Neal Barnard was born into a cattle ranching family in Fargo, North Dakota.
"My grandfather was a cattle rancher, and my uncles and my cousins are still in that business today," he says.
Barnard's father was a doctor who treated diabetes, and Barnard says practicing medicine was the last thing he wanted to do. Instead he became a psychiatrist. He worked for a decade in Washington, D.C., and then spent a year running the psychiatric ward at St. Vincent's Hospital in New York.
In 1985, he returned to Washington to launch the Physicians Committee for Responsible Medicine, a nonprofit organization that advocates for preventive medicine and higher ethical standards in research.
"If humans were being abused in research or if animals were being used when alternatives could be used instead, deal with those," he explains.
Advocating responsible research
PCRM has 7,000 members today. It has campaigned successfully to close down labs at many American medical schools that were experimenting with live dogs, a common practice that troubled Barnard during his medical training and in which he refused to participate.
"We made it a point to let medical schools know that there is a better way of teaching, and now more than 90 percent of schools have scrapped that," he says.
PCRM also fought against a controversial government-funded study that proposed to inject short - but not hormone-deficient - children. The researchers wanted to see if giving them extra hormones would make them taller.
"Now, because these growth hormones are associated with cancer risk," Barnard says, "We sued the National Institutes of Health to try to stop this. I am sorry to say we didn't win."
Targeting role of diet in causing disease
Barnard says such battles have spawned two advocacy programs within the Physicians Committee: The Cancer Project and The Washington Center for Clinical Research. Both focus on the critical importance of diet - and a plant-based, or vegan, diet in particular - in preventing many life-threatening diseases.
Too often, Barnard says, "Doctors clean up the wreckage of bad habits, bad genes or bad luck."
He adds that doctors most often fail in preventing disease.
"We don't do anything about the heart attack until it comes into the emergency room, and we especially don't deal with the causes of it. The cause of a heart disease is not a deficiency of cholesterol-lowering drugs. It's caused by food. I thought, 'Why are we not dealing with that?'"
Special focus on diabetes
That question led Barnard - like his father - to take a closer look at diabetes, a disease that affects 171 million people worldwide. A 2006 government-funded study tested a plant-based regimen head-to-head with a more typical diabetes diet. Barnard says the vegan diet was three times more effective than the American Diabetes Association dietary guidelines for controlling blood sugar.
"When we look at the changes week after week after week, we see dramatic weight loss. Their cholesterol levels fall. Their energy levels improve. You see people who are signing up for marathons when they never would do that before.
More than just medicine
Barnard often takes that message on the road. He's written more than a dozen books, produced video seminars and offers online courses on how a vegetarian diet can reduce the rate of certain cancers and protect against diabetes, heart disease and obesity.
"What we try to do is to do research that lays the groundwork so that we know how diets affect health. Then we work with the government to make sure their guidelines are more in sync with this approach and reach out to the public with materials."
After more than 20 years of medical activism, Barnard says there's still a lot of work to be done helping people live healthier lives.
"We are seeing more obesity, more health problems. And this, he says, is because more people are eating a meat, dairy-based, fatty and sugary diet. He says the answer is not entirely medicine.
"The answer is advocacy. The answer is sometimes litigation. The answer is changing the laws to determine what people eat and what they know."
The Physicians Committee for Responsible Medicine is leading a campaign to get nutrition into the medical school curriculum. The group is also lobbying Congress to mandate vegetarian options in school cafeterias through the Child Nutrition Act. As he charts PCRM's future, Barnard says he is still guided by the oath he took when he became a doctor - to ethically practice medicine and do no harm.