Quantification of Naturally Occurring Prebiotics in Selected Foods

Background: Prebiotics are non-digestible dietary compounds, defined as substrates that are utilised by host microorganisms conferring a health benefit. Although fructo-oligosaccharides (FOSs) and galacto-oligosaccharides (GOSs) are among the most studied prebiotics and support intestinal normobiosis, comprehensive data on their content in foods remain limited. Objectives: The objective was to quantify the content of FOSs (kestose, nystose, and 1 F-β-fructofuranosylnystose) and GOSs (raffinose and stachyose) in 35 foods, including fruit and nuts, legumes, and cereals. We also estimated the intakes of prebiotics in an Italian population. Methods: We analysed the prebiotic content in foods using high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD). We estimated the prebiotic intake of 100 healthy controls from a case-control study on colorectal cancer conducted in Italy between 2017 and 2019. We used dietary information collected through a food frequency questionnaire and the prebiotic data quantified in this and a previous study. Results: FOSs were mostly detected in cereal products, with wheat bran and whole-meal rye flour containing the highest amount (around 0.7 g/100 g each). GOSs were most abundant in legumes, especially in dried soy products (around 4.0 g/100 g each). Mean daily intake was 0.236 g for total FOSs and 0.371 g for total GOSs. Wheat bran, raspberries, chestnuts, walnuts, raisins, soy milk, and soy yoghurt overall 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 intakes. Conclusions: The present study enables the development of a comprehensive database on prebiotic content in foods through a consistent analytical method. This makes prebiotic intake assessments more accurate than previously available data and facilitates future epidemiological studies investigating their potential effects on health.