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ARS Home » Plains Area » Grand Forks, North Dakota » Grand Forks Human Nutrition Research Center » Healthy Body Weight Research » Research » Publications at this Location » Publication #199548
Title: Pinto beans are a source of highly bioavailable copper

Author
item Saari, Jack
item Reeves, Phillip
item Johnson, William
item JOHNSON, LUANN - UNIV NORTH DAKOTA

Submitted to: Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/9/2006
Publication Date: 12/1/2006
Citation: Saari, J.T., Reeves, P.G., Johnson, W.T., Johnson, L.K. 2006. Pinto beans are a source of highly bioavailable copper. Journal of Nutrition. 136:2999-3004.

Interpretive Summary: Dietary copper deficiency in laboratory animals has been shown to cause pathological impairment of the heart and blood vessels, promote experimental cancer development, and impair glucose metabolism and bone health. To counter these effects, copper has been provided in the diet as a purified chemical, generally copper sulfate. However, people are counseled to eat foods containing copper and because of the structural and chemical complexity of whole foods, it is not known whether copper can enter the body and function as well as from the purified chemical. To compare the efficacy of the two forms,rats were made copper deficient and then fed copper either as copper sulfate or in the form of pinto beans, a food noted for having a high copper content. The groups were tested for recovering of their tissue copper stores and recovery of function of copper-dependent enzymes and other variables. Pinto beans were found to deliver copper for return of these functions at least as well as copper sulfate and some of the variables were found to recover better with pinto beans than with copper sulfate. This study supports the view that pinto beans are a good source of dietary copper.

Technical Abstract: The trace element copper (Cu)is a required nutrient in the diets of humans. It has been shown in animal studies to be essential for efficient absorption of iron, efficient oxygen utilization, and for aiding in free-radical degradation. Dry beans are potentially good sources of Cu; thus, the objective of this study was to determine the bioavailability of Cu from dry beans by using the pinto bean as the source. Dry beans were obtained from a local market, cooked according to package directions, and dried. Weanling male rats (8 groups of 8 rats each were fed a Cu-deficient diet (AIN-93G) for four weeks followed by two weeks of Cu repletion with diets containing 0 to 6.5 mg Cu/kg diet added as CuSO4, or with 0.6 and 1.5 mg Cu/kg incorporated into rat diets as pinto beans at 10% and 20%. Standard response curves were developed based on repletion-induced recovery of ten indices of Cu status, including organ Cu concentrations and Cu-dependent enzyme activities, in response to increasing dietary Cu as CuSO4. Recovery of these variables in rats fed the pinto bean diets was compared to the standard response curve at similar levels of dietary Cu. Based on the recovery of all ten variables, the relative bioavailability of Cu from dry beans was at least 100% of that with the highly available CuSO4. For three of the variables, liver and heart Cu concentrations and serum superoxide dismutase 3 (SOD3) activity, estimated bioavailability values of Cu from beans were 138, 140 and 134%, respectively, of those from CuSO4. We conclude that the dry pinto bean is a good source of dietary Cu with respect to both concentration and bioavailability.