Can white kidney bean extract lower blood sugar or help me lose weight?

Answer:

White kidney bean (Phaseolus vulgaris) supplements and extracts are promoted to lower blood sugar or help with weight loss by acting as "starch blockers," potentially inhibiting the starch-digesting enzyme amylase which otherwise turns the starch you eat into absorbable sugar. However, results from clinical trials have been modest, and more studies are needed to prove a benefit.

Lowering blood sugar

In healthy people

A small study among 12 healthy men and women (average age 28) found that, overall, the rise in blood sugar over a 2-hour period after consuming two slices of white bread (containing 50 grams of non-fiber carbohydrates and 8 grams added sugar) was, on average, 26.4% lower when participants consumed a beverage containing 3.8 grams of a branded white kidney bean protein powder extract (Max Bloc, Mellitas Health Foods LLC) mixed into 4 oz. of water immediately before eating the bread, compared to when they consumed a placebo drink (3.8 grams of dry powdered milk added to 4 oz. of water) which contained equivalent amounts of protein and carbohydrate as the white kidney bean beverage, before eating the bread. It should be noted that three participants actually had higher blood sugar levels after the white kidney bean extract compared to placebo drink (Allen, Int J Res Med Sci 2024).

An earlier, laboratory study of Max Bloc using an in vitro model of digestion estimated that the extract could reduce the digestion of starch food such as white bread, rice, or pasta by 69 to 93%, and reported that the extract showed 10 to 16 times higher amylase inhibition compared to three other commercially available white kidney bean extract powders, although the brand names of the other extracts were not provided (Zhang, J Nutr Food Sci 2020). Interestingly, this study also noted that because Max Bloc "does not work instantaneously" and requires time to bind to and inhibit amylase, it should, ideally, be taken 10 to 20 minutes before a meal (rather than immediately before a meal, as in the study above). The author of the study was an employee of Mellitas Health.

In people with diabetes

A small study among six men and women with non-insulin-dependent diabetes found that taking 3,000 to 6,000 mg of white kidney bean extract with meals for one week reduced the rise in blood sugar up to 90 minutes after meals by an average of about 30% compared to baseline. However, this study did not include a placebo group, which is needed to prove a benefit. Two of the six participants reported nausea, vomiting, diarrhea, and/or gassiness after the initial dose of white bean extract, but these side effects decreased or resolved after a few days of supplementation (Boivin, Gastroenterology 1988). Longer and higher quality studies are needed to determine if white bean extract supplementation is safe and effective in people with diabetes and those taking insulin or blood-sugar lowering medication.

Weight loss

A review of six clinical trials of white kidney bean extract with no other weight loss ingredient in daily doses of between 445 mg and 1,500 mg per day found a statistically significant reduction in body fat (averaging about 4 pounds) when compared to placebo, although there was insufficient evidence to demonstrate weight loss (Onakpoya, Br J Nutr 2011). Three of the studies used the branded extract Phase 2(Pharmachem Labs). Most were funded by the makers of the extracts, were short in duration (about one to two months) and included lifestyle interventions such changes in diet or exercise.

A review (funded by Pharmachem Labs) of ten clinical studies using Phase 2 (including the studies mentioned above) at doses between 445 mg and 3,000 mg per day concluded that the extract "promotes weight loss when taken concurrently with meals containing carbohydrates." (Barrett, Nutr J 2011). Most of the studies were randomized, double-blind and placebo controlled and ranged in duration from one to three months; however, most of the studies also incorporated diet and/or exercise changes, and several included products which contained additional weight loss ingredients, such as chromium picolinate, inulin, or Garcinia cambogia. A more recent, company-funded study among 123 overweight men and women found those who took 1,000 mg of Phase 2 white kidney bean extract three times daily with meals (on a reduced-calorie diet) for 3 months lost significantly more weight compared to those who took a placebo (an average loss of 6.5 lbs. vs. 2 lbs., respectively) (Grube, Obesity 2014). During a 5 ½ month follow-up period after the initial study, 36 of 49 participants who chose to continue taking the same daily dose of extract without dietary restrictions maintained their weight, but did not lose more weight. The researchers noted that adverse events reported during the study were not severe, serious, nor related to the use of the extract.

In the U.S., Phase 2 makes the claims that it "May assist in weight control when used with diet and exercise," and "May reduce enzymatic digestion of dietary starch," and the FDA has not objected to these claims.

Canada allows the following claims for Phase 2 Carb Controller: "At 6 capsules (3000 mg) per day: Assists in weight management when used with a program of reduced intake of dietary calories and increased physical activity," and "At 4-6 capsules (2000-3000 mg) per day: Provides support for healthy glucose metabolism following a carbohydrate rich meal."

The European Food Safety Authority (EFSA) concluded there was insufficient evidence "to establish a cause and effect relationship between the consumption of the standardized aqueous extract from white kidney bean (Phaseolus vulgaris L.) and reduction of body weight." (EFSA 2014).

Safety and side effects

White kidney bean extracts have been shown to be safe in short-term studies - the most common side effects being mild gastrointestinal symptoms such as gas and bloating, which tends to occur early on. Phase 2 is self-affirmed GRAS (Generally Recognized As Safe). However, people who are diabetic, or who have kidney or liver disease should consult their physician before using. It should not be taken by women who are pregnant or breastfeeding (Health Canada 2013).

Dosage

In clinical studies, Phase 2 has been taken in doses of up to 3,000 mg per day, typically in divided doses before meals, for up to 8 months for weight and/or fat loss or weight maintenance. A single dose of 2,000 to 3,000 mg taken with a meal may lessen increases in blood sugar after the meal. Dosage should not exceed 10 grams per day.

The bottom line

Taking white kidney bean extract before meals may modestly decrease the rise in blood sugar after a starchy meal. It may help fat loss (particularly if you eat a high starch diet) and, if combined with a sensible diet and exercise, with modest weight loss. White kidney bean extract appears to be safe for healthy individuals when taken short-term. Mild gastrointestinal symptoms such as nausea, vomiting, gassiness, or diarrhea may occur, especially after the first dose, although these side effects appear to lessen over time. Due to its potential effects on blood sugar levels, people with hypoglycemia, diabetes or those who take medication to lower blood sugar should consult with their healthcare provider before using. Long-term efficacy and safety have not been evaluated.

You can find information about other popular weight loss ingredients in ConsumerLab.com's  Weight Loss Supplement Review, Garcinia Cambogia Supplements Review, Green Coffee Bean Extract Supplements Review, CLA Supplements Review, and Green Tea Supplements Review.