According to the Brussels-based International Diabetes Foundation’s (IDF) 2014 Diabetes Atlas, there are 387 million people worldwide living with diabetes for a prevalence of 8.3 percent. Some 46.3 percent of these cases are undiagnosed. The incidence of diabetes in North America and the Caribbean make it the second highest region in the world at 9.6 percent, beaten only by MENA (Middle East/North Africa). In North America, the U.S. has the highest incidence at 24.4 million, followed by Mexico, Canada and Haiti.
Additionally, many more are pre-diabetic with IGT (impaired glucose tolerance, high blood glucose after eating) or impaired fasting glucose (IFG, high levels after fasting). IDF notes those with IGT are at high risk to develop type 2 diabetes, the most common kind. Pre-diabetics share many characteristics with type 2 diabetics, including the ability to prevent the disease through diet, physical activity and lifestyle changes. IDF notes that up to 80 percent of type 2 diabetes is preventable by such changes.
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With the close link between diet and weight, “simply” keeping one’s weight down is a key strategy to reduce the risk of diabetes. However, researchers also look at specific dietary components for diabetes risk reduction, such as dietary fibers and the emerging role of gut “microbiota,” the relative abundance of types of bacteria and other microbes in the digestive system.
Fiber and microbiota
In a report published in the May 29 issue of Diabetologia, researchers evaluated the association between dietary fiber consumption and type 2 diabetes with an EPIC-InterAct study and a meta-analysis including 18 other studies.
The EPIC-InterAct study showed that dietary fiber, particularity cereal fiber, reduced the risk of diabetes. However, after adjusting for weight (BMI), the result was no longer statistically significant; that is, reduced diabetes risk was directly associated with reduced weight. The meta-analysis of the 19 studies indicated the greatest reduced incidence of diabetes and increased consumption occurred for total fiber, followed by cereal, fruit and then vegetable fiber.
Claudia O’Donnell is co-owner of Global Food Forums, Inc.
However, an important mechanism at least partially explains the association between fiber and type 2 diabetes that moves beyond weight management and includes fiber from other sources. "Soluble dietary fiber, more specifically fermentable soluble fiber, from foods such as whole grains and pulses, slows gastric emptying, delays glucose absorption and improves postprandial glycemic response,” says Kelley Fitzpatrick, M.Sc., R.D., of NutriTech Consulting. “Insulin resistance is a major risk factor for type 2 diabetes. In addition to being beneficial for individuals with diabetes, both whole grain and pulse consumption have been shown to prevent insulin resistance and also may improve insulin sensitivity among those with impaired glucose tolerance, even in the absence of weight loss.”
Rhonda Witwer of Witwer Works LLC adds: “Fermentable resistant starch offers the strongest data of any of the individual dietary fibers.” She notes Denise Robertson, Ph.D., University of Surrey, has published numerous studies examining the glucose metabolism impact of resistant starch over the past decade. Witwer quotes Robertson’s writing: “Chronic resistant starch intake has been found to improve peripheral insulin sensitivity in both adipose tissue and skeletal muscle, to change gene regulation in pathways linked to fatty acid metabolism, to enhance first-phase insulin secretion, and to increase fat oxidation and reduce appetite.” You can read more here.
Some of the most recent research in this area appeared in an unpublished thesis and a conference abstract, which can be accessed through Witwer’s website www.resistantstarch.us.
As of 2015, nine clinical studies have shown that RS2 resistant starch from high-amylose corn improved insulin sensitivity in healthy adults, in adults with pre-diabetes (i.e., people with high insulin levels) and in individuals with type 2 diabetes, says Witwer.
“The driver for these improvements is a cascade of biochemical changes caused by gut fermentation,” Witwer goes on to explain. Fiber fermentation changes the composition of the microbiota in the large intestine, and more importantly, changes the expression of hundreds of genes that actually improve insulin sensitivity and other aspects of metabolism.
The link between diabetes and an individual’s microbiota is so strong, some have even proposed it as a diagnostic tool. At the Endo 2015 meeting in San Diego this year, researchers from the University of Illinois at Chicago reported that a certain microbiota “is associated with stable, normal blood glucose levels, while a different profile is associated with glucose levels that indicate pre-diabetes.” Their research found bacteria from a specific genus, Akkermansia, was more abundant in the gut of men whose blood sugar levels had improved over the year of the study. See the UIC press release.
Although they note that one’s microbiota is greatly influenced not by environmental factors and genetics as well as diet, the study’s principal investigator, Dr. Elena Barengolts, commented that the study provides additional reasons for physicians to recommend foods, such as prebiotics. More research is needed, however, and she suggests that “the ‘signature’ of the gut microbiota … could be another useful tool in assessing a person’s risk for developing diabetes.”
With diabetes continuing to grow worldwide, a better understanding of how particular foods within a diet impact this disease will be highly beneficial.
