According to the assessment conducted by RIVM (National Institute for Public Health and Environment) together with RIKILT Wageningen University and Research, potentially harmful effects of synephrine, which behaves in a similar manner to ephedrine, 'cannot be ruled out.'
The substance is a naturally occurring compound in citrus fruits, especially bitter orange (Citrus aurantium), and it is often included as an ingredient in weight loss or sports performance supplements. Like ephedrine, which is now prohibited in food supplements in the Netherlands, synephrine can increase blood pressure, warns the assessment.
The RIVM report adds that the compound also interacts with many medications, and may have other adverse effects on the cardiovascular system - adding that such effects are increased if synephrine is taken with caffeine or during physical exercise.
Furthermore, overweight individuals are more vulnerable to adverse events as they are more likely to consume synephrine-containing supplements for weight loss, but also have an increased risk of cardiovascular disease.
According to RIVM, there is inadequate data to determine a safe dose of synephrine, while the long-term effects of the substance are also unknown. Available data may nevertheless enable the establishment of a maximum intake level in food supplements -which, unlike in other EU Member States, is something that is not legally defined in the Netherlands currently.
Legal limits: Different interpretations
The approach taken by the Dutch authorities, until now, contrasts with that of other Member States.
France permits up to 20mg in food supplements provided bitter orange is the source of the synephrine. However, labelling must include a warning against use by children, pregnant or breastfeeding women and in those on antihypertensive medication. Caffeine and caffeine sources are not permitted in food supplements containing bitter orange.
Belgium has similar legislation to France, while Italian laws allow up to 30mg of natural synephrine from C. aurantium (the source should be normally from 800mg of bitter orange extract at 4% synephrine).
“The differences in assessments should be resolved considering whether synephrine is naturally occurring, and taking the natural sources into consideration,” said EU nutrition and law expert Luca Bucchini, managing director of Hylobates Consulting.
The different interpretations on synephrine are also characteristic of the contrasting approaches taken towards food supplements by Northern (restrictive) and Southern (liberal) Member States, Bucchini added.
The Dutch Food and Consumer Product Safety Authority is expected to publish its guidance on the issue soon.