The simple supplement that retrained immune cells to fight cancer

The word “yeast” may bring to mind a fragrant loaf of bread, a glass of beer or the savory nutritional yeast flakes used as a substitute for cheese.

But researchers have identified a far more surprising possibility for a compound derived from yeast: It may be able to retrain the immune system to fight cancer more effectively.

In obese mice, a food-grade yeast beta-glucan reprogrammed developing immune cells inside the bone marrow, producing stronger cancer-fighting cells.

Even more remarkably, it reversed long-lasting immune defects that persisted after the animals lost weight — something no other therapy has yet been shown to accomplish.

And because the supplement is already commercially available and has an excellent safety record, researchers believe it could move rapidly into human clinical trials.

The immune-boosting power of yeast beta-glucan

Researchers from Trinity College Dublin and University College Dublin added a yeast-based supplement to the diets of obese mice and measured how their immune systems responded.

The supplement contained yeast beta-glucan derived from Saccharomyces cerevisiae, the same species used to make brewer’s yeast and nutritional yeast.

Beta-glucans are natural fibers found in the cell walls of yeast, fungi and certain grains. Depending on their source and structure, they can interact with immune cells and influence the body’s response to infection and disease.

The mice were fed either a standard or high-fat diet supplemented with yeast beta-glucan for four to 12 weeks. Researchers then challenged their immune systems with cells from colorectal, skin and breast cancers.

The supplement changed how the animals’ immune cells developed and helped their bodies produce stronger cells capable of fighting the cancers.

But this was not simply a temporary immune boost.

The yeast beta-glucan reached much further back in the immune-cell production process, reprogramming early-stage cells in the bone marrow.

Retraining immunity from its source

Your bone marrow contains stem and progenitor cells that develop into many of the immune cells circulating throughout your body.

The researchers wanted to find out whether yeast beta-glucan could reprogram those early-stage cells so they would continually produce more effective cancer-fighting immune cells.

This process is known as “trained immunity.”

Most people are familiar with the immune memory created when the adaptive immune system encounters a particular germ or vaccine. It learns to recognize that specific threat and respond more rapidly the next time it appears.

Trained immunity works differently. It changes how the innate immune system — the body’s first line of defense — responds to future threats.

In this study, the yeast beta-glucan reprogrammed bone marrow stem cells so they produced metabolically stronger monocytes and macrophages. These immune cells help identify, engulf and destroy potentially harmful cells, including tumor cells.

“This is the first demonstration that dietary delivery of yeast beta-glucan is sufficient to induce trained immunity through reprogramming of bone marrow stem cells,” says study co-lead Professor Helen Roche.

Previous research had required beta-glucan to be injected to produce this effect. This study showed that consuming it as part of the diet was enough.

Reversing the immune memory of obesity

The findings may be especially important for people living with obesity — including those who have successfully lost weight.

Obesity does more than affect body weight and metabolism. It can profoundly disrupt the immune system, increasing vulnerability to infection and making it harder for the body to fight tumors.

And losing weight may not completely erase that damage.

Research indicates that the immune system can retain a biological memory of obesity. That means some immune defects may continue even after the excess weight is gone.

In the mice, however, dietary yeast beta-glucan restored the innate immune system’s ability to fight tumors. It also reversed the lingering immune-memory defects that persisted after weight loss.

Professor Roche describes those persistent defects as a major unmet clinical challenge.

Correcting them could potentially provide people who currently have obesity — as well as those who have lost weight — with stronger defenses against cancer and infection.

Potential help for other weakened immune systems

The implications may extend beyond obesity.

Study co-lead Professor Frederick Sheedy says the research opens the door to dietary intervention studies involving people with chronic infections and those whose immune systems have been compromised by other illnesses.

The yeast beta-glucan used in the study is food-grade and already commercially available. That could eliminate some of the safety and manufacturing obstacles that often slow the movement from laboratory research to human trials.

Researchers hope that a yeast beta-glucan supplement could eventually be used alongside established cancer treatments rather than in place of them.

“Ultimately, a simple dietary supplement could help boost the immune system’s cancer-fighting ability, complementing existing treatments such as chemotherapy and immunotherapy, with potential to improve vaccine responses and resistance to infection,” Professor Sheedy says.

What these findings could mean

This study was conducted in mice, so clinical trials will be needed to determine whether yeast beta-glucan can produce the same immune reprogramming in people, who would benefit most and what amount would be needed.

It is also important to distinguish the specific beta-glucan preparation used in the research from ordinary baker’s yeast, brewer’s yeast or nutritional yeast. Although those products come from the same yeast species, they may not provide the same type, concentration or dose of beta-glucan used in the experiment.

But the path forward is unusually promising.

The tested beta-glucan is already food-grade, commercially available and supported by a strong safety record. That makes it a realistic candidate for rapid clinical trials.

Should human studies confirm these results, a simple nutritional intervention could one day help restore cancer-fighting immunity damaged by obesity, strengthen immune defenses that remain impaired after weight loss and possibly help other people whose immunity has been weakened by chronic illness or infection.

Sources:

Yeast dietary supplement may offer a safe nutritional strategy to boost cancer immunity — UCD

Yeast dietary supplement may offer safe nutritional strategy to boost cancer immunity — EurekAlert!

Yeast β-glucan supplementation supports immunometabolic anti-tumor responses and reverses obesity-induced dysfunction via trained hematopoiesis — Cell Reports

FAQ: Yeast beta-glucan and cancer immunity