The RNZ item addressed a raft of beliefs about food. It said:
Saturated fat is bad for your heart. We should eat five servings of fruit and vegetables a day. Forget salt. Eat no more than two eggs a day…
These are just a few of the myriad food rules we are encouraged to abide by each and every day. But how many of these common health advice rules are backed by science? And which of them are bunkum?
A new study out of Sweden says decades of official dairy wisdom is incorrect, suggesting dairy fats can actually protect us against heart attack and stroke. Dr Ali Hill is a Registered Nutritionist and Professional Practice Fellow in the Department of Human Nutrition at the University of Otago. She runs the rule over some of the most well-known food myths that are out there.
The Swedish research amongst the world’s biggest consumers of dairy foods shows that those with higher intakes of dairy fat — measured by levels of fatty acids in the blood — had a lower risk of cardiovascular disease compared to those with low intakes. Higher intakes of dairy fat were not associated with an increased risk of death.
Researchers then combined the results of this study in just over 4,000 Swedish adults with those from 17 similar studies in other countries, creating the most comprehensive evidence to date on the relationship between this more objective measure of dairy fat consumption, risk of cardiovascular disease (CVD) and death.
Dr Matti Marklund from The George Institute for Global Health, Johns Hopkins Bloomberg School of Public Health, and Uppsala University said that with dairy consumption on the rise worldwide, a better understanding of the health impact was needed.
“Many studies have relied on people being able to remember and record the amounts and types of dairy foods they’ve eaten, which is especially difficult given that dairy is commonly used in a variety of foods.
“Instead, we measured blood levels of certain fatty acids, or fat ‘building blocks’ that are found in dairy foods, which gives a more objective measure of dairy fat intake that doesn’t rely on memory or the quality of food databases,” he added.
“We found those with the highest levels actually had the lowest risk of CVD. These relationships are highly interesting, but we need further studies to better understand the full health impact of dairy fats and dairy foods.”
Dairy and dairy product consumption in Sweden is among the highest worldwide. An international collaboration between researchers in Sweden, the US and Australia assessed dairy fat consumption in 4150 Swedish 60-year-olds by measuring blood levels of a particular fatty acid that is mainly found in dairy foods and therefore can be used to reflect intake of dairy fat.
They were then followed up for an average of 16 years to see how many had heart attacks, strokes and other serious circulatory events, and how many died from any cause during this time.
After statistically adjusting for other known CVD risk factors including things like age, income, lifestyle, dietary habits, and other diseases, the CVD risk was lowest for those with high levels of the fatty acid (reflecting high intake of dairy fats). Those with the highest levels had no increased risk of death from all causes.
Dr Marklund added that the findings highlight the uncertainty of evidence in this area, which is reflected in dietary guidelines.
“While some dietary guidelines continue to suggest consumers choose low-fat dairy products, others have moved away from that advice, instead suggesting dairy can be part of a healthy diet with an emphasis on selecting certain dairy foods — for example, yoghurt rather than butter — or avoiding sweetened dairy products that are loaded with added sugar,” he said.
Combining these results with 17 other studies involving a total of almost 43,000 people from the US, Denmark, and the UK confirmed these findings in other populations.
“While the findings may be partly influenced by factors other than dairy fat, our study does not suggest any harm of dairy fat per se,” Dr Marklund said.
Lead author Dr Kathy Trieu from The George Institute for Global Health said that consumption of some dairy foods, especially fermented products, have previously been associated with benefits for the heart.
“Increasing evidence suggests that the health impact of dairy foods may be more dependent on the type — such as cheese, yoghurt, milk, and butter — rather than the fat content, which has raised doubts if avoidance of dairy fats overall is beneficial for cardiovascular health,” she said.
“Our study suggests that cutting down on dairy fat or avoiding dairy altogether might not be the best choice for heart health.”
“It is important to remember that although dairy foods can be rich in saturated fat, they are also rich in many other nutrients and can be a part of a healthy diet. However, other fats like those found in seafood, nuts, and non-tropical vegetable oils can have greater health benefits than dairy fats,” Dr Trieu added.
Kathy Trieu, Saiuj Bhat, Zhaoli Dai, Karin Leander, Bruna Gigante, Frank Qian, Andres V. Ardisson Korat, Qi Sun, Xiong-Fei Pan, Federica Laguzzi, Tommy Cederholm, Ulf de Faire, Mai-Lis Hellénius, Jason H. Y. Wu, Ulf Risérus, Matti Marklund. Biomarkers of dairy fat intake, incident cardiovascular disease, and all-cause mortality: A cohort study, systematic review, and meta-analysis. PLOS Medicine, 2021; 18 (9): e1003763 DOI: 10.1371/journal.pmed.1003763
Sources: RNZ and ScienceDaily