The study, from the University of Eastern Finland, was published in the British Journal of Nutrition. It also concluded that a “very high” consumption of non-fermented dairy products is linked to an increased risk of heart disease.
Adjunct professor in nutrition epidemiology and lead researcher Jyrki Virtanen said that the biological mechanisms underpinning this causal relationship are as yet are not “completely known”.
However, he continued: “The fermentation process adds, for example, probiotics and vitamin K2 in the products, which both may have beneficial health effects. For example, vitamin K2 has been linked to lower risk of cardiovascular diseases.”
This ongoing study, the Kuopio Ischaemic Heart Disease Risk Factor Study, provides further evidence on the health benefits that fermented dairy products may have versus non-fermented ones, the researchers concluded. They said this latest investigation builds on earlier studies that have shown fermented dairy products have more positive effects on blood lipid profiles and on the risk of heart disease than other dairy products.
High consumption of some products cuts risk by one-quarter
Approximately 2,000 men participated in Finnish observational study, which lasted two decades. Their dietary habits were assessed at the beginning of the research period in 1984–1989.
“We used 4-d food recording to assess the dietary intakes. The subjects could use a picture book to estimate portion sizes. A nutritionist gave instructions for filling the records and a nutritionist also checked the filled records with a participant to make sure that they were filled as completely as possible,” Virtanen told FoodNavigator.
The study participants were then divided into groups on the basis of how much they ate of different dairy products. The researchers compared those with the highest and lowest consumption, while also taking various lifestyle and nutrition factors into consideration.
Virtanen noted that the study was based solely on the baseline dietary data, which could represent a “limitation”.
“It is known that use of different dairy products has changed during the last decades in Finland. For example, milk and sour milk intakes have decreased and the use of cheese, quark and yoghurt have increased.
“The use of only one dietary assessment is a limitation in our study where the average follow-up was about 20 years. However, we also investigated the associations with a shorter, 11-year follow-up, and the findings were very similar compared to the findings with the 20-year follow-up.”
After the 20 year follow up, 472 of the 2,000 participants experienced an incident coronary heart disease event.
When participants were divided into four groups on the basis of their consumption of fermented dairy products with less than 3.5% fat, the risk of incident coronary heart disease was 26% lower in the highest consumption group compared to the lowest consumption group. Sour milk was the most commonly used low-fat fermented dairy product.
The consumption of high-fat fermented dairy products, such as cheese, was not associated with a higher risk of incident coronary heart disease.
However, the researchers linked very high consumption on non-fermented dairy products with an increased risk of incident coronary heart disease. Milk was the most commonly used product in this category, and a very high consumption was defined as an average daily milk intake of 0.9 litres. Lower consumption levels were not associated with higher risk.
‘Clinical studies are definitely needed’
The Kuopio Ischaemic Heart Disease Risk Factor findings point to the likelihood that eating lower-fat fermented dairy products reduce the risk of developing heart disease. However, Virtanen said, it is too early to issue health advise based on these results.
“Although there is some previous research data that fermented dairy products may have health benefits, more research is needed because there still are many open questions. Are all fermented dairy products good for health? Does the fat content of a dairy product affect the health effects?”
This research should take the form of clinical trials and advanced research methods, the nutrition expert suggested. “Clinical studies are definitely needed to investigate the health effects of different fermented and non-fermented dairy products. Besides effects on traditional risk factors (such as serum lipids or inflammatory markers or glucose metabolism), the studies are needed to investigate the impact on gut microbiota, which may have an important role for human health. Also, studies should make use of more advanced research methods, such as metabolomics, to get a comprehensive picture of the physiological effects of different dairy products in humans.”
While further study is necessary, some early conclusions can nevertheless be drawn. Virtanen summarised: “Based on the current research data, not all dairy products seem to have a similar impact on health.”
British Journal of Nutrition
‘Intake of fermented and nonfermented dairy products and risk of incident CHD: the Kuopio Ischaemic Heart Disease Risk Factor Study’
Published online 29.10.2018
Authors: Timo T. Koskinen, Heli E. K. Virtanen, Sari Voutilainen, Tomi-Pekka Tuomainen, Jaakko Mursu, Jyrki K. Virtanen.