The case for eating whole grains has grown stronger. Research from the past two decades associates diets rich in whole grains with lower risks of heart disease, high blood pressure, high cholesterol and type 2 diabetes, along with support for maintaining a healthy weight.

A new analysis published Tuesday in the European Heart Journal examined dozens of studies to explore how whole grains may influence cardiovascular and metabolic health at the molecular level. Researchers also sought to determine how much people need to eat before measurable benefits appear.

The findings suggest those benefits begin at about 90 grams, or three servings, each day. That amount could come from two slices of whole wheat bread and a bowl of oatmeal, while eating four to six daily servings may deliver even greater benefits.

Researchers found evidence that people who ate three to six servings for prescribed periods showed slight improvements in about a dozen health markers. The study periods ranged from as little as two weeks to as long as two years.

The markers included total cholesterol, LDL cholesterol, blood pressure, body weight and waist circumference. Each is associated with a greater risk of cardiovascular disease, and the collective findings supported patterns previously observed in large population studies.

Although the individual effects were small, the results strengthen the broader evidence, according to study coauthor Dagfinn Aune. Aune is a research fellow in the department of epidemiology and biostatistics at Imperial College London’s School of Public Health.

Aune concluded that there is “likely a causal effect” from eating whole grains and that “this may translate into a reduced risk of cardiovascular disease.” Still, the findings do not mean that simply adding whole wheat toast to a breakfast of bacon and eggs will improve heart health.

Doctors advise choosing whole grains instead of products made with refined grains. Whole grain foods include oatmeal, brown rice, whole wheat bread, farro, popcorn and quinoa, all of which retain every part of the grain as it exists in nature.

Refined grains, including white rice and products made with white flour, are processed to remove parts that may be less palatable. Those removed portions are also where much of the fiber and other nutrients are found.

Alice Lichtenstein, a professor at the Friedman School of Nutrition Science and Policy at Tufts University in Medford, Massachusetts, cautioned against treating one substitution as a complete solution. She was not involved in the new analysis.

“If you eat a cinnamon bun made of whole grain, as opposed to a cinnamon bun made with refined grain, I’m not sure you’re going to see a benefit,” Lichtenstein said. She also warned that adding more carbohydrates solely to reach a whole grain target could cause weight gain.

Most people in the United States do not eat the two to four daily servings recommended in the federal government’s latest Dietary Guidelines for Americans. One serving could be a slice of whole wheat bread or half a cup of cooked oats, brown rice or quinoa.

The American Heart Association recommends foods made with whole grains but does not set a specific daily target. Lichtenstein, lead author of the nonprofit’s dietary guidelines published in March, said no single amount is clearly best for every person’s body, genetics and lifestyle.

Rather than seeking one ideal quantity, she said, “we’re trying to keep the focus on the dietary pattern.” Those guidelines also emphasize a variety of fruits and vegetables while limiting saturated fat, added sugar, salt, ultraprocessed foods and alcohol.

For people who prefer a concrete starting point, replacing three daily servings of refined grains with whole grains could be useful. “My suggestion is as items run out in the pantry, replace them with whole grain versions,” Lichtenstein said.

Finding genuine whole grain products can require careful label reading. Dark brown breads and foods described as multigrain or made with whole grain may still consist predominantly of refined flour.

“Turn the package over and look at the ingredient list,” Lichtenstein said. “The first ingredient should be a whole grain.” If it is not, her advice is simple: leave the product on the shelf.