Eating four to six servings of whole grains each day may improve several major risk factors for cardiovascular disease, according to new research published September 15 in the European Heart Journal.
The findings come from a systematic review and meta-analysis that combined evidence from 87 clinical trials examining how whole grain consumption affects cardiovascular risk factors.
Across the studies, diets higher in whole grains were associated with improvements in body weight, blood pressure, cholesterol, and blood glucose. Together, these changes could help lower the long term risk of heart disease.
How Much Whole Grain Is Enough?
The research was led by Dr. Helda Tutunchi from Tabriz University of Medical Sciences, Iran. 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.”
The analysis included more than 6,500 participants from trials conducted across Asia, Europe, the United States, Canada, Australia, and Brazil. 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.
That amount is equivalent to about four to six servings of whole grains daily. In practical terms, that could include a bowl of oatmeal, a sandwich made with whole grain bread, and a serving of brown rice.
Benefits Across Several Heart Risk Factors
Dr. Tutunchi said: “This is the largest and most comprehensive meta-analysis of randomized controlled trials on wholegrain intake and cardiovascular risk factors. Unlike previous reviews, we looked specifically at how much wholegrain people need to eat to get the greatest benefits. We also evaluated the certainty of the evidence and found high-certainty evidence for improvements in several outcomes, including body weight, waist circumference, and total cholesterol.
“However, most of the trials we included were relatively short, with an average duration of about eight weeks. As a result, we cannot determine whether these benefits are maintained over the long term. In addition, relatively few studies evaluated very high wholegrain intakes, above 140 grams per day, so the effects at those intake levels remain uncertain.
“Our findings provide a practical indication of the amount of wholegrain that may be needed to achieve meaningful improvements in cardiovascular risk factors. Increasing wholegrain intake is a relatively simple, accessible and affordable dietary strategy that can complement other lifestyle and medical interventions.
“We found that most benefits occur at intakes of approximately 60 to 100 grams per day, toward the upper end of current dietary recommendations. These findings do not necessarily call for major changes to existing guidelines, but they support public health strategies that help people increase their whole-grain intake and move toward the higher end of current targets.
“One important finding is that whole grains may benefit cardiovascular health through several modest improvements acting together, rather than through one large effect on a single risk factor. We observed improvements across multiple pathways, including blood lipids, blood pressure, glucose regulation, body fat and some markers of inflammation. Although the change in each individual risk factor was generally modest, improving several risk factors simultaneously could contribute to a greater reduction in long-term cardiovascular risk. However, the included trials did not assess cardiovascular events directly, so longer-term studies are needed to confirm this.”
The researchers caution that the clinical trials mainly measured cardiovascular risk factors rather than actual heart attacks, strokes, or other cardiovascular events. Most of the trials were also relatively brief, so additional long term studies will be needed to determine whether the observed improvements persist and ultimately translate into fewer cases of cardiovascular disease.
What Makes Whole Grains Different?
In an accompanying editorial, Dr. Cecilie Kyrø from the Danish Cancer Institute, Copenhagen, and colleagues said: “More than half a century ago, Sir Denis Burkitt and colleagues proposed that the refining of staple carbohydrates, with the accompanying removal of cereal fiber (i.e. from whole to refined grains), underpinned a broad spectrum of ‘Western’ diseases via effects on stool bulk, transit time, and the colonic milieu. Whole grains refer to cereal grains where the three main parts — bran, germ, and endosperm — are all retained in the same proportions as in the intact kernel, whether consumed as whole kernels, flakes, or milled into flour and used in bread and other foods.
“A meta-analysis of trials investigating the effect of whole grains on cardiometabolic risk markers by Naghshi et al. is published in this issue of the European Heart Journal and includes 87 trials of 6529 study participants in total. The meta-analysis shows high-certainty evidence for reductions in body weight, waist circumference, total cholesterol. and interleukin-6 (IL-6), and moderate-certainty evidence for improvements in LDL cholesterol, triglycerides, systolic blood pressure, fasting plasma glucose, and insulin resistance (HOMA-IR).
“Importantly, the meta-analysis includes dose-response analyses, addressing differences in whole-grain intake between trials and providing quantitative evidence to inform food-based dietary guidelines. Overall, intakes of 60-100 g/day dry weight (∼4-6 servings) were found to be clearly related to relevant cardiometabolic improvements.
“For clinicians, the message from Naghshi et al. is reassuringly simple: encouraging patients to replace refined grain foods with minimally processed whole grains is likely to yield modest but meaningful improvements in body weight, waist circumference, and blood lipids, perhaps particularly in individuals with type 2 diabetes. At the population level, even small shifts in these markers can translate into substantial reductions in cardiometabolic events. Adding evidence from research into other disease endpoints indicates that the beneficial effects of whole-grain foods even go substantially beyond cardiometabolic disease.
“The dose-response analyses by Naghshi et al. suggest that intakes of around 60-100 g/day whole grains (∼4-6 servings) are needed to achieve measurable cardiometabolic benefits. Current US dietary guidelines recommend 2-4 servings of whole grains per day within an overall pattern that emphasizes ‘real food’ and reduced intake of ultra-processed products. While this is an important step in the right direction, the trial evidence indicates that higher whole-grain intakes than presently recommended in some guidelines may be optimal for cardiometabolic health.
“From a policy perspective, the challenge is to make minimally processed whole-grain staples accessible, affordable, and culturally acceptable, while avoiding a drift towards ultra-processed products that merely add whole grains to otherwise highly processed formulations.”
Taken together, the findings suggest that whole grains may support cardiovascular health not through one dramatic effect, but through several smaller improvements occurring at the same time. Replacing refined grains with minimally processed whole grain foods could therefore offer a relatively simple way to improve cholesterol, blood pressure, blood sugar regulation, body composition, and inflammation.
