WASHINGTON — The government is shutting down a study that was supposed to show if a single drink a day could prevent heart attacks, saying ethical problems with how the research was planned and funded undermine its credibility.

The National Institutes of Health used money from the alcohol industry to help pay for a study that ultimately was expected to cost $100 million. It’s legal for the NIH to use industry money in addition to taxpayer dollars for research as long as certain rules are followed.

The problem: An NIH investigation concluded Friday that a small number of its employees had close contact with industry officials that crossed those lines.

Some of those interactions “appear to intentionally bias” the study so that it would have a better chance of showing a benefit from moderate alcohol consumption, said NIH Deputy Director Lawrence Tabak.

Those employees, from the NIH’s National Institute on Alcohol Abuse and Alcoholism, then kept their interactions with industry secret, he said, even after the NIH started the normal process for asking companies or other outside groups to help fund a research project.

Those actions cast “doubt that the scientific knowledge gained from the study would be actionable or believable,” Tabak told a meeting of the NIH director’s advisers.

Another concern: Some outside experts who had reviewed the study plans raised concerns that it was too small and too short to address the potential problems of a daily drink – such as an increased risk of cancer or heart failure – and not just potential benefits such as a lowered risk of a heart attack.

“Purely on scientific grounds, I never really quite understood why this trial was being done,” Dr. M. Roy Wilson of Wayne State University told NIH Director Francis Collins after hearing the investigation’s conclusions.

People who have a glass or two of wine – himself included, he said – “don’t do it for health reasons.”

The research was supposed to track 7,800 people who were assigned to take either a drink a day, or totally abstain, for several years.

Only 105 people had enrolled in the study by last month, when Collins temporarily suspended the study after a New York Times article first raised questions about the funding policy violations.

On Friday, Collins announced he was completely shutting down the research. “This is a matter of the greatest seriousness,” he said.

The study was being led by Beth Israel Deaconess Medical Center in Boston, which said in a statement that it was “deeply committed to ensuring the scientific and ethical integrity of any research study involving our investigators” and would review NIH’s findings.