Refined grains

Carbohydrate foods from different sources have different impacts on the body, meaning that it is important to choose quality carbohydrates like whole grains. In this study, researchers analyzed the eating patterns and weight changes of 136,432 adults for more than 2 decades. Eating more whole grains, fruit, and non starchy vegetables was linked with a lower risk of weight gain, while eating more refined grains and starchy vegetables (peas, corn, potatoes) was linked with a higher risk of weight gain.
BMJ. 2023 Sep 27:382:e073939. doi: 10.1136/bmj-2022-073939. (Wan Y et al.)

Type 2 diabetes is one of the most prevalent chronic diseases around the world, impacting millions of people. In this study, researchers developed risk-assessment models to estimate how much various dietary habits contribute to type 2 diabetes risk in 184 countries around the world. The largest burden (26.1%) of type 2 diabetes was attributed to low whole grain intake. Other factors contributing to high type 2 diabetes burden included high intake of refined rice and wheat (24.6%) and high intake of processed meat (20.3%).
Nat Med. 2023 Apr;29(4):982-995. doi: 10.1038/s41591-023-02278-8. Epub 2023 Apr 17. (O’Hearn M et al.)

Larger waist sizes (as measured by waist circumference), high blood pressure, and high triglycerides are all signs of potential heart disease down the road, so researchers wonder how whole grains might play a role in these risk factors. In a study of 3,121 adults (average age 55), researchers analyzed the types of grain foods they ate and their health markers to see how different types of grains might relate to cardiometabolic risk. While all study participants got larger around the waist over the 18-year study period, eating the most whole grains (at least 48 grams whole grain per day, or at least 3 full servings) was linked with significantly smaller increases in waist size compared with eating the least whole grains (less than 8 grams whole grain per day, or less than a half serving). Additionally, eating more whole grains was also linked with significantly smaller increases in fasting blood sugar and systolic blood pressure, while eating more refined grains (4+ servings per day) was linked with greater increases in waist size and a smaller decline in triglycerides (a type of fat in the blood).
Journal of Nutrition. 2021 Jul 13;nxab177. doi: 10.1093/jn/nxab177. (Sawicki CM et al.)

Randomized controlled trials are the “gold standard” of nutrition research as they can be used to establish cause and effect. In this article, researchers analyzed more than 20 randomized controlled trials to see how replacing refined grains with whole grains can impact health. They found that for adults both with and without risk factors of heart disease, substituting whole grains for refined can improve total cholesterol, LDL (“bad”) cholesterol, hemoglobin A1c (a measure of blood sugar control), and C-reactive protein (a measure of inflammation). 
Journal of the Academy of Nutrition and Dietetics. 2020 Nov;120(11):1859-1883.e31. doi: 10.1016/j.jand.2020.06.021. (Marshall S et al.)

Many dietary guidelines recommend that people make at least half their grains whole, yet little has been published on the availability of whole grain options at supermarkets. In a February 2020 audit of the flour aisle at four major supermarkets in metropolitan Sydney, researchers identified 130 different flour products. Of those, only 19% were whole grain flour. The majority of products were refined wheat flour. Not surprisingly, the whole grain flours contained significantly more fiber and protein.
Nutrients. 2020 Jul 10;12(7):2058. doi: 10.3390/nu12072058. (Hughes J et al.)

Researchers analyzed 168 types of wheat flour purchased throughout the UK and Germany to compare their nutritional profiles. While spelt and organic wheat varieties had significantly higher levels of antioxidants and minerals than their conventional/modern counterparts, a far greater impact on nutrition was observed when comparing whole grain wheat to refined wheat. Whole grain wheat flours had 2-4.3x higher antioxidant concentrations and activity, 144% more phosphorous, 125% more potassium, and 209% more magnesium than refined wheat flours. The authors conclude that “refining (removal of the bran and germ) (a) has a substantially greater impact on the mineral nutrients and phytochemical concentrations in flour than wheat genetics/species choice (T. aestivum vs T. spelta) and production protocols (organic vs conventional), (b) diminishes the differences in antioxidant activity, and phenolic and mineral concentrations in wheat flour produced with grain from contrasting farming systems and wheat species.”
Food Chem X. 2020 May 4;6:100091. doi: 10.1016/j.fochx.2020.100091. (Wang J et al.)

Don’t let a poor diet keep you up at night. In this study, researchers analyzed the diets and insomnia rates of more than 50,000 post-menopausal women. Eating more whole grains, fiber, fruit, and vegetables was linked with lower odds of insomnia. On the other hand, eating more added sugar, starch, refined grains, and a high glycemic index diet (diet of foods that raise your blood sugar quickly) was linked with higher odds of insomnia.
American Journal of Clinical Nutrition. 2020 Feb 1;111(2):429-439. doi: 10.1093/ajcn/nqz275. (Gangwisch JE et al.)

The standard American diet is infamous for its high levels of refined carbs, sugar, and saturated fats. To see if nutrition initiatives are taking hold, researchers analyzed the diets of 43,996 U.S. adults in 1999 and then again in 2016. Over this time period, people got 1.23% more calories from high quality carbs (whole grains), 0.38% more calories from plant protein, 0.65% more calories from polyunsaturated fats, and 3.25% fewer calories from low quality carbohydrates (sugar and refined grains). Unfortunately, calories from saturated fat increased by 0.36%, and the general diet is still far from ideal, with 42% of calories still coming from low quality carbs, and saturated fat remaining above 10% of energy intake.
JAMA. 2019 Sep 24;322(12):1178-1187. doi: 10.1001/jama.2019.13771.(Shan Z et al.)

In this study, researchers asked 169 low-income adults to look at 11 foods in their original packaging and determine if each was a whole grain or a refined grain. The majority of participants (7 out of 10) correctly identified 4 out of 5 of the whole grain products as whole grain, and nearly as many (6 out of 10) participants correctly identified 5 out of the 6 refined grain products. Specifically, 9/10 people correctly identified whole grain bread, 8/10 correctly identified whole grain crackers & whole grain cereal, and 7/10 correctly identified oatmeal as a whole grain, while popcorn tripped most people up (with only 3/10 people correctly identifying it as a whole grain food). Similarly, 8/10 correctly identified refined crackers, 7/10 correctly identified refined macaroni and tortillas, and 6/10 correctly identified refined bread and cereal, while white rice was tricky for people (with only 4/10 correctly identifying it as a refined grain). Based on interviews with a subset of 60 of the participants, the researchers found that helping people more clearly identify whole grains on the package, and reducing the cost (or perceived cost) of whole grain foods may help increase whole grain consumption in low-income adults.
Current Developments in Nutrition. 2019 May 16;3(7):nzz064. doi: 10.1093/cdn/nzz064. (Chea M et al.)

Insulin is a hormone that helps your body manage your blood sugar, by keeping it from getting too high or too low. In this study, 13 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”).
Molecular Nutrition and Food Research. 2019 Apr;63(7):e1800967. doi: 10.1002/mnfr.201800967. (Malin SK et al.)