For people with established cardiovascular disease (CVD), higher consumption of various dairy products was associated with poorer health outcomes in a Norwegian study.
According to clinical dietitian Vegard Lysne, PhD, increased daily intakes of dairy products and total milk were significantly associated with increased risks of stroke, cardiovascular mortality, and all-cause mortality during a follow-up generally extending over 5 to 14 years in patients with stable angina. , University of Bergen and Haukeland University Hospital, and colleagues.
Acute myocardial infarction (MI) had no clear linear relationship with total dairy intake or milk consumption, but the risk was increased when butter exceeded 2 g/1000 kcal in the diet a person’s daily life.
Similarly, data were inconclusive regarding cheese consumption and cardiovascular risk, as higher cheese consumption had no significant association with acute MI, stroke, CVD mortality or all-cause mortality, the study authors reported in the report. European Journal of Preventive Cardiology.
Thus, the study paints a more complicated picture of dairy-related risks that supports other observational data suggesting that different dairy products may have different effects. “We can speculate that at least part of the differential associations observed for milk, butter and cheese may be due to the cheese containing intact MFGM. [milk fat globule membrane]while milk and butter do [sic] not,” Lysne’s team wrote.
Still, overall, dairy products are “likely harmful,” the verdict on cheese is unclear, and some fermented dairy products may be less harmful if dairy products are to be consumed, commented Andrew Freeman, MD. , a cardiologist at National Jewish Health in Denver, who was not involved in the study.
Even without a randomized trial, Freeman said in an interview, “there is enough signal in the noise to draw the conclusion that high-fat dairy products, the main source of saturated fat in our diets, are unlikely to be helpful. to human health, and heart health in particular.”
He cautioned, however, that there could be global variations in the effects of dairy products. Dairy products may differ between countries that place more restrictions on raising cattle with certain chemicals, such as growth hormones, and those that do not. For example, the United States allows recombinant somatotropin treatment of dairy cows, while the European Union, Australia and Japan do not.
Nevertheless, the large PURE study of people around the world consistently found the best clinical results in those who ate a balanced diet including plenty of fruits and vegetables and a modest amount of dairy products, unprocessed red meat, nuts and of legumes. The PURE researchers had separately challenged the association of fat (including saturated fat) with mortality and also reported that compared to no dairy, eating at least two servings a day was linked to less cardiovascular disease and mortality.
Current US dietary guidelines recommend a few servings of low-fat or fat-free dairy products per day. There is no mention of specific products except to discourage the consumption of cream, sour cream and cream cheese due to their low calcium content.
“Dairy products are a heterogeneous food group with divergent health effects and therefore dairy products should be studied individually,” Lysne and colleagues argued.
Their analysis was based on 1929 patients with stable angina (80% male, mean age 62 years) from the Western Norway B Vitamin Intervention Trial.
All had undergone coronary angiography for suspected coronary artery disease or aortic stenosis in 1999-2004. Preventive medication use was high and included aspirin (90%), statins (90%) and beta-blockers (77%).
Participants self-reported their eating habits on a food frequency questionnaire. The average consumption of dairy products would have been 169 g/1000 kcal; the main component was usually milk (133 g/1000 kcal).
The observational nature of the study left room for bias and confounding when assessing the relationship between dairy product consumption and CVD risk.
Indeed, Lysne’s group found that people who ate more dairy products tended to eat less meat, vegetables, fruits and berries, fish and potatoes. These people also got more calories from protein and less from fat (excluding saturated fat).
Other limitations of the study include the lack of additional dietary assessments over the years of follow-up and the potential for participants to mischaracterize their diet when surveyed. Additionally, the findings may have limited generalizability to the general population and to people in other settings, the study authors acknowledged.
Lysne and Freeman have disclosed no conflicts of interest.