Fasting can program certain immunity cells in the body to fight cancer better and improve the cell’s ability to survive in a tumor environment, according to a recent study.
The study, published in the journal Immunity on June 14, looked at how fasting affected natural killer (NK) cells, a type of white blood cell capable of killing damaged or abnormal cells like cancer and those infected by a virus. The presence of a higher number of killer cells within a tumor is usually seen as beneficial for a cancer patient. Researchers found that fasting can reprogram the metabolism of natural killer cells, improving their ability to fight cancer and enabling the cells to survive in the harsh environment within and around the tumors.
“Our findings identify a link between dietary restriction and optimized innate immune responses, with the potential to enhance immunotherapy strategies” of cancer patients, the paper said.
In the study, researchers analyzed cancer-infected mice that were not given food for a period of 24 hours, twice a week. As the mice were allowed to eat freely in between fasts, they did not lose any weight.
During the fasting period, glucose levels in the mice dropped, similar to humans, along with a jump in free fatty acids. Meanwhile, the natural killer cells were observed to have undergone a major change.
“During each of these fasting cycles, NK cells learned to use these fatty acids as an alternative fuel source to glucose,” said Rebecca Delconte, a co-author of the study.
“This really optimizes their anti-cancer response because the tumor microenvironment contains a high concentration of lipids, and now they’re able to enter the tumor and survive better because of this metabolic training.”
Fasting was also observed to have redistributed NK cells in the body. Some of the cells traveled into the bone marrow, getting exposed to high levels of a signaling protein. This led to NK cells producing more Interferon-gamma, a type of protein that plays a key role in the body’s anti-tumor response.
NK cells in the spleen experienced a separate programming that allowed them to better use lipids as a source of fuel.
“With both of these mechanisms put together, we find that NK cells are pre-primed to produce more cytokines within the tumor,” Ms. Delconte said.
“And with the metabolic reprogramming, they’re more able to survive in the tumor environment, and specialized to have improved anti-cancer properties.”
The research comes as clinical trials to study the safety and effectiveness of fasting together with standard cancer treatments are underway.
The study was funded through multiple sources, including the National Institutes of Health, Australia’s National Health and Medical Research Council, and the American Cancer Society. Authors declared no competing interests in the study.
Fasting Risks
While the June 14 study found positive links between fasting and fighting cancer, clinical dietitian Juhina Farooki says the safety of the process should only be determined on a case-by-case basis.
“Every patient is different, and what could be safe for one patient is not necessarily safe for the other patient,” she said, according to a Jan. 29 post at the MD Anderson Cancer Center.
Malnutrition is one of the risks of fasting while undergoing cancer treatment. A lack of proper nutrients can result in weight loss, slow down the healing process, and worsen fatigue, the post said. It can also add more stress during what is an already tense period for the individual.
Ms. Farooki advises cancer patients who wish to fast to only do so after consulting with their physician. This ensures the patient gets sufficient nutrition.
A February 2023 study that investigated the effect of skipping meals in mice found that there was a difference in the number of monocytes in the creatures. Monocytes are white blood cells made in the bone marrow that fight cancer.
One group of mice were given breakfast while the other group was denied. After four hours of fasting, 90 percent of monocytes in the fasting mice were found to have disappeared from the bloodstream, which fell further at eight hours. In the non-fasting mice, monocyte levels remained unaffected.
Meanwhile, a recent German study found intermittent fasting to have a protective effect against inflammation and cancer in the liver. The researchers conducted tests on mice already suffering from liver inflammation.
After the mice were subjected to four months of intermittent fasting, their liver function tests improved. The mice were found to be less likely to develop liver cancer.
