African plant foods rich in non-starch polysaccharides reduce postprandialblood glucose and insulin concentrations in healthy human subjects

The effects of two vegetable flours, prepared from the African plants Detar ium senegalense Gmelin, a legume, and Cissus rotundifolia, a shrub, on post prandial blood glucose and insulin concentrations in human subjects, were i nvestigated. Chemical analysis indicated that these flours contained signif icant amounts of NSP. The detarium in particular was found to be a rich sou rce of water-soluble NSP (SNSP). The flours were incorporated into two type s of breakfast meal, a stew meal and a wheat bread meal, containing 50 g an d 70 g available carbohydrate respectively. Both meals also contained 10-12 g NSP, the major fraction of which was SNSP. Control and fibre-rich meals were consumed on separate days in randomized order by two different groups of subjects (n 5, stew meals; n 10, bread meals). Venous blood samples were taken at fasting (0 min) and postprandially at 30 min intervals for 2.5 h and the plasma analysed for glucose and insulin. Compared with the controls , detarium and cissus meals elicited significant reductions (P < 0.006) in plasma glucose levels at most postprandial time points and for area-under-t he-curve (AUC) values (AUC reductions 38-62%). Significant reductions (P < 0.002) in plasma insulin levels at various postprandial time points and for AUC values were also seen after detarium and cissus breads (AUC reductions 43 and 36% respectively), but not after the fibre-rich stew meals. SNSP an d starch are possibly the main, but not the only, components responsible fo r the glucose- and insulin-lowering effects of cissus hour. The main SNSP f raction of detarium, identified as a high-molecular-weight xyloglucan, is l ikely to be a primary factor in determining the physiological activity of d etarium flour.