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Barley’s health benefits

The beta-glucan project results may help barley breeders and processors who want to work toward further enhancing the healthfulness of barley food products. Photo by Janet Kanters.

Research has already proven that barley beta-glucan lowers cholesterol. Now a major clinical trial has answered some previously unanswered questions about this effect. Plus it has identified improvements in gut microbes from eating beta-glucan and a possible link between a person’s genetic makeup and beta-glucan’s effectiveness. Results from the project could help advance the food barley value chain.

Beta-glucan is a type of viscous dietary fibre. “Both barley and oats are rich sources of beta-glucan. In contrast, wheat contains almost no beta-glucan, and corn and rice have none at all,” explains Nancy Ames, a food scientist with Agriculture and Agri-Food Canada (AAFC) in Winnipeg, who was the project’s principal investigator.

The health effects of consuming beta-glucan have been examined in many studies. The two best documented health benefits are cholesterol lowering, which helps reduce the risk of heart disease, and reduction of glycemic response after a meal, which helps control/prevent diabetes.

Several countries, including Canada and the United States, have approved health claims on the cholesterol-lowering effect of barley beta-glucan. According to Health Canada, consumption of at least three grams of barley beta-glucan per day helps reduce cholesterol.

Ames and her AAFC team were the ones who prepared the submission for this health claim, conducting a comprehensive analysis of all the scientifically valid studies on the topic. The claim was submitted by the Alberta Barley Commission to Health Canada in 2009 and was approved in 2012.

While preparing the submission, Ames and her team found certain gaps in the scientific information. So she and Susan Tosh of AAFC’s Guelph Food Research Centre developed a multi-year project to delve deeper into barley beta-glucan’s cholesterol-lowering effect.

“Our first interest was whether processing made a difference to the cholesterol-lowering effect. We knew that processing can sometimes affect beta-glucan’s viscosity, and we wondered: Is it possible that low versus high viscosity makes a difference in cholesterol lowering?” Ames says. “We also wanted to look at the optimal dose of beta-glucan required for health effects because there wasn’t a proper dose-effect study. So we decided to look at those together.”

The project also explored the physiological mechanism responsible for beta-glucan’s cholesterol-lowering effect; the influence of beta-glucan on gut microbes; and a possible genetic component in people’s response to beta-glucan. The project involved both barley and oats; the researchers used oats in much of the work to develop measurement methods, and they used barley for the clinical trial.

To carry out the project, Ames brought together a large, multidisciplinary team that included Tosh and several scientists from the University of Manitoba and its Richardson Centre for Functional Foods and Nutraceuticals, as well as technicians and graduate students.

A continuum of advances
The project involved a number of phases, with the progress made in each phase providing the foundation for subsequent work.

In the initial phase, the researchers used a range of processing treatments on barley to see if they could increase or decrease beta-glucan’s viscosity. They found that when normal barley is processed and prepared in normal ways, the beta-glucan has a higher viscosity than the untreated grain. Ames notes, “You always hear people say that processing is bad. But in this case, processing was good.”

The researchers also found certain techniques that reduced beta-glucan’s viscosity; those techniques are not commonly used in barley processing.

As part of doing this work, the researchers developed a faster way to measure beta-glucan’s viscosity. This method could also be used by processors to measure the beta-glucan characteristics of prototype food products, and by crop breeders to screen breeding materials.

Based on this initial work on processing and viscosity, the researchers were able to create barley foods with low and high viscosity beta-glucan for use in the clinical trial.

The trial compared the effects of four different breakfasts: a barley-based diet with three grams of high viscosity beta-glucan; a barley-based diet with three grams of low viscosity beta-glucan; a barley-based diet with five grams of low viscosity beta-glucan; and a heart-healthy wheat- and rice-based diet, as a control.

During the course of the trial, the researchers measured a number of health characteristics in the participants such as body weight, body fat distribution and blood pressure. They also collected blood and fecal samples, and analyzed the samples for various factors related to the cholesterol-lowering mechanism, gene-by-diet interactions, and gut microbes.

The clinical trial showed that viscosity definitely matters. Ames says, “Out of all the treatments, the high viscosity treatment had the greatest effect on lowering cholesterol.” Now in all their beta-glucan studies, the researchers measure not only the amount but also the viscosity of beta-glucan.

These results support the barley health claim. “Since normally processed barley foods have high viscosity beta-glucan, then health claims for the cholesterol-lowering effect of beta-glucan will be valid for the barley foods most commonly encountered by consumers,” Ames explains.

She adds, “It is easy to eat barley every day and get the amount of beta-glucan you need.”

The project also shed light on the mechanism of beta-glucan’s cholesterol-lowering effect. Through measurements of blood cholesterol and other factors, the researchers were able to identify which of several proposed mechanisms was likely to be the one responsible.

As well, they identified a possible gene-diet interaction. Although many studies have found that some individuals respond differently than others to dietary changes, this study is the first one to report a gene-related difference in response to beta-glucan. The results indicated that trial participants with a certain variant of a key gene had less of a response to beta-glucan’s cholesterol-lowering effect than participants with other variants of the gene.

That finding needs to be confirmed by further studies. If it is proven, then it would have implications for personalized nutrition. For example, potentially a doctor could simply do a blood test to see how well a patient would respond to beta-glucan as a possible treatment to lower his or her cholesterol.

The researchers were interested in the effects of beta-gluten on gut microbial populations because gut microbes are known to play a significant part in human digestion and health. The project’s results showed that consumption of the high viscosity beta-glucan meals significantly shifted gut microbe populations to a healthy pattern. This is the first clinical study to report gut microbial changes in humans due to eating beta-glucan.

The analysis showed that this microbial population shift was associated with reduction of risk factors for cardiovascular disease, such as body mass index, waist circumference and blood pressure. Ames says, “Together, our results suggest that altering gut microbiota may be playing a major role in mediating the health benefits of beta-glucan.”

“I am really excited about our findings,” notes Yanan Wang, a PhD student involved in this project. She explains that better understanding of beta-glucan’s cholesterol-lowering mechanism could provide practical benefits. “By knowing the mechanism, we can use the physiological effects of functional foods in a more effective way.”

Overall, the project has achieved important advances in understanding how beta-glucan works in the human body and how to measure key characteristics of beta-glucan. These findings are helping Ames and her colleagues in their current beta-glucan research, including several clinical trials on viscosity and one on glycemic response.

The project’s results can also help barley breeders and processors who want to work toward further enhancing the healthfulness of barley food products. As well, the findings could help raise interest among health-conscious consumers in food barley products.