Hypocholesterolaemia and cancer?

marathon season opens, with its expected further huge increase in participants, the public may be said-literally-to be voting with its feet. Vigorous exercise in leisure-time: protection against coronary heart disease. The serum cholesterol concentration of a population can be reduced and this is accompanied by a decrease in the incidence of coronary heart disease.' This observation raises some important questions: can the serum cholesterol concentration be reduced to an excessively low level by diet alone; is a low serum cholesterol concentration harmful; and is there an ideal range for the concentration of serum cholesterol ? Lewis and coworkers reported a decrease of 29% in mean serum cholesterol concentration in 12 Trappist monks after taking a modified fat diet supplemented with fibre for five weeks2-a result obtained with optimal compliance over a short period. The Oslo Study Group admitted 1232 healthy normotensive men with serum cholesterol concentrations between 7-5 and 9-8 mmol/l to a randomised controlled trial to determine the effects of reducing smoking and reducing serum cholesterol concentrations by modifying the diet.' Mean serum cholesterol concentrations were about 120% lower after five years in the treatment group, who experienced significantly fewer coronary events. This suggests that with appropriate dietary advice the mean serum cholesterol concentration in a population may be reduced by 10-15%/,, a reduction which can hardly be regarded as excessive. A highly significant positive correlation was obtained when death rates from different countries for coronary heart disease were compared with those from cancer of the colon.3 Rose and coworkers investigated the possibility that a raised serum cholesterol concentration might be a factor common to both diseases. Surprisingly, cancer of the colon was shown to be associated with low concentrations of serum cholesterol. The Framingham group studied 5209 people prospectively over 24 years,4 finding that in men there was a significant inverse association between serum cholesterol concentrations and cancer at several sites, of which cancer of the colon achieved the greatest significance. There are several explanations for this association. Firstly, it may be the effect of competing lethal risks: people with high serum cholesterol concentrations may have died prematurely from ischaemic heart disease while those with low concentrations survived to develop cancer of the colon. Secondly, possibly a low serum cholesterol concentration is a consequence of cancer of the colon rather than a predisposing factor, though if this were true the Framingham patients would have had low cholesterol concentrations …