Gourd: the blood sugar claim, and why the species matters

Bitter gourd is sold as a blood sugar remedy, and the strongest summary of the trials does not back it. A Cochrane review of 3 randomized trials in 350 people with type 2 diabetes found no significant difference from placebo, in trials at high risk of bias with a search that ended in 2009. The EU also refused the claim that bitter gourd helps maintain normal blood glucose, meaning the evidence fell short when it was assessed. The word gourd covers several plants, and they are not interchangeable. In the UK tables raw bitter gourd, or karela, has 185 mg of vitamin C per 3.5 oz (100 g) for 11 calories. Raw bottle gourd has 5 mg. Each number comes from a single sample, and vitamin C shifts with ripeness and storage.

The numbers, per 3.5 oz (100 g)

How much is actually in it

• Raw bitter gourd (karela) in the UK tables has 185 mg vitamin C per 3.5 oz (100 g) for only 11 calories. — raw karela, UK analytical sample Evidence E source
  Per 100 g: vitamin C 185 mg, potassium 330 mg, folate 45 ug, protein 1.6 g, water 93.3 g
• Raw bottle gourd in the UK tables has just 5 mg vitamin C per 3.5 oz (100 g), so the gourd a reader buys changes the nutrient picture almost fortyfold. — raw bottle gourd, UK analytical sample Evidence E source
  Per 100 g: vitamin C 5 mg, potassium 120 mg, folate 6 ug, energy 13 calories, water 95.7 g

What your body absorbs

• In 19 Thai women, 47.6% of the calcium in ivy gourd was absorbed against 55.2% from milk, about 86% of milk's value. — healthy women aged 20-45, Thailand, single test meals with rice (n = 19) Evidence B source
  Fractional Ca absorption 0.476 +/- 0.109 ivy gourd vs 0.552 +/- 0.119 milk

What cooking and storage change

• By the USDA retention table for vegetables boiled in covering water and drained, about 75% of vitamin C and 65% of folate stay in the vegetable. — USDA group factor, Vegetables and Vegetable Products, boiled in water to cover, drained Evidence E source
  Vitamin C 75%, folate 65%, thiamin 80%, potassium 90% retained

What it does to your health

• A single dose of freeze-dried bitter gourd before a glucose drink did not change blood glucose, insulin or appetite in 5 overweight men. — non-diabetic overweight men, acute test (n = 5) Evidence B source
  No difference between placebo, 50 and 100 mg/kg
• In an uncontrolled 3-month trial, 4.8 g a day of wild bitter gourd powder in 42 adults with metabolic syndrome cut its prevalence by 19% at the end of supplementation. — Taiwanese adults with metabolic syndrome, 3 months supplementation plus 3 months follow-up (n = 42) Evidence C source
  MetS incidence rate -19.0% (SE 5.7%) at 3 months, effect faded by months 5-6
• In the same Bangladeshi cohort, a gourd and root vegetable dietary pattern was linked with slightly thicker carotid artery walls, 7.74 um per standard deviation. — 1,149 adults from the HEALS cohort, mean age 45.5 (n = 1149) Evidence C source
  +7.74 um IMT per 1 SD pattern adherence (95% CI 2.86 to 12.62)

Safety, limits and interactions

• An Indian expert committee traced 3 deaths and 26 hospital admissions to extremely bitter bottle gourd juice, with vomiting of blood in 73% of admitted patients. — cases reported across India to the ICMR expert committee, 2010-2011 (n = 29) Evidence D source
  3 deaths (all over 59 with long-standing diabetes); hematemesis 19 of 26, diarrhea 18 of 26
• A 66-year-old woman developed bloody colitis, low blood pressure and vomiting after eating a bitter home-grown zucchini, a cucurbitacin poisoning in the same plant family as gourds. — one 66-year-old woman, Germany (n = 1) Evidence D source
  Hemorrhagic colitis, hypotension, recovered after IV fluids in 2 days
• Among 1,000 Sri Lankans with diabetes, 16.9% of those with hypoglycemia had eaten unprescribed native foods, bitter gourd most often. — patients with diabetes at a private clinic, Sri Lanka (n = 1000) Evidence C source
  Native foods behind hypoglycemia in 16.9% of cases; Momordica charantia in 54.5% of those
• A 60-year-old woman who took a pure bitter gourd extract for 7 months developed acute interstitial nephritis, which recovered after stopping it and steroids. — one 60-year-old Korean woman (n = 1) Evidence D source
  Creatinine 1.45 mg/dL, biopsy-proven AIN, near baseline after 3 months
• Across 3 months of wild bitter gourd capsules in 42 adults, side effects were mild: one case of abdominal pain, two of bloating, and no liver or kidney marker changes. — Taiwanese adults with metabolic syndrome, 4.8 g/day for 3 months (n = 42) Evidence C source
  1 abdominal pain, 2 bloating; ALT, AST, creatinine unchanged

What people believe that the data does not support

• A Cochrane review of 3 randomized trials in 350 people with type 2 diabetes found no significant glucose benefit of bitter gourd preparations over placebo. — adults with type 2 diabetes, trials up to 3 months (n = 350) Evidence A source
  No statistically significant difference vs placebo; no pooled estimate (preparations too varied)
• The EU did not authorize the claim that bitter gourd helps maintain normal blood glucose. — EU health claims register Evidence E source
  Claim status: non-authorized

Who this works differently for

• In a 12-week randomized trial in 38 adults with prediabetes, 3.6 g a day of freeze-dried bitter gourd lowered fasting glucose by about 0.9 mg/dL (0.05 mmol/L) a week against a cucumber control. — adults with prediabetes, 12 weeks (n = 38) Evidence B source
  FPG about -0.9 mg/dL (-0.05 mmol/L) per week; between-group FPG p = 0.026, HOMA-IR p = 0.045
• In a crossover trial of 52 Tanzanians with prediabetes, 2.5 g of bitter gourd powder daily for 8 weeks lowered fasting glucose by 5.6 mg/dL (0.31 mmol/L) more than cucumber juice. — adults with prediabetes, Tanzania, two 8-week periods (n = 52) Evidence B source
  FPG difference 5.6 mg/dL (95% CI 1.4 to 9.7; metric: 0.31 mmol/L, 0.08 to 0.54)
• In 9,677 Bangladeshi adults exposed to arsenic, those eating most gourds and root vegetables had a 31% lower hazard of arsenical skin lesions over about 6 years. — HEALS cohort, Araihazar, Bangladesh, 2000-2009 (n = 9677) Evidence C source
  HR 0.69 in top vs bottom quartile of gourd and root pattern (P trend 0.001)

The bottom line

Two newer trials in people with prediabetes point the other way, and the answer stays unclear for a concrete reason. Both were small, both used dried powder instead of the cooked vegetable, and we found no larger trial repeating them. In 38 adults over 12 weeks, 3.6 g a day of freeze-dried fruit lowered fasting glucose by about 0.9 mg/dL (0.05 mmol/L) a week against a cucumber control, while a 4-week crossover in the same paper showed no difference. In 52 Tanzanians, 2.5 g of powder a day for 8 weeks lowered fasting glucose by 5.6 mg/dL (0.31 mmol/L) more than cucumber juice (95% CI 0.08 to 0.54), with complete data for 44. A single dose given to 5 overweight men without diabetes changed nothing, in a pilot too small to say much. Ivy gourd leaves and shoots gave up 47.6 percent of their calcium against 55.2 percent from milk in 19 Thai women, in one rice meal carrying 100 mg of calcium. Boiling and draining keeps about 75 percent of vitamin C and 65 percent of folate by the USDA group factor for vegetables, a figure that was never measured on gourd itself. In a Bangladeshi cohort of 9,677 adults exposed to arsenic, those eating the most gourds and root vegetables had a 31 percent lower hazard of arsenical skin lesions over about 6 years (hazard ratio 0.69). In 1,149 adults from the same cohort the same pattern went with carotid walls 7.74 um thicker per standard deviation. In that population the pattern also marks poverty, so neither finding is about gourd alone. The cautions are real and mostly about bitterness and extracts. An Indian expert committee traced 3 deaths and 26 hospital admissions to extremely bitter bottle gourd juice, with vomiting of blood in 19 of the 26, from cases reported passively and with no toxin levels measured. A 66-year-old woman in Germany had bloody colitis and low blood pressure after eating a bitter home-grown zucchini from the same plant family, and that report names bitter taste as the key sign of this poisoning. A bottle gourd, its juice or a zucchini that tastes strongly bitter is one to spit out, not drink. The bitter gourd on this page is bitter by nature, so taste is no guide there. Among 1,000 Sri Lankans with diabetes, native foods were behind 16.9 percent of cases of low blood sugar by self-report, with bitter gourd named in 54.5 percent of those. If you take glucose lowering medicine, adding bitter gourd is a question for the person treating you. A 60-year-old woman who took a pure bitter gourd extract for 7 months developed kidney inflammation that recovered after stopping, a single case with probable causality. In an uncontrolled 3-month study, capsules of 4.8 g a day in 42 adults brought one case of abdominal pain and two of bloating, after people with G6PD deficiency and melon family allergy had been excluded. We found no safety data on gourd in pregnancy or in children.

Sources

1. gour-r2-01 · composition table
   CoFID 13-252 Gourd, karela, raw: Energy 11 kcal/100 g · Vitamin C 185 mg · Potassium 330 mg · Folate 45 µg · Protein 1.6 g · Carbohydrate 0.8 g · Water 93.3 g
   CoFID 2021, Public Health England, code 13-252 Gourd, karela, raw (OGL v3.0) · checked 2026-09-29
2. gour-r2-02 · composition table
   CoFID 13-249 Gourd, bottle, raw: Energy 13 kcal/100 g · Vitamin C 5 mg · Potassium 120 mg · Folate 6 µg · Protein 0.4 g · Carbohydrate 2.7 g · Water 95.7 g
   CoFID 2021, Public Health England, code 13-249 Gourd, bottle, raw (OGL v3.0) · checked 2026-09-29
3. gour-r2-03 · randomized crossover trial
   Fractional calcium absorption (X+/- SD) was 0.391 +/- 0.128 from winged beans, 0.476 +/- 0.109 from ivy gourd, and 0.552 +/- 0.119 from milk.
   J Food Sci, 2008 · checked 2026-09-29
4. gour-r2-04 · retention table
   USDA-RETN-R6:3775 VEG,OTHER,BLD,WATER COVER,DRAINED: vitamin_c_mg 75% · folate_total_ug 65% · thiamin_mg 80% · potassium_mg 90% · calcium_mg 95%
   USDA Table of Nutrient Retention Factors, Release 6, 2007, code 3775 · checked 2026-09-29
5. gour-r2-08 · randomized crossover trial
   Plasma glucose and insulin levels significantly increased during the OGTT (p < or =0.05) but no significant difference was observed between experimental conditions.
   J Ethnopharmacol, 2009 · checked 2026-09-29
6. gour-r2-09 · uncontrolled trial
   A total of 42 eligible (21 men and 21 women) with a mean age of 45.7 ± 11.4 years (23 to 63 years) were supplemented with 4.8 gram lyophilized WBG powder in capsules daily for three months ... After adjusting for sex and age, the MetS incidence rate (standard error, p value) decreased by 7.1% (3.7%, 0.920), 9.5% (4.3%, 0.451), 19.0% (5.7%, 0.021)
   Nutr J, 2012 · checked 2026-09-29
7. gour-r2-11 · cross-sectional
   We observed a positive association between the gourd/root vegetable diet and IMT, as each 1 sd increase in pattern adherence was related to a difference of 7·74 (95 % CI 2·86, 12·62) μm in IMT (P<0·01)
   Public Health Nutr, 2016 · checked 2026-09-29
8. gour-r2-12 · case series
   Three deaths were reported, one from Delhi and two from Uttar Pradesh after consumption of extremely bitter bottle gourd juice. ... Diarrhoea and vomiting of blood (haematemesis) was reported in 18 (69.2%) and 19 (73.1%) patients, respectively.
   Indian J Med Res, 2012, Assessment of effects on health due to consumption of bitter bottle gourd (Lagenaria siceraria) juice · checked 2026-09-29
9. gour-r2-13 · case report
   Acute food poisoning due to cucurbitacin - containing pumpkin is rare but can occur in small gardening units in association with higher outside temperatures. Cucurbitacin poisoning has to be taken into account for differential diagnosis in food poisoning. Bitter taste is essential to diagnose cucurbitacin intoxications.
   Dtsch Med Wochenschr, 2020 · checked 2026-09-29
10. gour-r2-14 · observational
    Non-prescribed native food items accounted for hypoglycaemia in 16.9% of patients (Momordica charantia 54.5%, Costus speciosus 52.3%, Salacia prinoides 11.4%, Coccinia grandis 6.8%, Adenanthera pavonina 4.5%).
    BMC Endocr Disord, 2018 · checked 2026-09-29
11. gour-r2-15 · case report
    We report an extremely rare case of AIN that occurred after a patient ingested a pure M charantia extract over 7 months.
    Medicine (Baltimore), 2021 · checked 2026-09-29
12. gour-r2-16 · uncontrolled trial
    Throughout the three-month supplementation period only one subject reported abdominal pain and two claimed bloat.
    Nutr J, 2012 · checked 2026-09-29
13. gour-r2-05 · systematic review
    Three randomised controlled trials with up to three months duration and investigating 350 participants met the inclusion criteria. ... There was no statistically significant difference compared to placebo.
    Cochrane Database Syst Rev, 2010 · checked 2026-09-29
14. gour-r2-17 · regulatory register
    POL-HC-7601 Momordica charantia (Common Name : balsam pear, bitter melon, bitter gourd, ampalaya, karela (karola), fu kwa) Helps to maintain a normal blood glucose Non-authorised
    EU Register on nutrition and health claims, claim POL-HC-7601, snapshot 2026-09-21 · checked 2026-09-29
15. gour-r2-06 · randomized trial
    Study 2 was a parallel trial (n = 38) lasting 12 weeks, with freeze-dried whole fruits (3.6 g/day) or a cucumber-based matched control supplement. ... On average, bitter gourd intervention reduced FPG by ∼0.05 mmol/L per week, whereas FPG remained unchanged following placebo.
    J Ethnopharmacol, 2025 · checked 2026-09-29
16. gour-r2-07 · randomized crossover trial
    In a randomized placebo-controlled single blinded clinical trial, 52 individuals with prediabetes were studied after consuming a bitter gourd or a cucumber juice. ... The effect was also proven by a general linear mixed model (estimate 0.31; SE: 0.12; p: 0.01; 95%CI: 0.08; 0.54).
    J Ethnopharmacol, 2018 · checked 2026-09-29
17. gour-r2-10 · cohort
    The gourd and root pattern score was inversely associated with skin lesion risk (P(trend) = 0.001), with hazard ratios of 0.86, 0.73, and 0.69 for the second, third, and fourth highest quartiles.
    Am J Epidemiol, 2011 · checked 2026-09-29