Written by: Sandeep Ravindran, Ph.D. | Issue # 99 | 2020
- Investigations of the effects of dairy products on cardiometabolic risk often have mixed or inconclusive results.
- A new study investigated the association between habitual consumption of various types of dairy products and markers of metabolic risk and adiposity (body fatness).
- Data from a large cohort of more than 15,000 adults from the European Prospective Investigation into Cancer and Nutrition–Norfolk (EPIC-Norfolk) study in the United Kingdom were evaluated.
- Different types of dairy products have different health effects, with fermented dairy products such as yogurt or low-fat cheese showing the most beneficial associations with metabolic risk.
- Dairy consumption and cardiometabolic risk are most likely linked through the adiposity and lipid pathways.
Researchers have long been interested in understanding the effects of different types of dairy products on cardiometabolic health (1–3). Studies have looked at the effects of consuming different types of dairy on metabolic markers such as body weight, body fat, lean mass, or cholesterol. Although some studies have found that dairy products are associated with lower cardiometabolic disease incidence, other study results have been mixed or inconclusive (4–10). As a result, there’s still a lot researchers don’t know about the effects of long-term habitual dairy consumption on cardiometabolic risk, or the potential pathways linking the two.
A new study led by Professor Nita Forouhi at the University of Cambridge investigated associations between habitual consumption of various dairy products and markers of metabolic risk and adiposity (body fatness) among adults in the United Kingdom (11). “We wanted to expand the understanding about a link between different types of dairy products and health,” says Forouhi. “Diet is a dynamic behavior, which might change over time, therefore it would be informative to assess how the change in dairy consumption would influence the change in intermediate markers of longer term disease,” she says.
Forouhi and her colleagues examined associations between changes in dairy consumption, assessed with a food-frequency questionnaire, and parallel changes in cardiometabolic markers. “We tested the parallel change of types of dairy consumption and the body’s metabolic markers of risk, which has not been done much in past research as this is more complex,” says Forouhi (10,12-14). “This approach can help to give results in observational studies, such as ours, to be closer to those from clinical trials, which are considered a better form of study design but are notoriously difficult to perform well for nutritional factors,” she says (15).
The researchers were also interested in teasing apart the effects of different types of dairy products. “Prior research from us and others had indicated that yogurt and cheese consumption might be favorably associated especially with type 2 diabetes,” she says. “Since there is sparse research on why that might be, we studied links with intermediate markers of disease processes such as body fatness, blood fats and blood sugar,” says Forouhi.
The researchers evaluated data from the European Prospective Investigation into Cancer and Nutrition–Norfolk (EPIC-Norfolk) study in the United Kingdom (16). “In the EPIC-Norfolk Study we had a rich data source on a large number of adults with data collection at two time points, which enabled us to do our research among more than 15,000 people with diet and other parameters measured an average of 3.7 years apart,” says Forouhi.
Their approach was not without its limitations. “Our study is observational, meaning we did not do a clinical trial of a dietary intervention with changing people’s consumption of different types of dairy products,” says Forouhi. “We have to be careful about the interpretation of findings as we cannot conclude about a cause and effect because other factors may interfere,” she says. “However we did the best we can to try and account for many such factors such as underlying other health behaviors and social and other dietary factors as well as age, sex and body mass index of the participants,” says Forouhi.
The new study found that different types of dairy products have different health effects, with fermented dairy products such as yogurt or low-fat cheese showing the most beneficial associations. “Of all the dairy types, fermented dairy products—including all yogurt or low-fat cheese—showed the most beneficial associations, with a lower increase in body weight and body mass index (BMI),” says Forouhi. “In general, low-fat dairy products were associated with a better blood fat profile,” she says. In contrast, increasing total high-fat dairy consumption was associated with higher increases in adiposity measures such as body weight or BMI and major lipid (or blood fat) markers.
The findings highlight differences among various types of dairy products. “Not all dairy products are equal for health,” says Forouhi. “There are differences in the health effects of different types of dairy products so we should think about individual types rather than all in the same category,” she says. “Our research findings also complement results from clinical trials, as we assessed the habitual consumption over longer periods of time,” says Forouhi.
The researchers also attempted to identify pathways linking dairy consumption to metabolic disease. “Of all the cardiometabolic markers we examined, including body fatness, blood fats, blood sugar, and blood pressure, dairy products were mostly associated with adiposity and lipids, making them the most likely pathways linking dairy consumption to cardiometabolic disease,” says Forouhi. “We previously showed that higher consumption of fermented dairy products was related with lower risk of future type 2 diabetes, and now our current study highlights that the body’s pathways that underpin this link are likely to be through body fat and blood fats,” says Forouhi (17).
Forouhi and her colleagues are planning to conduct follow-up studies. “We think it is really important to do follow up research as we still have further to go before we can make definitive dietary recommendations to the public,” she says. “For example, we are using blood metabolomics data, which refers to the group of small molecules in our body, to identify potential markers that may reflect dairy consumption,” says Forouhi. “This could open up a future way, together with other blood markers of dairy fat, to test links with diabetes and other diseases using objective methods,” she says.
“We are also using genetic data to identify potential predictors of dairy consumption and use them in a method called Mendelian randomization, which allows us to explore whether the associations under study may be about cause and effect,” says Forouhi. “This can also help to get results that can approximate the findings from clinical trials, which are very hard to do in nutritional research,” she says.
The researchers also suggest that it would be important to study other populations and countries, and to look at fermented and non-fermented dairy types separately rather than all dairy combined into one category. “Also, it would be really helpful to look at the effects of different types of dairy products on the gut, the gut microbes, and the gut microbiome that can influence health outcomes,” says Forouhi.
Forouhi’s research methodology could also help inform how follow-up studies are conducted. “The methods we used can inform better conduct of future research,” says Forouhi. “In nutritional research, to increase the confidence in findings, it is important to have consistency of results between different types of studies,” she says. “Our findings complement prior evidence and this is important for increasing our scientific understanding because previously there has been a lot of confusion about dairy products and health outcomes.”
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