Fifty years from now, Neal Barnard will be seen as either a consummate medical crank or a prophet. A psychiatrist turned activist, Barnard is a passionate advocate of diets with no meat or dairy, and an ardent agitator for animal rights.

Barnard's uncanny political instincts and his medical degree have propelled him into the limelight, from Newsweek to The Oprah Winfrey Show and a cameo appearance in the documentary Super Size Me. “I want to advocate for things that have been neglected,” he says. “We don't think about diet, we don't think about prevention, and we certainly don't think about the ethics of much of what we do in the laboratory.”

We don't think about diet, we don't think about prevention, and we certainly don't think about the ethics of much of what we do in the laboratory.

Barnard pushes for his beliefs as president of the Physicians Committee for Responsible Medicine. The group has relentlessly lobbied for alternatives to animal research and has been an endless source of vexation for federal nutrition-policymakers.

The committee is also expert at hijacking hot topics for its own interests. In May, after a mild strain of bird flu was detected in a live bird market in New Jersey, it sent out a press release offering a free 16-page vegetarian starter kit “to worried consumers.”

The group began in 1985 as a one-man mission in Barnard's tiny New York City apartment. But more than 20 years of direct mail, volunteer sweat and savvy public relations has added up to a large office in Washington, DC with a $7.2 million budget and a staff of 70, including 5 lawyers and 10 scientists. Barnard has written ten books of diet and nutrition advice that have collectively sold two million copies.

Barnard's message is not exactly medical gospel. In 2003, he told a US Food and Drug Administration working group that cheese is “dairy crack,” adding that he was only “halfway kidding.” His latest book, Breaking the Food Seduction, labels chocolate, sugar, meat and cheese addictive substances.

Still, he has fans high in the medical ranks. “He's a superb man,” says William Roberts, an adviser to Barnard's group, executive director of the Baylor Cardiovascular Institute in Dallas and editor of the American Journal of Cardiology. “Anybody who devotes their life like he has done to getting us all on the right dietary track, I admire.”

Barnard is an unlikely candidate for the animal-rights barricades. He comes from a long line of North Dakota cattle ranchers and grew up eating roast beef and hunting pheasants with his father. As an undergraduate psychology student, he considered a fellow student “soft” when the student complained about having to dispose of live rats by pouring chloroform over them in a trash can.

But months later, Barnard adopted a white lab rat he called 'Ratsky' and nursed it as it suffered from cancer. It was after Ratsky died that he decided his attitude toward animal suffering had been misguidedly cavalier.

In 1977, as a medical student at George Washington University, he refused to participate in a required class in which students tested heart drugs on anesthetized dogs. Barnard's newfound awareness also led him to rethink his dietary habits.

Barnard says his vegan diet is rooted in his conviction that meat and dairy foods are unhealthy. But it also reflects an intense compassion for animals. As scientists' understanding of animal biology—and particularly animal consciousness—has exploded over the last two decades, Barnard has doggedly used it to pose fundamental questions about the ethics of experimenting on animals.

“We understand their communication patterns, their social interactions, their hierarchies. We understand their exquisite sensitivity to environmental cues. Yet all of that is suddenly completely ignored when it comes to designing an experiment that would violate all those things,” he says. “It's as if ethics and science have no relationship anymore.”

For his controversial stance, Barnard has drawn the special ire reserved for those who goad the medical establishment.

“To think that we can rely totally upon [human] clinical trials or totally upon nonanimal theoretical models is irresponsible,” says Joseph Haywood, chair of pharmacology at Michigan State University in East Lansing. “We simply aren't at the place now that we can advance science without the use of animals in our research.”

Barnard has also irked such powerhouses as the American Medical Association, with which he had a running feud in the 1990s over his promotion of a meatless, milkless diet. Although the group declined to comment for this article, its policy spells out “strong objections” against Barnard's committee “for implying that physicians who support the use of animals in biomedical research are irresponsible.”

Barnard's group urges its backers not to give to medical charities that support animal research. The committee has long campaigned for medical schools to stop using animals to train students and takes some credit for the fact that 106 of 125 US medical schools have abandoned the practice.

The group may seem respectable because it appears to represent physicians' views, but its connection to the People for the Ethical Treatment of Animals (PETA) is evidence of its radical animal rights agenda, says Frankie Trull, president of the Foundation for Biomedical Research in Washington, which supports animal research.

Until 2005, PETA's president, Ingrid Newkirk, and Barnard sat on the board of the Foundation to Support Animal Protection, which is based at PETA's headquarters in Norfolk, Virginia. The foundation gave Barnard's group $592,000 in 1999 and 2000. PETA also directly donated another $265,000 between 1988 and 1999. Barnard still writes a column, “Doctor in the House,” for Animal Times, PETA's magazine.

Barnard dismisses those criticisms. “PETA does a lot of important work,” he says. “But we have a very different mission.”

Indeed, he publishes in reputable peer-reviewed journals such as Lancet Oncology and the American Journal of Cardiology. He's completing a $350,000 US National Institutes of Health–funded randomized trial to test the impact of diet on blood sugar control in people with diabetes, comparing a vegan diet with the nonvegetarian diet recommended by the American Diabetes Association. According to results he plans to present at the association's meeting in June, the vegan diet comes out significantly ahead.

Marion Nestle, a professor of nutrition at New York University, disagrees with Barnard's vegan philosophy. Still, she says, “I think he raises provocative questions that deserve serious attention.”