Potential risks of dietary supplements for weight loss containing synephrine and caffeine available in Portugal

ABSTRACT Objective Caffeine and synephrine are normally included in weight loss products due to their claimed thermogenic effects. We aimed to determine the amount of caffeine and synephrine in dietary supplements available on websites that could ship to Portugal. We also aimed to check if levels comply with those recommended by health and food authorities. Methods This observational study conducted a search on platforms selling dietary supplements and examined their labeling. The inclusion criteria were supplements containing both synephrine and caffeine, regardless of quantity or use. The exclusion criteria were products in which only one of the components was present or in which the formula and ingredient amounts were not fully described on the label. Results Within the established inclusion and exclusion criteria, 20 dietary supplements were found. Supplements contained synephrine in the form of bitter orange extract (Citrus aurantium). A median of 153 mg (95% CI: 40-334) was found for the extract. The estimated synephrine levels for those extracts were a median of 11 mg (95% CI: 6-20). Regarding caffeine, the median for content was 200 mg (95% CI: 176-250), though the real value is higher, given the presence of several vegetable sources of caffeine. Moreover, 65% of supplements exceed the limits recommended by the German Federal Institute for Risk Assessment for synephrine levels, and 30% exceed 200mg of caffeine. Conclusion It was possible to conclude that 65% and 30% of dietary supplements exceed the levels recommended by food security agencies for synephrine and caffeine, respectively, which might carry potential health risks for the consumer.