September 21, 2021

expert reaction to cohort study and review on biomarkers of dairy fat intake, CVD and all-cause mortality

A study, published in PLOS Medicine, looked at biomarkers of dairy fat intake, Cardio Vascular Disease and all-cause mortality. 

Dr Duane Mellor, Registered dietitian and Lead for nutrition and evidence based medicine, Aston Medical School, Aston University, said:

“This is an interesting study which uses a measure of dairy intake in blood, in the form of an odd chain length fat to assess risk of heart disease and risk of death in a population of 60 year olds in Sweden. Although it did not look at actual intake of dairy products, the particular fatty acid they looked at has been previously linked to dairy food intake. In some ways these types of marker can be better as they do not rely on people remembering what they ate and reporting it in a survey. The downside is as it only measures the fat aspect it cannot identify which dairy foods people actually ate, we simply do not know if they ate cheese or yoghurt or drank milk. They also combined they findings with a review of other studies which support the view that dairy food intake has been associated with a lower risk of heart disease. This appears to go against traditional views about saturated fat and heart health. It may be the odd length chain fatty acids which contain 15 or 17 carbon atoms in a chain instead of the usual even number which may make the difference, but to be sure more evidence is needed. Also when reviewing evidence, it is important to check potential influence of food, and in this case the dairy industry, funding research, although in this case no support or influence of food industry bodies were involved. However, the data used in meta-analysis part of the study may have been supported by industry funding which could be seen as a potential source of bias.

“Overall, this is another study which suggests potential reduction in risk of heart disease with consumption of dairy products. Something which many dietary guidelines actually state in their analysis of evidence and data. However when converting this to dietary guidelines, the message about reducing dairy fat can then come through when dietary models such as national plate based dietary guidelines are drawn up and include the need to balance estimated energy (calorie) requirements. Perhaps it is time to be more clear with the public about the effect of dairy fat on cardiovascular health, and that it does not need to be avoided, especially cheese and yoghurt which as well as being sources of protein and calcium have been consistently linked to reduced risk of cardiovascular disease. The evidence for butter is less clear as this can lack these beneficial components, and the extra fat and calories should factor into decisions about food intake.”

Prof Ian Givens, Professor of Food Chain Nutrition, Director, Institute of Food, Nutrition and Health, University of Reading, said:

“Broadly this study supports a good number of earlier studies and meta-analyses which show either a neutral or negative (beneficial) association between consumption of milk and dairy products and risk of CVD. This study used fatty acid biomarkers to specifically target dairy fat because it is rich in saturated fatty acids which are generally assumed to increase CVD risk. As the authors say, there is increasing evidence that the health effects of dairy foods depends on the food type. There is perhaps most evidence available for hard cheese where a range of studies show the physical and chemical food matrix reduces the amount of fat absorbed by the body which leads to moderated or nil increases in blood lipids which are CVD risk factors. But the paper is correct in saying that more studies are needed to better understand the protective effect of very complex dairy foods on CVD.”

‘Biomarkers of dairy fat intake, incident cardiovascular disease, and all-cause mortality: A cohort study, systematic review, and meta-analysis’ by name of first author et al. was published in PLOS Medicine at 19:00 UK time on Tuesday 21 September.

DOI: https://doi.org/10.1371/journal.pmed.1003763

Declared interests

Dr Duane Mellor: No conflicts of interest to declare

None received.