4/5/054 - Vitamins could actually increase levels of "bad cholesterol",researchers have suggested.It had been thought that vitamins could protect the heart.

But New York University researchers found vitamins including E, C and betacarotene stop the liver breaking down an early form of bad cholesterol.

Writing in the Journal of Clinical Investigation, the researchers saytheir findings mean they cannot recommend that people use the vitamins.

The vitamins are antioxidants, thought to be beneficial because theyattack free radicals, produced when the body fights infection, whichinflict damage on the body's tissues.

But studies carried out by the researchers at the university's school ofmedicine found that antioxidants actually hampered the body's fightagainst damaging cholesterol.

Normally, liver cells break down a key protein in harmful lipoproteinssuch as VLDL (very low density lipoprotein) which means they cannot beconverted into a form of LDL that can enter the bloodstream.

However, in laboratory tests, the New York researchers found vitamin E, Cand beta carotene prevented this process taking place in liver cells.

Further tests in mice and rat livers showed vitamin E prevented this"breakdown" process taking place, meaning the liver destroyed fewerlipoproteins.

Recommendations 'delayed'

Dr Edward Fisher, director of the Lipid Treatment & Research Center at theNYU Medical Center, said: "Our study is the first to document thisassociation between antioxidant vitamins and VLDL cholesterol.

"It does appear that antioxidant vitamins may be potentially harmful forthe heart based on their ability to increase the secretion of VLDL in theliver cells and in the mice that we studied."

But he added: "More studies are needed to back up our findings. Until moredata becomes available, we can't make any recommendations about whetherpeople should not use these vitamins."

However he said there was evidence from other animal studies thatantioxidants could have beneficial effects on other parts of the body,such as protecting the arteries from atherosclerosis and the pancreas andother organs from damage caused by diabetes.

Writing in the journal, Dr Ronald Krauss of Children's Hospital OaklandResearch Institute in California, added that, although there was"considerable" evidence for the benefits of antioxidants, "the potentialfor unintended outcomes of oxidant therapy should serve as a warningagainst proceeding with such treatment in the absence of clinical-trialevidence of benefit and safety".

Belinda Linden, head of Medical Information at the British HeartFoundation (BHF), told BBC News Online: "Most research tends to suggestthat supplementation with antioxidant vitamins, although not beneficial,does not lead to undue harm.

"Before any clear conclusions can be drawn from this study we would awaitthe results of larger randomized controlled clinical trials."