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ARS Home » Northeast Area » Ithaca, New York » Robert W. Holley Center for Agriculture & Health » Plant, Soil and Nutrition Research » Research » Publications at this Location » Publication #327984
Title: The cotyledon cell wall of the common bean (phaseolus vulgaris) resists digestion in the upper intestine and thus may limit iron bioavailability

Author
item Glahn, Raymond
item Tako, Elad
item Cichy, Karen
item WIESINGER, JASON - Michigan State University

Submitted to: Food & Function
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/16/2016
Publication Date: 7/13/2016
Citation: Glahn, R.P., Tako, E.N., Cichy, K.A., Wiesinger, J.A. 2016. The cotyledon cell wall of the common bean (phaseolus vulgaris) resists digestion in the upper intestine and thus may limit iron bioavailability. Food & Function. 7(7):3193-3200.

Interpretive Summary: Strategies that enhance the iron (Fe) bioavailability from the bean are of keen interest to nutritionists, bean breeders and growers. In beans, most of the Fe (75-80%) is in the cotyledon which is the main body of the bean seed. Most of this Fe also appears to be located within the cotyledon cells. These cell walls are known to be resistant to digestion in the stomach and the upper small intestine. Since the upper intestine is thought to be the primary site of human Fe absorption, the present study was designed to determine if the bean cotyledon cell wall represents a barrier to Fe absorption. To do so, we utilized high pressure to rupture bean cotyledon cells. Iron bioavailability of cooked bean samples was assessed using an in vitro digestion/Caco-2 cell culture model. Results confirmed that the cotyledon cell wall is highly resistant to stomach and upper intestine digestion, indicating that the cotyledon cell wall is a potential barrier to Fe absorption from the bean. Rupture of the cotyledon cell wall lysis did not result in a consistent or strong enhancement of bioavailable Fe. Thus, even though the barrier of the cell wall was eliminated, it appears that the liberated intracellular contents such as starch and protein influenced the Fe bioavailability by creating a matrix that inhibited exchange of Fe with the intestinal cell transport mechanism. Such effects warrant further pursuit in animals and humans as the intestinal microflora are also likely to play a role both in cell wall breakdown and in utilization of the protein, carbohydrates and Fe released from the bean cotyledon cell.

Technical Abstract: Strategies that enhance the Fe bioavailability from the bean are of keen interest to nutritionists, bean breeders and growers. In beans, the cotyledon contains 75-80% of the total seed Fe, most of which appears to be located within the cotyledon cell. The cotyledon cell wall is known to be resistant to digestion in the stomach and the upper small intestine. Therefore, given the above and the general belief that the primary site of human Fe absorption is the upper small intestine, the present study was designed to determine if the bean cotyledon cell wall represents a barrier to Fe absorption. To do so, we utilized high pressure to rupture bean cotyledon cells. Iron bioavailability of cooked bean samples was assessed using an in vitro digestion/Caco-2 cell culture model. Results confirmed that the cotyledon cell wall is highly resistant to pepsin, the low pH of the stomach, and the pancreatic enzymes, indicating it is a potential barrier to Fe absorption from the bean. Relatively high intracellular pressure (>4000 psi) was required to initiate cell rupture; however, cotyledon cell lysis did not result in a consistent or strong enhancement of bioavailable Fe. Thus, even though the barrier of the cell wall was eliminated, it appears that the liberated intracellular starch and protein influenced the Fe bioavailability by creating a matrix that inhibited exchange of Fe with the cell transport mechanism. Such effects warrant pursuit in vivo as the intestinal microflora are also likely to play a role both in cell wall breakdown and in utilization of the protein, carbohydrates and Fe released from the cotyledon cell.