Eating Even a Little More Whole Grains, Fruit, and Veggies May Cut Type 2 Diabetes Risk

For decades, dietary guidelines have urged adults to fill a majority of their plate with whole grains, fruits, and veggies. And for just as long, many people have failed to hit the targets outlined in MyPlate, a healthy-eating tool designed by the U.S. Department of Agriculture (USDA).

Now two new studies suggest that it’s worth the effort even if you don’t hit the targeted amounts of these foods. In these studies — one focused on fruits and veggies and the other focused on grains — getting more of these foods was associated with a lower risk of developing type 2 diabetes.

“We know diet is one of the most important factors that determine the risk of developing type 2 diabetes,” says Qi Sun, MD, a doctor of science and the senior author of the study that examined whole grains and a researcher at the Harvard T.H. Chan School of Public Health and Brigham and Women’s Hospital in Boston.

“Fruits, vegetables, whole grains, extra-virgin olive oil, nuts, yogurt, and other healthful foods may lead to reduced risk of developing this disease,” says Dr. Sun.

How Various Types of Whole Grains May Cut Type 2 Diabetes Risk

Sun and his colleagues examined data from dietary questionnaires and health surveys completed by 158,259 women and 36,525 men who didn’t have type 2 diabetes, heart disease, or cancer. After an average follow-up period of 24 years, 18,629 participants developed type 2 diabetes.

Overall, people who consumed the most whole grains were 29 percent less likely to develop type 2 diabetes than participants who ate the smallest amounts of these foods, according to results published in July 2020 in the BMJ.

Whole-grain foods included products with the following ingredients:

Whole wheat and whole-wheat flour
Whole oats and whole-oat flour
Whole cornmeal and corn flour
Whole rye and rye flour
Whole barley
Bulgur
Buckwheat
Brown rice and brown rice flour
Popcorn
Amaranth
Psyllium

People who ate the highest amounts of a variety of individual types grains — at least one daily serving — were less likely to develop type 2 diabetes than people who consumed the lowest amounts — less than one monthly serving. The reduced type 2 diabetes risk for different grains was:

21 percent lower for oatmeal
21 percent lower for dark whole-grain bread
19 percent lower for whole-grain breakfast cereal
18 percent lower for brown rice
18 percent lower for wheat germ

One limitation of the study is that it relied on participants to accurately recall and report on their eating habits, which leaves room for error. (If you've forgotten what you had for breakfast today, the issue becomes easy to understand.) Another drawback is that the study participants all worked in healthcare jobs and most were white; this may mean the results don’t reflect what happens for people with different educational or professional backgrounds or for people from other racial and ethnic groups.

The More Fruits and Veggies You Eat, the Lower Your Type 2 Diabetes Risk May Be

Another study published in the BMJ in July 2020 examined data from blood tests for two biomarkers for fruit and vegetable consumption — plasma vitamin C and carotenoids — in 9,754 people with type 2 diabetes and 13,662 individuals without this disease. Participants came from eight European countries: France, Italy, Spain, United Kingdom, Netherlands, Germany, Sweden, and Denmark.

Compared with people who had the lowest levels of plasma vitamin C and carotenoids in lab tests, study participants with the highest blood levels of these two biomarkers were 50 percent less likely to have type 2 diabetes, the analysis found. People who fell somewhere in the middle — not the lowest or the highest results — were still 23 percent to 41 percent less likely to have type 2 diabetes than participants with the lowest levels of these biomarkers in their blood.

In this study, researchers also asked participants about their eating habits. Median self-reported daily fruit and vegetable intake was 274 grams (g), or about 2¼ cups for people with the lowest levels of plasma vitamin C and carotenoids in their blood and 508 g, or about 4⅛ cups, for those with the highest levels of these biomarkers. Each 66 g increase, or about ¼ cup, in daily fruit and vegetable intake was associated with a 25 percent lower risk of type 2 diabetes.

While one advantage of this study is that it used blood biomarkers for an objective measurement of eating habits, a limitation is that the results didn’t account for a variety of other factors, such as income, education, and other lifestyle habits that could affect the risk of developing type 2 diabetes.

Still, the results suggest that even a modest increase in fruit and vegetable consumption may help prevent type 2 diabetes, says the senior study author, Nita Forouhi, PhD, of the University of Cambridge in the United Kingdom.

“Something is better than nothing,” Dr. Forouhi says.

The Challenges of Studying Dietary Patterns and Disease Risk

A study published in August 2016 in the European Journal of Clinical Nutrition looked at the relationship between fruit and vegetable consumption and type 2 diabetes risk in two different cohorts of adults under age 50 who had no history of cancer, heart disease, or diabetes. Overall, this study failed to find a connection, but in one of the two cohorts, people who ate the most fruit had a 5 percent lower risk of type 2 diabetes, and participants who ate the most vegetables had a 13 percent lower risk than people who consumed the smallest amounts of these foods.

An older study, published in PLoS Medicine, followed more than 160,000 women for more than a decade and found that people who consumed the most whole grains had a 25 percent lower risk of developing type 2 diabetes. Researchers also analyzed data pooled from six previous studies and found a 21 percent reduction in type 2 diabetes risk for every two daily servings of whole grains.

Part of the reason studies get inconsistent results is that much of this research — along with similar research on diet choices and disease risk — relies on dietary questionnaires that are only as good as participants’ ability to accurately recall and report on what they’ve eaten in the past, says Lauri Wright, PhD, RDN, the chair of the department of nutrition and dietetics at the University of North Florida in Jacksonville.

“Food recalls have notoriously been subject to recall bias and measurement error, which has resulted in some inconsistency in the research on the link between fruit and vegetable intake and diabetes,” says Dr. Wright, who wasn’t involved in either of the studies published in the BMJ.

Tips for Incorporating More Whole Grains, Fruit, and Veggies in Your Diet

One simple way to get more fruits and veggies is to fill half the plate at every meal with these foods, Wright says. Then, fill roughly one quarter with whole grains and one quarter with lean meats.

Another easy thing to do is think about swapping less healthy versions of foods for healthier alternatives, Wright suggests.

“Swap out white bread for whole-grain bread, choose a whole-grain breakfast cereal or oatmeal for breakfast, add barley or bulgur to your soups and casseroles, make half of your pasta whole grain,” Wright advises.

Buying a wide variety of fresh fruits and vegetables when they’re in season is also a great way to get more of these foods on the plate. But frozen alternatives are just as nutritious, and canned products can work in a pinch as long as you check the labels to avoid added sugars and sodium, Wright says.

Eating Approaches to Help Prevent Type 2 Diabetes

To eat foods that minimize type 2 diabetes risk, there are four main things people need to keep in mind, according to the Harvard T.H. Chan School of Public Health. These include:

Choose whole grains instead of refined or highly processed grains
Choose water over sodas and other drinks sweetened with sugar
Choose healthy fats in nuts, seeds, and olive oil over unhealthy trans fats
Choose poultry and fish instead of red and processed meats like bacon and deli meat

A variety of diets can accomplish these goals. Two that are widely recommended by clinicians include the Mediterranean diet and the Dietary Approaches to Stop Hypertension (DASH) diet. The Mediterranean and DASH diets both encourage eating fruits, vegetables, nuts, whole grains, low-fat dairy, fish, and poultry. And both these diets limit red meat, added sugars, and salt.

“Both the DASH and Mediterranean styles of eating are good options to start a more plant-based approach to eating, and there are many cookbooks based on them available,” says Samantha Heller, RD, a senior clinical nutritionist at NYU Langone Health in New York City.

Consulting cookbooks that are focused on plant-based eating may be enough to steer a lot of people in the right direction. If you are part of a group known to be at a higher risk for type 2 diabetes, however, you might want extra help.

“If you have a family history of type 2 diabetes or have been diagnosed with type 2 diabetes, work with a registered dietitian who can help create a personalized plan that takes into consideration your food preferences, culture, lifestyle, and budget,” Heller advises.

AUSTRALIA, KOREA, MALAYSIA, NETHERLANDS, THAILANDAnti Additive AssociationAugust 4, 2020EN, NEWS