Impact of dairy fat on cardiovascular disease

In our last interview, we spoke to Dr Kathy Trieu of the Food Policy Division’s George Institute for Global Health about the impact of dairy fat on cardiovascular disease.

What prompted your latest research on dairy fat and cardiovascular disease?

We undertook this study on dairy fat and cardiovascular disease because there was growing evidence to suggest that the health impact of dairy products is more dependent on the type – like cheese, yogurt, milk and butter – rather than just the fat content. This has raised doubts as to whether avoiding dairy fat overall is beneficial for heart health.
A better understanding of the link between dairy fat and cardiovascular disease is important as dairy products are increasingly consumed around the world and are a major source of nutrients.

What research has been done so far on cardiovascular disease and diet?

There is ample evidence from randomized trials, epidemiological studies, population studies, and animal studies that all suggest a clear link between eating habits and cardiovascular disease. These research findings have been widely used to inform national and international dietary guidelines aimed at preventing chronic disease.

The Global Burden of Disease study estimated that one in three deaths from cardiovascular disease worldwide was attributed to a poor diet in 2019.

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What are dairy products and what foods typically contain milk fat?

Dairy products are foods made from the dairy product of animals, usually cow’s milk, although some are derived from the milk of sheep, goats and other animals. Common dairy products include milk, yogurt, cheese, butter, and cream, and they contain varying levels of milk fat.

Why do some dietary guidelines suggest consumers choose products low in dairy?

Most dietary guidelines advise consumers to choose low-fat dairy products because of the high saturated fat and calorie content of high-fat dairy products. Eating more saturated fat can increase “bad” blood cholesterol (LDL) and the risk of cardiovascular disease.

However, more and more research shows that while dairy products can be high in saturated fat, they are high in other nutrients and can be part of a healthy diet. There is also more evidence to suggest that certain dairy products like yogurt and cheese may have more health benefits than others, like butter.

While most dietary guidelines continue to recommend low-fat dairy products, others focus less on the fat content and more on the type of dairy and avoidance of sugary products like flavored milks and sweets. yoghurts.

Why could this information be potentially dangerous?

There is good evidence to recommend low fat unsweetened dairy products, but there is more uncertainty about the health effects of whole dairy products.

Recommendations to avoid dairy fat can be potentially harmful, as consumers can choose low-fat dairy options that are instead loaded with sugar. Eating too much sugar is known to be harmful, leading to weight gain, cardiovascular disease, diabetes, and tooth decay.

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Can you describe how you conducted your latest research on dairy fat and cardiovascular disease?

Our research consisted of measuring the consumption of milk fat in more than 4,000 Swedish adults based on the blood levels of a particular fatty acid (called pentadecanoic acid 15: 0) which is mainly found in dairy products. Participants were then followed for an average of 16 years to see how many had had heart attacks, strokes, and other serious circulatory events, and how many had died of any cause during that time.

Additionally, we searched for all previously published studies that investigated the link between blood fatty acid levels reflecting milk fat intake and cardiovascular disease or death, so that we could combine the results and summarize all the evidence to this day.

What did you find out?

In the Swedish study, after statistical adjustment for other known risk factors for cardiovascular disease, including age, education, lifestyle, eating habits and other diseases, the risk of cardiovascular disease was lowest for people with high levels of fatty acids (reflecting high intake of dairy fat). Those with the highest levels did not have an increased risk of death from all causes.

Combining these results with 17 other studies, involving a total of nearly 43,000 people from the United States, Denmark and the United Kingdom, confirmed the link between higher levels of these fatty acids, reflecting higher intake. high in dairy fat, and a lower risk of cardiovascular disease. These results are very interesting but must be interpreted with caution.

We cannot determine any causality or mechanism of the associations observed. As with any observational study, there is also a possibility that other lifestyle factors may have impacted the associations, despite our attempts to statistically control for these. However, our results do not suggest any harmful effects of milk fat per se.

Many studies have relied on people remembering the amounts and types of dairy products they ate. What are the limits of this? How was your study different?

Many studies that measure milk fat intake by asking people to remember and remember what they ate have several limitations.

First, they rely on participants who honestly report what was eaten and how much, although research shows people tend to report what is considered socially desirable, such as healthier or smaller foods. amounts of unhealthy food compared to what was actually eaten.

Second, they rely on the participant’s memory to remember and report all foods and drinks consumed (including whether they are low-fat or high-fat products) and the amount. This is particularly difficult when quantifying milk fat intake because dairy products are often incorporated into mixed dishes and therefore the amount is difficult to estimate or may be overlooked, for example, cheese sprinkled on the dishes or butter and cream used in cooking.

Third, recalled dietary intakes should be matched with data on the nutritional composition (i.e., milk fat content) of foods in order to estimate the amount of dairy fat consumed that is not. not always available or may be out of date, inaccurate, and unbranded. specific.

Our study overcomes these limitations by objectively measuring the blood levels of certain fatty acids mainly from dairy products, thus acting as a marker of dairy fat intake. However, despite the many advantages of using fatty acids as objective markers, there are some limitations. For example, we have not been able to study associations of different dairy products (like yogurt versus butter) with health outcomes and the levels of these fatty acids may be influenced by other factors. than the simple consumption of milk fat.

What more research needs to be done to fully understand the health impact of fats and dairy foods?

More research is needed to confirm that a higher intake of milk fat leads to a lower risk of cardiovascular disease. Our study currently shows that there is an association between milk fat and cardiovascular disease risk, but we have no evidence that milk fat per se causes this lower disease risk.

Likewise, more research is needed to understand the biological mechanism behind the observed link between milk fat and cardiovascular disease, i.e. which nutrients or properties in dairy products or milk fat reduce the risk. cardiovascular.

What are the next steps in your research?

To better understand these results, we need well-designed randomized controlled trials to study the health benefits of different types of dairy products and compare the effects of low-fat dairy products versus whole dairy products.

Where can readers find more information?

About Dr. Kathy Trieu

Dr Kathy Trieu is a research fellow at the George Institute for Global Health in the Food Policy Division. She is also a Joint Senior Lecturer at the University of New South Wales. Her research is funded by an Early Career Research Fellowship from the National Health and Medical Research Council of Australia and the National Heart Foundation of Australia.

Kathy has completed her doctorate. in the implementation and evaluation of population strategies to reduce salt intake for the prevention of hypertension and cardiovascular disease at the University of Sydney. She also holds a Masters in Public Health and a Bachelor of Applied Science in Nutrition from the University of Sydney.

Kathy’s research focuses on studying the diet-related causes of noncommunicable diseases; the design, implementation and evaluation of nutritional interventions; and influence nutrition policies through modeling and assessments. So far, Kathy has worked with local academics, governments and non-governmental organizations on nutrition and food-related research in 10 countries. Its research aspirations are to undertake high-quality research that can usefully inform effective programs and policies to improve the nutrition and health of all people in countries around the world.