Research Evaluates Genetics, Diet as Predictors of Disease

PhD student explores growing field of nutrigenomics

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Grad student Amy Tucker

What affects your risk of developing heart disease or diabetes? What you eat and how you’re made are two key factors, says Amy Tucker, a PhD student in the Department of Human Health and Nutritional Sciences (HHNS). She hopes her studies of how bread choices alter risks for two of Canada’s top killer diseases will provide information for food producers and consumers alike.

Along with Prof. Alison Duncan, Tucker investigates nutrigenomics, or interactions between food and genes that can cause disease. Referring to those connections, she says, “Your DNA influences how you respond to dietary changes.”

Within HHNS, both researchers are among a growing group of experts in this field, including several co-authors of a 2010 bread study published in the journal Nutrition & Metabolism. Tucker was lead author for that paper, which looked at the health effects of whole-grain bread. Besides Duncan, her Guelph co-authors were master’s student Kathryn MacKay and Profs. Lindsay Robinson, Terry Graham and Marica Bakovic.

That study was the first to compare whole-grain sourdough bread with white bread. Other studies have found that whole grains can reduce risks of cardiovascular disease (CVD) by altering the mix of cholesterol and triglycerides in the blood.

Tucker says last year’s study was also the first to look at connections between bread and a particular gene involved in cardiovascular disease, a leading cause of death. Most people get most of their carbohydrates from bread, she says. “We’re ultimately trying to prevent or delay CVD risk through diet.”

The researchers tested subjects aged 45 to 70 eating either whole-grain bread or white bread. One group had normal blood glucose levels; the other group was dysglycemic, or had high glucose levels. Along with other measures such as weight and waist circumference, members of the latter group were at greater risk for CVD. After six weeks on one type of bread, the participants switched to the alternative for the same period.

Blood lipid levels showed no change from one bread type to the other in either group of participants. Tucker says that result might change if whole-grain choices were substituted for other carbohydrate sources besides bread, such as rice or pasta.

Says Duncan, “What you choose to eat every day really can make a difference in your long-term health, and this research provides evidence of that.”

In healthy subjects with a particular version of the marker gene, amounts of LDL (“bad”) cholesterol increased with whole-grain bread compared with white bread. In dysglycemic subjects with that gene version, triglycerides, or fats in the blood, increased.

That means it’s important to look at genetic variations in assessing CVD risk, says Tucker. And, she adds, consumers need to read food labels. Besides their specific effects on fats and blood glucose levels, whole-grain products provide nutrients and fibre that also promote health.

Following last year’s study, she’s now looking at bread consumption and Type 2 diabetes.

Heart disease and stroke are two of the three leading causes of death in Canadians. Up to 80 per cent of people with diabetes will die of heart disease, according to statistics from the Canadian Diabetes Association.

Last year, Tucker became a volunteer presenter with the association. She gives monthly talks to groups near her home in Milton, Ont. Those are presentations designed by the association rather than discussions of her research. But she says “it helps that I’m educated in the field. It means more to me because I’ve studied it.”

Originally from Windsor, Ont., she began undergrad studies in biochemistry but switched to nutritional sciences. She had taken a first-year nutrition course and liked the idea of applying her learning to everyday life.

That switch led to a work-study assignment with Robinson, an experience that whetted the student’s appetite for grad studies. “It’s always changing, you’re on the cutting edge of what’s happening, and there’s always so much to learn.”