Lupin and soya reduce glycaemia acutely in type 2 diabetes

Addition of fibre or protein to carbohydrate-rich foods can reduce the glycaemic response to those foods. This may assist with glycaemic management in individuals with type 2 diabetes. Lupin is a legume rich in fibre and protein. We assessed the acute effects of lupin- and soya-based beverages on glucose and insulin responses in type 2 diabetic individuals. We hypothesised that the lupin and soya beverages would lower the acute glycaemic response compared with a control beverage containing no protein or fibre, and that lupin would reduce the postprandial glucose more than soya. In a randomised, controlled, cross-over trial, twenty-four diabetic adults (nineteen men and five women) attended three testing sessions, each 1 week apart. At each session, participants consumed a beverage containing 50 g glucose (control), 50 g glucose plus lupin kernel flour with 12·5 g fibre and 22 g protein (lupin), or 50 g glucose plus 12·5 g fibre and 22 g protein from soya isolates (soya). Serum glucose, insulin and C-peptide were measured periodically for 4 h following beverage consumption. Compared with the control beverage, the 4 h post-beverage glucose response was lower (P < 0·001), and the 4 h post-beverage insulin and C-peptide responses were higher (P < 0·001) for lupin and soya. Glucose (P = 0·25) and C-peptide (P = 0·07) responses did not differ significantly between lupin and soya, but lupin resulted in a lower insulin response compared with soya (P = 0·013). Adding lupin or soya to a carbohydrate-rich beverage reduces glycaemia acutely in type 2 diabetic individuals. This may have a beneficial role in glycaemic management.