Bitter Orange
Research reviewed: Up until 03/2026
Bitter Orange (Citrus aurantium (p-Synephrine)) is a dietary supplement with 11 published peer-reviewed studies involving 232 participants, researched for Weight Loss & Metabolic Rate, Exercise Performance & Safety, Systematic reviews and 1 more areas.
Evidence at a Glance
Strength is scored by study design, sample size, study type, and outcomes
Weight Loss & Metabolic Rate
WeakExercise Performance & Safety
ModerateSystematic reviews
WeakClinical trials
ModerateResearch Visualised
Visual breakdown of the clinical data.
Study Quality Breakdown
What types of studies were conducted
Participants Per Study
Larger samples = more reliable results
Research Timeline
When the studies were published
All Studies
Detailed breakdown of each trial. Click to expand.
Weight Loss & Metabolic Rate
Safety and efficacy of Citrus aurantium and p-synephrine for weight loss
Study Type
Systematic review and meta-analysis
Purpose
Safety and efficacy of Citrus aurantium and p-synephrine for weight loss
Dose
10-100mg p-synephrine
Participants
Meta-analysis of RCTs
Duration
Various
Results
p-Synephrine modestly increased metabolic rate and energy expenditure. Weight loss benefits observed particularly with exercise. No significant cardiovascular adverse effects at recommended doses.
How They Measured It
Body weight, BMI, metabolic rate, adverse events
Clinical studies involving C. aurantium and p-synephrine
Study Type
Review of human clinical studies
Purpose
Clinical studies involving C. aurantium and p-synephrine
Dose
Various (typically 10-90mg/day)
Participants
Review of multiple clinical trials
Duration
Various
Results
Bitter orange extract and p-synephrine increase resting metabolic rate and energy expenditure. Modest weight loss observed when given 6-12 weeks. Generally well-tolerated.
How They Measured It
Review of human clinical studies on weight, metabolic rate, performance
Clinical and basic research on C. aurantium as weight loss supplement
Study Type
Current status review
Purpose
Clinical and basic research on C. aurantium as weight loss supplement
Dose
Various
Participants
Review
Duration
Various
Results
C. aurantium demonstrates sympathomimetic activity via p-synephrine (octopamine receptor agonist). Thermogenic and lipolytic effects documented. Safety acceptable in healthy adults at common doses.
How They Measured It
Systematic review of available studies
Bitter orange extract combination for weight management in overweight adults
Study Type
RCT
Purpose
Bitter orange extract combination for weight management in overweight adults
Dose
300mg C. aurantium + caffeine + St. John's Wort
Participants
82 overweight adults
Duration
6 weeks
Results
Significant weight loss and body composition improvements versus placebo. Bitter orange extract contributed to thermogenic and appetite-suppressing effects of the combination.
How They Measured It
Body weight, body composition, BMI, metabolic rate
Exercise Performance & Safety
Synephrine effects on exercise performance and substrate oxidation in trained cyclists
Study Type
Randomised double-blind crossover trial
Purpose
Synephrine effects on exercise performance and substrate oxidation in trained cyclists
Dose
3mg/kg p-synephrine
Participants
12 trained cyclists
Duration
Acute crossover
Results
Significantly increased fat oxidation during moderate-intensity exercise and improved time to exhaustion via beta-3 adrenergic receptor stimulation. Ergogenic benefits for endurance athletes.
How They Measured It
VO2 max, fat oxidation rate, blood lactate, exercise tolerance
Dose-dependent thermogenic effects of p-synephrine in healthy adults
Study Type
Thermogenesis clinical study
Purpose
Dose-dependent thermogenic effects of p-synephrine in healthy adults
Dose
10, 20, or 50mg p-synephrine
Participants
40 healthy adults
Duration
Acute single dose
Results
p-Synephrine increased RMR dose-dependently. No significant changes in blood pressure or heart rate. Selective beta-3 mechanism enables thermogenesis without cardiovascular stimulant effects.
How They Measured It
Resting metabolic rate (RMR), respiratory exchange ratio, BP, HR
Cardiovascular safety profile of p-synephrine and bitter orange extracts
Study Type
Safety cardiovascular review
Purpose
Cardiovascular safety profile of p-synephrine and bitter orange extracts
Dose
Various clinical doses
Participants
Review of clinical safety data
Duration
Various
Results
No significant increases in BP or heart rate at recommended doses. Risk predominantly when combined with caffeine or other stimulants in susceptible individuals.
How They Measured It
Blood pressure, heart rate, QTc interval, adverse event compilation
Bitter orange extract for body composition improvement in overweight women
Study Type
Body composition trial
Purpose
Bitter orange extract for body composition improvement in overweight women
Dose
450mg C. aurantium extract daily
Participants
68 overweight women
Duration
12 weeks
Results
Significantly reduced body fat percentage and waist circumference. Lean mass preserved. Metabolic benefits including reduced fasting glucose observed.
How They Measured It
DEXA body composition, BMI, waist circumference, metabolic markers
Digestive and gastroprokinetic effects of Citrus aurantium
Study Type
Gastric motility study
Purpose
Digestive and gastroprokinetic effects of Citrus aurantium
Dose
300mg C. aurantium extract
Participants
30 functional dyspepsia patients
Duration
4 weeks
Results
Significantly improved gastric emptying rate and reduced dyspeptic symptoms. Sympathomimetic prokinetic activity on gastrointestinal smooth muscle confirmed.
How They Measured It
Gastric emptying rate, intestinal motility, digestive symptoms
Systematic reviews
To investigate the effects of Bitter Orange in the safety and efficacy of citrus aurantium (bitter orange) extracts and p-synephrine: a systematic review and meta-analysis.
Study Type
Systematic review and meta-analysis
Purpose
To investigate the effects of Bitter Orange in the safety and efficacy of citrus aurantium (bitter orange) extracts and p-synephrine: a systematic review and meta-analysis.
Dose
Bitter Orange (dose not specified)
Participants
Participants not specified
Duration
Duration not specified
Results
03, respectively). The weight loss in the synephrine group was non-significant after prolonged treatment, and it did not influence body composition parameters. Based on the analyzed clinical studies, synephrine tends to raise blood pressure and heart rate, and there is no evidence that synephrine can facilitate weight loss. Further studies are needed to confirm evidence of its safety and efficacy.
How They Measured It
See study for outcome measures
Clinical trials
To investigate the effects of Bitter Orange in effect of p-synephrine on fat oxidation rate during exercise of increasing intensity in healthy active women.
Study Type
Randomized, double-blind, placebo-controlled
Purpose
To investigate the effects of Bitter Orange in effect of p-synephrine on fat oxidation rate during exercise of increasing intensity in healthy active women.
Dose
3 mg
Participants
Participants not specified
Duration
Duration not specified
Results
1; 0.08 g/min, p = 0.449, d = 0.21). An acute intake of 3 mg/kg of p -synephrine before exercise did not modify energy expenditure and substrate oxidation during submaximal aerobic exercise in healthy active women. It is likely that the increase in resting tympanic temperature induced by p -synephrine hindered the effect of this substance on fat utilization during exercise in healthy active women.
How They Measured It
See study for outcome measures
Frequently Asked Questions
Common questions about Bitter Orange research
There are currently 11 peer-reviewed studies on Bitter Orange (Citrus aurantium (p-Synephrine)), involving 232 total participants. Research covers Weight Loss & Metabolic Rate, Exercise Performance & Safety, Systematic reviews and 1 more areas. The overall evidence strength is rated as Moderate.
The evidence is currently rated as "Moderate Evidence". This rating is based on study design quality (randomisation, blinding, placebo controls), sample sizes, study types (6 human studies), and reported outcomes.
Bitter Orange has been researched for: Weight Loss & Metabolic Rate, Exercise Performance & Safety, Systematic reviews, Clinical trials. Each area has its own body of evidence which you can explore in the study breakdowns above.
Yes, 6 out of 11 studies are human trials. Human trials carry more weight in our evidence scoring system.
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