The Science Around Full-Fat Dairy

For decades, Americans were told to reach for the skim milk. In January, Washington changed its mind.

The scientists who study the question say the old advice and the new one share a flaw: Nobody ever ran the head-to-head test.

The 2025–2030 Dietary Guidelines for Americans, released on Jan. 7, list full-fat dairy among the whole foods that supply healthy fats and name butter among the fats suitable for cooking. Earlier editions favored fat-free and low-fat dairy.

But the guidelines did not give full-fat dairy a free pass. They still tell people to keep saturated fat below 10 percent of daily calories, or about 22 grams on a 2,000-calorie diet. Three cups of whole milk supply about 14 grams.

The guidelines also broke with their own scientific advisory committee, whose recommended eating patterns kept fat-free and low-fat dairy. Yet the committee’s evidence review found that swapping lower-fat dairy for higher-fat dairy makes no difference to cardiovascular risk. It still reaffirmed the 10 percent limit and advised replacing butter with vegetable oils.

The American Heart Association reached a different conclusion from the same research. Its March scientific statement acknowledges that limited evidence suggests swapping higher-fat for lower-fat dairy yields similar cardiovascular risk, and that the question remains debated.

It still recommends low-fat and fat-free dairy, because the swap increases the share of unsaturated fat in the diet, a pattern linked to better heart health. Alice Lichtenstein, a Tufts University nutrition scientist and the statement’s lead author, declined to comment.

The Comparison Nobody Ran

Benoît Lamarche, scientific director of the NUTRISS Centre at Université Laval’s Institute of Nutrition and Functional Foods, objects to the old advice not because low-fat dairy was harmful, but because the comparison was never properly made.

“If we are saying that low fat is better than high fat, we should have studies demonstrating that, you know, black and white,” he told The Epoch Times. “We don’t.”

Few studies have compared the two directly, he said, and those that have show the same effect either way. The reason is practical: Trials long enough to measure heart attacks would need thousands of people followed for years, while about six weeks is the realistic limit for keeping people on a controlled diet.

The federal advisory committee graded the evidence as limited, and the heart association said the data were inadequate to draw conclusions about blood lipids, blood pressure, or cardiovascular death.

A New Trial With Limits

In January, researchers at the University of Toronto published a 12-week trial in The Journal of Nutrition. Adults who ate three daily servings of full-fat dairy showed no meaningful increase in body weight, body fat, or blood cholesterol compared with those eating less. Blood pressure improved.

It is a real result, albeit a small one—with only 74 overweight adults. The trial was funded by the Canadian Dairy Research Cluster 3, a joint government and industry initiative, and the Mitacs Accelerate program.

A 12-week trial can rule out obvious short-term harm; it cannot show what happens over the decades in which heart disease develops.

Harvey Anderson, a University of Toronto nutritional sciences professor who led the work, framed the takeaway modestly. “Keep it simple, eat a variety of foods and not too much of anything,” he said in a statement released by the university.

Why the Food May Matter More Than the Fat

The idea behind the shift is called the “dairy matrix”: the theory that fat behaves differently inside a whole food than on its own.

The starting point is undisputed. Saturated fat raises LDL (“bad”) cholesterol, and LDL contributes to the plaque that narrows arteries. The dispute is whether saturated fat behaves the same way inside a complex food as it does as an isolated nutrient.

The clearest test has been cheese against butter. When the two are matched for saturated fat, every randomized trial to date has found that cheese produces lower LDL cholesterol, according to Emma Feeney, an assistant professor at University College Dublin’s Institute of Food and Health who studies the dairy matrix.

Feeney described two possible explanations. The calcium in cheese forms insoluble soaps with fat in the gut, blocking some of its absorption, and cheese retains more of the milk fat globule membrane, a thin layer of bioactive compounds that may also play a role. “None of these effects are necessarily competing,” she told The Epoch Times. “It’s possible that all are working in tandem.”

Feeney’s matrix research was funded through Food for Health Ireland, a technology center supported by Enterprise Ireland and dairy industry partners; she said the industry partners had no role in analysis or interpretation.

What the Wider Evidence Shows

Larger studies point the same way: dairy fat is not clearly harmful, but it is not clearly better than the alternatives.

A 2016 Harvard analysis followed more than 220,000 adults and found dairy fat was not significantly associated with cardiovascular disease compared with an equivalent amount of energy from carbohydrates. However, the same study found that replacing 5 percent of calories from dairy fat with polyunsaturated fat was linked to 24 percent lower cardiovascular risk, and the authors concluded that replacing animal fats, including dairy fat, with vegetable fats and polyunsaturated fats “may reduce” cardiovascular risk.

An international expert panel convened in Amsterdam in 2024 concluded that milk, yogurt, and cheese are neutrally associated with cardiovascular risk regardless of fat content. Lamarche, an author on the resulting paper, said some workshop participants received travel funding from the Dutch dairy federation, but that he paid his own way and received no funding for the work.

“Neutral” is not the same as “protective.” The question stays open for practical reasons, Feeney said. A trial measuring heart attacks and deaths would need thousands of people followed for years, while about six weeks is the realistic limit for keeping people on a controlled diet. Self-reported eating is also unreliable.

Outside heart disease, the fat and the food come apart entirely. A Harvard study that followed nearly 130,000 U.S. nurses and health professionals for more than two decades found total dairy intake was not significantly associated with Parkinson’s disease risk.

Low-fat dairy, however, was linked to higher risk. The effect appeared to be driven by skim and low-fat milk, and it held for both men and women. That is an observational finding with no established explanation, but whatever is happening, it does not appear to be the milkfat.

The Cap That Didn’t Move

The same document that welcomed butter back kept the ceiling that constrains it. The guidelines still recommend keeping saturated fat below 10 percent of daily calories, or about 22 grams on a 2,000-calorie diet. Three cups of whole milk supply about 14 grams.

The threshold itself has never been well explained, Lamarche said. “No one can explain where the 10 percent cap comes from,” he said. “It seems arbitrary.”

“It perhaps is more that there is no evidence to specify reduced fat over full fat,” Feeney said. Staying under the cap is harder with full-fat dairy, “but they are not necessarily incompatible.”

Frank Hu, who chairs the nutrition department at the Harvard T.H. Chan School of Public Health, told the school’s Nutrition Source that the guidelines’ mixed messages on foods like butter and beef tallow “may lead to confusion and potentially higher intake of saturated fat.”

What This Licenses, and What It Doesn’t

The evidence no longer supports singling out dairy fat as uniquely harmful. Nor does not establish that dairy fat is uniquely beneficial, and the two claims are easy to confuse.

“I would not like anyone to take away from this research that butter is a healthier fat than any other cooking fat,” Feeney said.

She has not compared butter against other fats, she said, and her studies used around 42 grams of dairy fat a day, a large amount of energy. In her studies, six weeks of dairy fat, butter included, tended to shift cholesterol particles toward larger sizes generally considered less harmful, though she said the analysis was exploratory.

For weight loss, a diet built on fruit and vegetables is the better approach. “As with any dietary advice, moderation is key.”

“It’s [butter] not going to kill anyone, for sure,” he said. “My perspective really is that diet is so complicated. Let’s focus on the big issues and not distract people with something we’re not sure about.”

“A lower consumption of so-called ultra-processed foods will reduce saturated fat intake and will be more likely to produce beneficial effects on cardiovascular health,” he said.

On that point, the heart association agrees: its statement also urges minimally processed foods in place of ultra-processed ones.

What remains unsettled is whether the matrix effect holds over decades, and whether it holds for butter. The trials that would answer it have not been run.

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