Bitter orange synephrine, blood pressure and weight loss
What it found
In 18 human trials, synephrine raised blood pressure with longer use and did not lead to significant weight loss.
The authors say it is not recommended for health promotion.
What they found
Studies in people
Blood pressure with longer use
After 8 weeks of taking 10 to 49 mg of synephrine daily, systolic blood pressure rose by about 6.37 mmHg and diastolic by about 4.33 mmHg compared with placebo. These rises were statistically significant.
Blood pressure in short term
In the hours after a single dose, synephrine did not significantly change systolic or diastolic blood pressure. The effects on systolic pressure tended to be small and not statistically significant.
Heart rate
Heart rate tended to increase after taking synephrine, with the largest rise about 3 hours after consumption, but the changes were not statistically significant. The authors say synephrine tends to raise heart rate.
Weight loss
In three trials lasting 6 to 8 weeks, synephrine did not lead to significant weight loss compared with placebo. The average difference was 0.60 kg, which was not statistically significant.
Body composition
Synephrine did not significantly change body fat percentage, fat mass, or fat-free mass. The authors say it had no beneficial effects on body composition.
Blood glucose and RER
Blood glucose levels did not change significantly after taking 6 to 103 mg of synephrine. The respiratory exchange ratio, a measure of fuel use, also did not change significantly.
What the authors conclude
“The currently available evidence indicates that synephrine influences blood pressure and heart rate but has no significant effects on weight loss and body composition; therefore, its use is not recommended to promote health.”
Also in their conclusions
- They conclude that synephrine tends to raise blood pressure and heart rate, and there is no evidence that it can facilitate weight loss.
- They state that the use of synephrine is not recommended to promote health.
- They call for further and larger trials to assess the efficacy and safety of synephrine with a lower risk of bias.
How it was done
Synephrine is widely used in weight loss and sports products, but its safety and effectiveness have not been fully established. The authors wanted to assess its weight loss effects and cardiovascular side effects.
They searched medical databases for placebo-controlled human trials of synephrine and found 18 studies with 341 adults. Doses ranged from 6 to 214 mg per day, and trials lasted from a single dose up to 8 weeks.
What it can’t tell you
- The trials used different products and doses, and many combined synephrine with other substances like caffeine, so the results may not apply to all bitter orange supplements.
- Most trials were short, and only a few looked at long-term use, so the effects of taking synephrine for months or years are not known.
- The studies mostly included healthy, physically active adults, so the findings may not apply to other groups such as older people or those with existing health conditions.
Who paid
- Conflicts
- The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
- Authors work at
- University of Szeged, Hungary; University of Pécs, Hungary; Universitas Hasanuddin, Indonesia
The paper
- Title
- The Safety and Efficacy of Citrus aurantium (Bitter Orange) Extracts and p -Synephrine: A Systematic Review and Meta-Analysis
- Type
- Systematic review and meta-analysisThe authors follow a set, published method to find every relevant study, then combine the numbers from them into one result.
- Evidence
- Studies in people
- Summarised from
- Full text
- Licence
- CC BY. Words in quotation marks are the authors’; the rest is our summary.
- Cite
- Koncz D, Tóth B, Bahar MA, Roza O, Csupor D (2022). The Safety and Efficacy of Citrus aurantium (Bitter Orange) Extracts and p -Synephrine: A Systematic Review and Meta-Analysis. Nutrients. doi:10.3390/nu14194019Free full textPubMed 36235672DOI
Summary written 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error