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ASU researchers find pinto beans may lower cholesterol more than oatmeal

August 24, 2007

MESA, Ariz. - Esther Martinez has eaten pinto beans most of her life and admits her family used to use lard when they prepared refried beans. “Now, I eat pinto beans boiled with fresh tomato, whole onion and green chiles or refry them with cheese in canola oil,” said Martinez.

Little did she know that eating pinto beans, prepared without lard, may help lower her cholesterol level, even more so than eating the same serving size of a half cup of oatmeal, according to research conducted by Arizona State University Nutrition scientists.

When Martinez learned that her cholesterol was getting close to 200, though, and was pre-diabetic in 2005, she knew she had to do something to lose weight to address the threat of diabetes or heart disease before it was too late.

As an office specialist senior at Arizona State University’s Polytechnic campus, she saw the bean study as an opportunity to improve her health. Donna Winham, ASU assistant professor of nutrition, was looking for subjects who met certain criteria, such as having higher cholesterol and/or being moderately insulin resistant (pre-diabetic), like Martinez.

“Beans are considered a very affordable, functional, healthy food rich in protein, complex carbohydrates, fiber, minerals and phytochemicals, which are non-nutritive plant chemicals that have protective or disease preventive properties,” said Winham.

In 2005 and 2006, Winham and colleague Andrea Hutchins, with the University of Colorado – Colorado Springs, conducted their 24-week experiment to understand the impact of long-term legume consumption on biomarkers for heart disease and type 2 diabetes risks. In their research they employed canned pinto beans and black-eyed peas and carrots as the placebo. The results of their efforts were published this past summer in the Journal of the American College of Nutrition.

“We chose these beans to study because they are a common legume varieties consumed around the world as part of traditional diets,” said Winham whose research focuses on the use of traditional foods in reducing risk factors for heart disease and type 2 diabetes, and consumer beliefs and attitudes about bean consumption.

The 17 subjects who participated in the nine-month study were asked to eat a half cup of pinto beans, black-eyed peas and carrots every day for eight weeks each. 

“We found that daily pinto bean consumption of a half cup resulted in an average drop of total cholesterol and LDL-cholesterol of more than 8 percent. In contrast, a half cup of oatmeal will reduce cholesterol 2-3 percent,“ said Winham.
Initial results from the study suggested that pinto beans were effective at lowering overall cholesterol levels and the black-eyed peas appeared to have little effect.  However, closer analysis of the data showed that a few participants appeared to be less compliant in eating the black-eyed peas than the pinto beans or carrots.  The researchers hope to retest black-eyed peas for cholesterol reduction.

“The benefit of the study is that it proves that long-term consumption of pinto beans does have a significant impact on lowering the risk of heart disease,” said Winham. “A diet that incorporates beans might be as productive as taking a statin.”

And while pinto beans have been proven to be effective, Winham and Hutchins stress that legume variety is key in the diet.

“Different beans are recognized for achieving different effects on biomarkers, so it’s important to incorporate an assortment into the diet,” said Winham.

The research was funded with a grant of $187,000 by Beans for Health Alliance (BHA) through the U.S. Agency for International Development (USAID).  Her research is part of a larger project, conducted by the BHA, where several studies are looking at these functional foods for health benefits.

All this research helps people like Martinez. Today, she continues to lose weight and incorporates beans into her diet almost on a daily basis. “I’m not pre-diabetic anymore and my overall cholesterol was at 186 after the study,” Martinez proudly claims, and she did it without medications.

For more information or to reach Winham, contact her by e-mail at