MILLIONS of people who take vitamin supplements in the belief that they protect against heart disease may be wasting their money.

New research suggests that far from reducing the risk, vitamin pills may increase the levels of the “bad” form of cholesterol by interfering with liver function. Since this form of cholesterol is strongly linked to an increased risk of a heart attack, the effect of the vitamins may be the precise opposite of what people hope for.

A team from New York and Philadelphia, led by Edward Fisher, of New York University School of Medicine, found that vitamins C, E and beta-carotene, far from boosting the body’s defences, undermined them.

The liver is the main source of lipoproteins — fats found in the bloodstream — including low-density lipoprotein (LDL) cholesterol, which is implicated in blockages of the arteries.Vitamins are supposed to help to defeat the damage done by cholesterol by acting as antioxidants. In the normal processes of metabolism, the body produces short-lived oxygen radicals, highly active chemicals that are believed to react with LDL cholesterol, causing changes that lead to the artery-blocking plaques found in patients with heart disease.

The role of vitamins, according to this theory, is to mop up the oxygen radicals and stop the plaques forming. But Professor Fisher and colleagues, writing in The Journal of Clinical Investigation, say that their experiments show that the liver cells have their own way of protecting against oxygen radicals.

They found that when under attack, the cells respond by activating a pathway that breaks down a protein called ApoB100, which is a key component of LDL cholesterol. Deprived of ApoB, the liver cannot produce LDL cholesterol and its secretion into the bloodstream is greatly reduced.

But antioxidant vitamins interrupted the breakdown of ApoB, enabling the liver to go on producing LDL cholesterol.

”It does appear that antioxidant vitamins may be potentially harmful for the heart based on their ability to increase the secretion of very low-density lipoproteins in the liver cells and mice we studied,” Professor Fisher said.

“But until more data is available we can’t make recommendations about whether people should not use these vitamins.”

In another series of experiments the team showed why fish oils may actually have benefits. Their effect was the opposite of vitamins — they enhanced the breakdown of ApoB, thereby further reducing the levels of bad cholesterol in the bloodstream.

The team’s conclusion is that the role of antioxidant vitamins is more complex than previously supposed.

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