Overweight and obese men and women who consumed the lupin-enriched bakery experienced decreases in their systolic and diastolic blood pressures of 3.0 and 0.6 mm Hg, according to findings published in the American Journal of Clinical Nutrition.
“These results suggest that a diet moderately higher in dietary protein and fibre can significantly reduce blood pressure,” wrote the researchers, led by Jonathan Hodgson from the University of Western Australia in Perth.
“They also confirm the potential of lupin kernel flour as a novel food ingredient to bring about these outcomes. This approach may be a relatively simple and acceptable dietary measure for helping to reduce cardiovascular risk in overweight and obese persons.”
Lupin flour has been earmarked as the next major competitor to soybean as a high protein source.
Lupin (Lupinus angustifolius L.), is the major grain legume grown in Australia and production exceeds 800,000 tons per year. Used mainly for feed, since 2001 in Australia lupin bran and flour have been used as a substitute in food formulations for more expensive traditional cereal grains.
The average protein content of lupin is just over 30 per cent, compared with 44 to 48 per cent in soybeans. In Europe, the flour is already being used in bakery and pasta products because it can replace eggs and butter to enhance colour and additional potential uses of lupins are in crunchy cereals and snacks, baby formula, soups and salads.
In addition to the protein, lupin flour is also said to contain non-starch polysaccharides which act like both soluble (oat fibre) and insoluble (wheat bran) fibre.
Hodgson and his co-workers recruited 88 overweight and obese men and women with an average age of 57.9 and an average BMI of 30.6 kg/m2, and randomly assigned them to receive either a white bread group or a lupin kernel flour-enriched bread group for 16 weeks. Both interventions contributed between 15 and 20 per cent of the participants’ usual daily energy intake.
At the end of the study, results for the 74 people who completed the study showed that systolic and diastolic blood pressures decreased by 3.0 and 0.6 mm Hg, respectively, in the lupin group. The pulse pressure of participants in the lupin-flour group also decreased by 3.5 mm Hg, but the researchers noted no change in heart rate.
In terms of the mechanism, the researchers could not clarify since “a range of mechanisms may be involved”, they said. One such possibility is the high content of arginine, which is a known precursor for the vasodilator nitric oxide.
“The decrease in blood pressure could result from an improvement in vascular tone mediated by nitric oxide, a potent endothelium-derived relaxing factor,” wrote the authors.
“However, it is difficult to speculate on the mechanisms behind the observed differences in blood pressure, given that multiple factors in the diet - protein, carbohydrate, and fibre - were changed,” they added.
Role for lupin in weight management
Previously, Dr Hodgson has reported that lupin flour may increase satiety and play a role in weight loss. A study from 2006 reported that eating a breakfast containing lupin bread resulted in significantly higher self-reported satiety than the white bread group, and a lower energy intake (488 kJ less) at lunch than the white bread breakfast.
Eating the lupin-enriched bread at lunch also reduced between meal energy intake (1028 kJ less) than the white bread lunch (American Journal of Clinical Nutrition, Vol. 84, pp. 975-980).
Source: American Journal of Clinical Nutrition2009, Volume 89, Pages 766-772“Effects of lupin kernel flour-enriched bread on blood pressure: a controlled intervention study”Authors: Y.P. Lee, T.A. Mori, I.B. Puddey, S. Sipsas, T.R. Ackland, L.J. Beilin, J.M. Hodgson