Better Bagels Aimed at Better Health

Research looks at effects of resistant starch on diabetes risk

Sarah Dainty, left, and Prof. Alison Duncan

Sarah Dainty, left, and Prof. Alison Duncan

What if reducing your risk of developing Type 2 diabetes or colon cancer was as easy as eating a bagel a day? That’s what researchers in the Department of Human Health and Nutritional Sciences (HHNS) are trying to find out as part of the “better bagel study.”

But not just any bagel has these potential health benefits. These bagels contain 20 grams of resistant starch, up to five times what people consume on average daily. The control bagels have no resistant starch.

“Resistant starch is a type of dietary fibre,” explains Prof. Alison Duncan, the study’s director. The study aims to determine whether resistant starch can reduce the body’s glycemic response, measured by an oral glucose tolerance test, which can diagnose Type 2 diabetes.

Resistant to digestive enzymes, the starch slows down digestion, making food travel more slowly through the digestive tract and reducing the body’s absorption of glucose. It’s not easy to get enough resistant starch from your diet, because it’s found in a limited number of food sources, such as legumes and unripe bananas.

“Overall dietary fibre intake is low as well,” says Duncan. Since resistant starch spends more time in the colon, it ferments, which “alters the bacterial composition of the colon.” One of those “gut-healthy compounds” produced by this fermentation is butyrate, a short-chain fatty acid. The researchers will also look at the effects of resistant starch on satiety – or feeling full – which is known to increase with fibre consumption.

The resistant starch being studied comes from maize developed by the Department of Plant Agriculture. “We’re turning the crop into a functional food, and now we’re testing it in a human clinical study,” says Sarah Dainty, a master’s student working with Duncan on the study.

The researchers worked with bagel producers at Canada Bread, Maple Leaf Foods to ensure that adding resistant starch had a minimal impact on the bagel’s taste and texture.

One difference they noticed was that the flour containing resistant starch absorbed more water than regular flour, making the dough more difficult to mix. “It increased the mixing time greatly,” says Dainty. “Because we added the resistant starch, the mixing time needed to be increased, especially at the initial low speed in order for the ingredients to be distributed evenly. A significant proportion of the flour was replaced with resistant starch.”

As part of the study, participants aged 40 and older will be asked to consume one control or test bagel a day for eight weeks at a time, separated by a four-week break. Financial compensation will be provided. The researchers chose bagels to deliver resistant starch because of their popularity and convenience.

Duncan says she is excited about the interdisciplinary nature of the study, which involves three U of G departments. Professor and CBS dean Michael Emes is the study’s principal investigator, looking at regulation of starch synthesis along with Prof. Ian Tetlow, Molecular and Cellular Biology (MCB). Prof. Emma Allen-Vercoe, MCB, is studying the starch’s effect on gut microflora. Prof. Elizabeth Lee, Plant Agriculture, is helping develop the maize crop high in resistant starch.

A previous study led by Emes and Prof. Terry Graham of HHNS showed that short-term consumption of the resistant starch bagel improved glycemic response in adults with diabetes. The current study will look at the effects of longer-term consumption in adults at high risk of developing diabetes.

For more information or to participate in the study, call 519-824-4120, Ext. 58081, or email bagel@uoguelph.ca.