1	Effects of high and low isoflavone soy foods on blood lipids, oxidized LDL, homocysteine, and blood pressure in hyperlipidemic men and women David JA Jenkins, et. al. Am J Clin Nutr 2002; 76:365-72
2	Soy and Isoflavones Soy and soy-containing products have increased in popularity in recent years. Researchers are interested in the benefits of soy and the reduction of coronary artery disease (CAD).
3	Soy and Isoflavones Particular attention has been paid to the isoflavones found in soy-protein. Isoflavones are classified as phytoestrogens. They have been associated with lowering cholesterol through LDL receptor up-regulation, antioxidant activity and improved vascular reactivity.
4	Soy and Isoflavones In addition to improving blood lipids and vascular reactivity, researchers wanted to know whether or not isoflavones would improve other cardiovascular risks, such as high blood pressure and lowering homocysteine levels.
5	Research A three-month study was conducted with 41 subjects (23 hyperlipidemic men and 18 postmenopausal women, with no evidence of diabetes, liver complications; none of the subjects were taking hypolipidemic medications). The study was divided into a three 1-month phases; each phase was separated by a two-week rest period.
6	Research The three phases consisted of a dairy and egg protein phase (control), and two soy-protein phases, one high and the other low in isoflavones. The subjects followed their own self-selected National Cholesterol Education Program Step II diet (<7% of energy from saturated fat and <200 mg dietary cholesterol/d).
7	Phases of the study In the first phase (the control), the subjects replaced their main-protein containing foods (meat, fish, eggs, nuts and legumes) with low fat dairy products (skim milk, cottage cheese, yogurt and cheese made from skim milk).
8	Phases of the study In the second and third phases, the main-protein containing foods were replaced with low-fat soymilk, soy hotdogs, soy burgers, tofu nuggets and soy cold cuts. These foods were made from either high or low isoflavone-containing soybeans. Subjects did not know the isoflavone content in their foods.
9	Phases of the study Foods were provided for the subjects. They were delivered to the subjects’ homes biweekly and were kept refrigerated or frozen until consumed.
10	Collecting data The subjects were given digital electronic scales to weigh all foods consumed and were required to check off the foods from a weekly list provided. A seven-day diet history was required during the fourth week of each phase.
11	Collecting data In addition, subjects were instructed to not consume additional dairy, soy, legumes, nuts or viscous fiber sources during the study. Blood samples and blood pressure measurements were collected at the start and end of each phase. Urine samples were collected in the last week of each phase.
12	Collecting data A dietitian reviewed the seven-day diet histories completed by the subjects. All uneaten foods were returned to clinic during visits.
13	Results Subject compliance in the study was good. No significant differences were seen in blood lipids between high and low isoflavone diets. The results for both were lower than the control values for total cholesterol, total:HDL cholesterol, LDL:HDL cholesterol, apolipoprotein B:A-I and estimated CAD risk.
14	Results In the high isoflavone phase, LDL cholesterol and apolipoprotein B were lower than in the control. LDL cholesterol and apolipoprotein B were also lower in the low isoflavone phase than the control, but results were not as significant. A lower systolic blood pressure was seen in men but not women during the isoflavone phases.
15	Discussion The results indicate that a diet containing soy-isoflavones provides a wide range of CAD reduction benefits. There are no distinguishable differences in benefits between high and low isoflavone content diets. Further studies are necessary to determine if benefits can be achieved by taking soy supplements or whether it is better to replace animal protein foods with soy.