How far north or south of the equator (at what latitude) do you spend most of your time? If unsure, simply skip the question or enter a note.
Possible responses:→ Don't know / can't work it out
→ 0-23° (The tropics)
→ 24-40° (U.S. south of Great Lakes; Australia)
→ 41-56° (Northern U.S.; Canada; Europe)
→ Over 56° (Scotland; Scandinavia; Alaska)
Malaria once extended widely throughout the old world, reaching as far north as 64°N latitude and as far south as 32°S latitude. Today, however, malaria is almost exclusively a problem of the geographical tropics.
The body's main source of vitamin D is sunlight, but higher latitudes mean less available sunlight – especially during the winter. At most latitudes in the United States, little or no vitamin D is made in the skin in the late fall (autumn) and early winter. In the most northern regions, the vitamin D blackout lasts for about six months. As a result, it has been estimated that up to 70% of Americans (and Europeans) may be deficient in vitamin D. Only in the last several hundred years has urbanization, industrialization, glass (UVB does not penetrate glass), excessive clothes (UVB does not penetrate clothes) and sunblock greatly lowered levels.