The Link Between Dairy Milk And Lowered Cholesterol and Reduced Risk Of Coronary Heart Disease

A new study talks about how drinking dairy milk is linked to lowered cholesterol levels. The researchers did a meta-analysis study involving three different surveys with more than 400,000 participants. What they found is that despite consuming milk leading to higher body fat and body mass index (BMI), it can also lower the risk of coronary heart disease.

Dairy milk is considered a complex substance, containing at least 18 of 20 essential proteins and amino acids, and it also comprised of saturated fats. This is also a large reason why there have been conflicting results on its role in cardiometabolic diseases, as well as its effect on cholesterol levels.

The University of Reading in the United Kingdom recently published a study that tries to resolve these conflicts. Notably, the study is also based on a meta-analysis of three other large population studies.

The authors deduce that those who drink dairy milk may possibly have lower levels of the two different kinds of cholesterol, alongside a lower risk of coronary heart disease as compared to those that don’t drink milk. Moreover, those that drink milk also have higher body fat and BMIs, factors that are normally linked to a higher risk of cardiovascular issues.

Vimal Karani, professor of nutrigenetics and nutrigenomics at the University of Reading, who also happens to be the lead author of the study, outlines the study as, “We found that among participants with a genetic variation that we associated with higher milk intake, they had higher BMI [and] body fat, but importantly had lower levels of good and bad cholesterol. We also found that those with the genetic variation had a significantly lower risk of coronary heart disease. All of this suggests that reducing the intake of milk might not be necessary for preventing cardiovascular diseases.”

The study was done in collaboration with other research groups from the University of Reading, the University of South Australia in Adelaide, the Southern Australian Health and Medical Research Institute which is also found in Adelaide, the University of Auckland in New Zealand and the University College London in the U.K. The study results can be seen in the International Journal of Obesity.

Taking A Genetic Approach

According to the authors of the study, they note that the possible reasons for such contradictory results of former studies could be due to unknown confounding factors. Or possibly, there were confounders which the other studies had not taken into account. One example of this could be that those who drink milk also smoke heavily and eat tons of butter, which in turn is what raises their cholesterol levels and risk of heart disease.

A large limitation to the study would be if researchers don’t bother to consider the confounders, which in turn could create a nonexistent association between drinking dairy milk and high cholesterol and a higher risk of heart disease.

Another issue with former studies is what’s known as reverse causation. More often than not, people are advised by their doctors to lessen their dairy intake. If researchers don’t know if people have actually lessened their dairy intake or not while doing their study, then their analysis could imply that ‘the excess weight was due to a low rather than a high dairy product intake.’

There is an approach which scientists could use to overcome this issue, which is to use information about genetic variation. These studies are called Mendelian Randomization Studies.

It’s important to note that because genetic variations begin at conception, reverse causation is not something that can affect them. Moreover, in this same manner, genetic variations also shouldn’t affect ‘the tendency of someone to undertake a genetically unrelated behavior or show a raised physiological variable that is unconnected.’

For instance, there are some individuals that have a genetic variation that makes milk consumption higher, and because of that it won’t influence the amount of cholesterol they have in their blood, or the other genes that also dominate that particular factor. Hence, those people with the variant that consume milk and have lower or higher cholesterol, then they can ascertain that the milk is what determines their cholesterol levels and not another variable.

In order to better understand this, the research group of the new study did exactly this, they found a strong link ‘between the lactase persistence genotype variation and people who drink milk.’ And what they found was that the association using data from the GWAS Catalog didn’t see any connection with the lactase persistent variant except for increased obesity in some.

In order to have better results, the scientists of the new study chose to classify those that drink milk as the ones with the gene variation.

Dr. Edo Paz of K Health was asked by Medical News Today to share what he thought on this particular approach. He explained that these studies “may minimize biases that we typically see in observational studies, although cofounding factors that affect the relationship between milk consumption and disease may still be present.”

The Data Was Collected from Hundreds of Thousands of People

The research group used the meta-analysis data taken from three big studies. They were the Health and Retirement Study, the UK Biobank, and the 1958 British Birth Cohort. All in all, the data was collected from 417,236 people in total.

What the study authors deduced that ‘people with the gene variant had lower levels of low-density lipoprotein, total, and high-density lipoprotein cholesterol.’

They share that there are four possible reasons for this, which are found below.

1. Those who drink milk could be consuming less fat than those who don’t drink milk. They also believe that this is a category includes lactose-intolerant individuals but can still manage to eat butter and high fat cheese.
2. The lactose and calcium in the milk actually enhances the absorption of calcium, which in turn lessens cholesterol levels.
3. There could be an change or lowering of cholesterol synthesis due to gut microbial fermentation of indigestible carbohydrates.
4. The calcium in milk could multiply bile acids excretions, which come from the cholesterol in the liver. If and when the bile excretions get higher, then cholesterol concentrations could ultimately drop.

The study also says that individuals that drink milk could also have a lowered risk of developing coronary heart disease by 14%.

According to Prof. Karani, “The study certainly shows that milk consumption is not a significant issue for cardiovascular disease risk even though there was a small rise in BMI and body fat among milk drinkers. What we do note in the study is that it remains unclear whether it is the fat content in dairy products that is contributing to the lower cholesterol levels or an unknown ‘milk factor’.”

The data taken from the UK Biobank study shows that those individuals that consume dairy milk actually had a lower risk of developing type 2 diabetes by 11%. The researchers were not completely convinced that there is a genuine link between this particular type of behavior and ultimately getting diabetes or at least the symptoms of diabetes.

Dr. Paz also explained to MNT about his thoughts on the study, “I would continue to follow the recommendation from the American Heart Association, which suggests that adults eats 2-3 servings of fat-free or low fat dairy products per day.”