Orange peel: the flavonoid trials used supplements rather than zest

The strongest numbers linked to orange peel come from its flavonoids taken as supplements. A meta-analysis of 8 randomized trials in 596 people found citrus flavonoid supplements widened blood vessels on a standard test by 2.75 percentage points (95% CI 1.29 to 4.20), about 1.09 more per extra 200 mg a day, with the trials disagreeing strongly (I2 87%). A 6-week trial in 37 overweight men did not repeat that with real drinks. Hesperidin from 11 fl oz (330 mL) of orange juice or a 210 mg drink was absorbed equally well, and neither changed blood vessel function. We found no trial of sweet orange peel eaten as food, as zest, candied peel or powder. As a food, raw peel holds 136 mg of vitamin C, 10.6 g of fiber and 161 mg of calcium per 3.5 oz (100 g) in one old USDA record, and nobody eats 3.5 oz (100 g) of zest.

The numbers, per 3.5 oz (100 g)

How much is actually in it

• Raw orange peel contains about 136 mg vitamin C, 10.6 g fiber and 161 mg calcium per 3.5 oz (100 g) in a single USDA record. — USDA reference composition record, single SR Legacy entry Evidence C source
  Per 100 g: vitamin C 136 mg, fiber 10.6 g, calcium 161 mg

What your body absorbs

• In a 6-week crossover RCT on 37 overweight men, hesperidin from orange juice or a 210 mg drink was absorbed equally well, but neither improved blood vessel function. — Thirty-seven centrally overweight men, three 6-week periods, 11 fl oz (330 mL) orange juice or 210 mg/day hesperidin drink (n = 37) Evidence B source
  Comparable plasma AUC and urinary excretion OJ vs HESP; no FMD effect vs control
• In a human trial compared with a gut model, hesperetin glucuronides rose in blood and urine after hesperidin, and in the gut model it was split in the proximal colon. — healthy humans in a randomized trial plus SHIME colon model and Caco-2 cells Evidence B source
  Plasma and urine hesperetin-glucuronide rose significantly; deconjugation in proximal colon

What it does to your health

• A meta-analysis of RCTs found hesperidin, the main orange peel flavonoid, lowered fasting glucose, triglycerides, total and LDL cholesterol and systolic pressure, mainly above 500 mg a day and beyond 12 weeks. — adults in randomized controlled trials of hesperidin supplements Evidence A source
  Significant reductions in FBS, TG, TC, LDL-C, SBP, TNF-alpha; no effect on insulin, HDL, DBP, hs-CRP
• A meta-analysis of 8 RCTs (596 people) found citrus flavonoid supplements improved flow-mediated dilation by 2.75%, about 1.09% per extra 200 mg a day. — eight RCTs, 596 participants (n = 596) Evidence A source
  FMD +2.75% (95% CI 1.29, 4.20); +1.09% per 200 mg/d (0.70, 1.48)
• In a 4-week pilot on 29 healthy adults, 20 g a day of low-methoxy pectin from citrus peel lowered inflammatory markers and cut anxiety scores from 8.38 to 4.46. — healthy volunteers, 20 g LM citrus pectin (N = 14) vs 10 g maltodextrin (N = 15), 4 weeks (n = 29) Evidence B source
  TNF-alpha, IL-1 beta, IL-6, IFN-gamma decreased (p < 0.05); anxiety 8.38 to 4.46 (p < 0.006)
• In an RCT on 80 adults with poor sleep, 300 mg a day of a standardized lime peel supplement for 2 weeks shortened sleep latency and raised sleep efficiency. — 80 subjects with sleep disturbance, 300 mg/day or placebo for 2 weeks (n = 80) Evidence B source
  Reduced sleep latency, wake after sleep onset; improved sleep efficiency and total sleep time (polysomnography)
• In a 6-week RCT on 44 obese adults on a diet, 6.8 fl oz (200 mL) a day of orange juice enriched with peel polymethoxyflavones lowered LDL and HbA1c more than placebo juice. — 44 obese participants on a hypocaloric diet, 200 mL/day for six weeks (n = 44) Evidence B source
  Significant decreases in LDL-C and HbA1c vs placebo juice; lower IFN-gamma and TNF-alpha
• Animal and cell data suggest d-limonene from orange peel reduces gut inflammation, with only observational human data on IL-6. — rats with TNBS colitis, cell cultures, elderly healthy subjects (observational, 56 days of orange peel extract) Evidence D source
  Colitis scores reduced at 10 mg/kg, comparable to ibuprofen (rats)

Safety, limits and interactions

• A systematic review found only one RCT (20 patients, 6 weeks) of bitter orange peel extract for weight loss, with no significant benefit. — 1 randomized placebo-controlled trial, 20 patients, 6 weeks (n = 20) Evidence B source
  No statistically significant weight loss
• NIH NCCIH states bitter orange, whose peel is used in cooking and supplements, is likely safe in amounts found in foods. — US consumers Evidence E source
  Likely safe in food amounts

What people believe that the data does not support

• An earlier meta-analysis of 10 RCTs (577 people) found hesperidin did not change total cholesterol (-1.04 mg/dl) or blood pressure. — 10 randomized controlled trials, 577 participants (n = 577) Evidence A source
  TC WMD -1.04 mg/dl (95% CI -5.65, 3.57); LDL -1.96 (-7.56, 3.64); SBP -0.85 mmHg (-3.07, 1.36)
• A meta-analysis of 6 RCTs (318 people) found hesperidin did not improve fasting glucose (-1.10 mg/dL) or HbA1c. — six trials with 318 participants (n = 318) Evidence A source
  FBG WMD -1.10 mg/dL (95% CI -3.79, 1.57); HbA1c -0.04% (-0.14, 0.04)
• A meta-analysis of 11 RCTs (512 adults) found hesperidin or orange juice did not reduce body weight (-0.68 lb / -0.31 kg) or waist size. — eleven RCTs with 512 individuals (n = 512) Evidence A source
  Body weight WMD -0.68 lb (95% CI -3.2 to 1.8; metric: -0.31 kg, -1.44 to 0.82); waist 0.03 in (-0.46 to 0.51; metric: 0.07 cm, -1.16 to 1.30)

The bottom line

Hesperidin, the main flavonoid in the peel, is where the evidence splits. A 2025 meta-analysis found hesperidin supplements lowered fasting glucose, triglycerides, total and LDL cholesterol and systolic pressure, with the clearest effects above 500 mg a day and in trials longer than 12 weeks. Earlier meta-analyses pooled fewer and shorter trials and found no effect on total cholesterol (-1.04 mg/dl, 95% CI -5.65 to 3.57) across 577 people, or on fasting glucose (-1.10 mg/dL, -3.79 to 1.57) across 318. The difference is probably dose and duration, and none of those doses come from a garnish. Hesperidin or orange juice did not reduce body weight across 11 trials in 512 adults (-0.68 lb (-3.2 to 1.8; metric: -0.31 kg, -1.44 to 0.82)). Other peel products were tested as extracts. In a 4-week pilot on 29 healthy adults, 20 g a day of pectin from citrus peel lowered inflammatory markers, and anxiety scores fell from 8.38 to 4.46 with no change in the control arm. In 44 obese adults on a diet, 6.8 fl oz (200 mL) a day of orange juice enriched with peel flavonoids lowered LDL cholesterol and HbA1c more than plain placebo juice over six weeks, with the sizes not given in the abstract. In humans, hesperidin shows up in blood and urine as hesperetin glucuronides. Rat data on d-limonene from the peel point to less gut inflammation, with only observational human data behind them. The safety cards are about bitter orange, a different species. NIH says bitter orange is likely safe in amounts found in foods, which does not cover supplements. A systematic review found one trial of bitter orange peel extract for weight loss, 20 patients for six weeks, with no significant benefit and limited information about the safety of the herb. We have no card on the safety of hesperidin or bitter orange supplements at trial doses, or on pesticide residues on the peel, pregnancy, children or medicines.

Sources

1. orpl-daily-r8-01 · dataset
   Orange peel, raw: vitamin C 136 mg; fiber 10.6 g; calcium 161 mg (per 100 g)
   USDA FoodData Central, SR Legacy 2018, FDC 169103, Orange peel, raw · checked 2026-09-29
2. orpl-daily-r8-07 · RCT, crossover
   Plasma exposure to phase II hesperetin metabolites (AUC0-6 h) and 24 h urinary excretion were comparable after OJ and HESP, indicating effective hesperidin delivery and limited matrix effects on bioavailability. Neither intervention significantly affected fasting or postprandial FMD, vascular, metabolic or anthropometric parameters, or oxylipin profiles versus CON.
   Food Funct, 2026 · checked 2026-09-29
3. orpl-daily-r8-08 · RCT plus in vitro
   In humans, plasma and urine hesperetin-glucuronide levels increased significantly, whereas the impact on small phenolics was limited.
   Mol Nutr Food Res, 2018 · checked 2026-09-29
4. orpl-daily-r8-02 · meta-analysis of RCTs
   The study's subgroup analyses also revealed that interventions lasting more than 12 weeks were effective in reducing FBS, TG, TC, and LDL-C. Moreover, hesperidin dosage exceeding 500 mg/day showed significance in reducing FBS, TC, and LDL-C levels.
   Nutr Rev, 2025 · checked 2026-09-29
5. orpl-daily-r8-06 · meta-analysis of RCTs
   The pooled data demonstrated a statistically significant augmentation in flow-mediated vasodilation (FMD) (2.75%; 95% CI: 1.29, 4.20; I2 = 87.3%; p < 0.001) associated with CFS compared to the placebo group.
   Phytother Res, 2024 · checked 2026-09-29
6. orpl-daily-r8-09 · controlled trial
   In addition, a significant drop in anxiety scores (from 8.38 to 4.46, p < 0.006) was found with the 20 g/day intervention but not in the control arm.
   Nutrients, 2024 · checked 2026-09-29
7. orpl-daily-r8-10 · RCT
   The randomized, double-blind, placebo-controlled clinical trial involved 80 subjects who received either SLPS (300 mg/day) or placebo for a 2-week period.
   Phytomedicine, 2025 · checked 2026-09-29
8. orpl-daily-r8-11 · RCT
   However, the flavonoid-enriched juice group showed more pronounced improvements in metabolic biomarkers, including significant decreases in low-density lipoprotein cholesterol (LDL-C) and glycated hemoglobin (A1c) levels.
   Food Res Int, 2025 · checked 2026-09-29
9. orpl-daily-r8-12 · animal and in vitro
   Administered per os at a dose of 10mg/kg p.o., d-Limonene induced a significant reduction of intestinal inflammatory scores, comparable to that induced by ibuprofen.
   Life Sci, 2013 · checked 2026-09-29
10. orpl-daily-r8-13 · systematic review
    identified only 1 eligible randomized placebo controlled trial, which followed 20 patients for 6 weeks, demonstrated no statistically significant benefit for weight loss, and provided limited information about the safety of the herb.
    Am J Cardiol, 2004 · checked 2026-09-29
11. orpl-daily-r8-14 · agency fact sheet
    Bitter orange is likely safe when used orally in amounts commonly found in foods.
    NCCIH (NIH), Bitter Orange: Usefulness and Safety, updated November 2024 · checked 2026-09-29
12. orpl-daily-r8-03 · meta-analysis of RCTs
    The meta-analysis revealed that hesperidin supplementation had no effect on serum total cholesterol (weighted mean difference [WMD] = -1.04 mg/dl; 95% confidence interval [CI]: -5.65, 3.57)
    Phytother Res, 2019 · checked 2026-09-29
13. orpl-daily-r8-04 · meta-analysis of RCTs
    The results showed that hesperidin had no significant effect on serum fasting blood glucose (weighted mean difference [WMD] = -1.10 mg/dL, 95% CI: -3.79, 1.57)
    Br J Clin Pharmacol, 2020 · checked 2026-09-29
14. orpl-daily-r8-05 · meta-analysis of RCTs
    The meta-analysis showed that orange juice and/or hesperidin had no significant effect on body weight [weighted mean difference (WMD) = -0.31 kg; 95% CI, -1.44 to 0.82, P = 0.592]
    Clin Nutr ESPEN, 2021 · checked 2026-09-29