Bitter Orange
Also known as: Citrus aurantium, p-synephrine, synephrine, Seville orange, sour orange, zhi shi
Effective Dosage
No established dose from provided studies alone
What the Science Says
Bitter orange is a citrus fruit whose peel and flowers are used in supplements. Its main active compound, p-synephrine, has been shown in one small study to modestly increase fat burning during an hour of cycling exercise, though it did not meaningfully raise total calorie burn. Bitter orange blossom extract (as a distillate) showed some benefit for sleep quality in a small clinical trial, and a combination formula including bitter orange extract showed improvements in cardiovascular markers like blood pressure and cholesterol over 8 weeks.
What It Doesn't Do
Won't melt fat at rest — the fat-burning effect only appeared during exercise, and it was small. Not a proven standalone weight-loss solution. No solid evidence it reduces anxiety on its own. The cardiovascular benefits seen in studies used a multi-ingredient formula, so you can't credit bitter orange alone. Lab studies showing anti-cancer effects mean nothing yet for humans taking supplements.
Evidence-Based Benefits
Bitter orange is often used as a weight loss aid due to its active compound synephrine, which may increase metabolic rate and fat oxidation. Some studies suggest it can help with appetite suppression and energy expenditure, although results can vary.
Moderate EvidenceEffective at: 500-1500 mg daily
Source: auto-research
Absorption & Bioavailability
Unknown from provided studies — no pharmacokinetic data reported in the available papers
Red Flags to Watch For
- Bitter orange was widely marketed as a 'safe' replacement for ephedra after ephedra was banned, but its cardiovascular safety profile has not been fully established in long-term human trials
- Most products contain synephrine in combination with caffeine and other stimulants, making it impossible to isolate bitter orange's effects or risks
- Several studies provided had incomplete or unavailable abstracts, limiting the quality of evidence that can be assessed
- Lab and animal findings (anti-cancer, cholesterol efflux) are frequently overhyped in marketing — none of these translate to proven human benefits yet
- Registered in over 1,000 supplement products (NIH DSLD), meaning it is extremely common in weight-loss stacks where dosing and purity vary widely
Research Sources
- PubMed
- NIH DSLD
This information is for educational purposes only and is not medical advice. Always consult a healthcare professional before starting any supplement regimen. Last updated: 2026-04-06