Pooled data from more than 60,000 adults who took part in 16 multi-national studies shows that higher concentrations of dairy-fat biomarkers were associated with lower risk of developing type 2 diabetes.
This lower risk was independent of other major risk factors for type 2 diabetes including age, sex, race/ethnicity, socioeconomic status, physical activity and obesity, said the team writing in PLOS Medicine.
The international consortium behind the meta-analysis was led by scientists at the UK’s Medical Research Council (MRC) Epidemiology Unit at the University of Cambridge, and the Friedman School of Nutrition Science and Policy at Tufts University. Together the team found that people with the highest concentrations of dairy-fat biomarkers had approximately 30% lower risk of type 2 diabete than those with the lowest levels of the biomarkers.
"Our results provide the most comprehensive global evidence to date about dairy fat biomarkers and their relationship with lower risk of type 2 diabetes,” commented lead author, Dr Fumiaki Imamura from the MRC Epidemiology Unit.
Professor Dariush Mozaffarian of Tufts University, a senior author on the paper, noted that while dairy foods are recommended as part of a healthy diet, dietary guidelines in both the US and internationally generally recommend low-fat or non-fat dairy – due to concerns about adverse effects of higher calories or saturated fat.
“Our findings, measuring biomarkers of fatty acids consumed in dairy fat, suggest a need to re-examine the potential metabolic benefits of dairy fat or foods rich in dairy fat, such as cheese,” he said.
International nutritional guidelines commonly recommend regular consumption of dairy products as an important source of key nutrients, however in many countries eating low-fat dairy products is encouraged as part of overall recommendations to limit saturated fat consumption.
Some previous research has suggested that consumption of dairy products, in particular yoghurt and cheese, may be linked with with a lower incidence of type 2 diabetes. However, these findings are inconsistent and the evidence remains controversial.
The FORCE Consortium was established by researchers from Europe, North America, Australia, and Asia to examine the relationships of fatty acid biomarkers with diseases.
Concentrations in body tissue of certain types of fat have been found to correlate with consumption of fat rich dairy foods, both in self-reported studies and in intervention studies where participants eat a controlled diet.
These biomarkers of dairy fat offer a complementary approach, alongside self-reporting of food consumption, to investigate associations of dairy fat consumption with type 2 diabetes in large populations.
“We hope that our findings and existing evidence about dairy fat will help inform future dietary recommendations for the prevention of lifestyle-related diseases,” said Imamura.
The team examined specific biomarkers of dairy fat consumption from a total of 63,682 adults from 16 multi-national studies that are part of the FORCE Consortium.
Participants were all free from type 2 diabetes when the first samples were taken, and 15,158 of them went on to develop type 2 diabetes over the follow-up period of up to 20 years.
In each of the studies, the researchers analysed the relationships of dairy fat biomarkers (odd-chain saturated fats and a natural ruminant trans-fat) with the risk of developing type 2 diabetes.
When all the results of the 16 studies were pooled together the researchers found that those with higher concentrations of dairy-fat biomarkers had a lower risk of developing type 2 diabetes.
Higher circulating and tissue concentrations of odd-chain saturated fats and a natural ruminant trans-fat are associated with lower risk of T2D.
Independently commenting on the research, Professor Tom Sanders of King’s College London noted that the biomarkers used in the study are not unique to dairy, and include oily fish.
“Generally, from the body of evidence as a whole, it seems consistent that dairy may protect from metabolic syndrome and type 2 diabetes – but not butter,” he said. “This review should not be used to advocate eating butter, especially as one large study the review looked at found butter increased insulin resistance compared with olive oil.”
Also commenting on the work Dr Nicola Guess of King’s College London also noted that some of the biomarkers are not specific to dairy, “and they can’t tell us precisely how much was consumed.”
“It is also not clear whether it is the dairy fat which could be behind the benefit, or the other nutrients contained in dairy foods (such as calcium, magnesium or even probiotics),” she said.
Despite the several advantages of evaluating fatty acid biomarkers, the team behind the study also noted that the results cannot distinguish between different types of dairy foods such as milk, cheese, yoghurt, and others.
“We're aware that our biomarker work has limitations and requires further research on underlying mechanisms, but at the very least, the available evidence about dairy fat does not indicate any increased risk for the development of type 2 diabetes,” said Imamura.
Source: PLoS Medicine
Published online, Open access, doi: 10.1371/journal.pmed.1002670
“Fatty acid biomarkers of dairy fat consumption and incidence of type 2 diabetes: A pooled analysis of prospective cohort studies”
Authors: Fumiaki Imamura, et al