Researchers around the world continue to investigate a wide array of natural compounds that could reduce levels of low-density lipoprotein (LDL), the major cholesterol carrier in the blood, and improve 'good' cholesterol or high-density lipoprotein (HDL).
But a new study published in the New England Journal of Medicine last week found that the benefits of reducing LDL dramatically were so significant that the role of these two cholesterol carriers may be rather different from current thinking. This could impact the way we research the potential of foods to improve cholesterol levels.
According to the World Health Organisation, almost one fifth (18 per cent) of global stroke events (mostly nonfatal events) and about 56 per cent of global heart disease are attributable to total cholesterol levels above 3.2 mmol/l. This amounts to about 4.4 million deaths (7.9 per cent of the total) and 2.8 per cent of the global disease burden.
It is generally believed that when too much LDL cholesterol circulates in the blood, it can slowly build up in the arteries causing deposits that lead to clots and heart attacks or strokes. On the other hand, HDL is thought to carry cholesterol away from the arteries and back to the liver, removing excess cholesterol from plaques and thus slowing their growth.
But the latest research, on two powerful cholesterol-lowering drugs, Lipitor, made by Pfizer, and the less potent Pravachol, made by Bristol-Myers Squibb, demonstrated that lowering cholesterol far beyond the levels currently recommended by most doctors can substantially reduce heart patients' risk of suffering or dying of a heart attack.
US guidelines urge those at high-risk of heart disease to reduce LDL to below 100mg per deciliter of blood. In the two-year study, those taking Lipitor eventually had a median level far below this (62mg), compared to 95mg for the other group. The death rate for Lipitor patients was 28 per cent lower than among those taking Pravachol, and the death rate from cardiovascular disease was 30 per cent lower.
This finding will further differentiate between powerful statin drugs for high-risk patients and the functional foods currently on the market to reduce moderately raised LDL levels, such as plant sterols and soy protein-enriched foods.
But in an editorial in the NEJM, Dr Eric Topol notes that more than 200 million people in the world meet the criteria for statin treatment but fewer than 25 million take statins. This is largely due to the cost of the treatment.
Sales of foods designed to improve heart health are rapidly growing on the other hand, and were worth 100.7 stg in the UK alone during 2002, with forecase annual growth of 7.6 per cent to 2007, according to Datamonitor.
The new research also calls into question the role of HDL cholesterol, previously believed to cancel out high levels of LDL. If reducing LDL levels further than normal could have such an impact on cuting heart attack risk, the role of HDL may not be so important.
In an interview with the New York Times, Dr Daniel Radar, a cholesterol researcher at the University of Pennsylvania School of Medicine, says: "Yes, high HDL is a good thing but it doesn't mean it is so powerful that it creates a total immunity to heart disease."
In some cases, HDL does not function properly and instead of being protected from heart disease, these patients may be particularly vulnerable, he suggests.