The Role of Whole Grains in Reducing Risk of Type 2 DiabetesLast updated: Oct 01, 2018
Foods containing carbohydrate, especially grain products like bread, cereal, pasta, crackers and tortillas have gotten a bad rap the past few years with many people promoting lower carbohydrate eating plans as a healthier alternative. However, a wide body of research shows that consuming whole grains is an important strategy to prevent type 2 diabetes.1 The 2018 Standards of Medical Care in Diabetes encourage consuming whole grains instead of refined grain products that often contain higher amounts of sugars and fats.2 In a large research study published in September 2018 the risk of developing type 2 diabetes was 34% lower for men and 22% lower for women who consumed the highest amount of whole grains compared to the group with the lowest whole grain intake.1
What are whole grains?
Whole grains contain all three of the naturally present major components of the grain seed or kernel: endosperm, germ and bran. The germ is the embryo which has the potential to sprout into a new plant. It contains many B vitamins, some protein, minerals, and healthy types of fats. The endosperm is the largest part of the kernel, containing starchy carbohydrates, proteins and small amounts of vitamins and minerals that supply essential nutrients to the growing seed. Bran is the edible outer part of the kernel that contains important antioxidants, B vitamins and ﬁber. A refined grain is missing one or more of these three parts due to processing. For example, white rice and white flour have had both the bran and germ removed from the original whole grain. Reﬁning a grain removes about a quarter of the protein and half to two thirds or more of the vitamins and minerals plus almost all the fiber.3 Whole grains include brown rice, whole wheat, bulgur wheat, oats, amaranth, barley, or quinoa.
Why are whole grains important in preventing type 2 diabetes?
The exact reasons why whole grains are an important mechanism to prevent type 2 diabetes aren’t crystal-clear, but there are several theories:1
- Whole grains improve insulin sensitivity, which means that the body uses blood sugar more effectively and efficiently.
- Whole grains are digested more slowly which leads to a far slower increase in blood sugar levels after eating.
- The nutrients in whole grains plus the fiber content help to lower our body’s level of inflammation which is strongly associated with type 2 diabetes.
- The fiber in whole grains is incompletely digested in the gastrointestinal tract which produces short-chain fatty acids which decrease insulin sensitivity.
Are certain types of whole grains more effective in preventing type 2 diabetes?
Recent research with 55,000 participants over 15 years from the Chalmers University of Technology, Sweden, and the Danish Cancer Society Research Center confirms decades of previous research findings on the importance of whole grains for prevention of type 2 diabetes. In this study, any type of whole grain provided similar benefits.1
How many servings of whole grains per day are necessary?
In the Swedish and Danish study, each serving of whole grain was associated with an 11% lower risk of type 2 diabetes for men and a 7% lower risk for women.1 A large meta-analysis of 16 studies recommends consuming 2-3 servings of whole grains per day to decrease risk of developing type 2 diabetes.4
What are examples of one serving of a whole grain?
- ½ cup cooked brown rice or other cooked grain such as amaranth, barley, millet, quinoa or wild rice
- ½ cup cooked 100% whole-grain pasta
- ½ cup cooked hot cereal, such as oatmeal
- 1 slice 100% whole grain bread
- 1 very small (1 oz.) 100% whole grain muﬃn
- 1 cup 100% whole grain ready-to-eat cereal5
How can I tell if a food contains whole grains?
Look at the ingredients list on packages of cereal, crackers, bread or other grain products to make sure that they contain whole grains. The word ‘whole’ with the first ingredient is your key that the food is made entirely from whole grains. For example:
- Whole grain wheat
- Whole grain oats
- Stoneground whole wheat
Other descriptions of whole grains include brown rice and wheatberries.6
Be wary of these descriptions that indicate both whole and refined grains are present in the food:
- Wheat or wheat flour
- Durum wheat
- Organic flour
If there are two grain ingredients and only the second ingredient listed is a whole grain, the product may contain as little as 1% or as much as 49% whole grain (in other words, it could contain a little bit of whole grain, or nearly half).6
Use these 5 simple tips to add more whole grains to your daily food choices:
- Start off gradually by using whole grains to replace half of the grains in recipes. For example, use half white rice and half brown rice in pilafs or casseroles or replace half of the white flour in recipes for breads or pancakes with whole grain flour.
- Read food labels and choose breads, cereals and crackers with the word ‘whole’ in the first ingredient. For example, the first ingredient in Triscuit crackers is ‘whole wheat’ and the first ingredient in Cheerios is ‘whole oats’ indicating that both of these products contain primarily whole grains.
- Reach for popcorn for a whole grain snack. Opt for popcorn that you pop yourself or choose a microwave variety with less added fat.
- Make soups with barley or brown rice instead of white rice or noodles that are typically made with white wheat flour.
- 5Add bulgur wheat or quinoa to vegetable salads.
- Cecilie Kyrø, Anne Tjønneland, Kim Overvad, Anja Olsen, Rikard Landberg; Higher Whole-Grain Intake Is Associated with Lower Risk of Type 2 Diabetes among Middle-Aged Men and Women: The Danish Diet, Cancer, and Health Cohort, The Journal of Nutrition, Volume 148, Issue 9, 1 September 2018, Pages 1434–1444. https://doi.org/10.1093/jn/nxy112
- American Diabetes Association. Lifestyle Management: Standards of Medical Care in Diabetes 2018. Diabetes Care 2018 Jan; 41(Supplement 1): S38-S50. https://doi.org/10.2337/dc18-S004
- Oldways Whole Grain Council. Whole Grains 101. What’s a Whole Grain? A Refined Grain? https://wholegrainscouncil.org/whole-grains-101/whats-whole-grain-refined-grain accessed 9-19-18.
- Aune D, Norat T, Romundstad P, Vatten LJ. Whole grain and refined grain consumption and the risk of type 2 diabetes: a systematic review and dose-response meta-analaysis of cohort studies. Eur J Epidemiol. 2013 Nov;28(11):845-58. doi: 10.1007/s10654-013-9852-5. Epub 2013 Oct 25.
- Oldways Whole Grain Council. Whole Grains 101. What Counts as a Serving? https://wholegrainscouncil.org/whole-grains-101/how-much-enough/what-counts-serving accessed 9-19-18
- Oldways Whole Grain Council. Whole Grains 101. Identifying Whole Grain Products. https://wholegrainscouncil.org/whole-grains-101/identifying-whole-grain-products accessed 9-19-18