Western diets generally contain too much refined carbohydrates, in the form of bread and cereals. Refined carbohydrates have been increased at the expense of whole grain carbohydrates many of which are also good sources of vegetable proteins. Evidence suggests that this substitution has been a disaster for public health and is contributing to the epidemic of obesity, cardiovascular disease and diabetes that is putting a heavy burden on health care systems. Substituting refined carbohydrates in the diet for whole grains has been shown to provide health benefits because of the high levels of fibre contained within the bran. In addition, raising the protein level of diets has also been shown to benefit health including weight loss and beneficial blood pressure changes. Incorporating whole grains with high protein contents to the diets may therefore produce health benefits.
Research1 has investigated the effects of moderately increasing protein and fibre levels on blood pressure, by substituting lupin kernel flour for normal refined wheat flour in bread. Eighty eight overweight and obese men and women were fed their normal diet for a two week baseline period. After this time subjects substituted 15 to 20% of the calories of their normal diet with normal white bread (control) or bread made with 40% lupin flour and 60% wheat flour. The bread supplied 9 MJ per day which was roughly four 40 gram slices of bread. The main differences between the bread were the high protein and fibre, but lower carbohydrate content of the lupin flour enriched bread. The mean differences between the lupin and control bread for protein, fibre and carbohydrate were 13.7 grams per day, 12.5 grams per day and -19.9 grams per day, respectively.
After 16 weeks, subjects consuming the lupin bread had a 3.0 mm Hg reduction in systolic blood pressure and a 0.6 mm Hg rise in diastolic blood pressure compared to the control. Pulse pressure was also 3.5 mm Hg lower in those subjects consuming lupin bread. These results suggest that increasing protein and fibre content of the diet might produce favourable blood pressure reducing effects. The subjects in this study were in the normal to mildly hypertensive range of blood pressure and so the results support previous findings that show a decrease in systolic blood pressure of ≈1-1.5 mm Hg per 13 grams of fibre added to the diet. Other studies have predicted that increasing protein by 14 grams per day might lower mean systolic blood pressure by ≈1 mm Hg and that reducing carbohydrate by 20 grams per day might lower mean systolic blood pressure by ≈0.5 mm Hg per day.
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