A new Italian study reveals which everyday foods are packed with prebiotics—and how much we actually eat—laying the groundwork for better gut health and disease prevention through targeted nutrition.
Study: Quantification of Naturally Occurring Prebiotics in Selected Foods. Image Credit: alicja neumiler / Shutterstock.com
In a recent study published in the journal Nutrients, researchers quantified the amount of prebiotics in different foods and estimated daily prebiotic intake in an Italian population.
What are prebiotics?
Prebiotics are non-digestible dietary components that promote the growth and activity of beneficial bacteria in the gastrointestinal (GI) system. Recently, the International Scientific Association of Probiotics and Prebiotics has clarified the definition of prebiotics as substrates selectively fermented by the gut microflora that confer health benefits to the host.
Some examples of prebiotics include lactulose, lactosucrose, oligofructose, and insulin. Fructo-oligosaccharides (FOSs) and galacto-oligosaccharides (GOSs), which promote the growth of Bifidobacteria and Lactobacilli, are also widely studied prebiotics for their role in maintaining normobiosis in the GI tract and enhancing the integrity of the intestinal wall.
Prebiotic supplementation has been shown to increase mineral absorption, reduce inflammation, support metabolism, and reduce the risk of colorectal, laryngeal, and gastric cancers. Despite these observations, few epidemiological studies have investigated the impact of prebiotics on different health outcomes due to the lack of publicly accessible data on the prebiotic content in foods.
Study design
In the current study, researchers created a comprehensive and analytically consistent database on the prebiotic content of 35 foods, including fruits and nuts, legumes and soy-based foods, and cereal products.
Within these food products, the amount of three types of FOSs, including kestose, nystose, and 1 F-β-fructofuranosylnystose, as well as raffinose and stachyose content, both of which are GOSs, was measured using high-performance anion-exchange chromatography with pulsed amperometric detection (HPAE-PAD). HPAE-PAD is a highly sensitive analytical method that allows for low quantification limits ranging from two µg up to 50 mg for every 100 grams, depending on the type of food.
The daily intake of prebiotics was also determined in a cohort of 100 healthy individuals from a case-control study on colorectal cancer conducted in Italy between 2017 and 2019. These estimates were based on dietary information collected from the study participants through a validated food frequency questionnaire.
An overview of prebiotic content in food products
FOSs were mostly abundant in cereal products, with wheat bran containing the highest amounts of kestose and nystose, whereas and whole-meal rye flour exhibited higher levels of 1 F-β-fructofuranosylnystose.
Among fruits and nuts, kestose was present in steamed chestnuts and raspberries, whereas nystose was detected in blueberries. Moreover, 1 F-β-fructofuranosylnystose was undetectable in all analyzed fruits and nuts. GOSs were detected in steamed chestnuts, raisins, and dried shelled walnuts.
Although kestose was present in toasted soybeans, no other legumes had detectable levels of FOSs. In contrast, GOSs were most abundant in legumes, especially dried soy products. Raffinose was the most abundant GOS detected in toasted soybeans, whereas stachyose was present in dried soy textured vegetable proteins.
All analyzed cereal products had detectable levels of raffinose, with wheat bran containing the highest amount and amaranth grains containing the lowest amount. Stachyose was present in amaranth grains, shelled millet grains, oat flour, quinoa grains, and wheat bran.
Dietary intake of prebiotics
The mean daily intakes of FOSs and GOSs were 0.236 and 0.371 grams, respectively. Overall, wheat bran, raspberries, chestnuts, walnuts, raisins, soy milk, and soy yogurt accounted for 3.9% of kestose, 1.2% of nystose, 0% of 1F-β-fructofuranosylnystose, 15.5% of raffinose, and 8.3% of stachyose total intake.
Conclusions
Both wheat bran and whole-meal rye cereals, as well as root vegetables, were identified as the richest sources of prebiotic FOSs. Comparatively, legumes, particularly dried soy products, had the highest levels of GOSs.
Gut dysbiosis refers to a disruption in gut microbiota, which is associated with cardiovascular disorders, gut inflammatory disorders, and digestive tract cancers. Foods rich in prebiotics have been shown to reduce the risk of these diseases, thus highlighting the potential health benefits that can be conferred following the regular consumption of prebiotic-enriched foods.
The study findings are being compiled and added to the Food Composition Database for Epidemiological Studies in Italy to facilitate future research on the impact of prebiotic intake on various health outcomes. These data, combined with additional studies clarifying this association, can inform dietary guidelines and public health interventions.