J Food Bioact

Journal of Food Bioactives, ISSN 2637-8752 print, 2637-8779 online

Journal website www.isnff-jfb.com

Original Research

Volume 35, September 2026, pages 69-80

Effects of tamarind seed husk extract on abdominal visceral fat: a randomized, double-blind, placebo-controlled trial in Japanese adults with mild obesity

Figure 1. Comparison of HPLC elution patterns of polyphenols in the TSHE-containing capsules and in the TSHE. Upper panel: HPLC chromatogram of polyphenols extracted from the TSHE-containing capsules; lower panel: HPLC chromatogram of polyphenols from TSHE. Peak a was identified as the epicatechin monomer; peaks c and d were identified as the epicatechin-thiol adduct formed via the thiolysis of procyanidin B2; peaks b and e were unidentified. TSHE, tamarind seed husk extract.

Figure 2. Flow diagram of the study design and procedures. SAF, safety analysis population; PPS, per-protocol set; TSHE, tamarind seed husk extract.

Figure 3. Abdominal visceral fat area (AVFA) at 12 weeks post-intervention (n = 50 per group). Differences between the TSHE and placebo groups were analyzed using a linear mixed-effects model with fixed effects for treatment group, time point, and the group × time point interaction, adjusting for baseline AVFA and the baseline × time point interaction. Subject-specific random effects were included to account for inter-individual variability. Individual participant values are shown as dots. Large, solid dots with vertical bars represent the mean ± SD, while EMMs and their 95% CIs are indicated by the horizontal line and shaded box, respectively. * p < 0.05 versus placebo.

**Table 1.** Composition of TSHE and of the test food
Ingredients and Nutritional components	TSHE (g/100 g)	Test food (g/two capsules)	Placebo (g/two capsules)
TSHE values are expressed as g per 100 g of extract; test food and placebo values as g per two capsules, which constitute one daily dose and provide 200 mg of TSHE. Total carbohydrate was obtained by subtracting total polyphenol from crude carbohydrate, and total polyphenol was determined by the Folin-Ciocalteu method and expressed as gallic acid equivalents. – , not applicable. TSHE, tamarind seed husk extract. The capsule contents and the TSHE bulk powder were analyzed at different times.
Tamarind seed husk extract (TSHE)	–	0.20	–
Syloid 760 (fine silicon dioxide)	–	<0.01	<0.01
Tricalcium phosphate	–	<0.01	<0.01
Calcium stearate	–	<0.01	<0.01
TK-16 (starch hydrolysate)	–	0.30	0.54
Capsule	–	0.12	0.12
Protein	0.8	0.12	0.12
Lipid	0.3	0.01	0.01
Moisture	8.6	0.04	0.04
Ash	1.2	0.01	0.01
Total carbohydrate	22.1	0.33	0.51
Total polyphenol	67.0	0.13	0.00
Energy (kcal)	–	2.13	2.59

Table 1. Composition of TSHE and of the test food

Ingredients and Nutritional components

TSHE (g/100 g)

Test food (g/two capsules)

Placebo (g/two capsules)

TSHE values are expressed as g per 100 g of extract; test food and placebo values as g per two capsules, which constitute one daily dose and provide 200 mg of TSHE. Total carbohydrate was obtained by subtracting total polyphenol from crude carbohydrate, and total polyphenol was determined by the Folin-Ciocalteu method and expressed as gallic acid equivalents. – , not applicable. TSHE, tamarind seed husk extract. The capsule contents and the TSHE bulk powder were analyzed at different times.

Tamarind seed husk extract (TSHE)

–

0.20

–

Syloid 760 (fine silicon dioxide)

–

<0.01

Tricalcium phosphate

–

<0.01

Calcium stearate

–

<0.01

TK-16 (starch hydrolysate)

–

0.30

0.54

Capsule

–

0.12

Protein

0.8

0.12

Lipid

0.3

0.01

Moisture

8.6

0.04

Ash

1.2

0.01

Total carbohydrate

22.1

0.33

0.51

Total polyphenol

67.0

0.13

0.00

Energy (kcal)

–

2.13

2.59

**Table 2.** Baseline characteristics of the intention-to-treat and per-protocol sets
	ITT	PPS
Data are presented as mean ± SD unless otherwise indicated. AVFA, abdominal visceral fat area; BMI, body mass index; ITT, intention-to-treat population; PPS, per-protocol set; SD, standard deviation; TSHE, tamarind seed husk extract.
Male, n (%)	30 (53.6%)	37 (66.1%)	28 (56.0%)	33 (66.0%)
Female, n (%)	26 (46.4%)	19 (33.9%)	22 (44.0%)	17 (34.0%)
Age (years)	51.0 ± 10.3 [min 21, max 70]	51.9 ± 9.7 [min 32, max 71]	50.9 ± 10.2 [min 21, max 70]	52.3 ± 9.7 [min 32, max 71]
Body weight (kg)	73.5 ± 9.7	74.9 ± 8.5	73.4 ± 9.9	74.2 ± 8.3
Height (cm)	164.1 ± 10.1	165.7 ± 8.0	164.2 ± 9.9	165.5 ± 8.1
BMI (kg/m²)	27.2 ± 1.4	27.2 ± 1.4	27.1 ± 1.3	27.0 ± 1.3
Systolic blood pressure (mmHg)	125.8 ± 16.0	125.9 ± 15.4	125.2 ± 15.8	126.1 ± 15.2
Diastolic blood pressure (mmHg)	82.9 ± 12.1	83.2 ± 11.7	82.4 ± 12.1	82.9 ± 11.5
AVFA (cm²)	122.4 ± 31.9	119.9 ± 37.1	123.9 ± 32.6	119.7 ± 37.5

Table 2. Baseline characteristics of the intention-to-treat and per-protocol sets

ITT

PPS

TSHE (n = 56)

Placebo (n = 56)

TSHE (n = 50)

Placebo (n = 50)

Data are presented as mean ± SD unless otherwise indicated. AVFA, abdominal visceral fat area; BMI, body mass index; ITT, intention-to-treat population; PPS, per-protocol set; SD, standard deviation; TSHE, tamarind seed husk extract.

Male, n (%)

30 (53.6%)

37 (66.1%)

28 (56.0%)

33 (66.0%)

Female, n (%)

26 (46.4%)

19 (33.9%)

22 (44.0%)

17 (34.0%)

Age (years)

51.0 ± 10.3 [min 21, max 70]

51.9 ± 9.7 [min 32, max 71]

50.9 ± 10.2 [min 21, max 70]

52.3 ± 9.7 [min 32, max 71]

Body weight (kg)

73.5 ± 9.7

74.9 ± 8.5

73.4 ± 9.9

74.2 ± 8.3

Height (cm)

164.1 ± 10.1

165.7 ± 8.0

164.2 ± 9.9

165.5 ± 8.1

BMI (kg/m²)

27.2 ± 1.4

27.1 ± 1.3

27.0 ± 1.3

Systolic blood pressure (mmHg)

125.8 ± 16.0

125.9 ± 15.4

125.2 ± 15.8

126.1 ± 15.2

Diastolic blood pressure (mmHg)

82.9 ± 12.1

83.2 ± 11.7

82.4 ± 12.1

82.9 ± 11.5

AVFA (cm²)

122.4 ± 31.9

119.9 ± 37.1

123.9 ± 32.6

119.7 ± 37.5

**Table 3.** Primary and secondary efficacy outcomes (n = 50, per group).
Outcome	Statistics	Week 0	Week 4	Week 8	Week 12
Data are presented as mean ± SD, or as EMM with 95% CI. Between-group differences were estimated by a linear mixed-effects model; * p < 0.05 versus placebo. Δ%, percent change from baseline; AVFA, abdominal visceral fat area; CI, confidence interval; EMM, estimated marginal mean; SD, standard deviation; SFA, subcutaneous fat area; TFA, total fat area; VSR, visceral-to-subcutaneous fat ratio.
AVFA (cm²)	Mean ± SD	123.9 ± 32.6	119.7 ± 37.5	116.1 ± 31.8* (p = 0.048)	120.8 ± 42.1	117.3 ± 36.2	119.9 ± 41.9	117.7 ± 33.9 (p = 0.077)	121.5 ± 39.5
EMM	–	–	114.3	122.6	115.3	122.0	115.9	123.3
95% CI	–	–	[108.4, 120.1]	[116.8, 128.5]	[109.6, 121.0]	[116.3, 127.6]	[110.0, 121.7]	[117.5, 129.2]
Δ% AVFA (%)	Mean ± SD	–	–	−5.5 ± 13.6	1.5 ± 23.1	−5.4 ± 14.8	0.5 ± 20.2	−4.5 ± 15.3	2.6 ± 22.2
EMM	–	–	−5.3	1.3	−5.3	0.4	−4.3	2.4
95% CI	–	–	[−10.6, 0.0]	[−4.0, 6.7]	[−10.3, −0.3]	[−4.6, 5.4]	[−9.6, 1.0]	[−2.9, 7.7]
SFA (cm²)	Mean ± SD	247.4 ± 64.5	241.5 ± 66.5	244.6 ± 72.8	241.0 ± 65.2	243.4 ± 73.3	244.8 ± 67.4	242.9 ± 70.4	244.4 ± 66.7
EMM	–	–	241.7	243.9	240.5	247.7	240.1	247.2
95% CI	–	–	[234.4, 249.1]	[236.6, 251.2]	[232.6, 248.4]	[239.8, 255.5]	[232.1, 248.0]	[239.2, 255.1]
Δ% SFA (%)	Mean ± SD	–	–	−1.3 ± 12.1	0.6 ± 9.2	−1.6 ± 13.4	1.8 ± 8.4	−1.8 ± 12.6	2.0 ± 10.7
EMM	–	–	−1.2	0.6	−1.5	1.7	−1.7	1.9
95% CI	–	–	[−4.2, 1.8]	[−2.5, 3.6]	[−4.7, 1.6]	[−1.4, 4.9]	[−5.0, 1.5]	[−1.4, 5.2]
TFA (cm²)	Mean ± SD	371.3 ± 66.7	361.2 ± 71.1	360.8 ± 78.9	361.8 ± 75.1	360.8 ± 81.9	364.7 ± 75.9	360.6 ± 77.2	365.9 ± 74.1
EMM	–	–	355.8	366.8	355.7	369.7	355.9	370.5
95% CI	–	–	[345.5, 366.1]	[356.5, 377.1]	[344.7, 366.8]	[358.7, 380.8]	[344.3, 367.5]	[359.0, 382.1]
Δ% TFA (%)	Mean ± SD	–	–	−3.1 ± 10.0	0.4 ± 9.7	−3.1 ± 11.1* (p = 0.043)	1.2 ± 9.9	−2.9 ± 11.4* (p = 0.048)	1.8 ± 11.3
EMM	–	–	−3.1	0.4	−3.1	1.2	−2.9	1.7
95% CI	–	–	[−5.9, −0.3]	[−2.3, 3.2]	[−6.1, −0.1]	[−1.7, 4.2]	[−6.0, 0.3]	[−1.5, 4.9]
VSR	Mean ± SD	0.5 ± 0.2	0.5 ± 0.3	0.5 ± 0.2	0.5 ± 0.3	0.5 ± 0.2	0.5 ± 0.3	0.5 ± 0.2	0.5 ± 0.3
EMM	–	–	0.5	0.5	0.5	0.5	0.5	0.5
95% CI	–	–	[0.5, 0.5]	[0.5, 0.6]	[0.5, 0.6]	[0.5, 0.6]	[0.5, 0.6]	[0.5, 0.6]

Table 3. Primary and secondary efficacy outcomes (n = 50, per group).

Outcome

Statistics

Week 0

Week 4

Week 8

Week 12

TSHE

Placebo

TSHE

Placebo

TSHE

Placebo

TSHE

Placebo

Data are presented as mean ± SD, or as EMM with 95% CI. Between-group differences were estimated by a linear mixed-effects model; * p < 0.05 versus placebo. Δ%, percent change from baseline; AVFA, abdominal visceral fat area; CI, confidence interval; EMM, estimated marginal mean; SD, standard deviation; SFA, subcutaneous fat area; TFA, total fat area; VSR, visceral-to-subcutaneous fat ratio.

AVFA (cm²)

Mean ± SD

123.9 ± 32.6

119.7 ± 37.5

116.1 ± 31.8* (p = 0.048)

120.8 ± 42.1

117.3 ± 36.2

119.9 ± 41.9

117.7 ± 33.9 (p = 0.077)

121.5 ± 39.5

EMM

–

114.3

122.6

115.3

122.0

115.9

123.3

95% CI

–

[108.4, 120.1]

[116.8, 128.5]

[109.6, 121.0]

[116.3, 127.6]

[110.0, 121.7]

[117.5, 129.2]

Δ% AVFA (%)

Mean ± SD

–

−5.5 ± 13.6

1.5 ± 23.1

−5.4 ± 14.8

0.5 ± 20.2

−4.5 ± 15.3

2.6 ± 22.2

EMM

–

−5.3

1.3

−5.3

0.4

−4.3

2.4

95% CI

–

[−10.6, 0.0]

[−4.0, 6.7]

[−10.3, −0.3]

[−4.6, 5.4]

[−9.6, 1.0]

[−2.9, 7.7]

SFA (cm²)

Mean ± SD

247.4 ± 64.5

241.5 ± 66.5

244.6 ± 72.8

241.0 ± 65.2

243.4 ± 73.3

244.8 ± 67.4

242.9 ± 70.4

244.4 ± 66.7

EMM

–

241.7

243.9

240.5

247.7

240.1

247.2

95% CI

–

[234.4, 249.1]

[236.6, 251.2]

[232.6, 248.4]

[239.8, 255.5]

[232.1, 248.0]

[239.2, 255.1]

Δ% SFA (%)

Mean ± SD

–

−1.3 ± 12.1

0.6 ± 9.2

−1.6 ± 13.4

1.8 ± 8.4

−1.8 ± 12.6

2.0 ± 10.7

EMM

–

−1.2

0.6

−1.5

1.7

−1.7

1.9

95% CI

–

[−4.2, 1.8]

[−2.5, 3.6]

[−4.7, 1.6]

[−1.4, 4.9]

[−5.0, 1.5]

[−1.4, 5.2]

TFA (cm²)

Mean ± SD

371.3 ± 66.7

361.2 ± 71.1

360.8 ± 78.9

361.8 ± 75.1

360.8 ± 81.9

364.7 ± 75.9

360.6 ± 77.2

365.9 ± 74.1

EMM

–

355.8

366.8

355.7

369.7

355.9

370.5

95% CI

–

[345.5, 366.1]

[356.5, 377.1]

[344.7, 366.8]

[358.7, 380.8]

[344.3, 367.5]

[359.0, 382.1]

Δ% TFA (%)

Mean ± SD

–

−3.1 ± 10.0

0.4 ± 9.7

−3.1 ± 11.1* (p = 0.043)

1.2 ± 9.9

−2.9 ± 11.4* (p = 0.048)

1.8 ± 11.3

EMM

–

−3.1

0.4

−3.1

1.2

−2.9

1.7

95% CI

–

[−5.9, −0.3]

[−2.3, 3.2]

[−6.1, −0.1]

[−1.7, 4.2]

[−6.0, 0.3]

[−1.5, 4.9]

VSR

Mean ± SD

0.5 ± 0.2

0.5 ± 0.3

0.5 ± 0.2

0.5 ± 0.3

0.5 ± 0.2

0.5 ± 0.3

0.5 ± 0.2

0.5 ± 0.3

EMM

–

0.5

95% CI

–

[0.5, 0.5]

[0.5, 0.6]

**Table 4.** Exploratory analysis of efficacy outcomes in participants with a visceral-to-subcutaneous fat ratio (VSR) ≥ 0.4
Outcome	Statistics	Week 0	Week 4	Week 8	Week 12
Exploratory post hoc analysis of participants with a baseline VSR ≥ 0.4 (TSHE, n = 35; placebo, n = 30). Data are presented as mean ± SD, or as EMM with 95% CI. Between-group differences were estimated by a linear mixed-effects model; * p < 0.05 versus placebo. Δ%, percent change from baseline; AVFA, abdominal visceral fat area; CI, confidence interval; EMM, estimated marginal mean; SD, standard deviation; SFA, subcutaneous fat area; TFA, total fat area; VSR, visceral-to-subcutaneous fat ratio.
AVFA (cm²)	Mean ± SD	134.9 ± 32.1	136.8 ± 38.5	122.8 ± 34.6* (p = 0.010)	137.1 ± 40.3	125.9 ± 39.0	137.2 ± 40.3	126.7 ± 35.4* (p = 0.024)	139.0 ± 33.8
EMM	–	–	123.6	136.2	126.8	136.1	127.5	138.1
95% CI	–	–	[117.2, 130.0]	[129.2, 143.1]	[120.3, 133.3]	[129.2, 143.1]	[121.3, 133.7]	[131.4, 144.8]
Δ% AVFA (%)	Mean ± SD	–	–	−9.0 ± 12.1* (p = 0.009)	1.0 ± 18.0	−7.2 ± 15.3* (p = 0.036)	0.5 ± 13.1	−5.7 ± 15.6* (p = 0.011)	3.3 ± 13.0
EMM	–	–	−9.0	1.0	−7.2	0.5	−5.8	3.4
95% CI	–	–	[−14.2, −3.9]	[−4.5, 6.6]	[−12.1, −2.3]	[−4.8, 5.8]	[−10.6, −1.1]	[−1.8, 8.5]
SFA (cm²)	Mean ± SD	220.9 ± 51.2	205.7 ± 55.6	216.3 ± 58.9	207.2 ± 51.6	216.7 ± 61.1	211.1 ± 56.7	214.6 ± 57.4	210.5 ± 54.5
EMM	–	–	209.8	214.8	209.8	219.0	208.1	218.1
95% CI	–	–	[200.7, 218.9]	[205.0, 224.6]	[200.0, 219.7]	[208.4, 229.7]	[199.0, 217.1]	[208.3, 227.9]
Δ% SFA (%)	Mean ± SD	–	–	−2.0 ± 13.6	1.9 ± 9.6	−1.7 ± 15.0	3.0 ± 7.8	−2.7 ± 13.4	3.2 ± 10.5
EMM	–	–	−1.7	1.5	−1.5	2.8	−2.5	2.9
95% CI	–	–	[−5.7, 2.3]	[−2.8, 5.9]	[−5.7, 2.7]	[−1.7, 7.3]	[−6.6, 1.6]	[−1.5, 7.3]
TFA (cm²)	Mean ± SD	355.8 ± 66.1	342.5 ± 78.2	339.1 ± 74.6* (p = 0.040)	344.3 ± 75.2	342.6 ± 80.1	348.3 ± 80.0	341.3 ± 75.6* (p = 0.027)	349.5 ± 74.8
EMM	–	–	333.4	351.0	336.5	355.3	335.7	356.1
95% CI	–	–	[321.9, 344.8]	[338.7, 363.3]	[323.8, 349.3]	[341.6, 369.1]	[323.5, 347.8]	[342.9, 369.2]
Δ% TFA (%)	Mean ± SD	–	–	−4.8 ± 10.4* (p = 0.018)	1.0 ± 7.9	−3.9 ± 12.0* (p = 0.028)	2.0 ± 7.6	−4.1 ± 11.6* (p = 0.014)	2.6 ± 8.4
EMM	–	–	−4.7	1.0	−3.8	2.0	−4.0	2.5
95% CI	–	–	[−7.9, −1.5]	[−2.5, 4.4]	[−7.3, −0.4]	[−1.8, 5.7]	[−7.4, −0.5]	[−1.2, 6.3]
VSR	Mean ± SD	0.6 ± 0.2	0.7 ± 0.2	0.6 ± 0.2	0.7 ± 0.2	0.6 ± 0.2	0.7 ± 0.2	0.6 ± 0.2	0.7 ± 0.2
EMM	–	–	0.6	0.7	0.6	0.7	0.6	0.7
95% CI	–	–	[0.6, 0.7]	[0.6, 0.7]	[0.6, 0.7]	[0.6, 0.7]	[0.6, 0.7]	[0.6, 0.7]

Table 4. Exploratory analysis of efficacy outcomes in participants with a visceral-to-subcutaneous fat ratio (VSR) ≥ 0.4

Outcome

Statistics

Week 0

Week 4

Week 8

Week 12

TSHE (n = 35)

Placebo (n = 30)

TSHE (n = 35)

Placebo (n = 30)

TSHE (n = 35)

Placebo (n = 30)

TSHE (n = 35)

Placebo (n = 30)

Exploratory post hoc analysis of participants with a baseline VSR ≥ 0.4 (TSHE, n = 35; placebo, n = 30). Data are presented as mean ± SD, or as EMM with 95% CI. Between-group differences were estimated by a linear mixed-effects model; * p < 0.05 versus placebo. Δ%, percent change from baseline; AVFA, abdominal visceral fat area; CI, confidence interval; EMM, estimated marginal mean; SD, standard deviation; SFA, subcutaneous fat area; TFA, total fat area; VSR, visceral-to-subcutaneous fat ratio.

AVFA (cm²)

Mean ± SD

134.9 ± 32.1

136.8 ± 38.5

122.8 ± 34.6* (p = 0.010)

137.1 ± 40.3

125.9 ± 39.0

137.2 ± 40.3

126.7 ± 35.4* (p = 0.024)

139.0 ± 33.8

EMM

–

123.6

136.2

126.8

136.1

127.5

138.1

95% CI

–

[117.2, 130.0]

[129.2, 143.1]

[120.3, 133.3]

[129.2, 143.1]

[121.3, 133.7]

[131.4, 144.8]

Δ% AVFA (%)

Mean ± SD

–

−9.0 ± 12.1* (p = 0.009)

1.0 ± 18.0

−7.2 ± 15.3* (p = 0.036)

0.5 ± 13.1

−5.7 ± 15.6* (p = 0.011)

3.3 ± 13.0

EMM

–

−9.0

1.0

−7.2

0.5

−5.8

3.4

95% CI

–

[−14.2, −3.9]

[−4.5, 6.6]

[−12.1, −2.3]

[−4.8, 5.8]

[−10.6, −1.1]

[−1.8, 8.5]

SFA (cm²)

Mean ± SD

220.9 ± 51.2

205.7 ± 55.6

216.3 ± 58.9

207.2 ± 51.6

216.7 ± 61.1

211.1 ± 56.7

214.6 ± 57.4

210.5 ± 54.5

EMM

–

209.8

214.8

209.8

219.0

208.1

218.1

95% CI

–

[200.7, 218.9]

[205.0, 224.6]

[200.0, 219.7]

[208.4, 229.7]

[199.0, 217.1]

[208.3, 227.9]

Δ% SFA (%)

Mean ± SD

–

−2.0 ± 13.6

1.9 ± 9.6

−1.7 ± 15.0

3.0 ± 7.8

−2.7 ± 13.4

3.2 ± 10.5

EMM

–

−1.7

1.5

−1.5

2.8

−2.5

2.9

95% CI

–

[−5.7, 2.3]

[−2.8, 5.9]

[−5.7, 2.7]

[−1.7, 7.3]

[−6.6, 1.6]

[−1.5, 7.3]

TFA (cm²)

Mean ± SD

355.8 ± 66.1

342.5 ± 78.2

339.1 ± 74.6* (p = 0.040)

344.3 ± 75.2

342.6 ± 80.1

348.3 ± 80.0

341.3 ± 75.6* (p = 0.027)

349.5 ± 74.8

EMM

–

333.4

351.0

336.5

355.3

335.7

356.1

95% CI

–

[321.9, 344.8]

[338.7, 363.3]

[323.8, 349.3]

[341.6, 369.1]

[323.5, 347.8]

[342.9, 369.2]

Δ% TFA (%)

Mean ± SD

–

−4.8 ± 10.4* (p = 0.018)

1.0 ± 7.9

−3.9 ± 12.0* (p = 0.028)

2.0 ± 7.6

−4.1 ± 11.6* (p = 0.014)

2.6 ± 8.4

EMM

–

−4.7

1.0

−3.8

2.0

−4.0

2.5

95% CI

–

[−7.9, −1.5]

[−2.5, 4.4]

[−7.3, −0.4]

[−1.8, 5.7]

[−7.4, −0.5]

[−1.2, 6.3]

VSR

Mean ± SD

0.6 ± 0.2

0.7 ± 0.2

0.6 ± 0.2

0.7 ± 0.2

0.6 ± 0.2

0.7 ± 0.2

0.6 ± 0.2

0.7 ± 0.2

EMM

–

0.6

0.7

0.6

0.7

0.6

0.7

95% CI

–

[0.6, 0.7]