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 50g glucose (control), 50g glucose plus lupin kernel flour with 12·5g fibre and 22g protein (lupin), or 50g glucose plus 12·5g fibre and 22g protein from soya isolates (soya). Serum glucose, insulin and C-peptide were measured periodically for 4h following beverage consumption. Compared with the control beverage, the 4h post-beverage glucose response was lower (P<0·001), and the 4h 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.