In terms of vitamins and minerals, a few studies have uncovered only minor differences between the two milks. In other words: Both types of milk “are practically the same nutritionally,” says Ermias Kebreab, PhD, a sustainable animal agriculture professor at UC Davis. But if you care a lot about eating healthy fats, organic milk might be the better choice.
Does organic milk have fewer pesticides, hormones, and antibiotics?
In 2019, researchers from Emory University School of Medicine tested 69 samples of organic and regular milk collected from supermarkets around the country. They were on the lookout for pesticides, which are used to grow feed for conventional cows; bovine growth hormones like bST, which occur naturally in cattle but can also be supplemented synthetically; and antibiotics, which are used to treat conventional cows when they’re sick or injured. She found higher levels of all three in the non-organic milks.
Pesticides and antibiotics were detected in several of the regular milks but none of the organics. There’s a simple explanation for these discrepancies: The milk from dairy cows treated with antibiotics can never be sold as organic within the US. Among the conventional samples which tested positive, though, various exceeded federal limits for the antibiotics amoxicillin (1 of the 35 samples), sulfamethazine (37% of samples), and sulfathiazole (26% of samples).
An FDA spokesperson says Emory’s antibiotic findings “appear inconsistent” with the agency’s own reporting: Of the 3,494,330 samples collected in 2021, only 290 (0.008%) tested positive for a drug residue. According to the spokesperson, all milk produced in the US is tested for antibiotic residue before it hits shelves—and samples that exceed tolerance levels are illegal for human consumption.
Though antibiotics are allowed at certain levels in conventional milk, there “should be a significant decrease in their use,” argues Kebreab, the UC Davis agriculture professor. That’s because the antibiotics in cows’ milk have been “shown to promote antimicrobial resistance” in humans, he says. In other words: By microdosing tiny amounts of antibiotics in milk, certain microbes might stop responding to them.
The Emory research team also found the growth hormone, bST, along with Insulin-like growth factor 1 (a hormone that increases as a byproduct of bST) in both the conventional and organic milks tested. While some growth hormone is present naturally in milk because cows produce it, the levels in the conventional samples were significantly higher. “This could reflect the use of synthetic growth hormones, which are allowed in conventional but prohibited in organic milk production,” says lead author Jean Welsh, PhD, MPH, RN, an associate professor of pediatrics at Emory.
Though the use of the synthetic hormones in animal agriculture has been shrouded in controversy for decades (and Insulin-like Growth Factor 1 has been linked to various cancers), the FDA hasn’t set a maximum safe limit for bST in milk because the agency considers it safe for humans. “It has been shown conclusively that hormones such as bST have no effect on consumers,” says Kebreab.
Is organic milk better for the environment?
There’s little scientific consensus among researchers. Animal agriculture in general is a huge contributor to total greenhouse gas (GHG) emissions—at almost 15% by some estimates—and red meat and dairy tend to do the most damage. But studies into the impacts of dairying are all over the place: Some have found that organic farms produce less, more, and roughly the same amount of emissions as regular farms.