White kidney bean extract

White kidney bean (Phaseolus vulgaris L) also known as common bean, is rich in starch, dietary fiber, protein, unsaturated fatty acids, and vitamin (see Tables 1 to 3 below) ¹. Common bean is widely consumed throughout the world, accounting for 50% of grain legumes indirect human consumption ². White kidney bean is recognized as the major source of dietary protein in many Asian, Latin American, and African countries ³.

In addition to nutrients, white kidney bean (Phaseolus vulgaris L) have been reported to contain high level of alpha-amylase inhibitors (α-amylase inhibitors) ³. Alpha-amylase inhibitors also called “starch blockers” or “carbohydrates blockers”, are a class of substances showing inhibitory activity against alpha-amylase (α-1,4-glucan-4-glucanohydrolase) ⁴. Alpha-amylase (α-amylase) is an enzyme that has a major role in carbohydrate metabolism ⁵, catalyzing the hydrolysis of starch into oligosaccharides, which contributes to the energy supply of organisms ⁶. This may represent a potential mechanistic target for interventions seeking to inhibit carbohydrate uptake in the body. Indeed, bioactive ingredients that inhibit catabolic enzymes (i.e., amylase and glucosidase) are becoming increasingly popular, with potential applications for both weight loss and metabolic health ⁷.

White kidney beans possess three isoforms of alpha-amylase inhibitors— α-AI1, α-AI2, α-AIL ⁸, with the α-AI1 isoform shown to inhibit amylase activity in mammals ⁹. Alpha-amylase inhibitor-1 (α-AI), extracts of white kidney beans have been shown to have multiple specific functions such as antiobesity, antidiabetic, and glycemic control activities ¹⁰. For example, the acute oral intake of common bean extract (50 mg/kg body weight) reduced the increase in glycemia (blood sugar) in adult Wistar rats treated with a starch load, without modifying the insulin response ¹¹. Moreover, common bean extract decreased glycemia (blood sugar) levels in rats in both acute and subchronic studies ¹². Due to their ability to inactivate amylase in the intestinal lumen, products containing common bean extracts have been marketed as dietary supplements for weight and glycemic control ¹³.

Alpha-amylase inhibitor-1 (α-AI) has been suggested to interact with pancreatic alpha -amylase at its active site, competitively inhibiting its binding with carbohydrate ⁹. Alpha-amylase inhibitor-1 (α-AI) can block the enzyme’s substrate-reducing end and obstruct the non-substrate-reducing end through a steric hindrance process, targeting all catalytically-competent components of the enzyme ⁵. Several commercially-available white kidney bean extracts now exist which reportedly contain high quantities of white kidney bean-derived alpha-amylase inhibitors, typically available in powder form, allowing their encapsulation or incorporation into drinks and foods ⁹. These supplements claim to reduce carbohydrate absorption and digestion via their alpha-amylase inhibitory properties, with attendant beneficial effects on body weight and metabolic health. Whilst this has been the subject of two meta-analyses, one was published almost ten years ago ¹⁴ and the other focussed on a specific brand (Phase 2) ¹⁵, and other forms of white kidney bean extract might be differentially effective.

The structure of alpha-amylase inhibitor-1 (α-AI) is a classic lectin fold, containing no α-helices and a plethora of antiparallel β-sheets ⁶. Alpha-amylase inhibitor-1 (α-AI) has no carbohydrate-binding abilities due to the complete absence of surface carbohydrate-binding loops on its three-dimensional structure ⁹. Functioning optimally within a pH range of 4.5–5.5 and a temperature range of 22–37 °C ⁹.

Irrespective of their nutritional and health benefits, common beans also contain a variety of antinutritional substances such as trypsin inhibitor, lectins, polyphenols (condensed tannins and anthocyanins), and some oligosaccharides ¹. These antinutritional factors may affect the digestibility and bioavailability of nutrients and limit their consumption ¹⁶. For example, trypsin inhibitors could interfere in protein digestion and decrease the bioavailability of sulfur-containing amino acids, causing metabolic disturbance ¹⁷. Phytohemagglutinins, a class of lectins that are present at high levels in raw common beans, may affect animal growth by interfering with the digestion and absorption of nutrients in the gastrointestinal tract ¹⁷. Consumption of common beans has been observed to induce negative effects including reduced feed efficiency, impaired weight gain, histopathological changes, and even death in animals ¹⁸. In humans, consumption of raw or undercooked kidney beans may induce severe but transient gastrointestinal disturbances such as nausea, vomiting, diarrhea, and abdominal pain ¹⁹.

White kidney bean nutritional values

White kidney beans are rich source of protein, carbohydrate, dietary fiber, some vitamins and minerals ²⁰. Inclusion of white kidney beans in the daily diet has many beneficial physiological effects in controlling and preventing various metabolic diseases such as diabetes mellitus, coronary heart disease, and colon cancer ²¹.

Table 1. White kidney bean raw mature seeds nutritional values (per 100 grams)

Name	Amount	Unit
Water	11.3	g
Energy	333	kcal
Energy	1390	kJ
Protein	23.4	g
Total lipid (fat)	0.85	g
Ash	4.2	g
Carbohydrate, by difference	60.3	g
Fiber, total dietary	15.2	g
Sugars, total including NLEA	2.11	g
Calcium, Ca	240	mg
Iron, Fe	10.4	mg
Magnesium, Mg	190	mg
Phosphorus, P	301	mg
Potassium, K	1800	mg
Sodium, Na	16	mg
Zinc, Zn	3.67	mg
Copper, Cu	0.984	mg
Manganese, Mn	1.8	mg
Selenium, Se	12.8	µg
Vitamin C, total ascorbic acid	0	mg
Thiamin	0.437	mg
Riboflavin	0.146	mg
Niacin	0.479	mg
Pantothenic acid	0.732	mg
Vitamin B-6	0.318	mg
Folate, total	388	µg
Folic acid	0	µg
Folate, food	388	µg
Folate, DFE	388	µg
Choline, total	66.2	mg
Vitamin B-12	0	µg
Vitamin B-12, added	0	µg
Vitamin A, RAE	0	µg
Retinol	0	µg
Carotene, beta	0	µg
Carotene, alpha	0	µg
Cryptoxanthin, beta	0	µg
Vitamin A, IU	0	IU
Lycopene	0	µg
Lutein + zeaxanthin	0	µg
Vitamin E (alpha-tocopherol)	0.21	mg
Vitamin E, added	0	mg
Vitamin D (D2 + D3), International Units	0	IU
Vitamin D (D2 + D3)	0	µg
Vitamin K (phylloquinone)	5.6	µg
Fatty acids, total saturated	0.219	g
SFA 4:0	0	g
SFA 6:0	0	g
SFA 8:0	0	g
SFA 10:0	0	g
SFA 12:0	0	g
SFA 14:0	0.001	g
SFA 16:0	0.205	g
SFA 18:0	0.013	g
Fatty acids, total monounsaturated	0.074	g
MUFA 16:1	0	g
MUFA 18:1	0.074	g
MUFA 20:1	0	g
MUFA 22:1	0	g
Fatty acids, total polyunsaturated	0.364	g
PUFA 18:2	0.198	g
PUFA 18:3	0.166	g
PUFA 18:4	0	g
PUFA 20:4	0	g
PUFA 2:5 n-3 (EPA)	0	g
PUFA 22:5 n-3 (DPA)	0	g
PUFA 22:6 n-3 (DHA)	0	g
Fatty acids, total trans	0	g
Cholesterol	0	mg
Tryptophan	0.277	g
Threonine	0.983	g
Isoleucine	1.03	g
Leucine	1.86	g
Lysine	1.6	g
Methionine	0.351	g
Cystine	0.254	g
Phenylalanine	1.26	g
Tyrosine	0.658	g
Valine	1.22	g
Arginine	1.45	g
Histidine	0.65	g
Alanine	0.979	g
Aspartic acid	2.82	g
Glutamic acid	3.56	g
Glycine	0.912	g
Proline	0.99	g
Serine	1.27	g
Alcohol, ethyl	0	g
Caffeine	0	mg
Theobromine	0	mg

Abbreviations: SFA = saturated fatty acids; MUFA = monounsaturated fatty acids; PUFA = polyunsaturated fatty acids

Table 2. White kidney bean canned mature seeds nutritional values (per 100 grams)

Name	Amount	Unit
Water	70.1	g
Energy	114	kcal
Energy	477	kJ
Protein	7.26	g
Total lipid (fat)	0.29	g
Ash	1.15	g
Carbohydrate, by difference	21.2	g
Fiber, total dietary	4.8	g
Sugars, total including NLEA	0.29	g
Calcium, Ca	73	mg
Iron, Fe	2.99	mg
Magnesium, Mg	51	mg
Phosphorus, P	91	mg
Potassium, K	454	mg
Sodium, Na	340	mg
Zinc, Zn	1.12	mg
Copper, Cu	0.232	mg
Manganese, Mn	0.515	mg
Selenium, Se	1.6	µg
Vitamin C, total ascorbic acid	0	mg
Thiamin	0.096	mg
Riboflavin	0.037	mg
Niacin	0.113	mg
Pantothenic acid	0.185	mg
Vitamin B-6	0.075	mg
Folate, total	65	µg
Folic acid	0	µg
Folate, food	65	µg
Folate, DFE	65	µg
Vitamin B-12	0	µg
Vitamin A, RAE	0	µg
Retinol	0	µg
Carotene, beta	0	µg
Carotene, alpha	0	µg
Cryptoxanthin, beta	0	µg
Vitamin A, IU	0	IU
Lycopene	0	µg
Lutein + zeaxanthin	0	µg
Vitamin E (alpha-tocopherol)	0.79	mg
Vitamin D (D2 + D3), International Units	0	IU
Vitamin D (D2 + D3)	0	µg
Vitamin K (phylloquinone)	2.9	µg
Fatty acids, total saturated	0.074	g
SFA 14:0	0	g
SFA 16:0	0.069	g
SFA 18:0	0.004	g
Fatty acids, total monounsaturated	0.025	g
MUFA 18:1	0.025	g
Fatty acids, total polyunsaturated	0.123	g
PUFA 18:2	0.067	g
PUFA 18:3	0.056	g
Fatty acids, total trans	0	g
Cholesterol	0	mg
Tryptophan	0.086	g
Threonine	0.305	g
Isoleucine	0.32	g
Leucine	0.579	g
Lysine	0.498	g
Methionine	0.109	g
Cystine	0.079	g
Phenylalanine	0.392	g
Tyrosine	0.204	g
Valine	0.38	g
Arginine	0.449	g
Histidine	0.202	g
Alanine	0.304	g
Aspartic acid	0.878	g
Glutamic acid	1.11	g
Glycine	0.283	g
Proline	0.308	g
Serine	0.395	g

Abbreviations: SFA = saturated fatty acids; MUFA = monounsaturated fatty acids; PUFA = polyunsaturated fatty acids; NLEA = Nutrition Labeling and Education Act

Table 3. White kidney bean (small white raw mature seeds) nutritional values (per 100 grams)

Name	Amount	Unit
Water	11.7	g
Energy	336	kcal
Energy	1410	kJ
Protein	21.1	g
Total lipid (fat)	1.18	g
Ash	3.75	g
Carbohydrate, by difference	62.2	g
Fiber, total dietary	24.9	g
Calcium, Ca	173	mg
Iron, Fe	7.73	mg
Magnesium, Mg	183	mg
Phosphorus, P	445	mg
Potassium, K	1540	mg
Sodium, Na	12	mg
Zinc, Zn	2.81	mg
Copper, Cu	0.635	mg
Manganese, Mn	1.28	mg
Selenium, Se	12.8	µg
Vitamin C, total ascorbic acid	0	mg
Thiamin	0.743	mg
Riboflavin	0.207	mg
Niacin	1.34	mg
Pantothenic acid	0.729	mg
Vitamin B-6	0.439	mg
Folate, total	386	µg
Folic acid	0	µg
Folate, food	386	µg
Folate, DFE	386	µg
Vitamin B-12	0	µg
Vitamin A, RAE	0	µg
Retinol	0	µg
Vitamin A, IU	0	IU
Vitamin D (D2 + D3), International Units	0	IU
Vitamin D (D2 + D3)	0	µg
Fatty acids, total saturated	0.304	g
SFA 14:0	0.001	g
SFA 16:0	0.285	g
SFA 18:0	0.018	g
Fatty acids, total monounsaturated	0.102	g
MUFA 18:1	0.102	g
Fatty acids, total polyunsaturated	0.507	g
PUFA 18:2	0.276	g
PUFA 18:3	0.231	g
Fatty acids, total trans	0	g
Cholesterol	0	mg
Tryptophan	0.25	g
Threonine	0.888	g
Isoleucine	0.932	g
Leucine	1.68	g
Lysine	1.45	g
Methionine	0.317	g
Cystine	0.23	g
Phenylalanine	1.14	g
Tyrosine	0.594	g
Valine	1.1	g
Arginine	1.31	g
Histidine	0.588	g
Alanine	0.885	g
Aspartic acid	2.55	g
Glutamic acid	3.22	g
Glycine	0.824	g
Proline	0.895	g
Serine	1.15	g

Abbreviations: SFA = saturated fatty acids; MUFA = monounsaturated fatty acids; PUFA = polyunsaturated fatty acids

White kidney bean extract benefits

Several human studies, typically conducted in overweight or obese individuals, have explored the effect of white kidney bean extract on weight loss and other body composition measurements, with supplement doses typically ranging from 445 to 3000 mg/d, study durations ranging from 28 to 84 days, and sample sizes ranging from 10 to 120 participants (Table 4) ²². The majority of studies were randomized, double-blind placebo-controlled trials, with some setting a daily calorie intake for participants or complementing with a multi-component weight-loss program ²³, ²⁴. The average weight loss from the human studies discussed was 2.6 kg and ranged from 1.8 to 3.5 kg ²².

Table 4. Human studies investigating the effects of white kidney bean extract on body composition and metabolic risk factors

Study	Design	Duration	Dose, Preparation and Other Ingredients	Participants	Effects of white kidney bean extract
Birketvedt et al. 25	Randomized controlled trial	90 days	Wellex capsules (LexMed ASA)- 900 mg white kidney bean extract per day	62 overweight/obese (BMI >25 kg/m²)	↓ body weight ↓ BMI ↓ body fat % ↓ WC ↓ systolic and diastolic BP ↓ total cholesterol No effect on HDL, LDL, triglycerides No effects on serum lipids or nutritional parameters (p < 0.05 vs. baseline)
Grube et al. 26	Randomized controlled trial	84 days	3000 mg/day Phase 2 capsules	117 overweight/obese (BMI 25–35 kg/m²)	↓ body weight ↓ body fat mass ↓ WC (p < 0.001 vs. placebo)
Rothacker 27	Randomized controlled trial	84 days	3000 mg/day Phase 2 capsules	88 overweight/obese (BMI 24–32 kg/m²)	↓ body weight No effect on body fat No effect on lean body mass No effect on WC No effect on HC
Thom 28	Randomized controlled trial	84 days	1200 mg/day Phase 2 capsules	40 overweight/obese (BMI 28–39 kg/m²)	↓ body weight ↓ BMI ↓ body fat % (p < 0.05 vs. baseline) No effect on WC No effect on HC No effect on BP
Wu et al. 29	Randomized controlled trial	60 days	3000 mg/day Phase 2 capsules	101 overweight/obese (BMI 25–40 kg/m²)	↓ body weight ↓ waist circumference No effect on HC No effect on blood biochemistry markers, e.g., cholesterol, triglycerides, blood glucose, creatinine, uric acid, apoliproteins
Udani et al. 30	Randomized controlled trial	56 days	3000 mg/day Phase 2 capsules	27 obese (BMI 30–43 kg/m²)	No effect on body weight No effect on body fat No effect on WC Trend for reduction in triglycerides No effect on blood biochemistry markers, e.g., HbA1C, total cholesterol No effect on appetite control, hunger or energy levels (vs. placebo)
Koike et al. 31	Open	56 days	750 mg/day Phase 2 capsules	10 (BMI 23–30 kg/m², body fat >25% men and >30% women)	↓ body weight ↓ BMI ↓ body fat % ↓ waist circumference ↓ hip circumference ↓ triglycerides ↓ HDL cholesterol ↓ systolic and diastolic BP No effect on waist:hip ratio No effect on blood glucose No effect on total or LDL cholesterol
Wang et al. 32	Randomized controlled trial	35 days	2400 mg/day white kidney bean extract capsules (Yunnan Tianbaohua Biological Resources Development)	120 obese	↓ body weight ↓ BMI ↓ body fat % ↓ fat mass ↓ overweight (%) ↓ subcutaneous fat thickness (triceps, subscapular, abdomen, suprailiac) ↓ waist circumference ↓ hip circumference (p < 0.01 vs. baseline) No effect on BP No effect on blood biochemistry markers, e.g., glucose, albumin, uric acid, creatinine No effects on haematological markers, e.g., haemoglobin, red blood cell count, white blood cell count
Celleno et al. 23	Randomized controlled trial	30 days	445 mg/day Phase 2 capsules, with carbohydrate-rich diet	60 overweight by 5–15 kg	↓ body weight ↓ BMI ↓ body fat % ↓ adipose tissue thickness ↓ waist circumference ↓ hip circumference ↓ right thigh circumference (p < 0.001 vs baseline and vs placebo)
Udani and Singh 24	Randomized controlled trial	28 days	2000 mg/day Phase 2 capsules (plus multi-component weight-loss program)	25 healthy (BMI 23–31 kg/m²)	↓ body weight ↓ waist circumference (p < 0.01 vs. baseline, but N.S. vs. placebo) No effect on fasted glucose No effect on triglycerides No effect on total cholesterol No effect on appetite control, hunger or energy levels
Udani et al. 33	Open, 6-arm crossover		1500, 2000 and 3000 mg white kidney bean extract in capsule and powder (incorporated into butter) form (consumed with white bread)	13 healthy normoglycemic (BMI 18–25 kg/m²)	↓ glycemic index of white bread
Vinson et al. 34	Double-blind, crossover		1500 mg Phase 2 capsules (consumed with 4 large slices of white bread)	11 healthy normoglycemic	↓ peak postprandial blood glucose ↓ time of blood glucose normalisation
	Double-blind, crossover		750 mg Phase 2 capsules	7 subjects	No effects on glucose absorption

Abbreviations: ↓ = reduced; ↑ = increased; BMI = body mass index; BP = blood pressure; HC = hip circumference; RCT = randomized controlled trial; WC = waist circumference; WKBE = white kidney bean extract.

White kidney bean extract on body weight and composition

A change in body weight following the consumption of white kidney bean extract is the most common primary outcome reported in the literature. The earliest study exploring the effects of a commercially available white kidney bean extract on body weight was by Thom ²⁸, who conducted a randomized controlled trial in 40 overweight or obese but otherwise healthy participants. The participants were supplemented with two supplemental tablets (each containing ~200 mg white kidney bean extract, 200 mg inulin and 50 mg Garcinia cambogia extract) or a placebo after each meal, three times per day for 84 days ²⁸. During this time, participants were also instructed to follow a low-fat diet comprising 1200 kcals/day. Those consuming the supplement containing white kidney bean extract significantly reduced their body weight (−3.5 kg), body fat percentage (−2.3%) and body mass index (BMI; −1.3 kg/m²) when compared with the baseline ²⁸. In contrast, there were no significant effects of the placebo on body weight (−1.3 kg), body fat (−0.7%) or BMI (−0.5 kg/m²), nor significant changes in the waist or hip circumference in either group. Nevertheless, given the presence of other bioactive ingredients in the supplement, this study did not allow the isolated effects of white kidney bean extract to be explored ²².

More recent studies have increased the dosage of white kidney bean extract, with the majority of studies administering >3000 mg/day, consumed in doses of ~1000 mg three times/day. In line with the findings observed by Thom ²⁸, an 84-day randomized controlled trial comprising 88 overweight participants reported a significant reduction in body weight in participants supplemented with 3 × 1000 mg/day white kidney bean extract (−3.1 kg) compared with those given the placebo (+0.36 kg) ²⁷. However, no significant changes in body fat, lean body mass or waist and hip circumferences were observed. In another study of the same duration ²⁶, a greater weight loss was achieved in overweight or obese participants randomized to 3000 mg/day of a commercially available white kidney bean extract (IQP-PV-101, Phase 2, Starchlite and PhaseLite) versus the placebo (−2.9 vs. −0.9 kg, respectively). Similarly, white kidney bean extract resulted in greater reductions than the placebo in BMI (−1.1 vs. −0.3 kg/m², respectively), fat mass (−2.2 vs. −0.65 kg, respectively) and waist circumference (−2.5 vs. −0.9 cm, respectively) at 84-days ²⁶. All participants in this study were on a hypocaloric diet, consuming 500 calories less than their basal energy needs per day, with 40% of daily energy intake from carbohydrates, demonstrating the potential complementary role of white kidney bean extract during a standard weight-loss regimen.

In another 84-day study ²⁵, 62 overweight and obese participants consumed two capsules containing 150 mg white kidney bean extract (Wellex, LexMed ASA, Bergen, Norway) or a placebo three times per day, 30 minutes before each meal. At the follow-up, participants randomized to white kidney bean extract had a significant reduction in body weight (−3.2 kg), BMI (−1.1 kg/m²), body fat (−2.8%) and waist circumference (−3.7 cm) when compared with the baseline ²⁵. In contrast, there were no observed changes in body composition measurements in the placebo group. Following the first intervention, Birketvedt et al. ³⁵ conducted an open-label trial for 252-days where the active participants (n = 24) were divided into a low-dose (two 150 mg capsules, three times per day) or a high-dose (four 150 mg capsules, three times per day) group. During the 252-day follow-up, body composition continued to improve (reductions in BMI, waist circumference, body weight, body fat) in both the low and high dose groups, and this was the first study to report a prolonged longer-term effect of white kidney bean extract supplementation on weight loss, without changes to lifestyle, for 365-days. However, no significant differences between the two doses used were observed, raising the interesting possibility that, with prolonged supplementation, low-dose white kidney bean extract—which could be more acceptable to users—may be equally as effective as higher doses. However, this notion requires further exploration, given this study did not have a control group during the 252-day open-label phase ²².

Shorter-term studies investigating the effects of white kidney bean extract on weight loss, generally 56-days in duration, have been conducted. Wu et al. ²⁹ randomized 101 healthy participants to consume either 1000 mg white kidney bean extract (Phase 2 Starch Neutralizer lV) or a placebo three times/day before each meal. Body weight and waist and hip circumference were reported at the baseline, 30 days in and the end of the intervention (60 days). The participants randomised to white kidney bean extract lost, on average, −1.9 kg post-intervention, compared with the placebo group, who lost −0.4 kg ²⁹. Those supplemented with white kidney bean extract achieved a greater reduction in waist circumference (−1.9 cm vs. −0.4 cm for white kidney bean extract and placebo groups, respectively), although the hip circumference was unchanged. In the smallest study conducted in humans ³¹, 10 healthy participants with body fat ratios over 25% and over 30% for men and women, respectively, consumed 750 mg of white kidney bean extract per day (3 × capsules of Phaseolamin™ 1600 diet (Phase 2), twice a day, 30 min before lunch and dinner) for 56-days. The participants achieved a significant reduction in body weight, body fat and BMI. Their waist and hip circumferences also decreased post-intervention when compared with the baseline, but there were no significant effects on the waist:hip ratio ³¹. It must be noted that the caloric intake decreased significantly over the 56-day intervention by approximately 200 kcals per day, suggesting that weight loss could have been a consequence of the reduction in energy intake as opposed to the white kidney bean extract alone ²².

In contrast, Udani et al. ³⁶ reported no significant difference in weight loss in 27 obese participants randomised to 3000 mg/day white kidney bean extract (2 × 1500 mg/day) for 56-days compared with those given a placebo (−3.8 lbs vs. −1.7 lbs, respectively). Likewise, there was no significant effect of white kidney bean extract on body fat and waist circumference, although, as with weight loss, the reduction in body fat (−0.5%) and waist circumference (−1.5 inches) tended to be greater compared with the placebo group, for whom these values were unchanged ³⁶. Similar findings were reported by this group in a later, shorter study, where 2000 mg/day white kidney bean extract did not enhance weight loss or changes in waist circumference in healthy participants on a multi-component weight-loss programme for 28-days (−6.0 lbs vs. −4.7 lbs, respectively) ²⁴. However, interestingly, further exploratory analyses revealed that participants randomized to white kidney bean extract in the highest carbohydrate intake experienced greater weight loss compared with individuals with a similar carbohydrate intake in the placebo group (white kidney bean extract −8.7 lbs vs. placebo −1.7 lbs). This suggests that white kidney bean extract may be a particularly effective weight-loss tool against the background of a high carbohydrate diet, where inhibiting carbohydrate digestion and absorption may have a more pronounced effect on overall energy intake compared with a lower carbohydrate diet ²². Furthermore, in a study performed in 60 weight-stable but overweight (by 5–15 kg) participants, a lower dose of white kidney bean extract (445 mg/day of Phase 2 Starch Neutralizer lV) consumed alongside a carbohydrate-rich diet was associated with significant reductions in body weight, BMI, fat mass, adipose tissue thickness and the waist:hip ratio whilst maintaining lean body mass when compared with the placebo—Celleno et al. ²³.

In the most recent study, Wang et al. ³² reported that obese participants supplemented with 2400 mg white kidney bean extract/day achieved a significant loss of weight and fat mass by, on average, −2.2 kg and −2.0 kg, respectively, following a 35-day intervention; this differed significantly from that reported in the placebo group. The reductions in the overweight percentage, BMI and body fat percentage were also significantly greater in the treatment group vs. the placebo group. The subcutaneous fat thickness measured at the triceps, subscapular, abdomen and suprailiac, as well as circumferences of the waist and hip, all reduced significantly with white kidney bean extract supplementation, but not with the placebo ³².

The results from human studies suggest that white kidney bean extract may represent a useful alternative or adjunct to traditional weight-loss strategies, particularly when higher supplement doses and longer supplementation periods are prescribed ²². Moreover, the results from Udani and Singh ²⁴ suggest that individuals with a greater carbohydrate intake may experience more pronounced weight loss with white kidney bean extract, which could be due to a greater reduction in carbohydrate absorption and thus a decreased energy yield from consumed food. Collectively, compared with the findings of animal model investigations, the findings from human studies present a more convincing case for an anti-obesity effect of white kidney bean extract ²².

White kidney bean extract on appetite and hunger

A limited number of studies have assessed the effects of white kidney bean extract on appetite and hunger in humans. Udani et al. ³⁶ did not observe any differences in changes in appetite control or hunger between those given the white kidney bean extract or placebo for 56-days. These findings were substantiated in a later, shorter study by the same group where 1000 mg per day of white kidney bean extract was provided for 28-days ²⁴. Nevertheless, given some reports of an anorexogenic effect of white kidney bean extract in rodent models, further exploration in humans may be warranted ²².

White kidney bean extract on cardiometabolic markers

Although much of the research in humans to date has focussed on the impact of white kidney bean extract supplementation on weight loss and body composition, outcomes related to metabolic risk factors, including blood glucose, triglycerides, cholesterol and blood pressure, have also been measured. The effects of white kidney bean extract on these parameters will be briefly discussed below.

Blood markers

In a small study supplementing 10 healthy participants with white kidney bean extract (750 mg/day) for 56-days, Koike et al. ³¹ reported a significant reduction in serum triglycerides and HDL cholesterol. However, there were no significant changes in blood glucose concentrations, total cholesterol or LDL (low density lipoprotein or “bad” cholesterol) cholesterol. Similarly, Wu et al. ²⁹ reported no effects of white kidney bean extract on circulating concentrations of cholesterol, triglycerides and glucose between the baseline and the 28 and 56-day follow-ups.

In a short-term randomized controlled trial where 25 healthy participants consumed 1000 mg/day of a white kidney bean extract, there were no improvements in triglycerides, fasting glucose or total cholesterol when compared with the baseline measurements or the placebo group ²⁴. Surprisingly, in an earlier study ³⁶, where participants consumed 3000 mg/day of a white kidney bean extract for 56-days, the authors reported a trend for an improvement in triglyceride levels, with a decrease of −26 mg/dL and −8 mg/dL in the white kidney bean extract and placebo groups, respectively. However, no additional blood biochemistry markers, e.g., HbA1C, or the total cholesterol improved ³⁶. Following the research group’s previous two studies, Udani et al. ³³ performed an extensive open-label, six-arm crossover study to investigate the effects of white kidney bean extract on the glycemic index of white bread. Thirteen healthy, normoglycemic participants with a normal BMI completed the study. During the active phase, the participants consumed white bread (50 g net carbohydrates) with butter and 1500, 2000 or 3000 mg of white kidney bean extract in either capsule form (taken immediately before the food) or powder form (mixed into the butter) ³³. The addition of 3000 mg of powdered white kidney bean extract to the butter reduced the glycemic index of the white bread by 34% when compared with no white kidney bean extract, but this was not evident in the lower dose. The findings from this study suggest that the incorporation of white kidney bean extract into foods may reduce the glycemic index when compared with capsules due to increased bioavailability, which has important clinical implications for the management of metabolic disorders, where blood glucose and insulin resistance are common ²².

In a similar manner, Vinson et al. ³⁴ conducted two double-blind, crossover pilot studies to investigate the effects of white kidney bean extract on glucose absorption. In the first study, 11 normoglycemic participants consumed three tablespoons of soybean oil margarine with or without 1500 mg of white kidney bean extract (Phase 2, Pharmachem Labs, Kearney, NJ, USA) with four large slices of white bread and 4 g of Sweet N’Low™. The peak postprandial blood glucose concentrations were lower, and the time taken for the blood glucose to return to normal was faster with white kidney bean extract (62 min) when compared with the controls (80 min). The area under the glucose vs. time curve was also 66% lower with white kidney bean extract, suggesting that white kidney bean extract inhibited the digestion and absorption of approximately two-thirds of the carbohydrates in bread. In the second study, seven participants were given a standardised meal after an overnight fast, with or without 750 mg of white kidney bean extract; however, no effects were observed on glucose absorption, likely due to the differences in dosage and smaller sample size ³⁴.

The hematology results from the most recent human study, including the red blood cell count, white blood cell count, platelet count and haemoglobin, did not change significantly with white kidney bean extract supplementation for 35 days, nor did they differ significantly from those given the placebo ³². Likewise, serum biochemical parameters, including the total serum protein, albumin, glucose, uric acid and creatinine, did not change and remained within the normal ranges for these markers after a 35-day white kidney bean extract intervention in obese subjects, demonstrating the safety of white kidney bean extract.

Blood pressure

To date, a small number of studies have investigated the effects of white kidney bean extract on blood pressure ³². Improvements in systolic and diastolic blood pressures of −5.6 and −3.9 mmHg, respectively, were reported following a 84-day supplementation with white kidney bean extract compared with the placebo ³⁵. Similar findings were also observed in a shorter study (56-days) ³¹. In contrast, Thom ²⁸ reported no significant improvements in blood pressure following a 84-day white kidney bean extract intervention. In obese individuals, there were no significant changes to blood pressure or heart rate with 2400 mg/day white kidney bean extract supplementation for 35 days when compared with the placebo ³². Although a limited number of studies suggest that white kidney bean extract may improve blood pressure, it is unclear if this is a direct effect of the white kidney bean extract or secondary to weight and body fat loss, and requires further investigation ²².

Does white kidney bean extract work?

As a single agent, white kidney bean resulted in a statistically significant weight loss compared to placebo, although this was not considered clinically significant ³⁷. The evidence presented in this review ²⁴ indicates that white kidney bean extract aids weight loss, inducing small (average −2.6 kg) but potentially meaningful reductions in body weight in humans on a short- to medium-term basis (28 to 84 days) compared with a placebo, particularly when consumed alongside a high-carbohydrate diet. However, longer duration randomized controlled trials would be useful to help establish whether similar or greater effects are apparent with more protracted supplementation periods ²². The potential to combine white kidney bean extract with other bioactive food extracts has received only a small amount of attention to date ²⁸ and future studies may wish to explore the potential additive effects of white kidney bean extract alongside other bioactive compounds, such as those which may inhibit the activity of lipase, to simultaneously attenuate fat digestion and absorption ²². An additional avenue for future research could be to establish acceptable and effective vehicles for the provision of white kidney bean extract, such as cereal bars or incorporation into meals with a high carbohydrate content ²². Such studies will need to carefully consider the production methods to ensure that the viability and efficacy of white kidney bean extract is not compromised. The effects of white kidney bean extract on blood glucose concentrations and metabolic control warrants further investigation, given the possible role this bioactive food extract could play in the prevention or management of diabetes and related conditions such as cardiovascular disease ²². Moreover, animal studies suggest a potential beneficial effect of white kidney bean extract on the gut microbiota, which could have applications both in weight management and in the treatment of other conditions where gut microbial dysbiosis has been implicated (e.g., diabetes, dementia, cardiovascular disease) ³⁸.

White kidney bean extract side effects

There have been no significant side effects reported with white kidney bean extract supplementation for up to 84-days (randomized controlled trials) or up to 365-days in an open-label trial ²². A short-term study (28-days) reported no adverse effects of white kidney bean extract on kidney and liver function or blood counts (including white blood cells, hemoglobin and platelets) ²⁴. Similar findings were reported by this research group in an earlier study, although one participant in the white kidney bean extract group reported more tension headaches and one participant randomized to the placebo reported abdominal side effects ³⁶. More recently, Udani et al. ³³ assessed the impact of a white kidney bean extract in capsule or powdered form on gastrointestinal symptoms and reported no significant effects on diarrhoea, flatulence, bloating or nausea. In a longer study, Rothacker ²⁷ also reported no adverse events following white kidney bean extract supplementation. In one study, a participant from the intervention group withdrew due to constipation ²⁵.

In the most recent human study, blood markers, including white blood cell and platelet counts all as indicators of adverse health effects, were not affected by supplementation in 120 obese participants consuming 2400 mg white kidney bean extract per day for 35 days ³². Wang et al. ³² also explored the additional potential measures of adverse effects, including electrocardiogram, chest X-ray, abdominal ultrasound examinations, and heart rate and oxygen consumption during steady-state cycle ergometry (5 minutes at 100 watts power on an exercise bike). There were no significant changes within nor between the white kidney bean extract and placebo groups following the 35-day intervention ³². In addition, tests on urine and stools were performed and the authors found no colour, trait, pH nor microscopic abnormalities in the faeces or urine of participants in the treatment group when compared with those given the placebo ³².

The inhibition of digestion and absorption of carbohydrates consequently alters the substrate delivery to the gastrointestinal tract, specifically the bacteria residing in the gastrointestinal, as demonstrated by the significant changes in composition and diversity indices following white kidney bean extract consumption ³⁹, which has been suggested to increase methane, carbon dioxide and hydrogen, which have been linked with bloating, flatulence and diarrhea ⁸. However, the data presented here suggest that white kidney bean extract is well tolerated and safe for consumption, even at the higher dosages of 3000 mg/day and with longer-term supplementation ²².

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