The prevalence of asthma has nearly doubled over the last decades. Twentieth century changes in environmental and lifestyle factors, including changes in dietary habits, physical activity and the obesity epidemic, have been suggested to play a role in the increase of asthma prevalence and uncontrolled asthma worldwide. A large body of evidence has suggested that obesity is a likely risk factor for asthma, but mechanisms are still unclear. Regarding diet and physical activity, the literature remains inconclusive. Although the investigation of nutritional factors as a whole (i.e., the “diet, physical activity and body composition” triad) is highly relevant in terms of understanding underlying mechanisms, as well as designing effective public health interventions, their combined effects across the life course has not received a lot of attention. In this review, we discuss the state of the art regarding the role of nutritional factors in asthma, for each window of exposure. We focus on the methodological and conceptual challenges encountered in the investigation of the complex time-dependent interrelations between nutritional factors and asthma and its control, and their interaction with other determinants of asthma. Lastly, we provide guidance on how to address these challenges, as well as suggestions for future research.

Background: Dispositional optimism is a psychological trait that has been associated with positive health outcomes such as reduced risk of cardiovascular diseases. However, there is little knowledge on the relationship between optimism and dietary intake in the population. The objective of this cross-sectional study was to assess whether optimism was associated with overall diet quality, food group consumption and snacking. Methods: In 2016, 32,806 adult participants from the NutriNet-Santé study completed the Life-Orientation Test Revised (LOT-R) which assesses dispositional optimism. Overall diet quality (assessed by the mPNNS-Guideline Score) and consumption of 22 food groups were evaluated using at least three self-reported 24-h dietary records. Snacking behavior was evaluated by an ad-hoc question. Logistic and linear regressions were used to analyze the associations between optimism and these dietary behaviors, taking into account socio-demographic, lifestyle and depressive symptomatology characteristics. Results: Optimism was associated with greater overall diet quality (β (95% CI) = 0.07 (0.004-0.11), P < 0.0001) and higher consumption of fruit and vegetables, seafood, whole grains, fats, dairy and meat substitutes, legumes, nonsalted oleaginous fruits, and negatively associated with consumption of meat and poultry, dairy products, milk-based desserts, sugar and confectionery. In addition, optimism was associated with less snacking (OR (95% CI) = 0.89 (0.84, 0.95)). In contrast, optimism was associated with higher consumption of alcoholic beverage (β (95% CI) = 5.71 (2.54-8.88), P = 0.0004) and appetizers (OR (95% CI) = 1.09 (1.04, 1.14)). Finally, no association was observed between optimism and energy intake. Conclusions: Optimism was associated with better overall diet quality and less snacking. It was also associated with consumption of healthy food groups as well as unhealthy food groups typically consumed in social eating occasions. These findings suggest that optimism could be taken into account in the promotion of a healthy eating behavior.