Lead researcher Dr. Kevin Maki told NutraIngredients.com that such a reduced response may translate into the blood pressure reduction observed in the obese/ high-BMI people participating in the study.
Dr. Maki, formely with Radiant Research, Chicago, and now with Provident Clinical Research, wrote in the European Journal of Clinical Nutrition: "The results of the present trial suggest beneficial effects of foods containing beta-glucan from oats on carbohydrate metabolism, and on blood pressure in obese subjects."
Beta-glucan, a non-starch polysaccharide found in oats, has been the subject of increasing attention with some reports showing the soluble fibre can decrease LDL-C levels.
The new study, funded by the Quaker Oats Company, focussed on 97 men and women with systolic and/or diastolic blood pressure of 130-179 mmHg and 85-109 mmHg, respectively. The average age of the subjects was 60 and the average BMI was 32.4 kg per sq. m.
The subjects were randomly assigned to foods containing oat beta-glucan or control foods (maltodextrin) for 12 weeks in a double-blind, controlled design.
Peak insulin levels were found to have decrease after 12 weeks of consuming beta-glucan-containing foods, while the control group's levels were not significantly changed, said the researchers.
Blood pressure was not changed significantly for the study population, they added. "However, in subjects with body mass index above the median (31.5 kg/m2), both systolic (8.3 mmHg) and diastolic (3.9 mmHg) blood pressures were lowered in the beta-glucan group compared to controls," they said.
This is not the first time that blood pressure reductions have been reported following beta-glucan-containing foods. Indeed, a pilot study from 2002 by Joseph Keenan at the University of Minnesota reported that daily consumption of an oat cereal containing 5.5 grams per day of beta-glucan led to systolic and diastolic blood pressure reduction of 7.5 and 5.5 mmHg, respectively in moderately hypertensive men and women with high insulin levels (Journal of Family Practice, Vol. 51, p. 369).
No dietary differences between the beta-glucan group and the control group were documented at the start of the study, and as expected the total insoluble and soluble fibre intake of the beta-glucan group increased, compared to controls. Magnesium intake in the beta-glucan group also increased as a result of the higher magnesium in the beta-glucan-containing products. Dietary analysis also showed that sodium and calcium levels decreased, while potassium intakes increased.
Moreover the researchers state that, based on previous studies, it was unlikely that the blood pressure reduction observed in the obese people in this trial were exclusively to the changes in mineral levels.
Compliance amongst the beta-glucan groups was lower than the control group, said Maki, but this was more likely to be due to palatability of the products rather than tolerance.
"Additional research is needed to test [that alterations in carbohydrate homeostasis may have played a role] and define the mechansisms by which repeated consumption of viscous soluble fibre enhances the blunting of postprandial insulin response," concluded the researchers.
Dr. Maki confirmed that research was continuing in this area with future focus likely to be on loger-term studies with people with documented insulin resistance.
Source: European Journal of Clinical Nutrition Published on-line ahead of print, doi: 10.1038/sj.ejcn.1602562 "Effects of consuming foods containing oat beta-glucan on blood pressure, carbohydrate metabolism and biomarkers of oxidative stress in men and women with elevated blood pressure" Authors: K.C. Maki, R. Galant, P. Samuel, J. Tesser, M.S. Witchger, J.D. Ribaya-Mercado, J.B. Blumberg and J. Geohas