Feb. 11, 2000 (Atlanta) -- Veggie burgers, soy milk, heart-healthy margarine -- consider them options in a well-diversified, cholesterol-lowering 'portfolio,' say authors of a new study. Their results show that small daily investments in these readily available foods can improve blood cholesterol levels significantly -- when combined with a low-fat, low-cholesterol diet. Ratios of 'good' and 'bad' cholesterol are important indicators of heart disease risk.
Describing his results as "very hopeful," lead author David J. A. Jenkins, MD, PhD, professor of metabolic/nutritional sciences at the University of Toronto School of Medicine, tells WebMD that 13 to 14 grams daily of soy or vegetable protein foods -- such as the typical veggie burger -- increased good cholesterol (HDL) levels and reduced total cholesterol. The study was published recently in the scientific journal Metabolism: Clinical and Experimental.
"We showed that people can make big differences in their cholesterol ratios -- and without eating particularly large portions. [People in the study] quite easily accommodated 14 grams of soy protein on a regular basis, just one meal in the day," says Jenkins. "Many companies are producing soy products, taking it quite seriously. There's much to choose from. It's much easier for our Western-diet eaters to get satisfaction from the manufactured products than from a block of tofu."
Previous research has shown that dietary changes can reduce bad cholesterol (LDL) by as much as 18%. By increasing intake of soluble fiber and vegetable protein, total cholesterol levels can be reduced by an additional five to 10% or more. Also, other plant products -- including flavonoids in fruits and vegetables, isoflavones in soy, and lignans in flaxseed -- may help prevent harm from cholesterol.
Cholesterol-lowering medications can achieve reductions of 15-20% -- but Jenkins says the same can be achieved through dietary changes.
In this study, the authors recruited 15 men and five women, average age 58, and all with high cholesterol. The 20 people were already participating in an eight-week National Cholesterol Education Program (NCEP) study that required a daily diet low in saturated fat (less than 7 mg daily) and cholesterol (less than 200 mg cholesterol daily). Every day, each person in the study substituted a meal item with something from a list of readily available soy, fiber, or vegetable protein foods.
The study participants were divided into two groups. Frozen dinners, veggie burgers and wieners, and vegetarian cold cuts were among the treatment group's choices. Soluble-fiber food choices consisted of dried soups and breakfast cereals containing oat, barley, and legumes. On the comparison group's list: typical low-fat items such as skim-milk yogurt, low-fat cheese, and cottage cheese, and a number of low-fat, low-soluble-fiber microwavable frozen foods.
At the end of the eight-week study, the treatment group's cholesterol levels showed significantly higher HDL cholesterol. The LDL cholesterol was also significantly reduced. While one woman was on hormone replacement therapy and one man was being treated with a cholesterol-lowering medication, neither responded differently from the other subjects, says Jenkins.
While describing this study as "a modest attempt at introducing soy foods into the diet," Jenkins says that even higher dietary levels of soy, water-soluble fiber -- and other new options like cholesterol-lowering margarines -- could bring the 15-20% reductions possible with medications.
Providing objective commentary, William Wong, PhD, research scientist at Children's Nutrition Research Center in Houston, tells WebMD, "The findings are very interesting. ... But at this time, you cannot tell if it was the soy protein or the soluble fiber [that created their results]. Especially since the amount of soy protein they were given was 14 grams a day, which was pretty small. To my knowledge, the lowest amount [of soy protein] to be shown effective is about 20 grams. I wish they had put one group on soluble fiber, one group on soy protein, then combined the two. That would be a very, very interesting study."
Erica Frank, MD, lipid researcher at Emory University School of Medicine in Atlanta, tells WebMD, "They did a really good job. ... It's pretty fair to say that the results were attributable to soy. Putting this in the context of other studies, it's pretty clear this is another vote for plant-based diets and soy. ... People need suggestions for good-tasting soy products ... soy milk, soy nuts, smoked tofu is fabulous. It's easy to marinate tofu, sprinkle soy sauce on it and marinate it for an hour and it actually tastes pretty good."
- According to a recent study, just 13 to 14 grams of soy or vegetable protein foods, the amount found in a veggie burger, can raise levels of 'good' cholesterol and lower total cholesterol.
- One researcher argues that dietary changes can improve cholesterol levels just as well as medications.
- One critic of the study says that it is unclear whether the soy or soluble fiber was responsible for the change in cholesterol, as the study subjects were eating both.