Not only digestion depends on intestinal health but also, through connections and biological processes, the proper functioning of the brain, the immune system, mood and body weight. This is why it is important to take care of the microbiota, which is the set of bacteria that make up our intestine. In this regard, it is important to take probiotics and prebiotics through the diet. Probiotics are live microorganisms that, once ingested, populate the microbiota. Prebiotics, on the other hand, are parts of food that are not digested but nourish the good bacteria of the microbiota, supporting and strengthening them. So today let's talk about prebiotics, their properties and in which foods they can be found.
Prebiotics, what they are and properties
The first definition of prebiotics was given in 1995 by Glenn Gibson and Marcel Roberfroid. Specifically, the two scientists state that a prebiotic is a non-digestible food ingredient that positively affects the host by selectively stimulating the growth and activity of one or a limited number of bacteria in the colon, while also improving the health of the host. These non-digestible substances, generally belonging to the group of carbohydrates, and in particular fibers, are degraded by the bacteria of the microbiota to obtain energy useful for survival. In general, the bacteria in the microbiota that most benefit from taking prebiotics are Lactobacilli and Bifidobacteria, the classic good bacteria of the gut. The microbiota, well nourished, can therefore carry out its function, including fighting pathogens and guaranteeing the integrity of the intestine (Davai Davari et al, Foods, 2019). But the function of prebiotics certainly does not end there. In fact, after the prebiotics are degraded by the microbiota, by-products are released, including lactic, butyric and propionic acid and peptidoglycan. These substances enter the bloodstream and bring their benefits to the body. For example, propionic acid supports the action of T Helper 2 cells, which are a type of white blood cell of the immune system, in the airways. Peptidoglycan stimulates the innate immune system, which is our first line of defense, against the threats of pathogenic microorganisms. The by-products of prebiotics also have an action on the brain, improving memory and reducing anxiety. Not only that, prebiotics are able to reduce inflammation and cardiovascular risk (Davai Davari et al, Foods, 2019).
Prebiotics and bones
The role of prebiotics on calcium absorption is more debated. In fact, some studies have observed that the intake of prebiotics is able to increase the absorption of calcium with benefits for the bones and skeleton. The fact that other studies have not reported this effect is probably due to differences in the studied population sample. In particular, adolescents and postmenopausal women may be more receptive than others to changes in the microbiota and exhibit greater calcium absorption following taking prebiotics due to their higher requirement of this mineral, but other studies will need to follow to shed some light on this aspect (Carlson et al, Curr Dev Nutr, 2018).
Prebiotics, food sources
Prebiotics are contained in several foods, including asparagus, garlic, chicory, onion, artichokes, Jerusalem artichoke, whole wheat, honey, banana, barley, tomato, rye, peas and beans (Davai Davari et al, Foods, 2019). For example, the intake of two bananas a day led to an increase in the microbiota of bifidobacteria (Slavin, Nutrients, 2013). There are also prebiotic supplements, however care must be taken and never exaggerated, as possible side effects following a high intake of prebiotics are diarrhea, abdominal bloating and cramps (Davai Davari et al, Foods, 2019).