People with low levels of cholesterol are at higher risk of dying from a range of diseases, claim doctors.
Their findings apply to the elderly, but raise fears that healthy middle-aged people could put their health at risk by excessive reductions in their cholesterol.
Researchers from the University of Hawaii studied fat and blood cholesterol concentrations in around 3,500 Japanese/American men who were aged 71 to 93 in the early 1990s.
They compared concentrations with measurements taken during a 20-year period.
Death from all causes in relation to cholesterol concentration was calculated, says a report today in The Lancet. Average concentrations fell as the men grew older, but lower levels were linked to higher death rates.
Males with low cholesterol levels maintained over 20 years had the worst outlook for death from any cause. Those with higher levels had reduced death rates of up to 40 per cent.
Research leader Dr Irwin Schatz said the findings showed for the first time that long-term persistence of low cholesterol concentration actually increased risk of death.
The British Heart Foundation said the findings did not change the over-whelming medical view that most Britons had too-high cholesterol levels which put them at risk of heart problems.