White kidney beans, also called cannelini beans, are a concentrated source of the compound phaseolamin. Phaseolamin, which is sold under the trade name Phase 2 or StarchLite, may aid weight loss by inhibiting the body's production of alpha-amylase, an enzyme involved in the digestion of carbohydrates. In 2007, the International Journal of Medical Science published the results of a study suggesting that phaseolamin significantly interferes with the digestion of starch, and that subjects who take phaseolamin were more significantly likely to lose weight than those who take a placebo. However, some early and "knock-off" forms of the supplement fail to inhibit enzymes reliably; most practitioners recommend only standardized extracts.
Theoretically, phaseolamin's enzyme-blocking powers reduce the number of carbohydrate-based calories that are absorbed and converted into body fat. Unable to break starches down into simpler sugars, the digestive system expels partially digested starches during bowel movements. A study conducted at the University of California theorized that phaseolamin inhibits or delays the digestion of complex starches, thereby reducing the overall weight and waist size of overweight participants. Though some fat-blocking counterparts such as orlistat (trade name Alli) produce unpleasant gastrointestinal side effects due to their enzyme-blocking activity, most clinical trials have demonstrated a relatively low incidence of diarrhea and stomach pain among phaseolamin users.
Reducing Glycemic Index
Because white kidney bean extract interferes with the absorption of carbohydrates and their conversion into simpler sugars, it may offer a potential treatment for diabetes and reactive hypoglycemia. Dr. Jay Udani--the medical director of Medicus Research and author of the 2007 University of California study of phaseolin--has suggested that the compound can lower the glycemic index of starchy foods such as white bread. By impairing the body's ability to derive glucose from these foods, phaseolin may prevent abrupt spikes in blood sugar and resulting complications. Additionally, routine supplementation may prevent or delay the onset of Type 2 diabetes in people with reactive hypoglycemia (pre-diabetes). Although these theoretical uses seem promising, they have not been investigated by large-scale clinical trials.