A review of studies on cereals, legumes and prevention of coronary heart disease published in 2006 has summarised most of the relevant research. Four epidemiological studies reported legume consumption was significantly and inversely associated with cardiovascular disease (CVD) risk. Three of those studies were conducted in Asia, where the main legume is soy, but at least one American study, where other legumes are more commonly consumed, also reported a protective association.
The NHANES I Epidemiologic Follow-up Study found that legume consumption was significantly and inversely associated with the risk of CHD and CVD. Legume consumption four times or more a week (compared with less than once a week) was associated with a 22% lower risk of CHD and an 11% lower risk of CVD.
The Japanese are one population who have a traditionally high intake of legume based foods. The Japan Collaborative Cohort Study followed over 60,000 adults for 13 years and found the highest bean intake (4.5 serves a week) was associated with a 16% reduction in total CVD risk and a 10% reduction in total mortality.
It is possible that the high soy intake in Japan is responsible for this effect. A meta-analysis of 23 trials using intact soy isoflavones found an LDL cholesterol lowering effect of 5%, independent of initial cholesterol levels.
In another meta-analysis using soy studies (20-133g/d soy protein), the mean LDL-cholesterol reduction for soy was 0.17 mmol/L (n = 22; P < 0.0001) or 4.3%, which was confirmed in 11 studies reporting balanced macronutrient profiles.
Since 1999 the US FDA has permitted food manufacturers to claim that foods high in soy protein may help lower heart disease risk and recent meta-analyses continue to support this relationship.
New research suggests diets higher in protein and fibre derived from lupin-enriched foods may provide cardiovascular health benefits in terms of insulin sensitivity and blood pressure. In a 12-month parallel-design trial with 131 overweight participants, the effects of a lupin-enriched diet on body weight and cardiovascular disease risk factors, including blood pressure and fasting insulin levels, was investigated. The lupin-enriched diet, relative to control, did not significantly influence weight loss or measures of body fat and fat-free mass. However, relative to control, 24-hour ambulatory systolic and diastolic blood pressures were lower at 12 months, as were fasting insulin concentrations.
The positive effect of lupin kernel four-enriched bread on blood pressure has further been verified in a controlled intervention study with 88 overweight men and women. A diet moderately higher in dietary protein and fibre, attained by substituting lupin kernel flour for wheat flour in bread, resulted in significant decreases in blood pressure.
Suggested Mechanisms:
The fatty acid profile, dietary fibre, isoflavones and antioxidants in legumes may contribute to reducing the risk of cardiovascular disease through their hypocholesterolaemic effect. Legumes are also good sources of saponins and phytosterols which may assist with decreasing absorption of cholesterol from the gut. With regards to blood pressure, soy isoflavone extracts have been found to reduce this major risk factor for heart disease, especially systolic blood pressure.
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