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Foods that have undergone fermentation have greater absorbability than their fresh counterparts, and they are also enriched with a higher concentration of vitamins, probiotics, and other potentially beneficial substances.
Although there is limited research on the full benefits of these products, experts suggest that incorporating fermented dairy products into one’s diet can decrease the risk of developing chronic diseases and help to maintain a healthy weight.
However, individuals who are unaccustomed to consuming fermented foods may need to introduce them gradually to avoid potential stomach discomfort. Furthermore, it is crucial to purchase fermented foods from trustworthy sources to prevent harmful microorganisms from contaminating them as a result of inadequate production methods.
What are fermented products?
The International Scientific Association for Probiotics and Prebiotics, ISAPP, defines fermented products and beverages as those that are produced by the intentional cultivation of microbes and enzymatic conversion of food components that were naturally present in the food.
This means that foods such as yogurt, miso, and bread made with yeast can be classified as fermented products, while vegetables that are pickled in brine or vinegar are not.
What happens to food during fermentation?
Various lactic acid bacteria, molds, and yeasts have the ability to ferment food. These microorganisms metabolize the sugars present in the food, and as a byproduct of their life processes, enrich it with substances such as vitamins, alcohols, carbon dioxide, and organic acids. As a result, the composition of the food changes significantly from its original form.
Methods of food fermentation
There are two main methods of food fermentation:
- The process of natural fermentation involves the transformation of food by microorganisms that are either present in the raw ingredients or on the surface of the container used for preparation. This method is commonly utilized in the creation of various traditional fermented foods, such as sauerkraut and kimchi.
- The process of fermentation by adding starter cultures involves the introduction of a small amount of pre-made culture of microorganisms, like yeast or a starter culture, or a small quantity of already fermented food to the raw ingredients. This approach is typically employed in the production of food, as it enables the creation of products with specific characteristics, such as bread loaves with consistent quality or yogurt containing a particular amount of probiotic microorganisms.
What foods can be fermented
Fermentation is a process that can be applied to nearly any type of food, including meat, fish, milk, vegetables, legumes, and tea. For instance, pu-erh tea is produced through fermentation. Additionally, not only tea leaves, but also pre-brewed sweet tea can undergo fermentation, resulting in the creation of popular drinks such as kombucha.
What are the different types of fermented products?
There are more than 5,000 different types of fermented foods and beverages found worldwide. The use of different microorganisms during fermentation results in significant differences in composition and properties across these products. From a health perspective, they can be categorized into two primary groups:
- Products containing live microorganisms: These are produced using microorganisms that can survive in their own waste products for a long enough period to remain alive when ingested. Examples include yogurt, sour cream, kefir, some cheeses, miso, tempeh, certain types of beer, and fermented vegetables, grains, and sausages that have not been pasteurized or heated.
- Products without live microorganisms: This category includes fermented food that is heated before consumption, such as bread, coffee, or pasteurized fermented vegetables. It also encompasses food created by microorganisms that cannot survive in their own waste, such as wine, most types of beer, and strong alcoholic beverages, as the microorganisms used to make them die in the alcohol. Although fermented products without live microorganisms offer several benefits, they are still considered slightly less healthy. The reasons behind this will be discussed later on.
What Makes Fermented Foods Special?
Fermented products are more satisfying and nutritious than the same products before fermentation.
The microorganisms that perform fermentation consume all available carbohydrates, but they tend to prefer the simplest and most easily digestible ones, such as glucose, fructose, and sucrose.
As a result, fermented products like sourdough bread and yogurt have a lower glycemic index compared to their non-fermented counterparts like grain and milk. This means they lead to a smaller increase in blood glucose levels after eating, which can make the products more satiating and harder to overeat.
Another advantage of microorganisms’ preference for simple sugars during fermentation is that they consume most of the lactose in milk. As a result, people with lactose intolerance can consume some fermented dairy products like cheddar cheese.
Furthermore, microorganisms decompose:
- Certain animal proteins that are difficult to digest, such as casein, which increases the nutritional value of fermented dairy products.
- Antinutrients that hinder the absorption of dietary minerals in plant-based foods, increasing the nutritional worth of fermented dishes made from legumes, such as peas.
Some fermented products contain probiotics.
Probiotics are specific strains of bacteria and yeasts that, when consumed in sufficient quantities, can have a positive impact on human health in the gastrointestinal tract.
In Canada, the Ministry of Health recognizes over 20 types of lactic acid bacteria from the Lactobacillus and Bifidobacterium genera as probiotics, provided that they are present in amounts of no less than 10^9 colony-forming units per serving.
Research has shown that some fermented products that contain live microorganisms, such as kefir and sauerkraut, also contain probiotic microorganisms that can survive long enough to reach the human intestine in a live form, which can be beneficial for health.
An important point to note is that to be classified as a probiotic product, fermented food must meet specific criteria. Experts at ISAPP stress that manufacturers must identify all bacteria and yeasts present in the product down to the strain level, and that the beneficial microorganisms must be present in the required amount throughout the product’s entire shelf life. This means that commercially sold kefir with detailed information on the package can be considered a probiotic product. However, homemade sauerkraut or kimchi that is purchased at the market cannot be considered as such.
In fermented foods, there are more B-group vitamins.
One example is the fungus Rhizopus oligosporus, which enhances the vitamin content of the fermented soybean product tempeh, while the lactic acid bacteria Leuconostoc mesenteroides does so for kimchi. These microorganisms contribute to the appearance of vitamin B12 in fermented products, which is not found in fresh plant products. In fact, sometimes the amount of vitamin B12 can significantly increase in these products, such as in tempeh where 100 grams can provide between 0.7 to 8 mcg, which is higher than the adult daily requirement of 3 mcg of vitamin B12.
Fermented products contain potentially beneficial biologically active substances.
Fermentation leads to the appearance of several compounds in products, some of which have intriguing properties. Laboratory studies suggest that bioactive peptides found in fermented fish may have the ability to dissolve blood clots. If such an effect can be validated in humans in the future, it would provide further evidence for the health benefits of fermented foods.
What do we know about the benefits of fermented foods for health?
The benefits of fermented foods on human health are not yet well-understood, and much of the available evidence centers around the presence of substances known to be beneficial, such as vitamins and probiotics. While many fermented foods have not been studied in depth, dairy products like yogurt and kefir are some of the most extensively researched. A 2021 meta-analysis of 108 studies on dairy products found that 76 studies confirmed the benefits of fermented dairy products on health.
The researchers concluded that fermented dairy products are easily digested, even for people with lactose intolerance. Additionally, there is a consistent link between the consumption of fermented dairy products and a reduced risk of breast cancer, colorectal cancer, and type 2 diabetes. The meta-analysis suggests that these products can help with weight management, strengthen bones, and improve cardiovascular and gastrointestinal health.
It’s worth noting that the benefits of fermented dairy products may not be solely due to their fermentation. It’s possible that people who prioritize healthy eating consume more fermented products of all kinds, not just yogurt and kefir, and that’s why they experience better health outcomes. If future research confirms this hypothesis, then the findings of this study will have implications for the benefits of fermented products more broadly.
Can fermented foods be harmful?
Challenges may occur with any type of food, including those that have undergone fermentation.
Harmful microbes can get into fermented products.
Lactic acid bacteria, yeast, and mold are generally not associated with disease or the production of harmful substances, with very few exceptions. Additionally, their acidic byproduct inhibits the growth of pathogens that may cause foodborne illness. In fact, some experts believe that fermentation was originally developed to preserve food and protect against food infections.
If weakly acidic fermented products, such as some types of cheese, sausage, fish, and kombucha, are not stored or prepared properly, they can become contaminated with harmful microorganisms such as Listeria, Salmonella, and Clostridium. Thus, it is important to adhere to safe preparation guidelines when making fermented food at home, which include the following:
- Use fresh ingredients and wash them before cooking to prevent harmful microbes from already being present in the food.
- Use clean utensils, knives, and cutting boards. If you plan to preserve fermented products, sterilize the jars.
- Prepare the brine correctly with a 1-15% salt solution to ensure optimal multiplication of lactic acid bacteria.
- Adhere to the specified timeframes. For most fruits and vegetables, fermentation usually takes between three to six weeks.
In some fermented products, there are many harmful substances.
Alcoholic beverages are an obvious example of a fermented product that should be consumed in moderation. However, other non-alcoholic fermented foods may also contain components that require caution, such as salt, which can contribute to high blood pressure if consumed in excess.
Furthermore, the fermentation process of cheese, meat, vegetables, soybeans, and wine results in the production of significant amounts of biogenic amines like histamines and tyramines. Although not fully established, it is suggested that consuming such products could induce migraines in individuals who are sensitive to biogenic amines.
How to properly consume fermented products
How much fermented products can you eat?
The dietary guidelines in the United States, Canada, and India solely focus on dairy products, recommending that adults consume two to three servings of any dairy product daily.
In the case of other fermented products, there are no precise instructions, and one must consider the product’s composition and their specific requirements. Nonetheless, on average, it is advisable for most individuals to incorporate one serving of any fermented product into their daily diet. This is due to the possibility that products that contain high levels of probiotics may cause flatulence and abdominal pain if ingested in excessive amounts.
Can children consume fermented products?
Based on international clinical guidelines, children can start consuming dairy products at the age of one.
Between the ages of one and two, it is recommended to consume one and a half to two servings of dairy products per day, while from two to three years, two servings are suggested. For children between the ages of four and eight, it is advisable to consume two and a half servings, and children older than nine years can consume the same amount of dairy products as adults.
There are no specific recommendations for other fermented products. Nonetheless, Portuguese nutrition experts suggest introducing fermented products to children from the beginning of weaning, which is typically around six months of age. According to their viewpoint, allowing a child to taste a little juice from the surface of a spoon can encourage the formation of healthier eating habits. As the child grows, servings can be gradually increased.
Can fermented foods be consumed by pregnant and breastfeeding women?
Pregnant and breastfeeding women are not restricted from consuming dairy or other fermented products and can consume them in the same amounts as any other adult.
For most other fermented products, there are no prohibitions for pregnant women as they can be a valuable source of probiotics. However, it is advisable to avoid unpasteurized products, particularly those from unverified sources, to minimize the risk of foodborne illness.
The only fermented product that pregnant women may need to avoid is kombucha. Although its effects on the health of pregnant women have not been extensively studied, some medical professionals recommend avoiding it. Kombucha may contain a small amount of ethyl alcohol, which is not recommended for pregnant women, and it may also occasionally contain pathogens that a pregnant woman’s body may be unable to handle.
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