Digestibility and Biological Value of Whole Wheat Breads as Compared with White Bread

Abstract

Digestibilities and biological values of the proteins of whole wheat and white breads were determined on ten healthy male subjects averaging 29 years of age. Average daily intake of energy was 2914 kg. cal., distributed, with slight variations, 4.8% to protein, 48.6% to carbohydrate and 46.6% to fat. Six-day periods on egg as the source of 80% of the N alternated with like periods on bread as the source of this fraction. Ten per cent of the N in all periods came from cream and butter and 10% from fruits, vegetables, and accessories. Twenty-four-hour urines were analysed on the last 4 days, feces in one lot for the full period. Three whole wheat breads and one whole wheat cereal biscuit were compared with three white breads. In general the whole wheat breads gave lower true digestibility values for the protein than the white, but at the same time produced higher biological values. One white bread containing 5% non-fat milk solids produced a higher B.V. than a whole wheat with the same milk content. Taking the B.V. of egg proteins as 100% the B.V.'s for the proteins of the four whole wheat breads were: whole wheat cereal biscuit, 81.6; a locally made whole wheat bread containing 5% non-fat milk solids, 77.8; “peeled wheat” bread eaten with extra B vitamins, 79.6; same baked with high vitamin yeast, no other extra vitamins, 81.0; same with ordinary yeast, no extra B vitamins, 77.9. For the white breads: lean white I eaten with the same extra B vitamins as with the “peeled wheat” bread, 75.3; similar bread II eaten with no extra B vitamins, 74.6; white bread containing 5% non-fat milk solids and baked with high vitamin yeast, eaten with no extra B vitamins, 79.8. The results suggest that making bread with “high vitamin” yeast is of some importance from the standpoint of the biological value of proteins; also that eating extra B-complex vitamins improves biological values.