Let us eat cake? Refined grains “falsely” linked to obesity and chronic disease risk

11 Apr 2019 --- Contrary to previous research findings, refined grain consumption is not associated with any of the adverse health effects it has been linked to, such as obesity, heart disease and diabetes. This is according to a new study from the Healthy Lifestyles Research Center at Arizona State University (ASU) published in Advances in Nutrition. The researchers note that what counts is the number of consumed calories, not so much their source.

Analyses of existing research – including 32 publications with data from 24 distinct cohorts – showed that refined grains are not linked to increased disease risk or premature death. The study highlights that current dietary recommendations to reduce refined grain consumption conflict with the substantial body of published scientific evidence.

Professor Glenn Gaesser, Ph.D., Director of the Healthy Lifestyles Research Center at ASU“Simply put, refined grains are not the bad guy,” says study author, Professor Glenn Gaesser, Ph.D., Director of the Healthy Lifestyles Research Center at ASU. “Contrary to popular belief and current dietary guidance, refined grain intake is not associated with type 2 diabetes, cardiovascular disease, coronary heart disease, stroke, hypertension, cancer or death.”

Gaesser theorizes that refined grains have developed a guilt-by-association reputation. He explains that while refined grains are frequently characterized as unhealthy, this can be attributed to their inclusion in a dietary pattern that contains a range of foods that are the real culprits in the link between an unhealthy dietary pattern and increased risk of a number of chronic diseases. 

More specifically the study found that:

• No association was observed between refined grain intake and cardiovascular disease or coronary heart disease.
• No association was found between refined grain intake and stroke risk. In fact, one study demonstrated a 10 percent lower reduction of stroke risk.
• No association was found between refined grain intake and risk of Type 2 diabetes.
• Cancer studies are limited. Nonetheless, one meta-analysis shows an inverse association between refined grain intake and total cancer deaths. A second meta-analysis shows that refined grain intake was not associated with risk of rectal or colorectal cancer.
• Five out of six studies show no relationship between refined grain intake and death rate. The other study shows a statistically significant inverse association between refined grain intake and all-cause death rate.
• Three systematic reviews show no consistent relationship between refined grain intake and body mass index (BMI).

Refined grains and obesity link
Especially in the case of obesity, the demonization of refined grains has deterred people from consuming them and opting for whole grains instead, which are higher in calories but touted as more nutritionally-rich. 

“The association between refined grain consumption and obesity is murky, with no clear relationship. Weight gain is essentially a result of consuming more calories than one burns. It’s the number of calories that matters most, not so much the type of calories,” Gaesser tells NutritionInsight. 

He also notes that in studies that do indicate that refined grains are associated with increased risk of weight gain, the association is “trivially small.” 

“Randomized dietary interventions of whole grains and refined grains compared head-to-head reveal no differences between the two. Moreover, for weight control, it’s the number of calories that is important, more so than the type.”

Misguided dietary guidelines?
Gaesser also explains how dietary guidance on refined grains became misguided. The “make-half-your-grains-whole” recommendation from the US Dietary Guidelines Advisory Committee was based largely on studies that focused on dietary patterns, not specific food groups. This Western dietary pattern, which includes red and processed meats, sugar-sweetened foods and beverages, French fries, high-fat dairy products and refined grains is linked to many chronic diseases. 

“However, when analyzed as a distinct food group, refined grain consumption is not linked to chronic diseases or death,” he highlights.

Both refined grains and whole grains are important in people’s diet, Stephen McCauley, Founder of The Ginger Network – which communicates on food and nutrition issues – tells NutritionInsight.

Whole grains are important for health since they provide fiber and essential vitamins. Enriched/refined grains provide fiber too, and 39 percent of the dietary fiber Americans eat comes from refined grains. “As a population, US consumers still fall far short of reaching their daily goals for fiber,” McCauley says.

“The important takeaway of this study is that consumers need to know their stuff before they cut [foods out of their diet],” says Sylvia Klinger, a Registered Dietitian and Nutritionist from the Scientific Advisory Board of the Grain Foods Foundation. 

She adds that eliminating enriched grain products will result in nutrient shortfalls. Refined grain foods that have been enriched and/or fortified help to alleviate shortfalls including B-vitamins, folic acid, thiamin, niacin, riboflavin and iron. “For example, enriched grains are the largest contributor of folic acid in the American diet. This is key to preventing neural tube birth defects.”

“At the end of the day, you can have your refined grains and eat them too,” Klinger continues. “The most scientifically sound recommendation may be to simply encourage increased consumption of whole grains without specific recommendations to reduce refined grain intake. Consumers can enjoy up to six or seven servings per day of refined grains without increasing risk for coronary heart disease, Type 2 diabetes, hypertension or premature death.”

Earlier this year, a Lancet study noted that higher intake levels of dietary fiber and whole grains are linked with a lower risk of non-communicable diseases, body weight and cholesterol levels. The research highlighted the importance of carbohydrate quality in our diets, which may be particularly salient as low carb diets continue to trend. 

Next in research
Future research efforts must distinguish between staple grain foods, such as cereals, breads and pasta and indulgent grain foods, such as cakes, cookies and donuts, according to Gaesser. Most of the studies included in the current paper did not make such distinctions, so it’s impossible to know whether the results would be different if refined grains were categorized separately as staple or indulgent grain foods. 

“My guess is that the risk of chronic diseases would be different for consumption of staple grain foods as compared to consumption of indulgent grain foods,” Gaesser says.

Randomized-comparison trials are needed to better differentiate the health effects of whole grain and refined grain foods. Most published studies have been too short and do not include enough outcome measures to draw definitive conclusions. 

“Currently, the results of randomized-comparison trials show no consistent benefits of whole grain foods over refined grain foods. These findings are at odds with the results of large-scale observational studies, that show a clear superiority of whole grains over refined grains. This is a paradox that needs to be resolved,” Gaesser concludes.

By Kristiana Lalou