Could milk reduce the risk of coronary heart disease?

  • A new study suggests that consuming dairy milk may lower cholesterol levels.
  • The study consists of a meta-analysis of three surveys involving more than 400,000 people.
  • Scientists have found that even though drinking milk leads to an increase in body mass index (BMI) and body fat, it still lowers the risk of coronary heart disease.

Cow’s milk is a complex substance. For example, it contains 18 of 20 essential proteins and amino acids, but it also contains saturated fat.

Perhaps this is why attempts to definitively identify its role in cardiometabolic disease and its effect on cholesterol levels have produced conflicting results.

A recently published study from the University of Reading in the UK attempts to resolve these contradictions. The study is based on a meta-analysis of three existing studies on a large population.

The authors conclude that people who consume cow’s milk have lower levels of both types of cholesterol and a lower risk of coronary heart disease than people who do not drink milk.

Despite this, people who drink milk have a higher BMI and more body fat. These are generally considered to be risk factors for cardiovascular problems.

Principal author of the study Vimal karani, professor of nutrigenetics and nutrigenomics at the University of Reading, summarizes the results of the study:

“We found that among the participants with genetic variation that we associated with higher milk consumption, they had a higher BMI. [and] body fat, but had lower levels of good and bad cholesterol. We also found that people with the genetic variation had a significantly lower risk of coronary artery disease. All of this suggests that reducing milk intake may not be necessary to prevent cardiovascular disease. “

The study was a collaboration involving researchers from the University of Reading, University of South Australia in Adelaide, Southern Australian Health and Medical Research Institute, also in Adelaide, University College London in the UK Uni and the University of Auckland in New Zealand.

The results appear in the International Journal of Obesity.

The study authors note that conflicting results from previous studies may have to do with unknown confounding factors, or confounding factors that the studies did not measure well enough. For example, people who drink milk may also eat more butter and smoke more, which increases their risk for cholesterol and heart disease.

If researchers ignore these confounding factors, they can identify an association between drinking milk and high cholesterol and a risk of heart disease that may not exist.

Another problem with previous studies is reverse causality. People who are overweight often receive advice on how to reduce their intake of dairy products. If scientists do a study without knowing when these people cut back, the analysis could suggest that the excess weight was due to low rather than high consumption of dairy products.

One approach that scientists can take to overcome this problem is to use information about genetic variation. These studies are called Mendelian randomization studies.

Since genetic variations arise from conception, reverse causation cannot influence them. Also, they should not affect a person’s tendency to engage in behavior that is not genetically related or to show a high physiological variable that is not related.

For example, a genetic variation that makes milk consumption more likely will not directly influence the amount of cholesterol a person has in their blood because other genes control this factor. Therefore, if people with the variant drink milk and have higher or lower cholesterol levels, we can deduce that it was the milk that influenced the cholesterol rather than some other variable.

This is exactly what the researchers behind this new study did. They took advantage of a strong association between persistence of lactase genotype variation and people who drink milk. They then confirmed this link using data from the GWAS Catalog and found no other association with persistent lactase variant other than increased obesity.

Therefore, for the purpose of the present study, the researchers identified people who drink milk as those with the gene variation.

Medical News Today request Dr Edo Paz, of K Health, to comment on this approach. He said that such studies “can minimize the bias that we typically see in observational studies, although confounding factors that affect the relationship between milk consumption and illness may still be present.

The researchers performed their meta-analysis on data collected for three large studies: 1958 British birth cohort, the Health and retirement study, and the British Biobank. In total, they included data for 417,236 people in their research.

The study authors conclude that people with the gene variant had lower levels of low-density lipoproteins, total cholesterol, and high-density lipoproteins.

Researchers suggest four possible explanations for this:

  • Calcium and lactose in milk can improve calcium absorption, which lowers cholesterol levels.
  • People who drink milk may consume less fat than people who do not drink milk, a category that includes people who are lactose intolerant who may still consume fatter cheese and butter.
  • Calcium in milk can increase the excretion of bile acids. These acids come from cholesterol in the liver, so if excretion increases, cholesterol concentrations may eventually drop.
  • Intestinal microbial fermentation of nondigestible carbohydrates may alter and reduce cholesterol synthesis.

The study also found that people who drink milk have a 14% lower risk of developing coronary heart disease.

Professor Karani says:

“The study certainly shows that milk consumption is not a significant issue for cardiovascular disease risk, even though there was a slight increase in BMI and body fat in milk drinkers. What we do note in the study is that it is still not known whether it is the fat content of dairy products that contributes to lowering cholesterol levels or an unknown “milk factor”.

In data from UK Biobank, people who drink milk had an 11% lower risk of developing type 2 diabetes, although researchers are not convinced of a real link between this behavior and the development of diabetes. or its symptoms.

Regarding the findings of the study, Dr Paz said MNT, “I would continue to follow the recommendation of American Heart Association, which suggests that adults consume 2-3 servings of fat-free or low-fat dairy products per day. “


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