A diet rich in fresh veggies, fruit, and fiber has meaningful benefits for people with diabetes, a new research review confirms.

Doctors have long recommended this kind of "low-glycemic" eating regimen to help patients manage their diabetes and keep blood sugar levels steady. The new review of findings from 29 different trials lends support for that advice.

"Although it was small, the effects were important," said study co-author Dr. John Sievenpiper, an associate professor of nutritional sciences and medicine at the University of Toronto. "I think it provides an opportunity for patients to help them achieve their diabetes treatment goals using diet," he added.

The trials reviewed in this study investigated the effects of a low-glycemic index/glycemic load diet for three or more weeks in 1,617 patients with type 1 or type 2 diabetes. Most were middle-aged and overweight or obese. Their diabetes was moderately controlled and they were using medication or insulin.

Glycemic index is a measure of how quickly different foods affect blood sugar levels.

Past research has found that low-glycemic index foods help keep blood sugar levels steady and reduce the risk of heart disease in people with diabetes.

In this research review, low-glycemic diets were associated with lower blood sugar levels with a high degree of certainty of evidence.

With moderate certainty, the diet was associated with reductions in fasting blood sugar, LDL ("bad") cholesterol, weight and a protein involved in inflammation.

The diets did not seem to affect blood levels of insulin and HDL ("good") cholesterol, waist circumference or blood pressure, the review found.

Diet is a cornerstone of diabetes therapy, Sievenpiper said. Though patients in the reviewed studies were already on medications or insulin, adding in a low-glycemic diet later could also help, the evidence showed.

Laura Chiavaroli, a postdoctoral fellow at the University of Toronto, led the research review.

When it comes to choosing carbohydrates, she said people with diabetes ideally would choose whole and plant-based foods, including vegetables, fruit, legumes and whole grains.

"With the rise in popularity of plant-based diets right now, [this research] is coming out at a good time where people are a bit more aware of those kinds of foods," Chiavaroli said.

A big takeaway from the study is that all carbohydrates aren't created equal.

Sievenpiper said, "All carbohydrates aren't bad. And there's advantages to selecting lower-glycemic carbohydrates."

That includes scrapping refined grains in favor of whole grains with "sticky" fiber, such as oats and barley, he said. In its traditional form, a Mediterranean diet has a low-glycemic index, he added.

The findings were published online Aug. 5 in the BMJ.

The research was done, in part, for an update to European Association for the Study of Diabetes' guidelines.

The American Association of Clinical Endocrinology is updating its guidelines, too, and the American Diabetes Association has included updates in its standards of care, according to Dr. Karl Nadolsky, assistant clinical professor at Michigan State University College of Human Medicine, in East Lansing.

Replacing food that's refined, processed and high-energy with whole foods will automatically result in a diet that's lower in glycemic index and energy intake, he said.

"Energy balance matters. We know that reducing our energy intake will help obesity and … diseases like type 2 diabetes," said Nadolsky, who was not involved in the study. "We know that Mediterranean-pattern diet, getting fat from nuts and seeds and all that stuff is better for cardiovascular risk and diabetes."

People may need individualized diets based on their circumstances. For example, Nadolsky said, an athlete with 5% body fat will have different needs than most, including more high-glycemic foods. Others may want to increase their consumption of plant-based foods, while sometimes eating high-quality fish or meat.

Replacing white bread, pizza crust, sugar-sweetened beverages and baked goods with veggies, beans, legumes and fruit makes sense, he added.

"It's low-glycemic index, low-glycemic load. It's a lower energy intake. It has higher fiber, which they do talk about in this study," Nadolsky said. "So you end up getting all those benefits when you do that."