Got (Skim) Milk? - Dr. Chan’s work reveals non-fat milk consumption may help to prevent liver fat accumulation
Dr. Catherine Chan
Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD) is one of the most common liver diseases with over 1.3 billion people affected worldwide. Much like other serious chronic ailments, like cancer and cardiovascular disease, it’s considered a silent condition as many of the symptoms are not noticed until the disease has progressed. In that case, the consequences are life-altering and may only be remedied through liver transplantation.
The problem behind MASLD is too much fat, more specifically, too much fat in the liver. The liver is important for whole body metabolism, especially for fat metabolism. It receives fat from the food we eat and from our own fat stores (specially during fasting). Inside the liver, fat can be burned into energy inside mitochondria (the powerhouse of the cell) or packaged and sent to other parts of the body.
But there is only so much fat that the liver can handle. Too much fat makes it hard for the mitochondria to keep up. This causes the production of toxic molecules, named reactive oxygen species, or ROS. As ROS increases, so does the chance for inflammation and the risk of liver tissue becoming stiffer and non-functional, also known as fibrosis. Over time, long-lasting inflammation reduces the liver’s ability to regenerate. In individuals consuming high fat diets as well as those suffering from obesity and type 2 diabetes, a vicious cycle occurs that eventually disrupts liver function and causes the need for liver transplant.
It would seem the easiest way to prevent MASLD would be to eat less fat. That’s partly true. After all, diet and exercise are the first management steps recommended to prevent or MASLD. The Canada’s Food Guide promotes several options for ensuring a healthy diet. This includes dairy, an excellent source of protein and calcium. The guidelines usually suggest replacing high fat dairy for low fat options to improve health, such as switching from whole-milk to low fat milk. At first glance, this seems to be a good idea. But in terms of MASLD, does the fat content really matter? Or does the benefit of milk at any fat content take precedence?
With this in mind, Dr. Catherine Chan’s group investigated the benefits that cow’s milk consumption would bring to the table in the context of obesity and MASLD. Led by former MSc student Emily Berg, they tested whether milk could prevent fat buildup in the liver caused by a high-fat diet. They also compared whole milk with nonfat milk.Their results are published in The Journal of Nutrition.
In their study, mice were fed a high-fat diet to induce obesity and later a very low amount of milk was added to their diet. The mice that consumed nonfat milk had less body fat and less fat in the liver than the mice that received only a high-fat diet or whole-milk. They observed that the ingestion of nonfat milk might have increased the capacity of the liver to burn fat (fatty acid oxidation) by boosting the liver’s mitochondria. The exact mechanism for the protective effects still needs further investigation. However, dairy is considered a functional food containing bioactive molecules that may change how fat and other nutrients are metabolized in the body. This per se, might have contributed to their findings.
Even though per capita cow’s milk consumption has decreased over the past 2 decades, their work makes one think twice and realize that, maybe, we are not ready to ditch the milk just yet! It highlights that the food that we eat are more than just calories, they have a real impact on our metabolism. Although studies in the human population are still needed to consolidate the role of milk in the prevention of MASLD, dairy products might act as a functional food supporting better health.