Sales of dietary supplements purported to support or boost immunity increased dramatically during the COVID-19 pandemic. Researchers conducted a study to determine whether the product labels of select dietary supplements marketed online to support and boost the immune system were accurate and whether any products were mislabeled or adulterated.

Thirty products with ratings of four or more stars were selected and purchased from Amazon. Liquid chromatography-mass spectrometry was used to evaluate the quality of these products. The list of ingredients detected for each product was compared with the product's supplement facts label to determine the label's accuracy. Claims made on product labels were also evaluated using the Operation Supplement Safety (OPSS) scorecard, an educational tool designed to help consumers evaluate the information on a product's label. A score of 4 or more on the OPSS scorecard indicates the product is "likely okay/less risky."

The researchers found that of the 30 dietary supplements evaluated, only 13 had accurate labels based on product analysis. Of the 17 products with inaccurate labels, 13 listed ingredients on the label that weren't detected through analysis. For nine products, substances were detected that weren't listed on the label. Although 15 products had scientific-sounding claims, none had a third party certification seal. Only 13 of the 30 supplements evaluated had an OPSS score of 4 or more.

Among several limitations of their study, the authors point out that the 30 products analyzed weren't representative of all dietary supplements marketed for immune health, and the analytical method used was not sensitive for the analysis of certain ingredients.

They advise that consumers be aware that dietary supplements marketed for immune health may not contain the ingredients listed on the label.