A new study reveals that individuals who enjoyed whole milk during the 1970s and early 1980s had a higher risk of mortality. However, beginning in the mid-1980s, a significant change occurred.

Before 1984, the only milk options available in Norway were whole milk and skimmed milk. While milk is known for its numerous health benefits, whole milk contains a substantial amount of fat, with most of its cream remaining intact, resulting in approximately 3.5 percent fat content. The introduction of semi-skimmed milk, with only 1.5 percent fat, in 1984 led to a rapid increase in its popularity. Until now, no one had examined the impact on public health and mortality when consumers switched from whole milk to semi-skimmed and skimmed milk.

Researchers from the Department of Nutrition at the Institute of Basic Medical Sciences at the University of Oslo collected data from three county surveys conducted during the 1970s and 80s, involving nearly 74,000 participants. The researchers then linked these participants to the Norwegian Cause of Death Registry, 40 years later, to assess their health outcomes.

"In the first survey, only whole milk and skimmed milk were available, and milk consumption was high. Whereas two-thirds of participants consumed whole milk in the initial survey from 1974 to 1976, only one-third did during the last survey period from 1985 to 1988—following the introduction of semi-skimmed milk," explains researcher Erik K. Arnesen, the study's first author.

Whole milk and increased mortality risk

The new study, published in The American Journal of Clinical Nutrition, found that individuals who drank a significant amount of whole milk during the 1970s and 80s had a higher risk of dying from cardiovascular diseases and from all causes combined.

"Among different types of milk, this increased risk was only associated with whole milk, not semi-skimmed or skimmed milk. Compared to those who primarily consumed whole milk, participants who drank semi-skimmed or skimmed milk had about a 10 percent lower mortality rate," Arnesen notes.

The research team also specifically examined the risk of mortality from cardiovascular diseases.

"The group that consumed mostly whole milk—an average of 5 dl per day—showed a 13 percent higher mortality rate from heart diseases, with the association being strongest among women. In contrast, individuals who drank semi-skimmed or skimmed milk had a 10 to 12 percent lower risk of dying from heart diseases and heart attacks compared to those who preferred whole milk," he explains.

Arnesen emphasizes that the study assessed only milk intake as a beverage, not milk used in cooking, such as soups or sauces.

Positive effects on public health from switching to semi-skimmed milk

This study suggests that the shift from whole milk to semi-skimmed milk has had a beneficial impact on public health, a development that has not been directly researched until now, according to Arnesen.

The researchers made efforts to account for other factors that might influence health, such as smoking habits, physical activity, education, and the consumption of other beverages, meat, butter, and margarine. One limitation of the study was that participants self-reported their milk intake, which is often subject to inaccuracies.

"Whole milk was a significant source of not only saturated fats but also trans fatty acids. We believe that the fat content in milk primarily accounts for the differences in mortality rates. The nutritional profiles of the different milk varieties are otherwise quite similar," says Arnesen.

Recommendations for low-fat milk consumption

Professor Kjetil Retterstøl, last author of the study, notes the rising popularity of higher-fat milk varieties.

"We're witnessing a growing interest in milk with higher fat content, possibly because it's perceived as being more natural and healthful than low-fat options. However, our findings indicate that this perception is misleading,” he remarks.

Retterstøl emphasizes that for people who consume a lot of milk, the type of milk can significantly affect their health.

The researchers strongly recommend that people continue to drink milk but opt for low-fat varieties, such as semi-skimmed or skimmed milk.

"Nutritional guidelines suggest consuming three servings of milk or dairy products daily, equating to around 5 dl of milk. Regardless of fat content, milk is a valuable source of calcium, iodine, and B vitamins," concludes Retterstøl.

More Information:
Low-fat and Whole Milk Consumption in relation to Cardiovascular and All-Cause Mortality: A prospective cohort study in three Norwegian counties