Whole-Fat or Nonfat Dairy? The debate continues – JAMA 2018

Forty year ago US federal government recommended first recommended that everyone except young children opt for low- fat or nonfat dairy products over high-fat dairy products as part of an overall goal of reducing saturated fat intake and calories. However recent studies have suggested that high-fat milk, cheese, and yogurt are at least as healthful as their low-fat or nonfat counterparts, and their authors are questioning the wisdom of advising people to avoid whole milk and products made with it. Just as the evidence suggests that not all food sources of saturated fats—ie, animals, plants, and dairy—are the same, neither are all sources of dairy fats. [Ref]

One of the largest observational studies to look at the association between dairy intake and cardiovascular disease (CVD) and mortality, the Prospective Urban Rural Epidemiology (PURE) study published in 2018, involved 136 384 individuals aged 35 to 70 years in 21 countries on 5 continents. A higher intake of total dairy, defined as more than 2 servings a day, was associated with a lower risk of death or a major cardio- vascular event than no intake.

However, the authors found no significant association between dairy intake and heart attack, and only consumption of milk and yogurt, not cheese or butter, was significantly associated with the studied outcomes. Whole-fat dairy products appeared to be more protective than nonfat or low- fat products, which aren’t available in some PURE countries, including India and South Africa. In Malaysia, people do not drink milk or consume yogurt. Ioannidis states that “extensive residual confounding and selective reporting” in nutritional epidemiologic research can lead to “implausible estimates of benefits or risks associated with diet.”.  In addition self-reported consumption may be limited by errors or reporting bias.

Instead of depending on study participants to accurately report their dairy intake, another study [Ref] looked at the relationship between circulating biomarkers of fatty acids found in dairy products and total mortality, cause-specific mortality, and CVD risk among 2907 US adults aged 65 and older who did not have CVD when the study began. The researchers measured participants’ fatty acid concentrations at baseline and then 6 years and 13 years later. During 22 years of follow-up, none of the fatty acids was significantly associated with total mortality. But high levels of one type of fatty acid, heptadecanoic acid, were inversely associated with CVD and stroke mortality. However, the authors note that other components of dairy products, such as protein, lactose, and minerals, could have confounded these findings.

One reason people opt for low-fat or nonfat dairy products is because they think consuming whole-fat milk, yogurt, and cheese will make them gain weight and will elevate their blood lipids. In fact,  “the data never overwhelmingly showed that full-fat dairy made you gain weight, contributed to heart disease, contributed to metabolic disease.” Actually, he added, “people who eat the most full-fat dairy products in observational studies are usually among the ones who gain the least amount of weight.” That seems counterintuitive, but, it’s very likely that there’s a type of compensation going on.” Low-fat or nonfat dairy isn’t as filling as whole-fat dairy, so people might end up craving unhealthy snacks if they opt for the former, he said. However, he added, “I would never recommend people consume large amounts of butter and cream.”

However another review [Ref] of current evidence suggests null or weak inverse association between consumption of dairy products and risk of cardiovascular disease. However, replacing dairy fat with polyunsaturated fat, especially from plant-based foods, may confer health benefits. More research is needed to examine health effects of different types of dairy products in diverse populations.

The US Department of Agriculture and the US Department of Health and Human Services publish Dietary Guidelines for Americans every 5 years. Development of the 2020-2025 guidelines is already under way, and it might be time to revise the decades-old recommendation about choosing low-fat or nonfat dairy products over full-fat versions. However it is important to remember that ‘Overall dietary pattern is very important, and dairy is only 1 of many food items on our plate’


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