January 4, 2011 — Daily consumption of 3 portions of whole-grain foods (WGF) is linked to lower cardiovascular disease (CVD) risk in healthy, middle-aged people mainly by lowering blood pressure (BP), according to the results of a randomized controlled dietary trial reported in the American Journal of Clinical Nutrition.
"Three daily portions of whole-grain foods could lower cardiovascular disease risk, but a comprehensive intervention trial was needed to confirm this recommendation," write Paula Tighe, from the Division of Applied Medicine, University of Aberdeen, Aberdeen, United Kingdom, and colleagues. "We aimed to assess the effects of consumption of 3 daily portions of whole-grain foods (provided as only wheat or a mixture of wheat and oats) on markers of cardiovascular disease risk in relatively high-risk individuals."
After a 4-week run-in period during which volunteers followed a refined wheat diet, they were randomly assigned to continue the refined diet (control) or to switch to a whole-wheat diet or to a whole-wheat plus oat diet, for 12 weeks. The main endpoint of the study was the effect of dietary intervention with whole grains on cardiovascular risk factors, including concentrations of lipid and inflammatory markers, insulin sensitivity, and BP.
Of 233 volunteers recruited, 3 were excluded, and 24 volunteers withdrew from the study. Compared with the control group, the WGF groups had a significant reduction in systolic BP (6 mm Hg) and a significant reduction (3 mm Hg) in pulse pressure. Cholesterol concentrations decreased slightly but significantly in the refined group, but other systemic markers of CVD risk remained unchanged.
"Daily consumption of 3 portions of whole-grain foods can significantly reduce cardiovascular risk in middle-aged people mainly through blood pressure–lowering mechanisms," the study authors write. "The observed decrease in systolic blood pressure could decrease the incidence of coronary artery disease and stroke by ≥ 15% and 25%, respectively."
Limitations of this study include significant differences in baseline BP between the groups, but the significant decreases in BP resulting from the interventions were not artifactual because they were not in a direction that could be explained by regression to the mean.
"Although the mechanisms by which WGFs decrease BP remain unclear, our findings have important public health implications and provide a sound scientific basis for advising the daily consumption of 3 servings of WGF to combat CVD," the study authors conclude. "In addition, dietary intervention with whole grains along with pharmacologic treatment of hypertension may have significant cost benefits to the National Health Service in the United Kingdom and decrease drug-related side effects."
The Food Standard Agency and the Scottish Government (Rural and Environment Research and Analysis Directorate) supported this study. Paterson Arran Ltd, Livingston, United Kingdom, provided oat cakes used in this study. The study authors have disclosed no relevant financial relationships.
Am J Clin Nutr. 2010;92:733-740. Abstract
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