The evidence-based prescription for improved health for Americans threatens the financial interests of powerful industries, according to a new food documentary coming to theaters this Independence Day.

“PlantPure Nation” makes a case for not relying on the medical establishment or the government to spread the word about the “overwhelming evidence” that eating whole, plant-based food is the key to good health. Instead it’s up to those of us who know the benefits of vegetarian food to start a nationwide health revolution.

This documentary is a follow-up to the influential 2011 film “Forks Over Knives,” produced and written by the same filmmakers. The feature-length film will be released nationally on July 4 and will be screened sometime this summer at the Nickelodeon in Portland. Early versions of the film have been showing across the country for three months now.

Renowned Cornell University biochemist T. Colin Campbell and his oldest son Nelson Campbell star in the film. One of the key figures in “Forks Over Knives,” T. Colin Campbell is also the author of “Whole: Rethinking the Science of Nutrition” and “The China Study”; the latter has sold more than 1 million copies.

Nelson Campbell, who narrates and directs, aims to show the remarkable power of a plant-based diet to prevent and in some cases reverse chronic conditions, such as diabetes, heart disease, cancer, erectile dysfunction and obesity. At the same time, the film demonstrates how deeply entrenched meat-eating is in our society.

We see this play out in the Kentucky legislature, where in 2011 T. Colin Campbell and heart disease expert Dr. Caldwell Esselstyn testify about the scientific evidence supporting a whole-food, plant-based diet as a treatment for chronic disease. The testimony comes in support of a bill that would establish a pilot program using vegan food to improve the health of residents in a low-income Kentucky community. The program would be carried out at no cost to the state. But when the meat lobby gets wind of the bill, it’s quickly killed, according to the film.

Disappointed but not defeated, Nelson Campbell returns to his rural hometown of Mebane, North Carolina, and launches the program there – in the land of Southern comfort food and Carolina barbecue.

Though Mebane doesn’t have any vegetarian restaurants, Campbell and his team recruit hundreds of locals to take part in a series of 10-day trial programs. The programs measure the participants’ vital signs, provide them with freshly prepared vegan meals for 10 days and then check each person’s vital signs at the end. As shown in the film, participants are shocked to find dramatic drops in their cholesterol and triglycerides, with one man asking incredulously: “Is that accurate?”

Later we learn participants with a cholesterol level of 175 or higher experienced on average a 20 percent drop during the 10-day program. Even the head of the company hired to do the pre- and post-testing is surprised by the improvements, saying he’s never seen such dramatic change in such a short period of time.

With such impressive results, Nelson Campbell returns to the Kentucky and works with Democratic Rep. Tom Riner to try again to achieve legislative action around the link between diet and health.

As Campbell explains in the film, he and Riner “decided to pursue a strategy to force government to do something it has a hard time doing these days, which is acknowledging facts that are unsettling to rich and powerful interests but vital to the interests of the people.”

Predictably, they run into resistance again from legislators in agricultural districts, and their effort fails. But the message from the filmmakers is clear: Government will not lead the way to better health.

Interwoven with this political narrative is a hopeful story of reviving farmers markets and rising demand for organic food. The film also addresses the related issues of food deserts, dwindling numbers of small farms, chemical-intensive monoculture farms and agricultural subsidies.

Nelson Campbell and a small group of investors financed the film. He and his team also raised more than $160,000 on Kickstarter to help pay for distribution costs.

During the more than 20 preview screenings, there were “sold-out, or nearly sold-out theaters for much of the tour,” Campbell told me, “The reaction has always been the same: strong applause followed by a lively Q & A. One strong point of interest for people has been our idea for a national network of local organizations we are calling PlantPure Pods.”

Anyone can set up a pod through plantpure nation.com. “Our goal is to launch well over 100 Pods by the end of the year,” Campbell said. Each will be a local chapter of PlantPure Nation Foundation, a national nonprofit the filmmakers organized to provide the local pods with tools to run their own 10-day health programs, including prepared meals and educational materials.

“The purpose of each PlantPure Pod will be to promote the message of plant-based nutrition in the local community,” Campbell said.

Campbell hopes the pods will combat the back-sliding that happened among the Mebane participants after the 10-day trials ended.

“Some stayed plant-based, but quite a few also fell off the wagon,” Campbell told me. “There are few food options for plant-based eaters in a place like Mebane, and certainly little, if any, community around this idea.”

As a result, one of the first pods will be launched in Mebane, Campbell said.

“Our health care crisis can be solved only by engaging millions of people in this effort,” Campbell told me. “Top-down solutions don’t work because they almost always end up getting captured by the rich and powerful.”

When I asked him whether the reaction to the early screenings confirmed his idea that radical dietary change can spread from average citizens on up, Campbell answered, “I have no doubt about this.”

“We have been inundated with interest in our film and pod strategy from communities in this country, but also from abroad,” he continued. “People are hungry to be part of a solution. We have an opportunity to launch one of the most important movements in the modern age.”

Avery Yale Kamila is a freelance food writer who lives in Portland. She can be contacted at:

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Twitter: AveryYaleKamila