People without heart disease should think twice before taking cholesterol-lowering statins, British researchers warn in a report out Wednesday.

While the popular drugs require a prescription in the US, they are sold over the counter in England, and one in three Brits over 40 are currently using them, according to researchers from the London School of Hygiene & Tropical Medicine.

In a review of the medical literature, they found the drugs did appear to slash deaths ever so slightly in patients at low risk of heart disease. But many of the reports they looked at - all but one funded by drugmakers - were flawed.

In particular, while all the studies focused on benefits, only half provided information on the side effects of the drugs, said Dr. Shah Ebrahim, whose group’s findings are published by the Cochrane Collaboration, an international organization that evaluates medical research.

“There is evidence that the reports cherry-picked the best outcomes for presentation,” he added, “which will tend to inflate apparent benefits of treatment.”

Ebrahim and colleagues found 14 trials that tested statins in more than 34,000 patients, most of whom were considered at low risk of heart attack and strokes - the world’s top killers.

Pooling the results, they estimated that treating 1,000 people with statins for one year would lower the number of deaths from nine to eight.

Statins - including Pfizer’s Lipitor and AstraZeneca’s Crestor - help prevent new heart attacks in people who’ve already had one, but the effects are less certain in individuals at lower risk.

The drugs also appeared to reduce the number of heart attacks and strokes - fatal and not - and the need for surgery.

While there appeared to be no difference in side effects between trials participants taking dummy pills and statins, the researchers say those results aren’t credible.

“Any appraisal we can make of adverse events is biased by failure to report these events,” Ebrahim said in an e-mail to Reuters Health.

“We believe that trial funders, investigators and journal editors have failed to provide adequate information to doctors and their patients to assess the benefits and harms of statins in primary prevention.”

One statin, a generic drug called simvastatin, is already available in low doses over the counter at pharmacies in Britain without a prescription, at a cost of only a few pence per pill.

But Ebrahim advised people to think twice before buying the drug, even if they have raised cholesterol levels.

“If you have self-prescribed a statin, buy it “over the counter” in a pharmacy, or do not know your level of risk and are taking a statin, get a check of your level of cardiovascular risk and discuss your decision with your family doctor,” he urged.