Researchers look at fructose, high blood pressure link

Posted June 14, 2012

Left to right: Dr. Sofia Ahmed, Michelle Mann, and study coordinator Darlene SolaResearchers with Alberta Health Services (AHS) and the University of Calgary are trying to better understand how consumption of a particular sugar – fructose – elevates blood pressure.

“Our theory is that fructose, in effect, turns on a hormonal switch that raises blood pressure,” says Dr. Sofia Ahmed, an AHS nephrologist and member of the University of Calgary’s Libin Cardiovascular Institute and the Alberta Kidney Disease Network. “This has been proven in animal studies but it’s never been demonstrated in humans.”

Researchers are trying to find out if the renin-angiotensin system (RAS) becomes activated – releasing the angotensin II hormone – when people consume fructose.

“We’re not concerned about the levels of fructose people consume from natural sources, like fruits and honey. We’re looking specifically at the consumption of high levels of fructose found in sweetened beverages and foods,” Dr. Ahmed says.

In the study, healthy people will consume fructose in amounts equivalent to six or seven 12-oz. (355 ml) soft drinks daily for two weeks.

“We know from previous human studies that this daily amount temporarily increases blood pressure in healthy adults,” says Dr. Ahmed, who expects the blood pressure of her healthy study participants to elevate to ‘high-normal’ range after two weeks then return to normal after they stop consuming high levels of fructose.

During the test period, researchers will measure RAS activity, blood flow to the kidney, blood pressure, arterial stiffness, heart rate variability, and insulin and glucose biochemistry. The same routine will then be repeated, but with dextrose, a different type of sugar. Increased activity of the RAS tells the body to hold on to salt and water, and puts additional stresses on the kidneys.

“While high blood pressure is a health concern in and of itself, there is also a danger that continued activation of the RAS can damage the heart and kidneys in the long term. If you think of the kidney like a car, the harder it is driven, the sooner it stops working,” Dr. Ahmed says.

If researchers can pinpoint whether fructose activates the RAS, then health care providers will be able to provide more complete and accurate nutrition advice to patients when it comes to consuming foods that contain fructose.

Fructose is sweeter per gram than conventional sugar and has been used widely in processed foods and beverages since the mid-1970s, often in the form of high fructose corn syrup.

“The problem is, the introduction of high fructose corn syrup has paralleled a rise in obesity, high blood pressure and irritable bowel syndrome,” Dr. Ahmed says. “It’s been part of an evolving fast food diet that does more harm than good.”

Albertans consume an average of 400 litres of sugar-sweetened beverages per person per year, according to current data from Statistics Canada and consumer research. This includes products like non-diet bottled and fountain soft drinks, energy drinks, iced tea, sports drinks and flavoured waters.

“Most people are shocked when they learn how much of this stuff we consume,” says Sue Buhler, dietitian and research and academic lead for AHS Nutrition Services. “But there is little, if any, nutritional value in these drinks – they contain only empty calories. We also know that they’ve been linked to multiple chronic diseases.”

AHS and Health Canada recommend that consumers choose foods and beverages with little or no added sugar.

Anyone interested in participating in the study is asked to phone 403-944-2745 or email dsola@ucalgary.ca. Researchers are looking for healthy non-smokers who can commit to three mornings from 8 a.m. to noon.

Dr. Ahmed maintains a clinical practice, is an Assistant Professor in the University of Calgary’s Department of Medicine, an Alberta Innovates – Health Solutions Clinical Investigator and a Canadian Institutes for Health Research New Investigator.

Alberta Health Services is the provincial health authority responsible for planning and delivering health supports and services for more than 3.7 million adults and children living in Alberta. Its mission is to provide a patient-focused, quality health system that is accessible and sustainable for all Albertans.