β2-1 fructans are considered to be prebiotics. Current literature indicates that β2-1 fructans may modulate some aspects of immune function, improve the host's ability to respond to certain intestinal infections, and modify some inflammatory outcomes in human subjects. However, there is a need to find out more about the modulation of immune markers by β2-1 fructans in humans. Healthy human subjects aged 45–65 years were randomly allocated to β2-1 fructans (Orafti® Synergy1; 8 g/d; n 22) or the digestible carbohydrate maltodextrin as placebo (n 21) for 4 weeks. Blood, saliva and faecal samples were collected at study entry and after 4 weeks. Immune parameters were measured using the blood and saliva samples and bifidobacteria were measured in the faecal samples. Faecal bifidobacteria numbers increased in the Orafti® Synergy1 group (P < 0·001) and were different at 4 weeks from numbers in the placebo group (P = 0·001). There was no significant effect of Orafti® Synergy1 on any of the immune parameters measured (blood immune cell subsets, total serum Ig, salivary IgA, neutrophil and monocyte phagocytosis of Escherichia coli and respiratory burst in response to E. coli or phorbol ester, natural killer cell activity, T cell activation and proliferation, production of six cytokines by T cells). It is concluded that, compared with maltodextrin, Orafti® Synergy1 has a bifidogenic effect in healthy middle-aged human subjects but does not alter immune responses examined in the absence of an in vivo immune challenge.

β2-1 Fructans are carbohydrate molecules with prebiotic properties. Through resistance to digestion in the upper gastrointestinal tract, they reach the colon intact, where they selectively stimulate the growth and/or activity of beneficial members of the gut microbiota. Through this modification of the intestinal microbiota, and by additional mechanisms, β2-1 fructans may have beneficial effects upon immune function, ability to combat infection, and inflammatory processes and conditions. In this paper, we have collated, summarised and evaluated studies investigating these areas. Twenty-one studies in laboratory animals suggest that some aspects of innate and adaptive immunity of the gut and the systemic immune systems are modified by β2-1 fructans. In man, two studies in children and nine studies in adults indicate that the adaptive immune system may be modified by β2-1 fructans. Thirteen studies in animal models of intestinal infections conclude a beneficial effect of β2-1 fructans. Ten trials involving infants and children have mostly reported benefits on infectious outcomes; in fifteen adult trials, little effect was generally seen, although in specific situations, certain β2-1 fructans may be beneficial. Ten studies in animal models show benefit of β2-1 fructans with regard to intestinal inflammation. Human studies report some benefits regarding inflammatory bowel disease (four positive studies) and atopic dermatitis (one positive study), but findings in irritable bowel syndrome are inconsistent. Therefore, overall the results indicate that β2-1 fructans are able to modulate some aspects of immune function, to improve the host's ability to respond successfully to certain intestinal infections, and to modify some inflammatory conditions.