Coronary heart disease (CHD) is the most common, most frequently reported, and most serious form of cardiovascular disease, and is the No. 1 cause of death in the United States. Despite the decline in deaths from CHD over the past 30 years, this disease still causes more than 500,000 deaths annually, and contributes to another 250,000 deaths. High blood total cholesterol and high low-density lipoprotein (LDL) cholesterol levels are proven risk factors for CHD.
The American Heart Association (AHA) recommends a variety of foods to target four major goals: achieve a healthy overall diet, achieve a healthy weight, promote desirable lipid levels, and promote desirable blood pressure. Specific foods recommended by the AHA include fruits and vegetables, grain products (including whole grains), fish, lean meat and poultry, fat-free or low-fat dairy products, and legumes.1
The Food and Drug Administration (FDA) has evaluated many foods to determine their role in reducing the risk of CHD. The FDA has found a relationship between reduced CHD risk and soy protein (25 g/d), plant sterols/stanols (1.3/3.4 g/d), and soluble fiber (3 g/d).2 If a food product meets certain criteria established by the FDA, the manufacturer may include a health claim for reduced CHD risk in the product labeling.
In addition, the National Cholesterol Eduation Program Adult Treatment Panel III recommends reduction in saturated fat and cholesterol and therapeutic dietary options for enhancing LDL-cholesterol lowering, with inclusion of plant sterols/stanols (2 g/d) and increased soluble fiber (10-25 g/d).1
Although the cardiovascular benefits of soy endorsed by the FDA have been attributed to soy protein, researchers at the Clinical Nutrition and Rsik Factor Modification Center, St. Michael’s Hospital, in Toronto, Ontario, studied the effects of high- and low-isoflavone soy-protein foods on the risk factors for cardiovascular disease (CAD).3 Forty-one hyperlipidemic men and postmenopausal women participated in the study with three one-month diets: a low-fat dairy food control diet and a high- (50 g/d soy protein and 73 mg/d isoflavones) and low- (52 g/d soy protein and 20 mg/d isoflavones) isoflavone soyfood diets. All three diets were very low in saturated fat (< 5% of energy) and cholesterol (< 50 mg/d).
No significant differences were seen between the high- and low-isoflavone soy diets. Compared with the control diet, however, both soy diets resulted in significantly lower total cholesterol, estimated CAD risk, and ratios of total to high-density lipoprotein (HDL) cholesterol, LDL to HDL cholesterol, and apolipoprotein B to A-I. No significant sex differences were found, except for systolic blood pressure, which in men was significantly lower after the soy diets than after the control diet. On the basis of blood lipid and blood pressure changes, the calculated CAD risk was significantly lower with the soy diets (10.1 ± 2.7%).
The authors concluded that the substitution of soy-protein foods for animal products reduces CAD risk, with reductions in blood lipids, oxidized LDL, homocysteine, and blood pressure. Importantly, both diets provided at least 50 g/d of soy protein, twice the FDA recommendation.
Most research on the effects of plant sterols/stanols on cholesterol levels has focused on sterol/stanol-enriched margarines and salad dressings. These oil-based products can lower LDL cholesterol concentrations by 10-14%; however, few studies have examined the effects of low-fat sterol/stanol-enriched products. Mensink et al assessed the effects of plant stanol esters emulsified into a low-fat yogurt on fasting concentrations of plasma lipids and lipid-soluble anitoxidants.4 Sixty non-hypercholesterolemic subjects first consumed three cups (3 ´ 150 mL) of placebo yogurt daily for three weeks. For the next four weeks, 30 subjects continued with the placebo yogurt, while the other 30 subjects received three cups of stanol-enriched (0.71 g sitostanol + 0.29 g campe-stanol) yogurt.
LDL cholesterol increased 0.06 ± 0.21 mmol/L in the placebo group, but decreased 0.34 ± 0.30 mmol/L in the experimental group. The difference in changes between the two groups (0.40 mmol/L or 13.7%) was highly significant (P < 0.001). Effects were maximal after one week. HDL cholesterol and triacylglycerol concentrations did not change. Total tocopherol levels increased by 1.43 micromol/mmol LDL cholesterol (14%, P = 0.015). Beta-carotene levels decreased by -0.02 micromol/mmol LDL cholesterol (-14.4%, P = 0.038).
The authors concluded that low-fat yogurt enriched with plant stanol esters lowers within one week LDL cholesterol levels to the same extent as oil-based products.
Research recently published not only has supported the FDA’s health claim for soluble fiber and cholesterol,5 but also has examined the effects of soluble fiber on hypertension.6,7
In a randomized, controlled, parallel-group pilot study, Keenan et al compared an oat cereal group (5.52 g/d beta-glucan) to a low-fiber cereal control group (< 1.0 g/d total fiber) over six weeks.6 The oat cereal group experienced a 7.5 mm Hg reduction in systolic blood pressure and a 5.5 mm Hg reduction in diastolic blood pressure; there was virtually no change in blood pressure in the control group. The oats group also experienced a significant reduction in total cholesterol (9%) and LDL cholesterol (14%).
Pins et al randomized 88 hypertensive men and women to a 12-week controlled parallel-group trial of whole grain oat-based cereals vs. refined grain wheat-based cereals.7 After four weeks of baseline feeding, antihypertensive medication dose was maintained or reduced by half or completely throughout the middle four weeks of the study. In the final four weeks, participants continued cereal consumption and medication was adjusted according to protocol. Seventy-three percent of participants in the oat group vs. 42% in the control group were able to stop or reduce their medication by half. Treatment group participants whose medication was not reduced had substantial decreases in blood pressure. The oats group also experienced a 24.2 mg/dL reduction in total cholesterol, a 16.2 mg/dL reduction in LDL cholesterol, and a 15.03 mg/dL reduction in plasma glucose levels vs. controls.
1. Kris-Etherton PM, et al. Recent discoveries in inclusive food-based approaches and dietary patters for reduction in risk for cardiovascular diesease. Curr Opin Lipidol 2002;13:397-407.
3. Jenkins DJ, et al. Effects of high- and low-isoflavone soyfoods on blood lipids, oxidized LDL, homocysteine, and blood pressure in hyperlipidemic men and women. Am J Clin Nutr 2002;76:365-372.
4. Mensink RP, et al. Effects of plant stanol esters supplied in low-fat yoghurt on serum lipids and lipoproteins, non-cholesterol sterols and fat soluble antioxidant concentrations. Atherosclerosis 2002;160:205-213.
5. Jenkins DJ, et al. Soluble fiber intake at a dose approved by the U.S. Food and Drug Administration for a claim of health benefits: Serum lipid risk factors for cardiovascular disease assessed in a randomized controlled crossover trial. Am J Clin Nutr 2002;75: 845-849.
6. Keenan JM, et al. Oat ingestion reduces systolic and diastolic blood pressure in patients with mild or borderline hypertension: A pilot study. J Fam Pract 2002;51:369.
7. Pins JJ, et al. Do whole-grain oat cereals reduce the need for antihypertensive medication and improve blood pressure control? J Fam Pract 2002:51: 353-359.