Sunlight, cholesterol and coronary heart disease

We investigated the relationship between geography and incidence ofcoronary heart disease, looking at deficiency of sunlight and thus ofvitamin D as a factor that might influence susceptibility and thus diseaseincidence. Sunlight deficiency could increase blood cholesterol by allowingsqualene metabolism to progress to cholesterol synthesis rather than tovitamin D synthesis as would occur with greater amounts of sunlightexposure, and the increased concentration of blood cholesterol during thewinter months, confirmed in this study, may well be due to reduced sunlightexposure. We show evidence that outdoor activity (gardening) is associatedwith a lower concentration of blood cholesterol in summer but not in thewinter. We suggest that the geographical variation of coronary heartdisease is not specific, but is seen in other diseases and sunlightinfluences susceptibility to a number of chronic diseases, of whichcoronary heart disease is one.