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Higher intake of dairy fat associated with lower risk of cardiovascular disease

Higher intakes of dairy fat – measured by levels of fatty acids in the blood – were associated with decreased risk of cardiovascular disease (CVD) and had no affect on all-risk mortality, found an international meta-analysis combined with a large Swedish cohort study, published in PLOS Medicine.

Researchers then combined the results of this study,  in just more than 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 4,150 Swedish 60-year-olds by measuring blood levels of a particular fatty acid mainly found in dairy foods and that therefore can be used to reflect intake of dairy fat.

They were 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.

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,” 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.”

Study details
Biomarkers of dairy fat intake, incident cardiovascular disease, and all-cause mortality: A cohort study, systematic review, and meta-analysis.

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.

Published in PLOS Medicine on 21 September 2021

Abstract

Background
We aimed to investigate the association of serum pentadecanoic acid (15:0), a biomarker of dairy fat intake, with incident cardiovascular disease (CVD) and all-cause mortality in a Swedish cohort study. We also systematically reviewed studies of the association of dairy fat biomarkers (circulating or adipose tissue levels of 15:0, heptadecanoic acid [17:0], and trans-palmitoleic acid [t16:1n-7]) with CVD outcomes or all-cause mortality.

Methods and findings
We measured 15:0 in serum cholesterol esters at baseline in 4,150 Swedish adults (51% female, median age 60.5 years). During a median follow-up of 16.6 years, 578 incident CVD events and 676 deaths were identified using Swedish registers. In multivariable-adjusted models, higher 15:0 was associated with lower incident CVD risk in a linear dose–response manner (hazard ratio 0.75 per interquintile range; 95% confidence interval 0.61, 0.93, P = 0.009) and nonlinearly with all-cause mortality (P for nonlinearity = 0.03), with a nadir of mortality risk around median 15:0. In meta-analyses including our Swedish cohort and 17 cohort, case–cohort, or nested case–control studies, higher 15:0 and 17:0 but not t16:1n-7 were inversely associated with total CVD, with the relative risk of highest versus lowest tertile being 0.88 (0.78, 0.99), 0.86 (0.79, 0.93), and 1.01 (0.91, 1.12), respectively. Dairy fat biomarkers were not associated with all-cause mortality in meta-analyses, although there were ≤3 studies for each biomarker. Study limitations include the inability of the biomarkers to distinguish different types of dairy foods and that most studies in the meta-analyses (including our novel cohort study) only assessed biomarkers at baseline, which may increase the risk of misclassification of exposure levels.

What do these findings mean?
The findings from our study using fatty acid biomarkers suggest that higher intake of dairy fat were associated with lower CVD risk in diverse populations including Sweden (a country with high dairy intake), though more trials are needed to understand if and how dairy foods protect cardiovascular health.

Conclusions
In a meta-analysis of 18 observational studies including our new cohort study, higher levels of 15:0 and 17:0 were associated with lower CVD risk. Our findings support the need for clinical and experimental studies to elucidate the causality of these relationships and relevant biological mechanisms.

 

PLOS article – Biomarkers of dairy fat intake, incident cardiovascular disease, and all-cause mortality: A cohort study, systematic review, and meta-analysis (Open access)

 

See more from MedicalBrief archives:

 

Dairy consumption linked to lower rates of CVD and mortality

 

Unsaturated fat improves cholesterol but not weight loss – research review

 

Regular milk consumption not associated with increased cholesterol

 

The rise and rise of the cholesterol deniers

 

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