Sudden drop in outdoor temperature
The natural environment encompasses all living and non-living things occurring naturally. The term is most often applied to the Earth or some part of Earth. Examples include a forest, a park, a beach or mountains. This is opposed to synthetic enviroments such as cities, highways, airports etc. A natural environment may provide an environmental setting for an activity or exercise programme, thus promoting increased physical activity
The ultraviolet radiation in sunlight has both positive and negative health effects, as it is both a principal source of vitamin D3 and a mutagen. Vitamin D has a wide range of positive health effects, which include strengthening bones and possibly inhibiting the growth of some cancers. UV exposure also has positive effects for endorphin levels, and possibly for protection against multiple sclerosis. Visible sunlight to the eyes gives health benefits through its association with the timing of melatonin synthesis, maintenance of normal and robust circadian rhythms, and reduced risk of seasonal affective disorder.
The Ultimate reference of diseases and their link to the food we eat.