The study, published in the December 2002 issue of Metabolism, is the first to examine the effects of these dietary components in combination. Scientists have known for many years that, individually, soy proteins, nuts, viscous fibres such as those found in oats and barley, and plant sterols (a substance found in vegetable oils and also in leafy green and non-starch vegetables) have the ability to reduce blood cholesterol levels by approximately four to seven per cent. However, the study found that mixing these components together in a "combination diet" reduced levels of LDL cholesterol - the so-called "bad" cholesterol believed to clog coronary arteries - by a dramatic 29 per cent. The finding suggests this combination diet may be as effective as the first generation of a class of drugs known as statins, which have been the standard drug therapy for high cholesterol for the last 15 years.
"This opens up the possibility that diet can be used much more widely to lower blood cholesterol and possibly spare some individuals from having to take drugs," said lead author David Jenkins, a professor in U of T's Department of Nutritional Sciences and director of the Clinical Nutrition and Risk Factor Modification Centre at St. Michael's Hospital.
Jenkins and his research colleagues measured the cholesterol levels of 13 people who went on the combination diet for a month. The diet followed a seven-day plan using foods available in supermarkets and health food stores, including vegetables such as broccoli, carrots, red peppers, tomato, onions, cauliflower, okra and eggplant; oats, barley and psyllium; vegetable-based margarine; soy protein from products such as soy milk and soy sausages, cold cuts and burgers; and almonds, among other ingredients. A typical day on the diet might include a breakfast of soy milk, oat bran cereal with chopped fruit and almonds, oatmeal bread, margarine and jam; a lunch of soy cold cuts, oat bran bread, bean soup and fruit; and a stirfry dinner with vegetables, tofu, fruit and almonds.
Jenkins cautioned that more study is needed before the combination diet will be able to give relief from the use of statins. "The take home message right now is that there is hope for a drug-free treatment for some people with high cholesterol. For us, the main feature now is to move this forward into longer-term studies," he said.
Jenkins noted, for example, that the researchers also plan to examine the effects of the combination diet after a six-month period, including a look at how well people are able to incorporate the diet into their daily lives.
"We see this as being a work in progress and we shall look at new plant components to add to the diet," said Jenkins. He added that although the combination diet is vegetarian, people who follow the principles of the diet but also take animal proteins may also see a dip in their cholesterol levels. However, he explained, "The closer they follow this diet, the closer they're going to get to a 30 per cent reduction in blood cholesterol levels."
The study received funding from Loblaw Brands Ltd., the Almond Board of California and the federal Canadian Research Chair Endowment. Other Department of Nutritional Sciences researchers participating in the study included post-doctoral fellow Cyril Kendall, graduate student Augustine Marchie, technician George Koumbridis and research dietitians Dorothea Faulkner and Tina Parker, both also of St. Michael's Hospital. The research team also included Professors Robert Josse, Lawrence Leiter and Philip Connelly of the Faculty of Medicine and St. Michael's Hospital; statistical consultant Edward Vidgen; Elke Trautwein, a scientist with Unilever R&D Vlaardingen, The Netherlands; and Karen Lapsley, science director of the Almond Board of California.
The University of Toronto, Canada's leading research university with 60,000 students, is celebrating its 175th anniversary in 2002. On March 15, 1827, King's College - precursor to the University of Toronto - was granted its royal charter by King George IV. The university now comprises 31 divisions, colleges and faculties on three campuses, including 14 professional faculties, numerous research centres and Canada's largest university library system - the fifth largest research library in North America.
Department of Nutritional Sciences