[Illness, health and sunlight].

New scientific insights show that the influence of sunlight on health is profound. Recent data suggest that our skin is well adapted to the Dutch climate, but changes in the exposure pattern cause a steady increase in skin cancer. These changes mainly consist of a decrease in daily exposure and a shift from a regular to an intermittent exposure. In the Netherlands, probably the best advice is for moderate, frequent exposure to the sun. Evidence is accumulating that frequent exposure to sunlight is a protective factor against colorectal, prostate, and breast cancer and non-Hodgkin lymphoma, multiple sclerosis and metabolic syndrome. The circadian rhythm is affected by light. Too low levels of exposure to light in daytime and too high levels of exposure to light in the evening and at night can weaken and disrupt the circadian rhythm. This disruption most probably is a risk factor for some types of cancer and metabolic syndrome.