Whole White Beans and White Bean Pasta Exhibit High Iron Bioavailability Relative to Whole Black Beans and Black Bean Pasta: Studies in Caco-2 Cells and Poultry.

Background: Bean seed coat flavonoids are known to profoundly influence iron bioavailability from beans and bean flour products. Effects of bean flavonoids on iron bioavailability in a diet where beans are a major ingredient are not well known.

Objective: To compare Fe bioavailability from diets containing 42% whole white or whole black beans; and from diets containing 42% white bean pasta or black bean pasta, where bean cotyledon cell walls are disrupted due to the pasta making process.

Methods: Four diets were formulated, each containing 42% white beans, white bean pasta, black beans or black bean pasta. Diets were designed to be similar to a human school lunch meal. The diets were evaluated using the Caco-2 cell bioassay and poultry(n=15 male birds/diet) models for human Fe bioavailability. Equal amounts were fed for 6 weeks with weekly monitoring of iron status, body weight, food consumption. Fecal iron retention (24 hr) was measured at 5 weeks. Results analyzed via ANOVA.

Results: White bean pasta had the highest Fe bioavailability, followed closely by white beans, as indicated via significant increases in hemoglobin, from baseline of 80 to greater than 115 g/L (p<0.05) . Black beans and black bean pasta were very low in Fe bioavailability, as indicated via no change in hemoglobin from the baseline (80 g/L). Fecal balance studies showed that animals consuming black beans and black bean pasta retained Fe but did not incorporate Fe into hemoglobin formation.

Conclusions: The absence of bean seed coat flavonoids that inhibit Fe bioavailability allowed for high Fe bioavailability. Breakage of the cotyledon cell walls via the pasta making process released additional bioavailable Fe in the absence of inhibitory seed coat flavonoids. Seed coat flavonoids found in the whole black beans and black bean pasta, profoundly inhibit the nutritional quality of Fe in the diet.