BONN, Germany — The cult German police television drama “Tatort” usually features murders committed by organ smugglers, baby thieves and international spies. But on one Sunday this May, the suspects were a widely appreciated group: traditional, back-to-the-land organic farmers.

Their bucolic farm in the Black Forest had a dark side, however, and the detectives slowly discovered the farmers’ care for ancient crops and eschewal of modern technologies was based on a far-right “blood and soil” ideology. Like all good fiction, the episode has its roots in truth. These so-called Bio-Nazis are no invention of the show’s writers but reflect a growing embrace of natural farming and eating among right-wing extremists.

Vegetarianism, veganism and other forms of “clean” eating and organic farming are often associated with leftist, progressive movements. These food practices often combine a desire for bodily health with moral and social concerns. Indeed, interest in animal rights or in the protection of the environment seems to be within the special purview of Green politics.

In recent years, however, “clean” food production and even the ethical treatment of animals have been co-opted by far-right individuals and organizations. This kind of appropriation is not new. In Germany, natural eating started out primarily as a left-wing idea in the 19th century but was adapted to a fascist message in the 20th. Diet and politics have always been closely entwined, but in ever-changing ways. Clean eating is shifting back to the right.

White supremacists in Germany and elsewhere are embracing diets free of animal products, demonstrating recipes on YouTube and arguing for the suitability of vegetarian diets for “Aryan” people. A 2012 study carried out by the Heinrich Böll Foundation, which is affiliated with the German Green party, drew attention to the phenomenon of right-wing organic farming movements in the state of Mecklenburg-Vorpommern.

Because a vegetarian diet requires less arable land to produce than a meat-based one, adopting it could help Germany become agriculturally self-sufficient.

The Böll report warns that the buyer of an innocent-looking organic salad might be indirectly funding an organized far-right movement. More importantly, the state’s neo-Nazi National Democratic Party had a history of opposing genetic engineering, patents on living organisms and foreign investment in coal-based energy. It was thus well positioned to present itself as an advocate for the environment.

The rhetoric of right-wing environmentalism is particularly evident in the Bavarian magazine, Umwelt & Aktiv (Environment and Active). With covers alternating between bucolic sunset photos of German landscapes and political cartoons, the periodical advertises an interest in the protection of the environment, animals and Heimat, or “homeland.”

Some articles are innocuous, listing helpful kitchen herbs, offering theories for declining bee populations and arguing against the hunting of dolphins. Interspersed among these are unabashedly xenophobic pieces. An article on the pedagogical values of “forest kindergartens” presents them as an alternative to multicultural preschools. Another piece rails against the “barbarism” of halal butchering practices, calling for animal rights activists to stand up to “narrow-minded and coldhearted Islamic fundamentalism.”

Does this mean that “Green” is in fact “Brown”? Not quite. Although people use food to signify their class, religion, politics and ethics, the ways they do so are changeable and complex. Historian Corinna Treitel, author of the recent book, “Eating Nature in Modern Germany: Food, Agriculture and Environment, c. 1870-2000,” explains that “natural foods” are “very politically promiscuous” in modern German history.

“Natural” itself is a malleable term. It could mean avoiding processed food or dropping sugar, alcohol and tobacco from one’s diet. It might entail cutting back on meat once in a while, becoming a vegetarian or buying food produced on biodynamic farms. Any of these choices could be made to serve different ideologies and political agendas.

One of the pioneers of the natural eating movement was Eduard Baltzer, a politically progressive religious reformer. In the 1860s, against the background of recent hunger crises in Prussia, Baltzer argued that a vegetarian, natural diet would make Germans healthier and fitter. It would have economic benefits too.

Because a vegetarian diet requires less arable land to produce than a meat-based one, adopting it could help Germany become agriculturally self-sufficient. At the heart of this was a larger social vision. Baltzer, says Treitel, “was imagining diet as a tool for promoting material equality between Germans so that political democracy could emerge.”

At the start of the 20th century, natural diets appealed to different groups for idiosyncratic reasons. The pacifist Magnus Schwantje founded a society for animal protection, its journal arguing for vegetarianism as part of an ethics of compassion. Germany’s natural food subculture includes a number of Jews, possibly because a meatless meal rendered food taboos inconspicuous. At around the same time, the racial nationalist Karl Weinländer worried that a massive war between Germans and “Mongols” would take place in which the Mongols would win because of their vegetarian diet.

The Nazis seized the back-to-nature ideas popularized by the life reform movement of the 19th and early 20th century and shaped them to their own ideological ends. A popular story holds that Hitler was a vegetarian. In fact, he did occasionally eat meat, but he also embraced a broader natural diet to improve his energy and fitness.

Many of us continue to associate environmentalism, organic agriculture and vegetarianism with left-wing progressives — but right-wing nationalists now find them ripe for the picking.

Nazi propagandists held up the natural diet as being proper to modern, hard-working people. As culinary historian Volker Bach explains, this was partly achieved by educating housewives on the best ways to feed the “body of the nation, an almost mystical organic whole.” Cookbooks, household management guides and organized home economics training taught women to feed their families in a way that would ensure Germany’s “food liberty.” They were encouraged to use locally grown products, raw if possible, and to reduce consumption of meat, fat and eggs.

The idea of eating “naturally” has deep roots in German history, but there has never been an immutable connection between any given diet and identity or political position. After World War II, scientists who had been active in the Third Reich rebranded themselves. Some worked to develop organic farming in West Germany, others promoted reform diets in East Germany.

The politics of food choice continue to change today. Many of us continue to associate environmentalism, organic agriculture and vegetarianism with left-wing progressives — but right-wing nationalists now find them ripe for the picking.

Irina Dumitrescu is professor of English medieval studies at the department for English, American and Celtic studies, Rheinische Friedrich-Wilhelms-Universität, Bonn.