Main Research Findings

Bitter orange extract and its main component, p-synephrine, are widely used in dietary supplements worldwide for weight loss. P-synephrine is structurally similar to ephedrine and adrenaline, and is a weak adrenergic agonist that primarily acts on β3-adrenergic receptors, stimulating lipolysis. 1 However, there are concerns regarding the safety of bitter orange extract and p-synephrine, as they can cause cardiovascular side effects, especially when combined with caffeine and physical activity. 1 Studies in mice have shown that acute oral administration of bitter orange extract and p-synephrine can lead to a reduction in locomotor activity, piloerection, gasping, salivation, exophtalmia, and other adverse effects. These effects were reversible and persisted for 3-4 hours. A meta-analysis of human clinical trials indicated that synephrine can significantly increase both systolic and diastolic blood pressure after prolonged use. 2 Furthermore, there was no significant weight loss observed in the synephrine group compared to the placebo group. 2

Reasons for Side Effects

The side effects of bitter orange extract and p-synephrine are likely due to their adrenergic stimulating properties. Both substances act on adrenergic receptors, which are involved in regulating heart rate, blood pressure, and metabolism.

Common Side Effects

Increased Heart Rate

Bitter orange extract and p-synephrine can increase heart rate. 2 This is because they stimulate adrenergic receptors, which can lead to a faster heartbeat.

Increased Blood Pressure

Bitter orange extract and p-synephrine can increase blood pressure. 2 This is because they stimulate adrenergic receptors, which can cause blood vessels to constrict, leading to higher blood pressure.

Headache

Bitter orange extract and p-synephrine can cause headaches. This is possibly due to the vasoconstriction (narrowing of blood vessels) caused by adrenergic stimulation.

Gastrointestinal Issues

Bitter orange extract and p-synephrine can cause gastrointestinal issues such as nausea, vomiting, and stomach upset. These effects may be related to the stimulation of adrenergic receptors in the digestive tract.

Insomnia

Bitter orange extract and p-synephrine can lead to insomnia due to their stimulatory effects on the central nervous system.

Anxiety

Bitter orange extract and p-synephrine can cause anxiety or nervousness. This may be attributed to the activation of the sympathetic nervous system, which is responsible for the ‘fight or flight’ response.

Countermeasures for Side Effects

Increased Heart Rate

If you experience an increased heart rate, you should reduce your dosage or stop taking bitter orange extract or p-synephrine.

Increased Blood Pressure

If you experience an increase in blood pressure, you should reduce your dosage or stop taking bitter orange extract or p-synephrine.

Headache

If you experience headaches, reduce your dosage or stop taking bitter orange extract or p-synephrine.

Gastrointestinal Issues

If you experience gastrointestinal issues, reduce your dosage or stop taking bitter orange extract or p-synephrine.

Insomnia

To avoid insomnia, try taking bitter orange extract or p-synephrine earlier in the day or stop taking it if you find it is interfering with your sleep.

Anxiety

If you experience anxiety, reduce your dosage or stop taking bitter orange extract or p-synephrine.

Comparison Between Studies

Common Points

Most studies agree that bitter orange extract and p-synephrine can cause an increase in heart rate and blood pressure. 2 They also share the view that these substances can stimulate metabolism due to their adrenergic properties. 1

Differences

Some studies suggest that bitter orange extract and p-synephrine may have a positive effect on weight loss. 1 However, other studies fail to demonstrate this effect. 2 There are also variations in the reported severity and frequency of side effects among different studies.

Things to Keep in Mind When Applying to Real Life

It’s crucial to be aware of the potential side effects of bitter orange extract and p-synephrine, especially for people with pre-existing health conditions like heart disease or hypertension. 1 Additionally, exercise and caffeine consumption can exacerbate these side effects. It is strongly recommended to consult with a healthcare professional before taking bitter orange extract or p-synephrine.

Limitations of Current Research

The available research on the safety and efficacy of bitter orange extract and p-synephrine is still limited. More studies, particularly those exploring long-term effects, are needed to fully understand their impact on human health.

Future Research Directions

Further research is required to comprehensively understand the safety and efficacy of bitter orange extract and p-synephrine. This research should include long-term studies to assess their impact on human health, as well as studies on diverse populations with varying age groups and health conditions.

Conclusion

Bitter orange extract and p-synephrine can have significant cardiovascular side effects, so it is important to exercise caution when considering their use. 1 If you have any pre-existing health conditions, it’s crucial to consult with a healthcare professional before taking these substances. 1 It’s important to weigh the potential benefits against the potential risks before making an informed decision about using bitter orange extract or p-synephrine.