New research makes a case for putting down the skim. 

If non-fat milk is in your weekly grocery rotation, you may want to pause before heading to the store. According to a new study from Tufts University, eating full fat dairy might reduce the risk of developing diabetes. The results are published in the journal Circulation.

To determine the correlation between dairy fat and diabetes, the researchers examined blood samples from 3,333 adults, ages 30 to 75, from two large U.S. prospective studies—the Nurses’ Health Study and Health Professionals Follow-Up Study. All participants were free of prevalent diabetes at the beginning of the 15-year study period.

The results were significant—and in many ways, surprising. Those who ate more full-fat dairy were 46 percent less likely to develop diabetes than those who ate less of it, even after adjusting for variables such as weight gain, physical activity, education, smoking, etc.

“Most health-conscious people are eating non-fat dairy, and one would expect that [eating full-fat dairy] would tend towards harm,” Dariush Mozaffarian, lead researcher of the study, told “The really strong associations with full-fat dairy and lower risk is really unusual to see, and makes me think there is something very real going on.”

Prior research on this topic has been primarily based on self-reporting (in which participants record their food consumption in journals), which takes into account chunks of cheese and glasses of milk, but can fail to include dairy hidden in the food supply, such as that in bakery products and prepared foods. By instead looking for by-products of full-fat dairy in the blood of the participants, the Tufts researchers obtained a more accurate measurement of dairy fat exposure.

The findings conflict with the current U.S. dietary guidelines, which suggest replacing full-fat milk and yogurt with low-fat or non-fat. Additionally, the 2012 school lunch program guidelines banned whole milk from school cafeterias, but said chocolate skim milk is A-OK.

“Our findings are directly in opposition to those recommendations,” says Mozaffarian. “I’m pretty conservative in interpreting science, so I wouldn’t say our findings say it’s definitely true that full fat dairy is better, but I think our findings suggest it’s at least no worse. I think it’s time for national policies to at least be agnostic, at least be neutral about dairy fat. Have dairy, but have whatever [fat content] you prefer.”

While the reason for the correlation between full-fat dairy and reduced risk of diabetes is yet to be determined, it likely has to do with the fact that more dairy fat means less starch and sugar, says Mozaffarian. And he’s not the first to identify a correlation. A study published in February in The American Journal of Clinical Nutrition showed that female participants who ate the most full-fat dairy were 8 percent less likely to be overweight or obese.

The takeaway? Don’t assume skim or low-fat is the healthier option, and refrain from thinking about all dairy as interchangeable.

“Milk and cheese and yogurt are different foods, and have different affects on health,” Mozaffarian says. “Cheese is fermented, yogurt has probiotics, they are really different foods. There is no data to support no fat, and there are some things that are very encouraging that says maybe full-fat is beneficial. You choose based on your preference.”