Conclusions
In summary, as a whole, no nutrient fully satisfies the criteria for causality defined by HILL [2]. Existing data indicate that an increase in the consumption of vegetables, fruit and (although with less evidence) fibre may contribute to the prevention of COPD. However, because of the paucity of longitudinal data, these relationships can only be considered possible. Inversely, based on some data that need to be confirmed, cured and red meats, desserts, and refined grains constitute potential risk factors for COPD. There is no clear evidence for beans, which has been specifically considered in only one study. Additionally, in Latin American countries, beans are often eaten with other fibres (specifically cereal fibres) and without cured meat, which could protect against COPD. Such habits are also very common in less affluent classes where a sedentary lifestyle has, so far, been exceptional.