Prebiotics are nondigestible polysaccharides and oligosaccharides that stimulate the growth of beneficial bacteria in the digestive system. Prebiotics are considered to be functional foods in that they provide numerous health benefits and aid in the prevention and treatment of diseases and health conditions.
A dietary substance should satisfy the following physiological properties in order to be defined as a prebiotic:
- Resist degradation by gastric acid and enzymatic degradation by pancreatic and intestinal enzymes.
- Should be selectively fermented by intestinal beneficial bacteria like lactobacilli and bifidobacteria, thus promoting their proliferation and/or metabolic activity.
Lactulose and most soluble fibers meet these criteria and are considered prebiotics. Another group of prebiotics are inulin-like prebiotics. These oligosaccharides (also called inulin-like fructans) include inulin, fructo-oligosaccharides (FOS), and galactooligosaccharides (GOS).
In a 2012 review article, the journal 3 Biotech stated that “The introduction of functional compounds like prebiotics in the diet seems to be an attractive alternative to ameliorate the quality of life ridden with obesity, cancer, hypersensitivity, vascular diseases, and degenerative ailments.” Examples of food sources rich in prebiotics are Chicory root, Onions, Oatmeal, Wheat bran, Asparagus, Dandelion greens, Jerusalem artichoke, bananas, barley, and apples.
Chicory root is an extraordinary source of prebiotic fiber inulin. Inulin promotes gut bacteria, which aids digestion and reduces constipation. Chicory roots have been reported to induce hypocholesterolemia, protect against hepatocellular damage and inhibit lipid peroxidation. It also has an antihyperglycemic effect, regulates appetite and carbohydrate and lipid metabolism.
Dry roots of chicory and cichorium flowers. Image Credit: Nata Studio / Shutterstock
Onions are immune-boosting foods rich in fructans. They consist of inulin and FOS, which strengthen the digestive flora and help with fat breakdown. Raw onions also contain chromium. This boosts insulin production, vitamin C, and quercetin, which fights off free radicals. Onions are believed to have anticancer and antibiotic properties and may prove beneficial in heart diseases.
Whole oats are rich in beta-glucan fibers and resistant starch, and are a great source of prebiotics. Oats increase healthy gut bacteria, which improves overall digestion. They also lower the levels of LDL cholesterol and stabilize blood glucose levels. Oats help control weight by promoting satiety.
Wheat bran contains arabinoxylan-oligosaccharides (AXOS), which elicits the prebiotic effect. AXOS fiber modulates intestinal fermentation and overall gastrointestinal properties in healthy humans. Wheat bran consumption has been associated with an increase in fecal bifidobacteria levels, which help in improving digestion and strengthening the immune system.
Asparagus is a great source of inulin and promotes the growth of healthy bacteria in the gut. Asparagus has a strong radical scavenging capability and hence might be used to diminish radicals in the body and consequently prevent certain cancers, as well as aging.
Dandelion greens support gut flora as it contains constituents, such as inulin that act as a prebiotic. Dandelion also has antioxidant and anti-inflammatory activities that result in diverse biological effects. Studies have shown them to possess lipid-lowering and anticancer activities too.
A bunch of fresh dandelion greens. Image Credit: Andris Tkacenko / Shutterstock
Popularly known as sunroot or sunchoke, Jerusalem artichoke has impressive fiber content and has been associated with increased Bifidobacterium populations in the colon. Studies have also shown it to have a potential use in the prevention of type 2 diabetes and non-alcoholic fatty liver disease. The positive effect on lipid profile and glucose tolerance may be attributed to their inulin content.
Jerusalem artichoke. Image Credit: Valentyn Volkov / Shutterstock
Bananas are packed with a wide variety of vitamins, minerals, fiber, and prebiotics. The slightly unripe variety of bananas contains the highest concentration of resistant starch and prebiotics, which boost healthy gut bacteria and help to get rid of bloating.
Barley is a cereal grain with high β-glucan levels, which boost the levels of beneficial bacteria in our gut. β-glucans have also been proven to possess immune-modulating properties and beneficial effects on obesity, cardiovascular diseases, diabetes, and cholesterol levels.
The prebiotic effect of Apples is due to pectin, which is beneficial for the development of fermentative processes in the large intestine.
The high content of phenolic compounds in apple peels makes them a valuable source of antioxidants. Regular consumption of one or more apples a day can help reduce the risk of lung and colon cancer.