Eating four to six servings of whole grains daily can significantly improve cardiovascular health markers, according to a large systematic review and meta-analysis published September 15 in the European Heart Journal. Researchers found that consuming 60 to 100 grams per day optimizes blood pressure, cholesterol, and body weight. The findings were based on 101 publications, including 87 studies.
Finding the Whole-Grain Sweet Spot for Heart Health
Public health guidelines have long recommended eating whole grains, but clinical trials have historically yielded mixed results regarding exact intake levels. To resolve these discrepancies, researchers combined data from 87 clinical trials examining how whole grain consumption affects cardiovascular risk factors. The systematic review and meta-analysis encompassed more than 6,500 participants across Asia, Europe, the United States, Canada, Australia, and Brazil.
Dr. Helda Tutunchi from Tabriz University of Medical Sciences, Iran, led the research. She said: "Although higher whole-grain intake has long been linked to better heart health in population studies, clinical trials have produced mixed findings. This left an important practical question unanswered: how much whole grain should people eat to meaningfully improve cardiovascular health? To address this, we systematically combined and analyzed all available randomized controlled trials to identify the amount of whole grain associated with the greatest benefits."
What the Data Shows Across Cardiometabolic Risk Factors
The analysis revealed that participants consuming higher amounts of whole grains experienced improvements in multiple pathways simultaneously. Across the studies, diets higher in whole grains were associated with improvements in body weight, blood pressure, cholesterol, and blood glucose. People who consumed more whole grains tended to have lower body weight, smaller waist circumference, and reduced blood pressure. Higher whole grain intake was also associated with lower levels of total cholesterol and low-density lipoprotein cholesterol (LDL or ‘bad’ cholesterol), as well as lower triglycerides, glucose, and interleukin-6 (a sign of inflammation) in the blood.
Benefits were already apparent among people consuming 30 to 40 grams of whole grains per day (dry weight). However, the strongest effects were generally observed at 60 to 100 grams per day. The great reductions in total cholesterol, for example, were seen at 80 grams per day of whole grain intake, according to the findings. That amount is equivalent to about four to six servings of whole grain, corresponding to a bowl of oatmeal, a sandwich made with whole-grain bread and a serving of brown rice.
Whole grains are just as they sound – grains that keep intact the bran and germ, which each contain tons of essential nutrients. When you refine grains, it strips these parts away just leaves the endosperm, which removes most of the grain’s vitamins, minerals, fiber and protein. Common whole-grain foods include brown rice, oats, whole wheat, barley, rye, quinoa, millet and corn, as well as products made from whole-grain flour such as wholemeal bread, pasta and cereals. Other common whole grains include farro, bulgur, and black, red and wild rice, according to the Mayo Clinic.
Evaluating Evidence Quality and Related Research
The authors explained cardiometabolic diseases are a cluster of disorders, including cardiovascular disease and Type 2 diabetes. Whole grains may help in these areas due to their ability to lower insulin, blood pressure and bad cholesterol as well as create a feeling of fullness that can aid in weight management.
“Our findings are in line with and provide support for the results from cohort studies, which report lower risks of all-cause mortality, (cardiovascular disease), (coronary heart disease), Type 2 diabetes, and hypertension incidence with higher intakes of whole grains,” the authors note.
Additionally, a separate systematic review searched four electronic databases from inception to August 2021 for potentially relevant observational and interventional studies to better understand the relationship between whole-grain intake, cognition, mood, and anxiety. In total, 23 studies (4 randomized controlled trials and 19 observational studies) met predefined eligibility criteria, with 12 studies including analysis of whole-grain intake and cognitive decline, 9 including mood outcomes, and 2 including both cognition and mood outcomes. That review concluded that the overall evidence for an association between whole-grain intake and cognition is inconclusive, while evidence regarding mood outcomes suggested that higher intake is linked to improved outcomes for mood and depression, though the strength of available evidence was low or very low for all outcomes.
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