A common supplement made from yeast may help the immune system fight cancer more effectively, according to new research in mice.
Scientists at Trinity College Dublin and University College Dublin found that yeast beta-glucan changed the development of important immune cells and strengthened their response to tumors.
The research was published in the scientific journal Cell Reports. The study was led by Frederick Sheedy of Trinity College Dublin and Helen Roche of University College Dublin, with Anna Ledwith as the first author.
Beta-glucans are natural fibers found in the cell walls of yeast, mushrooms, oats and some other foods. Different forms can affect the body in different ways, and yeast beta-glucan has attracted attention because it can interact with the immune system.
The immune system does much more than protect people from viruses and bacteria. It also constantly checks the body for damaged or unusual cells, including cells that could develop into cancer.
Cancer can be difficult for the immune system to control because tumor cells can avoid or weaken normal immune defenses. Obesity can add another problem because long-term changes caused by excess body fat may interfere with the way immune cells are produced and how well they work.
The researchers wanted to know whether eating yeast beta-glucan could change this process. In particular, they studied whether the supplement could influence young immune cells in the bone marrow before those cells fully developed.
Bone marrow is the soft tissue inside bones where many blood and immune cells begin their lives. Changes at this early stage could potentially affect how later generations of immune cells respond when the body encounters a threat.
The team fed mice either a standard diet or a high-fat diet and added yeast beta-glucan to some of the animals’ food. The supplement was given for periods ranging from four to 12 weeks.
The scientists then exposed the animals’ immune systems to cancer cells from colorectal cancer, skin cancer and breast cancer. This allowed them to examine whether the dietary supplement changed the immune response across several types of cancer.
The results suggested that yeast beta-glucan produced a form of long-lasting immune training. It changed early cells in the bone marrow in ways that led to stronger cancer-fighting activity later.
This idea is sometimes called trained immunity. Unlike the highly specific memory created by some immune cells after an infection or vaccination, trained immunity involves broader changes that can make the body’s first line of defense respond differently to later threats.
An important finding involved mice with obesity. Obesity can leave lasting changes in the immune system, and some of these problems may continue even after weight is lost.
In the experiments, the yeast supplement helped restore anti-tumor immune activity in obese mice. It also appeared to reverse some lasting immune problems that remained after weight loss.
The researchers say this is important because losing weight does not necessarily return every part of the body to its earlier state immediately. Previous obesity can leave a biological memory that may continue to influence inflammation, metabolism and immune function.
The study also differs from some earlier work on beta-glucan because the compound was given through the diet. Previous experiments showing immune training often delivered beta-glucan by injection.
A dietary approach would be much easier to use if similar benefits were eventually confirmed in people. The specific yeast beta-glucan used in the study is already produced as a food-grade commercial ingredient, which could make human testing easier to organize.
The researchers believe the approach could eventually be studied in people with obesity, chronic infections or other conditions in which immune defenses do not work normally. It might also be investigated as an addition to established cancer treatments rather than as a replacement for them.
However, the results need careful interpretation. The experiments were conducted in mice, and treatments that produce strong immune effects in laboratory animals often do not work in exactly the same way in humans.
The research also does not show that taking an over-the-counter yeast supplement can prevent or treat cancer in people. Human clinical trials will be needed to determine an effective dose, possible risks, which patients might benefit and whether the supplement improves meaningful cancer outcomes.
Overall, the findings provide an interesting example of how diet may influence the immune system at a surprisingly early stage of immune-cell development.
If the effect can be confirmed in people, dietary beta-glucan could one day become a relatively simple way to support other treatments, but the evidence is still at an early preclinical stage.
Source: Trinity College Dublin and University College Dublin.
