For years, health-conscious Americans were urged to steer clear of saturated fat, turning skim, low-fat and fat-free dairy into the go-to options for people concerned about weight gain and heart disease.
Now, new research out of Canada is raising questions about whether that familiar nutrition message was too simple.
Scientists from the University of Toronto and Mount Saint Vincent University tracked 74 overweight adults over a 12-week period.
The volunteers were placed on one of three eating plans: a reduced-calorie diet with little dairy, a weight-maintenance diet that included full-fat dairy, or a full-fat dairy diet with no calorie restrictions.
What they found challenged decades of diet advice. People who consumed three servings of full-fat dairy a day did not put on weight or experience increases in cholesterol, whether or not they were limiting calories. Instead, both full-fat dairy groups showed better blood pressure readings and consumed more calcium, protein and vitamin D.
“Those who had three servings of dairy, you don’t have adverse levels of blood cholesterol or lipids or evidence of insulin resistance,” lead researcher Dr Harvey Anderson, a nutrition scientist at the University of Toronto, said in a statement.
The results add weight to what researchers call the “dairy matrix hypothesis” — the idea that dairy’s natural structure may slow digestion and limit how much saturated fat is absorbed, helping explain why full-fat dairy may not affect cholesterol in the same way as fats found in many processed foods.
The study also comes as the USDA’s newly revised food pyramid under Health Secretary Robert F Kennedy Jr. places greater emphasis on full-fat dairy, protein and “healthy fats,” marking a notable shift away from earlier low-fat nutrition guidance.
When researchers followed 74 overweight adults for 12 weeks, they found that those eating three daily servings of full-fat dairy didn’t gain weight or raise cholesterol
At the start of their study, published in the Journal of Nutrition, the researchers split 74 overweight or obese adults into three groups. One group followed a low-calorie diet with no more than one serving of low-fat dairy per day.
A second group ate three servings of full-fat dairy each day while keeping their calorie intake neutral.
A third group ate three servings of full-fat dairy with no calorie restrictions at all.
After 12 weeks, researchers found that neither full-fat dairy group gained a significant amount of weight. In fact, the group that ate three daily servings of full-fat dairy with no calorie restrictions actually saw a small decrease in hip circumference.
Both full-fat dairy groups – those who kept calories steady and those who ate without calorie restrictions – saw their systolic blood pressure drop by an average of 2.72mmHg.
The low-fat group saw a slightly larger drop of 4.25 mmHg, though researchers noted the difference was not statistically significant.
The key takeaway, they determined, was that full-fat dairy still improved blood pressure; it just didn’t outperform the low-fat diet in this specific measure.
Researchers also determined that there were no meaningful differences in cholesterol levels between any of the groups. Triglycerides temporarily spiked at week four but returned to normal by week 12.
The graph shows body weight change over 12 weeks. LD-ER is low-dairy, calorie-restricted. 3D-EN is full-fat dairy, steady calories and 3D-AL is full-fat dairy, no restrictions. Full-fat dairy didn’t cause significant weight gain, even when people ate as much as they wanted
Total cholesterol, including ‘bad’ LDL cholesterol, ‘good’ HDL cholesterol and blood sugar all remained stable across all three groups.
Nutrient intake was where the full-fat dairy groups truly outperformed the low-fat dairy group.
‘With dairy products, it’s got two proteins – casein and whey – that are bound together with fat and with nutrients mixed in,’ Anderson said.
He added that it is precisely this complex physical structure that ensures a slow, steady release of nutrients, giving dairy health benefits that go beyond the sum of its isolated nutrients.
Participants who consumed three daily servings of full-fat dairy significantly increased their protein and calcium intake compared to the low-dairy, calorie-restricted group.
Calcium intake in the high-dairy groups averaged more than 1,100 mg per day, slightly above the recommended 1,000 mg daily target.
The low-dairy, calorie-restricted group averaged just 760 mg, falling short of the daily requirement.
Protein intake also increased substantially in the full-fat groups, while the low-dairy, calorie-restricted group actually saw a slight decline.
The full-fat dairy groups came out ahead on nutrition, consuming significantly more protein, calcium and vitamin D than those on the low-dairy diet
Vitamin D intake, while still below recommended levels across all groups, improved in the full-fat dairy groups.
The researchers noted that Canada has since doubled its mandatory vitamin D fortification requirements for milk, which could make dairy an even more effective source of this crucial nutrient going forward.
This does not mean it’s a free-for-all, however. The USDA’s new dietary guidelines still cap saturated fat at 10 percent of daily calories – about 22 grams on a 2,000-calorie diet.
And as researchers have pointed out, three servings of whole dairy a day can easily push you to the limit.
One cup of whole milk, one serving of whole-fat yogurt, and one serving of cheese already add up to about 17 grams of saturated fat, before you have eaten anything else.
Fat is not always a bad thing, however.
The body needs several types of fats to function, and whole dairy is a good source of ‘healthy’ fats that help absorb fat-soluble vitamins such as vitamins A and K. It also contains more omega-3 fatty acids and helps you feel full for longer compared to reduced-fat options.
The choice between whole and low-fat dairy depends on a person’s individual needs. If you are watching your saturated fat intake, reduced-fat options still offer many of the same nutrients without the extra fat.
But if you are struggling to get enough protein, calcium or vitamin D, full-fat dairy may be the better choice.
As Anderson put it: ‘Keep it simple, eat a variety of foods and not too much of anything.’
