
- The strains are present in the final food product in sufficient numbers to confer the health benefit.
In the case of yogurt, the live cultures do provide health benefits. Several studies show that yogurt with live active cultures may significantly enhance lactose digestion and reduce symptoms of intolerance in people with lactose maldigestion.
The European Food Safety Authority (EFSA) has approved the claim that yogurt improves digestion of lactose. According to EFSA, yogurt must contain at least 108 Colony Forming Units (CFU) of live microorganisms ((L. bulgaricus and S. thermophilus) per gram of yogurt, to obtain these probiotic beneficial effects (9).
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