by Elizabeth A. Rondini and Maurice
R. Bennink
Food Science and Human Nutrition
Michigan State University
Introduction
Heart disease remains the leading cause
of death in the United States (1). Factors that increase one's risk of
developing heart disease include high levels of total cholesterol and LDL
cholesterol ("bad cholesterol"), low levels of HDL cholesterol
("good cholesterol"), obesity, diabetes, smoking, and high blood
pressure. Both what you eat and how you live can alter one's risk of heart
disease (2-4).
How
Beans Can Help Reduce the Risk of Heart Disease
Only one epidemiological study has examined the frequency of
legume consumption and risk of coronary heart disease in US men and women.
After adjusting for confounding risk factors, individuals consuming legumes at
least 4 times per week were found to have a 22% lower risk of heart disease
than individuals consuming legumes less than once per week (4). In the Health
Professionals Follow-up Study, men that adhered to a more "prudent
diet" which included greater consumption of whole grains, legumes, fish,
and poultry had a 30% lower risk of having heart disease. Conversely,
individuals following a more "Western" diet, characterized by
increased consumption of red meat, refined grains, sweets, French fries, and
high fat desserts had a higher risk of heart disease (3). Similar trends were
seen in the Nurses Health Study (5). The relative risk of coronary heart
disease in the 20% of women that followed the "prudent" dietary
pattern more closely was 0.76 compared to 1.46 for women eating a
"Western" type pattern (5). Thus, those that most consistently ate
the "prudent" type of diet had one half the risk of developing heart
disease compared to those that most often ate the "Western" type of
diet.
A 1% reduction in total cholesterol
corresponds to about a 2% decrease in the risk of developing heart disease (6).
Beans are a good source of soluble dietary fiber, containing approximately 4 g
per 1cup cooked portion (7). Soluble fiber has been shown to reduce blood
cholesterol in epidemiologic (8), clinical (9-12), and animal (13, 14) studies.
Data from several human intervention trials indicate that consumption of canned
(11, 15, 16) and dry beans (11, 12, 17-19) reduce serum cholesterol.
Differences in experimental design, the control diet used, and heterogeneity in
the intervention groups make direct comparisons among the studies difficult.
Only two studies (20, 21) did not find favorable changes in serum lipoproteins
when beans were consumed. Generally, in carefully controlled clinical studies
where the macronutrient intake was matched and the fiber content in the bean
fed group was at least twice that of the control diet, significant reductions
in both total and LDL cholesterol occurred (9, 11). Significant increases in
HDL cholesterol (11, 12, 16) and/or reductions in triglycerides (12, 22) were
also seen in many but not all of the studies (9, 11). The consumption of
dietary fiber in the US is only 12-13 g/day, well below the recommended 25-35
g/day. Incorporating one cup of cooked beans into the diet would add 12 g of
total fiber and 4 g of soluble fiber per day. This increase in fiber intake
would be expected to modestly lower serum cholesterol and risk of heart
disease, especially in hyperlipidemic individuals.
In addition to cholesterol, recent
attention has focused on high levels of plasma homocysteine as an independent
risk factor for vascular disease (23, 24). Using meta-analysis, Boushey et al.
(23) determined that individuals with elevated homocysteine had 1.7 to 2.5
times greater risk for developing cardiovascular disease. In the Framingham
Heart Study 29.3% of the subjects had elevated homocysteine (>14 umol/L).
Within this group, plasma homocysteine was inversely related to plasma folate
levels and with intake of dietary folate and vitamin B6 (24). Cleophas (25)
suggests that increasing the consumption of folate-containing foods may lower
the prevalence of vascular disease in people with elevated homocysteine.
Controlled studies examining the potential of folate-containing foods to reduce
homocysteine and therefore vascular disease need to be conducted (25). The
current RDA for folate is 400 mg/day for adult men and women, and beans provide
a significant amount of folate (approximately 110 mg per cup of cooked beans),
ranging from 140 mg in blackeyed peas to 87 mg in red kidney beans (calculated
from (26)).
Beans also contain compounds called
phytonutrients. Phytonutrients are non-essential compounds in foods that can
provide health benefits and some of the phytonutrients found in beans have been
reported to reduce risk factors associated with cardiovascular disease.
Eating beans can help maintain
desired weight, can help reduce blood glucose, insulin, and cholesterol
concentrations, and can help reduce the incidence and adverse consequences of
diabetes. Thus, eating beans will help reduce your risk of premature
atherosclerosis (heart attacks, strokes, and peripheral vascular disease). Of
course other dietary factors, lifestyle and genetic background all strongly
influence cardiovascular risk. Eating beans is just one practice that you can
do to help reduce cardiovascular disease.
