Do you routinely choose skim milk or fat-free yogurt in the interest of a smaller waistline?
New research strongly suggests that those well-intentioned choices will likely do you no good.
Conventional wisdom about full-fat dairy foods has been reeling from scientific body blows.
And recent findings deliver sharp jabs that may finally floor fears about full-fat dairy's impact on weight, heart, and metabolic health.
Rather than harming heart and metabolic health, it now appears that full-fat dairy — preferably fermented foods like yogurt and aged cheese — heighten them.
Past population studies have produced varying findings on low-fat dairy foods, with some showing benefits from consumption.
But most research links diets featuring full-fat dairy — especially fermented foods — to better outcomes.
Let’s take a quick look at two very recent studies that add evidence in favor of full-fat dairy.
Tufts study links whole, full-fat milk to reduced diabetes risk
Late last year, researchers from Harvard and Tufts Universities published positive findings about full-fat dairy foods.
They analyzed data from two prior studies, collected over a 20-year period from 3,333 nurses, doctors, and other health professionals aged 30 to 75 years.
The Boston-based researchers had access to information about the participants’ health status, diets, and “bio-markers” of dairy fat in their blood.
All of the participants were free of diabetes at the outset of the two studies, in 1989 and 1993.
The Harvard-Tufts team compared the diets and blood profiles of the study participants who developed diabetes to the diets and blood profiles of those who did not (Yakoob MY et al. 2016).
And their analysis suggests that the dairy fat in milk, yogurt and cheese may help prevent diabetes.
Specifically, the health professionals who consumed the most dairy fat were 46% less likely to develop diabetes, compared with those who ate the least.
The study couldn’t reveal why people who ate more dairy fat ran a lower diabetes risk — but the research team attributes the benefit to the appetite-satisfying effect of full-fat dairy.
Lead study author Dariush Mozaffarian, M.D., noted that people who favor low-fat dairy tend to eat more carbohydrates — probably to compensate for a lack of appetite-satisfaction — causing blood sugar spikes linked to risk of diabetes.
Irish study further supports full-fat dairy foods
Last month, scientists from University College Dublin reported more positive findings about full-fat dairy.
They examined the impacts of dairy foods — milk, cheese, yogurt, cream, and butter — on risk for heart disease, obesity, and diabetes in 1,500 healthy Irish adults aged 18-90 years (Feeney EL et al. 2017).
In short, their findings support the majority of similar studies, which favor full-fat dairy:
As you’d expect, the Irish team found that those who reported eating lots of cheese were consuming higher amounts of saturated fats, which predominate in milk.
However, the new study did not link cheese-rich diets to obesity, greater body fat, or higher LDL cholesterol levels.
This finding echoes other recent ones showing that cheese — despite being high in saturated fats — doesn’t adversely impact people’s blood cholesterol profiles.
Current US health guidelines still advise people to limit foods high in saturated fats, such as cheese.
The purpose of that advice is to keep blood cholesterol levels in check — especially LDL-cholesterol, which is linked to higher risk for heart disease and stroke.
It’s true that some — but by no means all or even most — saturated fats raise total blood cholesterol and LDL levels.
Nonetheless, fast-growing evidence exonerates saturated fat as a cause of heart disease — and broad advice to avoid saturated fat often leads to unhealthful outcomes.
The Irish researchers attribute the failure to see any negative impact of cheesy diets on cholesterol to the complex nutritional matrix in which that saturated fat occurs.
As study lead author Emma Feeney, Ph.D., said, “We have to consider not just the nutrients themselves but also the matrix in which we are eating them, and the overall dietary pattern — so it’s not just about the [individual] foods, but the pattern of other foods we eat with them as well.”
Earlier evidence reviews see metabolic benefits from whole dairy
Most recent research links diets rich in full-fat dairy to lower risks for obesity, cardiovascular disease, and diabetes.
For example, studies from Dr. Mario Kratz and his colleagues at Seattle’s Fred Hutchinson Cancer Research Center link higher intakes of dairy fat to better blood sugar control and lower liver-fat levels.
(Elevated liver-fat levels raise the risk for diabetes, because excess fat in liver cells makes them less sensitive to insulin.)
And an evidence review published by Dr. Kratz’s team concluded that full-fat dairy does not raise risks for obesity and heart disease.
In fact, his Seattle group found that most of the studies in their review linked higher dairy fat intakes to lower rates of obesity.
What about milk's estrogen compounds?
The naturally occurring estrogenic hormones in cow's milk may stimulate the growth of cancer cells, while reducing the risk of certain types of breast cancer.
Although some population studies link dairy products to very slightly higher risks for prostate, ovarian, and uterine cancers, others do not.
As it happens, fat-free (skim) milk has the lowest levels of naturally occurring estrogenic hormones, while low-fat (1%, 2% and buttermilk) milk has higher levels than those found in full-fat milk.
And while this remains a matter of debate, the levels of IGF-1 growth hormone in milk from the (less than one in five) American dairy cows treated with rbGH (aka rbST) appear too low to exert a significant effect.
However, it seems wise to avoid milk from dairy cows treated with rbGH, if only because of its negative effects on the animals, such as higher risk for painful udder infections that require antibiotic treatment.
Organic, pasture-fed milk looks best
Growing research favors milk and dairy foods from pasture-fed cows.
We covered some of this research in Organic Milk Found Richer in Omega-3s, Grass-Fed Cows' Milk Seen as Healthier, and Organic Produce and Milk Offer Abundant Antioxidants.
In short, the available research shows that milk from pasture-fed cows has more omega-3 fatty acids, a higher (healthier) ratio of omega-3 to omega-6 fatty acids, less saturated fat (which may not matter), and higher levels of CLA … a fatty acid linked to weight control and anti-cancer benefits.
Although these studies compared organic milk to conventionally produced milk, researchers note that these benefits of certifed-organic milk come from the fact that the cows providing it were mostly pasture-fed.
In other words, you shouldn't expect these benefits in organic milk from farms that feed their cows mostly grain — a practice that's more common on large organic dairy farms.
It appears the vast majority of dairy cows in the U.S. are fed a mostly-grain diet, because it's cheaper than grazing them on pasture in temperate months and feeding them cut grasses during winter months.
For what it's worth, you may want to check out a 2006 ranking chart from the Cornucopia Institute, which rates organic milk brands based on criteria described on pages 7-13 of their 2006 report, Maintaining the Integrity of Organic Milk.
Raw-milk debate still rages
We summarized the arguments for and against unpasteurized dairy in Raw Milk Fight Heats Up, and little seems to have changed during the seven intervening years.
Raw milk advocates claim it's more healthful than pasteurized milk, and no less safe when purchased from responsible farms.
And they say that the FDA misrepresents reports of illness caused by raw milk consumption — in ways that exaggerate its dangers — while ignoring nutritional and health shortcomings of the pasteurized product.
Both sides make good points, leaving it up to consumers to research the risks and rewards of raw milk products carefully before making their choice.
What’s the upshot?
Advice to avoid saturated fat often yields unhealthful consequences.
These typically include higher intakes of carbs and polyunsaturated omega-6 fats from vegetable oil — excesses that exert damaging, pro-inflammatory effects.
We need to understand why full-fat dairy foods produce seemingly counterintuitive benefits.
But for now, the available evidence reveals few-to-no reasons to choose low-fat dairy products.
The benefits of whole-fat dairy foods seem to greatly outweigh any potentially negative effects from their saturated fats.
Those benefits include healthy “probiotic” bacteria, if you choose fermented dairy foods like full-fat yogurt and aged cheese.
And the feeling of fullness that whole dairy foods provide can help keep calorie consumption — particularly from carbs that raise blood sugar levels — in check.