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Advice to limit dairy should be reconsidered

Only milk appears to increase the risk of coronary heart disease, other dairy products protect against cerebrovascular events

Ingrid Torjesen

Wednesday, 29 August 2018

Advice to limit intake of dairy produce to reduce cardiovascular risk should be reconsidered, research* presented at ESC Congress 2018, the annual congress of the European Society of Cardiology, suggests.

The consumption of dairy products has long been thought to increase the risk of death, particularly from coronary heart disease (CHD), cerebrovascular disease, and cancer, because of dairy's relatively high levels of saturated fat. Yet evidence for any such link is inconsistent.

They found, that with the exception of milk, which appears to increase the risk of coronary heart disease, dairy products protect against both total mortality and mortality from cerebrovascular causes. Therefore, current guidelines to limit consumption of dairy products, especially cheese and yogurt, should be relaxed, they say, and the drinking of non-fat or low-fat milk should be recommended, especially for those who consume large quantities of milk.

They examined data from a 1999-2010 National Health and Nutrition Examination Surveys (NHANES) study of 24,474 adults with a mean age of 47.6 years, 51.4% of whom were female. NHANES is conducted by the US's Centers for Disease Control and Prevention.

During the follow-up period of 76.4 months, 3,520 total deaths were recorded, including 827 cancer deaths, 709 cardiac deaths, and 228 cerebrovascular disease deaths. The researchers found consumption of all dairy products to be associated with a 2% lower total mortality risk and consumption of cheese to be associated with an 8% lower total mortality risk (hazard ratio [HR]: 0.98, 95% confidence interval [CI]: 0.95-0.99; HR: 0.92, 95% CI: 0.87-0.97, respectively). For cerebrovascular mortality, they found a 4% lower risk with total dairy consumption and 7% lower risk with milk consumption (HR: 0.96, 95% CI: 0.94-0.98; HR: 0.93, 95% CI: 0.91-0.96, respectively).

These results were confirmed in a meta-analysis, also conducted by the researchers, of 12 prospective cohort studies with 636,726 participants followed for approximately 15 years. Milk consumption was associated with a 4% higher CHD mortality, while consumption of fermented dairy products such as yogurt was associated with a 3% lower rate of total mortality. The yogurt finding, however, was not significant after further adjustment (Q4: HR: 0.98, p=0.125).

The researchers concluded that among US adults, higher total dairy consumption protected against both total mortality and mortality from cerebrovascular causes. At the same time, higher milk consumption was associated with an increased risk of CHD, an association that needs further study. Causality, however, could be difficult to determine, as most people who consume milk also consume other dairy products.

Professor Maciej Banach, from the Department of Hypertension at Medical University of Lodz, Poland, said: "In light of the protective effects of dairy products, public health officials should revise the guidelines on dairy consumption. And given the evidence that milk increases the risk of CHD, it is advisable to drink fat-free or low-fat milk."

*Mazidi M,Mikhailidis DP, Howard G, et al. Consumption of dairy product and its association with total and cause specific mortality - A population-based cohort study and meta-analysis. European Heart Journal (2018) 39 (Supplement), 1115.

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