Indoor nature integration for stress recovery and healthy eating : a picture experiment with plants versus green color

Aim: Urbanized environments may stimulate unhealthy food choices and stress. Several theories explain that exposure to green nature can counter these stress effects. Since we spend most time indoors, integrating nature in the interior could be a promising health promotion tool. Hence, we tested whether the beneficial effect of nature for stress recovery is also present in indoor settings via the use of plants or green colors, and whether it is applicable on eating behavior as a new outcome. Methods: The 92 participants (18-30y, 16% men) were divided into four groups. Each viewed a 6-min slideshow with room pictures containing either green plants, green objects, greyscale plants or greyscale objects to allow distinction between color- and plant-effects. Group differences were tested for the perceived restorativeness scale, psychological recovery and eating behavior. To allow psychological recovery testing, participants were exposed to a stressor before the picture slideshow via the Trier Social Stress Test. The change of self-reports (stress, positive and negative affect) and psychophysiology (heart rate and vagal-induced heart rate variability RMSSD) post-slideshow versus pre-slideshow was checked. Eating behavior outcomes included change in hunger, craving, and food choice (for fruits, vegetables and snacks). Results: From the four picture sets, the green plants pictures were reported as most mentally restorative and appeared most beneficial for post-stressor recovery of positive affect, but not for negative affect or stress recovery. The green plants group also had higher preference for vegetables and lower preference or craving for (unhealthy) snacks. Those significant group differences were mainly due to the presence of plants and only occasionally due to the green color. Conclusion: Indoor green plant pictures were associated with higher mental restorativeness and healthier food choices. Integrating plants in the interior seems to be a relevant health promotion approach, while applying green colors seems less relevant