Supplements made from white kidney beans ( Phaseolus vulgaris) are sold as starch blockers, supplements said to interfere with the digestion of carbohydrates and thereby promote weight loss.
Technically, starch blockers are amylase inhibitors. Amylase is one of the main enzymes the body uses to digest starch. In theory, when amylase is blocked, ingested starch can pass through the body undigested, contributing no calories.
However, theory is one thing, reality another. Most studies of amylase inhibitors have generally failed to find them effective.1-3
Several possible reasons for this discrepancy have been proposed, such as that the amylase inhibitor may be broken down in the stomach, the product may supply enough of its own amylase to counteract any benefit, and that another enzyme, glucoamylase, may be able to take over when amylase can’t do the job. Whatever the cause, the net results in these studies were poor. Use of amylase inhibitors did not in fact block the digestion of starch.
However, according to the manufacturer of a current product, more concentrated extracts of Phaseolus vulgaris, taken in higher doses, do work. Up until recently, the evidence for this claim rested entirely on unpublished studies that could not be independently verified..4-6
In 2007, however, a relevant trial was at last published.8 . In this double-blind, placebo-controlled study, 60 slightly overweight people were given either placebo or a phaseolus extract once daily 30 minutes prior to a main meal rich in carbohydrates. Over the thirty days of the study, the results indicated that phaseolus treatment led to a significantly greater reduction of body weight and and improvement of lean/fat ratio as compared to placebo. While this is promising, independent confirmation in larger trials will be necessary before phaseolus can be considered a proven weight-loss product.
One published study failed to find that use of a phaseolus product reduced the usual blood sugar rise that follows a meal.7
The recommended dose of amylase inhibitors varies among products. Follow label instructions.
On the basis of their widespread presence in commonly consumed foods (beans), amylase inhibitors are believed to be quite safe. One side effect, however, is to be expected: flatulence. It is the amylase inhibitors in beans that are responsible for their notorious gassiness.
Maximum safe doses in pregnant or nursing women, young children, or individuals with severe hepatic or renal disease have not been established.
1. Layer P, Zinsmeister AR, DiMagno EP. Effects of decreasing intraluminal amylase activity on starch digestion and postprandial gastrointestinal function in humans. Gastroenterology. 1986;91:41–8.
2. Starch blockers do not block starch digestion. Nutr Rev. 1985;43:46–8.
3. Draeger KE, Vertesy L, Grigoleit HG. Starch blockers. Lancet. 1983;1:354–5.
4. Summary of clinical study evaluating effectiveness of Phase 2™. Dr. R. Ballerini, Managing Director of Pharmeceutical Development and Service srl. Milano, Italy. On file with manufacturer, Pharmachem Laboratories, Kearny, NJ.
5. In vivo effectiveness or a starch absorption blocker in a double-blind placebo-controlled study with normal college-age subjects. Joe A. Vinson, PhD, and Donna M. Shuta, BS, Department of Chemistry University of Scranton, Scranton, PA 18510.
6. In vivo effectiveness of a starch absorption blocker in a double-blind placebo-controlled study with normal subjects. Joe A. Vinson, PhD, Donna M. Shuta, BS, and Hassan Al Kharrat, MS, Department of Chemistry, University of Scranton, Scranton, PA 18510.
7. Cerovic A, Miletic I, Konic-Ristic A et al. The dry plant extract of common bean seed (phaseoli vulgari pericarpium) does not have an affect on postprandial glycemia in healthy human subject. Bosn J Basic Med Sci. 2006;6:28-33.
8. Celleno L, Tolaini MV, D'Amore A, et al. A dietary supplement containing standardized Phaseolus vulgaris extract influences body composition of overweight men and women. Int J Med Sci. 2007;4:45-52.
Last reviewed August 2013 by EBSCO CAM Review Board
Last Updated: 8/22/2013