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Nutrition experts around the country continue to recommend making more of your grains whole in part because of whole grains’ strong and consistent relationship with diabetes prevention. However, because many of the reﬁned grains eaten in epidemiological studies tend to be discretionary foods like sweets, muﬃns, cakes, cookies, and most whole grains eaten tend to be core grain foods like bread and rice, some wonder if the relationship has less to do with the type of grain and more to do with the type of food.
Luckily, there exists a strong body of research to help us answer this question. Randomized controlled trials, in which diﬀerent groups are assigned to diﬀerent diets, are the “gold standard” of nutrition research as they can be used to establish cause and eﬀect. By randomly assigning certain people to whole grain diets and others to reﬁned grain diets, without signiﬁcant diﬀerences in the categories of grain foods oﬀered, scientists can then observe and see if one group is more likely to develop diabetes or have poor blood sugar management.
In one such small study, adults with “pre-diabetes” were given a diet with either whole grains or reﬁned grains for 8 weeks, then given a glucose test to assess how well their blood sugar was being managed. They then had a washout period of their normal diet for 8-10 weeks, before switching to the other diet for 8 weeks and taking the glucose test again, thus serving as their own controls. The whole grain diet improved the function of beta cells (the cells that secrete insulin) compared with the reﬁned grain diet, and this eﬀect was found to be independent of gut hormones (such as grehlin, the “hunger hormone”).
Similarly, in a 2020 analysis of more than 20 randomized controlled trials, researchers found that for adults both with and without risk factors of heart disease, substituting whole grains for reﬁned can improve hemoglobin A1c (a measure of blood sugar control), among numerous other health beneﬁts.
In another study, researchers randomly assigned more than 100 adults with metabolic syndrome from Finland and Italy to a diet with whole grains or a control diet without whole grains for 12 weeks. The whole grain group had better blood sugar control after meals (as measured by an oral-glucose-tolerance test and a meal-glucose-tolerance-test). Researchers hypothesize that this may be because eating whole grains may help stimulate the production of certain chemical compounds (betaine compounds, such as pipecolic acid betaine) which are linked with improved insulin resistance and insulin secretion.
In addition to supporting better blood sugar management, whole grains can also be a source of substantial savings in diabetes-related healthcare costs. In a 2021 study from Finland, researchers calculated that increasing the number of Finnish people who eat whole grains daily and/or increasing the number of servings of whole grains eaten by habitual whole grain consumers in Finland could lead to a savings of 286-989 million Euros in diabetes-related healthcare costs over a 10-year period.
Whether or not you’re at risk of diabetes, it is important to make every carbohydrate count and opt for choices that oﬀer the biggest nutritional bang for your buck. No matter how you slice it, study after study conﬁrms that whole grains are a wise choice for reducing your risk of type 2 diabetes. (Kelly)