Effect of wheat bran on serum lipids: Influence of particle size and wheatprotein

Objective: Wheat fiber appears to protect from cardiovascular disease despi te ifs lack of consistent effect on serum lipids. We therefore wished to de termine whether reported inconsistencies in the effect of wheat bran result ed from differences in particle size or its high gluten content. Methods: Two studies were conducted. In one-month metabolic diets, 24 hyper lipidemic subjects consumed breads providing an additional 19 g/d dietary f iber as medium or ultra-fine wheat bran and extra protein (10% of energy as wheat gluten). In two-week ad libitum diets, 24 predominantly normolipidem ic subjects consumed breakfast cereals providing an additional 19 g/d of di etary fiber as coarse or a mixture of ultra-fine and coarse wheat bran with no change in gluten intake. Both studies followed a randomized crossover d esign with control periods when subjects ate low-fiber breads and cereals r espectively with no added gluten. Fasting blood lipids were measured on day zero and at the end of each phase. Results: Wheat bran had no effect on total, LDL or HDL cholesterol irrespec tive of particle size or level of gluten in the diet. However, consumption of increased gluten in the metabolic study was associated with a 13+/-4% re duction in serum triglycerides (p=0.005) which was not seen in the normal-g luten ad libitum study. Conclusions: The protective effect of wheat fiber in cardiovascular disease cannot be explained by an effect of wheat bran in reducing serum cholester ol although in hyperlipidemic subjects displacement of carbohydrate by glut en on the high-fiber phases was associated with lower serum triglycerides.