White Kidney Bean Extract

White Kidney Bean extract, or Phase 2, is a dietary carbohydrate blocker similar to Chlorogenic Acid and is sometimes used alongside carb containing meals to reduce the absorption of carbohydrates. It does appear to work, but its potency is quite unreliable and relatively subpar.

This page features 13 unique references to scientific papers.


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White Kidney Bean extract (also known by the brand Phase 2) is a carbohydrate blocker that works by inhibiting the digestion of starches.

By inhibiting their digestion, starches that are eaten are either left undigested in the gut or the amount of which is digested is reduced. These starches are either excreted and their calories not absorbed, or they are given to colonic bacteria to ferment (eat).

When given to people who are not otherwise on a diet (during their highest carb containing meal), white kidney bean extract is able to reduce body weight and body fat levels similar to simple caloric restriction. In cases of overfeeding, white kidney bean extract can alleviate the expected increase of body fat gain and blood parameters like triglycerides and Blood Glucose over time.

It is also possible that white kidney bean extract can protect against colon cancer in the same manner as soluble fiber.

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Also Known As

Phaseolus Vulgaris, Phase 2 (Brand name)


Things to Note

  • White kidney bean extract is non-stimulatory.

Is a Form of


Does Not Go Well With

  • Carbohydrates (specifically starches)

Caution Notice

Examine.com Medical Disclaimer

Phase 2 tablets (800mg in weight comprised of 445mg phaseolus vulgaris) appear to be effective in reducing carbohydrate absorption. These tablets must be taken alongside a carbohydrate containing meal.

It is unsure if higher doses are significantly better at blocking intestinal absorption of carbohydrates or not.


Table of Contents:


Edit1. Overview and Pharmacology

White kidney bean extract is specifically known as alpha-amylase inhibitor isoform 1. It is extracted from any legume source although it is known as white kidney bean extract due to it's high prevalence in that specific bean.

Alpha-amylase inhibitor isoform 1 (henceforth Alpha-AI1) is one of the main starch inhibitors alongside Alpha-AI2 and Alpha-AIL. The starch inhibitors are bean lectins, alongside arcelins and phytohaemagglutinin (PHA), although they do not confer the same harms that PHA does since, despite a very similar structure, they have a differently structured 'binding loop' which does not allow carbohydrate binding.[1] PHA, arcelins, and Alpha-AIL fail to inhibit amylase to a large degree due to steric hindrance from their looped structures, and only Alpha-AI1 shows effective amylase binding abilities in vivo in mammals.[2]

Alpha-AI1 seems to have highly unpredictable effects on in vivo carbohydrate metabolism as the activity of the binding process is influenced highly by pH, temperature (when away from optimum pH) and coingestion with particular ions as Nitrate, chloride, bromide, iodide, thiocyanate, and calcium ions all increase the ability for Alpha-AI1 to bind to amylase, whereas potassium, Magnesium, sulfate and sodium showed no effect.[3] As well as other indirect effects like an increased secretion of amylase from the pancreas in response to slower intestinal transit time.


Edit2. Phase 2

Phase 2 is a brand name for a specific processed extract of Phaseolus Vulgaris.

Subpar extracts of Phaseolus vulgaris can result in a very high phytohaemagglutinin (PHA) content[4], which would reduce the high safety threshold of white kidney bean extract significantly. They also have been reported to have much lower intestinal action on the amylase enzyme.[5][6]

Phase 2 undergoes a process that inactivates the PHA content and increases the activity of Alpha-AI1 and is used in the majority of human studies.[7]


Edit3. Colonic Activity

Via inhibition of Alpha-amylase, Alpha-AI1 prevents long chain carbohydrates from being taken up in the small intestine for nutritional value to the human. This causes said starches to pass through to the colon where they have the potential to be fermented by bacteria. In this manner, Alpha-AI1 can make ingested carbohydrates act like a probiotic.

When fermented, these carbohydrates can release short-chain fatty acids including propionic acid, butyric acid, and acetic acid. These short chain fatty acids are thought to be involved in reducing the risk of colon cancer (as has been shown in experimentally induced animal models[8]) as well as having other benefits, such as modulating insulin/glucagon release and acting as a low grade systemic Histone deacetylase(HDAC) inhibitor.


Edit4. Human Studies

It has been noted in humans to effectively decrease amylase activity.[5]

Initially, studies in animals noted that raw bean consumption was able to ameliorate weight gain[9] and later studies found that it could wholly be accounted for by a combination of reduced food intake and increased starch excretion[8], suggesting that the mechanism of action in vivo is due to malabsorption and that in vitro studies carry over.

Human studies measuring weight loss typically report a small, variable, but always present effect on nutrients absorbed during a meal[10][11] and fat loss over time[12][13]


Edit5. Safety Profile

The acute toxicity of Phase 2 has been established as greater than 5g per kg of body weight in rats, a dose well above recommended human consumption, leading white kidney bean extract to have an excellent safety profile.

Chronic intake over the span of 28 days in doses up to 2500mg/kg bodyweight have been concluded as safe in lab animals additionally.[7]


Edit6. Conclusion

Alpha-AI1, specifically in the patented form of Phase 2, seems to be effective in inducing starch malabsorption and thus induce weight loss by ways of mimicking a caloric deficit. Human studies all show benefit in supplementation with the highest starch containing meal, although the degree of benefit seems highly variable.

It is not recommended as a first-line fat burner due to it's inability to induce fat loss, but can be used as a band-aid supplement to a subpar diet like most calorie blockers.

Enhanced weight loss in overweight subjects

Phaseolus Vulgaris review as a nutraceutical

References

  1. Purification and Properties of Phaseolamin, an inhibitor of alpha-amylase, from the Kidney Bean Phaseolus vulgaris
  2. Ishimoto M, Yamada T, Kaga A. Insecticidal activity of an alpha-amylase inhibitor-like protein resembling a putative precursor of alpha-amylase inhibitor in the common bean, Phaseolus vulgaris L. Biochim Biophys Acta. (1999)
  3. Characterization of a purified α-amylase inhibitor from white kidney beans (Phaseolus vulgaris)
  4. Liener IE, Donatucci DA, Tarcza JC. Starch blockers: a potential source of trypsin inhibitors and lectins. Am J Clin Nutr. (1984)
  5. Layer P, Carlson GL, DiMagno EP. Partially purified white bean amylase inhibitor reduces starch digestion in vitro and inactivates intraduodenal amylase in humans. Gastroenterology. (1985)
  6. Layer P, Zinsmeister AR, DiMagno EP. Effects of decreasing intraluminal amylase activity on starch digestion and postprandial gastrointestinal function in humans. Gastroenterology. (1986)
  7. Subchronic oral toxicity of a standardized white kidney bean (Phaseolus vulgaris) extract in rats
  8. Hangen L, Bennink MR. Consumption of black beans and navy beans (Phaseolus vulgaris) reduced azoxymethane-induced colon cancer in rats. Nutr Cancer. (2002)
  9. Pusztai A, et al. Lipid accumulation in obese Zucker rats is reduced by inclusion of raw kidney bean (Phaseolus vulgaris) in the diet. Br J Nutr. (1998)
  10. Layer P, et al. Effect of a purified amylase inhibitor on carbohydrate tolerance in normal subjects and patients with diabetes mellitus. Mayo Clin Proc. (1986)
  11. Boivin M, et al. Gastrointestinal and metabolic effects of amylase inhibition in diabetics. Gastroenterology. (1988)
  12. Udani J, Hardy M, Madsen DC. Blocking carbohydrate absorption and weight loss: a clinical trial using Phase 2 brand proprietary fractionated white bean extract. Altern Med Rev. (2004)
  13. A Dietary Supplement Containing Standardized Phaseolus vulgaris Extract Influences Body Composition of Overweight Men and Women

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