Knowledge about dietary supplements and trust in advertising them: Development and validation of the questionnaires and preliminary results of the association between the constructs

Michał Seweryn Karbownik, Ewelina Paul, Maja Nowicka, Zuzanna Nowicka, Radosław Przemysław Kowalczyk, Edward Kowalczyk, Tadeusz Pietras, Michał Seweryn Karbownik, Ewelina Paul, Maja Nowicka, Zuzanna Nowicka, Radosław Przemysław Kowalczyk, Edward Kowalczyk, Tadeusz Pietras

Abstract

Background: Despite offering little overall benefit and emerging concerns about their safety, dietary supplements have become increasingly popular. Trust in advertising them may contribute to high confidence in dietary supplements in public opinion.

Aim: To develop and validate a screening questionnaire intended for the general public regarding knowledge about dietary supplements and a questionnaire on trust in advertising dietary supplements, and to identify the association between these constructs.

Materials and methods: The development and validation of the measures was overseen by the panels of experts. The conceptual frameworks of the constructs were scientifically well grounded. A set of semi-structured interviews and anonymous web-based surveys was performed. The final questionnaire was applied to 220 non-medically educated people and 121 medically educated people.

Results: A 17-item questionnaire on knowledge about dietary supplements and eight-item questionnaire on trust in advertising dietary supplements were developed. The measures presented satisfactory proof of validity, however, the psychometric properties of the questionnaire on knowledge were modest. Both the knowledge about dietary supplements in the study group and trust in advertising them were low. A significant negative relationship was found between knowledge about dietary supplements and trust in advertising them among the general public (Pearson's r = -0.42, 95%CI: -0.52 to -0.30, p<0.0001). This association was especially pronounced in people who reported not taking dietary supplements (Pearson's r = -0.61, 95%CI: -0.76 to -0.39, p<0.0001).

Conclusions: The extensive advertising of dietary supplements appears to be in conflict with promoting evidence-based knowledge about them, which raises substantial concerns for the public health. The results of the study are only preliminary and require further confirmation and exploration.

Conflict of interest statement

I have read the journal's policy and the authors of this manuscript have the following competing interests: EP is employed in OSOM STUDIO, an e-marketing agency. This does not alter our adherence to PLOS ONE policies on sharing data and materials. OSOM STUDIO had no role in study design, data collection and analysis, data interpretation, decision to publish, or preparation of the manuscript.

Figures

Fig 1. Flowchart illustrating the development of…
Fig 1. Flowchart illustrating the development of the questionnaire to assess knowledge about dietary supplements (KaDS).
Fig 2. Flowchart illustrating the development of…
Fig 2. Flowchart illustrating the development of the questionnaire to assess trust in advertising dietary supplements (TiADS).
Fig 3. The association between knowledge about…
Fig 3. The association between knowledge about dietary supplements and trust in advertising them in non-medially educated people.
Knowledge about dietary supplements was measured as a total score in the 17-item questionnaire, whereas trust in advertising dietary supplements with the eight-item questionnaire. The size of the circles represents the number of cases with the given coordinates.

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