Supplement
Bitter orange is a citrus fruit whose peel extract contains synephrine, a stimulant-like compound that acts on adrenaline-related receptors. People mostly look at it for weight management, but the evidence is very limited, and research in 86 people found no clear difference in blood glucose. Small trials also found no clear difference in alertness, anxiety symptoms or headaches.
- Updated
- How we grade
- 19 studies cited
- Best evidence
- Grade D
- Conditions studied
- 8
- Outcomes
- 20
- Graded outcomes
- 0006
Evidence by condition
- Strong
- Moderate
- Limited
- Very limited
General Cardiovascular Health
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Alertness No effect | NoneNo effect | 50 people | ||||
| Anxiety Symptoms No effect | NoneNo effect | 50 people |
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Alertness No effect | NoneNo effect | 50 people |
Weight Loss & Maintenance
- Blood glucose
- Blood Pressure: changes; see studies
- Weight: changes; see studies
Anaerobic Exercise Performance
- Headaches
- Sprint Performance Metrics: improves
- Insomnia Signs and Symptoms: changes; see studies
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Headaches No effect | NoneNo effect | 13 people | ||||
| Sprint Performance Metrics | Improves (the measure goes up) | 1 study | 13 people | |||
Studies that measured sprint performance metrics | ||||||
| Insomnia Signs and Symptoms | Changes; see studies | 13 people | ||||
Mood Improvement
- Alertness
- Appetite: changes; see studies
- Anxiety Symptoms: changes; see studies
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Alertness No effect | NoneNo effect | 50 people | ||||
| Appetite | Changes; see studies | 1 study | 50 people | |||
| Anxiety Symptoms | Changes; see studies | 50 people | ||||
| Headaches | Changes; see studies | 50 people | ||||
| Heart Rate | Changes; see studies | 50 people | ||||
| Metabolic Rate | Improves (the measure goes up) | 50 people | ||||
| Sedation | Improves (the measure goes up) | 50 people | ||||
Cycling Performance
- Carbohydrate Oxidation: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Carbohydrate Oxidation | Improves (the measure goes up) | 6 studies | 45 people | |||
Studies that measured carbohydrate oxidation
| ||||||
Muscle Size & Strength
- Carbohydrate Oxidation: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Carbohydrate Oxidation | Improves (the measure goes up) | 6 studies | 12 people | |||
Studies that measured carbohydrate oxidation
| ||||||
Aerobic Exercise Performance
- Carbohydrate Oxidation: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Carbohydrate Oxidation | Improves (the measure goes up) | 6 studies | 66 people | |||
Studies that measured carbohydrate oxidation
| ||||||
Key findings
- Alertness
- Anxiety Symptoms
- Blood glucose
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- Grade D
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Studies cited
19 studies from PubMed
- Effects of p-synephrine alone and in combination with selected bioflavonoids on resting metabolism, blood pressure, heart rate and self-reported mood changes
- Seville (sour) orange juice: synephrine content and cardiovascular effects in normotensive adults.
- Safety evaluation of p-synephrine following 15 days of oral administration to healthy subjects: A clinical study.
- Blood pressure and heart rate effects following a single dose of bitter orange
- Absence of QTc-interval-prolonging or hemodynamic effects of a single dose of bitter-orange extract in healthy subjects
- Acute cardiovascular effects of bitter orange extract (p-synephrine) consumed alone and in combination with caffeine in human subjects: A placebo-controlled, double-blind study.
- Cardiovascular Safety of Oral p-Synephrine (Bitter Orange) in Healthy Subjects: A Randomized Placebo-Controlled Cross-over Clinical Trial.
- The Safety and Efficacy of (Bitter Orange) Extracts and -Synephrine: A Systematic Review and Meta-Analysis.
- A 60day double-blind, placebo-controlled safety study involving Citrus aurantium (bitter orange) extract.
- Acute hematological and mood perception effects of bitter orange extract (p-synephrine) consumed alone and in combination with caffeine: A placebo-controlled, double-blind study.
- Dietary herbal supplements with phenylephrine for weight loss.
- Effects of p-Synephrine and Caffeine Ingestion on Substrate Oxidation during Exercise.
- Acute p-synephrine ingestion increases whole-body fat oxidation during 1-h of cycling at Fatmax.
- Acute p-synephrine ingestion increases fat oxidation rate during exercise
- Effect of -Synephrine on Fat Oxidation Rate during Exercise of Increasing Intensity in Healthy Active Women.
- Does the Time of Day Play a Role in the Acute Effect of -Synephrine on Fat Oxidation Rate during Exercise in Women? A Randomized, Crossover and Double-Blind Study.
- Acute consumption of p-synephrine does not enhance performance in sprint athletes.
- Bitter Orange Intake Before Submaximal Aerobic Exercise Is Safe for Cardiovascular and Autonomic Systems in Healthy Males: A Randomized Trial.
- The Effects of Supplementation with p-Synephrine Alone and in Combination with Caffeine on Metabolic, Lipolytic, and Cardiovascular Responses during Resistance Exercise.