There may be antibiotics in our milk—unless it’s certified organic. A new study published in Public Health Nutrition found residues of at least one antibiotic in most non-organic milk samples tested—and about a third of the non-organic samples contained residues of antibiotics that are illegal for use in dairy cows. In contrast, no antibiotic residue was detected in organic milk samples.

The Organic Center, 2019, based on data from J. Welsh et al., Production Related Contaminants (pesticides, antibiotics and hormones) in organic and conventionally produced milk samples sold in the USA. Public Health Nutrition, 1-9. doi:10.1017/S136898001900106X

Beyond being concerning on their face, these findings are indicative of a broader crisis of antibiotic overuse in food animals. In conventional, non-organic agriculture, antibiotics are fed routinely en masse to many cows, pigs, and other animals raised for food, often to compensate for high-stress, filthy—and avoidable—conditions. In fact, 2017 FDA data shows that nearly two-thirds of the antibiotics that we rely on to treat sick people are actually sold for use on animals, not people, in the U.S.

Based on 2017 animal data and 2015 human data. FDA, Center for Veterinary Medicine, FDA Annual Summary Reports on Antimicrobials Sold or Distributed for Use in Food-Producing Animals. Center for Disease Dynamics, Economic & Policy, IQVIA MIDAS. Data on human use in 2016 is not yet available.

This kind of constant, low-level dosing of animals with antibiotics creates a dangerous breeding ground for antibiotic-resistant “superbugs,” which can make their way to us through food, soil, air, water, animals, and people. New estimates now rank hard-to-treat antibiotic-resistant infections as the third leading cause of death in the U.S., behind heart disease and cancer, killing up to 162,000 people every year. Ideally, antibiotics should only be used to treat sick animals, rather than routinely as a standard practice.

U.S. laws require non-organic cows to go through an antibiotic “withdrawal” period prior to milking, to allow time for the antibiotics to leave the cows’ bodies. But these new findings suggest that antibiotic cheating may be rampant in the non-organic milk industry. In addition to exposing us to antibiotics in the food supply, this cheating could exacerbate the antibiotic resistance crisis for some of the most important drug classes in human medicine.

Fortunately, the study’s findings also show that the strict rules prohibiting antibiotic use in organic agriculture, paired with third-party verification, are working. In the U.S., organic food animals cannot be treated with antibiotics. Instead, organic producers find safer ways to manage their animals and prevent illness—for example, using better feed, resilient breeds, cleaner housing, more time outside, and more space per animal. If animals still become sick and require antibiotics, they must be treated and removed from the organic herd—so organic producers have a strong incentive to keep their animals healthy.

Responsible antibiotic use should be the practice across all dairy and meat industries—organic or not—so these life-saving medicines will continue to work for people (and animals) when we really need them. Responsible antibiotic use does not require giving up antibiotics entirely; rather, as for humans, antibiotics should be reserved for treating sick animals. But routine use of antibiotics in U.S. livestock production remains the norm in far too many instances. For now, in addition to helping us avoid toxic pesticides and protect soil, the organic label offers one of the easiest ways to identify meat and dairy produced without the routine use of antibiotics.