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Br J Health Psychol. 2016 Feb;21(1):204-23. doi: 10.1111/bjhp.12158. Epub 2015 Sep 10.

Towards an understanding of adult judgments of synergistic health benefits.

Author information

Centre for Risk Research, Southampton Business School, University of Southampton, UK.
Department of Psychology, Social and Economic Cognition I, University of Cologne, Germany.



Numerous scientific studies show that certain combinations of dietary and/or lifestyle factors produce health benefits which are greater than the sum of the benefits associated with each factor alone. To address an existing knowledge gap, we assessed the extent to which individuals understand that certain combinations present these 'synergistic health benefits'.


Health benefit judgments were obtained from lay adults for a range of dietary and/or lifestyle combinations that have been found to present synergistic benefits. Association between these judgments and socio-cognitive characteristics such as numeracy, education, and health interest (HI) were examined.


Three hundred and fifty-two Swiss adults were presented with a description of one of eight synergistically beneficial combinations. Each participant provided a categorical benefit judgment (i.e., subadditive, additive, or synergistic) for the combination and explained the cognitive reasoning underlying their judgment. Participants completed measures of numeracy and HI.


The proportion of combinations judged to present a synergistic benefit was modest for 'macro-level' combinations (e.g., diet and exercise), but low for 'micro-level' combinations (e.g., two phytochemicals). Cognitive reasoning data showed that a higher proportion of judgments for micro-level (cf. macro-level) combinations were based on greater subjective epistemic uncertainty. Higher interest in health was associated with a better understanding of synergistic benefits, but numeracy and education level were not.


There is considerable scope to improve the extent to which lay adults understand that specific combination of diet and lifestyle behaviours can synergistically benefit their health. Our results enable us to make informed recommendations for public health interventions.


What is already known on this subject? Combining certain dietary and/or lifestyle factors can result in synergistic health benefits. People could maintain/enhance their health by combining these synergistic combinations. No previous studies have assessed the extent to which people understand that certain factors produce synergistic health benefits. What does this study add? This is the first study to identify that lay awareness of synergistic health benefits could be substantially improved. Neither education level nor numeracy moderate judgments of synergistic benefits, but health interest does. Individuals better understand that broad lifestyle behaviours (cf. specific foods and phytochemicals) are synergistic.


diet; exercise; health benefits; judgment; synergistic

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