Hidden sodium in effervescent-tablet dietary supplements and over-the-counter drugs: a comparative cross-sectional study.

Objective: Dietary sodium intake represents a risk factor for cardiovascular disease and mortality. The study sought to analyse the sodium content of effervescent dietary supplements and drugs in Germany and the USA.

Design: Comparative cross-sectional study.

Setting And Methods: The sodium content of 39 dietary supplement effervescent tablets available in Germany was measured in May and June 2022 using optical emission spectrometry with inductively coupled argon plasma. The sodium content of 33 common pharmacy-only effervescent tablets (over-the-counter (OTC) drugs) in Germany was obtained from the summary of product characteristics. We compared the sodium content of the measured German dietary supplement effervescent tablets to that of 51 dietary supplement effervescent tablets available in the USA (data: National Institutes of Health's Dietary Supplement Label Database).

Results: The measured sodium content in the German dietary supplements was 283.9±122.6 mg sodium/tablet, equivalent to 14±6% of the maximum recommended daily sodium intake (MRDSI). Vitamin products had the highest (378.3±112.8 mg, 19±6% of MRDSI), and calcium products had the lowest mean sodium content (170.4±113.2 mg, 9±6% of MRDSI). Vitamin products contained significantly more sodium than magnesium (378.3 mg vs 232.7 mg; p=0.004), calcium (378.3 mg vs 170.4 mg; p=0.006) and mineral products (378.3 mg vs 191.6 mg; p=0.048). The sodium content measured in products available in Germany was higher when compared with the declared sodium content on the label of the products sold in the USA (283.9 mg vs 190.0 mg; p<0.001). The median summary of product characteristics-declared sodium content of a single dose of the German OTC drugs was 157.0 mg (IQR: 98.9-417.3 mg); pain/common cold drugs contained the most sodium (median: 452.1 mg; IQR: 351.3-474.0 mg).

Conclusion: Effervescent tablets of nutritional supplements and OTC drugs contain high amounts of sodium, which often is not disclosed.