The food industry must stop dosing healthy livestock with antibiotics, the World Health Organization said Tuesday. For decades animals’ food and drinking water have often been spiked with medications aimed at boosting growth and preventing disease. But that practice can provide the necessary spark for antibiotic resistance that endangers human health, the agency warned.

In a series of new recommendations aimed at preserving the efficacy of important drugs for people, the global health body called for national governments and food companies to follow rules that have existed in the European Union since 2006—such as not using drugs to promote livestock growth. The guidelines also urge farmers to wait until animals are medically diagnosed with a problem before administering antibiotics and, whenever possible, to select medications that are not important for human health.

“These [guidelines] are a great starting place, and taking these actions would make a huge difference,” says microbiologist Lance Price, director of the Antibiotic Resistance Action Center at The George Washington University. “Some countries take these kind of things—WHO recommendations—more seriously than others, but I do think it is important to have these guidelines codified by a very respected international group dedicated to protecting human health.” Ramanan Laxminarayan, director of the Center for Disease Dynamics, Economics and Policy, agrees. “I think WHO recommendations are very important,” he says. “Without them, countries can be confused and say they don’t have evidence to take action.”

But these recommendations are not law. “WHO recommendations are not mandatory,” says Kazuaki Miyagishima, director of WHO’s Department of Food Safety and Zoonoses. “These are aspirational in the sense that there is no reward and no punishment to countries that do or do not  implement them,” he adds. “It is not mandatory and it is not legally binding.” Still, Miyagishima notes the CODEX Alimentarius’s task force on antimicrobial resistance—an intergovernmental group that reviews these recommendations and other data—will consider them in a meeting later this month. The body could eventually decide to codify them into international standards that could be used to regulate global trade.

There is a long backstory to this issue. In the U.S. there has been a push to curb routine antibiotic use on farms since 1977. But many food producers have insisted that staying competitive—and maintaining healthy flocks and herds—requires regular use of antibiotics (especially as animals have increasingly been housed in close quarters on factory farms). This practice has had a big hoofprint: The Food and Drug Administration’s most recent data, for 2015, says some 34.3 million pounds (pdf) of antibiotics were sold for use on animals in the U.S. that year (and that roughly 21.4 million pounds of that load were drugs considered medically important for humans).

But numbers like that are expected to drop in the years ahead. Earlier this year that landscape tilted when new FDA regulations took effect, making it illegal to drug farm animals purely for growth promotion. The rules do not ban all antibiotic use for purposes such as disease prevention, so critics say this regulation is a big step in the right direction, but they worry loopholes will still enable unnecessary antibiotic use.

Yet even as the U.S. has moved toward reducing antibiotic use in agriculture, China and other countries have started using more—and evidence has accumulated indicating those decisions are driving antibiotic resistance and putting humans at risk. Take colistin—it’s a last-resort antibiotic for humans, used sparingly due to serious side effects. After Chinese pig farmers wanted to boost livestock growth and started routinely dosing our porcine pals with this old, cheap medication, however, drug resistance started showing up in the pigs on an alarming scale—even outside the country. In some places almost 100 percent of hogs carry the resistance gene, called mcr-1. And what’s particularly concerning is this resistance gene is on a DNA ring called a plasmid that can be easily transferred from one bacteria species to another, multiplying the problem. Moreover, that drug use and subsequent resistance in animals appears to have already led to human health concerns: Last year, for example, this resistance gene was detected in an American patient.

There are some indications that more conclusive science and recommendations like the WHO’s could lead to more judicious antibiotic use. In response to the spread of mcr-1 China has banned use of the drug in animal feed. “That does give hope that countries like China do recognize the need for action, and that’s a really positive sign,” Laxminarayan says. (Although he notes China’s current ban may not be enforced everywhere in the vast country.) Slashing the use of drugs like colistin can still make a difference, Price adds. “You need both that successful resistance gene and a successful bug—one good at colonizing and infecting people—to really get this to mushroom, and we haven’t seen that yet, so reducing its use would help protect people and get a real payoff,” he says.

Evidence has also started to pile up that curbing drug use on the farm would specifically combat resistance. On Monday a WHO-funded systematic review was published in The Lancet Planetary Health. The work, which helped inform the new WHO recommendations, concluded that implementing restrictions on antibiotic use could reduce antibiotic-resistant bacteria in farm animals by up to 39 percent—although in most of the reviewed studies, cutting antibiotic use led to reductions in resistance between 10 and 15 percent. The analysis is based on a diverse mix of about 180 papers that look at various drugs and outcomes in animals or humans. This makes it hard to apply those numbers across the board, Price notes. But overall, he says, “I think that what they show is that there is clearly a reduction in resistance with these interventions.”

Although scientists agree that dosing animals is a problem, it still remains difficult to pin down what percentage of the antibiotic-resistance problem comes from animal use. “I think it is impossible to truly quantify the relative contribution of antibiotics in animals versus people, because they work synergistically,” Price says. “Cutting antibiotic use in animals in an environment where people take a lot of these same drugs will have a different effect than if it’s in an environment where few people take those drugs.”

For now, the WHO says, it hopes these recommendations will fuel speedy action. It says countries should swap out unnecessary antibiotic use in favor of better housing and vaccination practices that would keep animals healthy. “These guidelines apply universally, regardless of region, income and setting,” the organization says—although it notes low- and middle-income countries may require more assistance and time. In another five years, the WHO says, it expects to review and update its guidance.