Starch Blockers 101: White Kidney Bean Extract
By Mary_RD on Apr 27, 2011 10:00 AM
By Carolyn Richardson
The rate of obesity has doubled worldwide since 1980. As scientists continue to explore the effects of obesity on public health, they are also looking into new ways to help people lose weight. Research has consistently found a positive correlation between an over-consumption of complex carbohydrates and obesity, thus piquing the interest of researchers in practical ways to mimic results found with reducing complex carbohydrates in the diet. Some are looking to dietary supplements known as starch blockers.
While it is known that an excessive intake from all macronutrients, including carbohydrates, contributes to the development of obesity, scientists are studying how starch blockers may affect weight loss. Phaselous vulgaris, the clinical name for white kidney bean extract, is the principle ingredient in products known as starch blockers. The concept behind these dietary supplements, according to manufacturers, is to prevent a natural enzyme in saliva and the pancreas, called alpha-amylase, from breaking down carbs into simple sugars which could prevent the body from absorbing carb calories and thereby promote weight loss.
A study, published in the Internal Journal of Medical Science, conducted a double-blind, placebo-controlled study, in which 60 slightly overweight people were given either placebo or Phase 2, a highly concentrated phaseolus extract, once daily. This single daily dose was given 30 minutes prior to a large meal rich in carbohydrates. Over the 30 days of the study, subjects receiving Phaseolus vulgaris extract had significantly greater reduction of body weight, BMI, fat mass, adipose tissue thickness, and waist/hip/ thigh circumferences while maintaining lean body mass compared to subjects receiving placebo. A similar study showed comparable results with 92% of the group receiving white kidney bean extract losing weight versus 62% of the placebo group. While there is no lack of positive studies regarding white kidney bean extract, as with any dietary supplement, research studies of long term effects of use are scant.
Can it work long term?
Christine Gerbstadt, MD, RD, cites side effects and a lack of widespread studies as the reason why she doesn’t recommend using starch blockers. Regarding side effects she tells WebMD white kidney bean extract may block starches from digestion in the small intestine, “But when they get to the large intestine, the starches ferment, give off gas, and cause bloating and diarrhea,” Gerbstadt tells WebMD. Another issue is adherence to continued use. While Nora Cosgrove, an overweight woman at risk for developing Type 2 Diabetes, credits Phase 2 pills for helping her lose 30 pounds and 6 dress sizes in 3 months, doctors say that using starch blockers may be hard to stick to over time. Obesity expert Louis Aronne, MD, says “We just don’t see people taking stuff like this on an ongoing basis. When patients come in taking a carb blocker, they end up stopping either because of the side effects or because of lack of effectiveness, or both…”
Even though white kidney bean extract may be a boon to the dietary supplement industry, Duffy MacKay, ND, and Vice President for Scientific and Regulatory Affairs for the Council for Responsible Nutrition, tells WebMD that while some study results show that "extracts of phaseolus vulgaris appear to be safe and have potential promise" helping overweight people lose weight can only be sustained through healthy diet and exercise. He adds, dietary supplements for weight loss, “are not magic bullets…”
Will you go for white kidney bean extract or just control your carb intake?