There is a growing body of evidence supporting the role of fasting in both cancer treatment and prevention.
Some research suggests that fasting helps fight cancer by lowering insulin resistance and levels of inflammation. Also, some researchers believe that fasting may make cancer cells more responsive to chemotherapy while protecting other cells. Fasting may also boost the immune system to help fight cancer that is already present.
Now, researchers from USC and the IFOM Cancer Institute in Milan have found that the combination of a fasting-mimicking diet, plus vitamin C supplementation, can delay tumour progression in multiple mouse models of colorectal cancer. They even found it caused disease regression in some mice.
Valter Longo, the study senior author and the director of the USC Longevity Institute at the USC Leonard Davis School of Gerontology, said: "For the first time, we have demonstrated how a completely non-toxic intervention can effectively treat an aggressive cancer.
"We have taken two treatments that are studied extensively as interventions to delay ageing - a fasting-mimicking diet and vitamin C - and combined them as a powerful treatment for cancer."
In the report, published in the journal Nature Communications, the authors state that while fasting remains a challenging option for cancer patients, a safer, more feasible option is a low-calorie, plant-based diet that causes cells to respond as if the body were fasting.
Results of prior research on the cancer-fighting potential of vitamin C have been mixed. Recent studies, though, are beginning to show some efficacy, especially in combination with chemotherapy. In this new study, the research team wanted to find out whether a fasting-mimicking diet could enhance the high-dose vitamin C tumor-fighting action by creating an environment that would be unsustainable for cancer cells but still safe for normal cells.
"Our first in vitro experiment showed remarkable effects," said Longo. "When used alone, fasting-mimicking diet or vitamin C alone reduced cancer cell growth and caused a minor increase in cancer cell death. But when used together, they had a dramatic effect, killing almost all cancerous cells."
Longo and his colleagues detected this strong effect only in cancer cells that had a mutation that is regarded as one of the most challenging targets in cancer research. These mutations in the KRAS gene signal the body is resisting most cancer-fighting treatments, and they reduce a patient's survival rate. KRAS mutations occur in approximately a quarter of all human cancers and are estimated to occur in up to half of all colorectal cancers.
The study also provided clues about why previous studies of vitamin C as a potential anti-cancer therapy showed limited efficacy.
The authors say a vitamin C treatment alone appears to trigger the KRAS-mutated cells to protect cancer cells by increasing levels of ferritin - a protein that binds iron. But by reducing levels of ferritin, the vitamin C's toxicity can be increased. Amid this finding, the scientists also discovered that colorectal cancer patients with high levels of the iron-binding protein have a lower chance of survival.
"In this study, we observed how fasting-mimicking diet cycles are able to increase the effect of pharmacological doses of vitamin C against KRAS-mutated cancers," said Maira Di Tano, a study co-author at the IFOM, FIRC Institute of Molecular Oncology in Milan.
"This occurs through the regulation of the levels of iron and of the molecular mechanisms involved in oxidative stress. The results particularly pointed to a gene that regulates iron levels: heme-oxygenase-1."
The scientists believe cancer will eventually be treated with low-toxicity drugs in a manner similar to how antibiotics are used to treat infections that kill particular bacteria, but which can be substituted by other drugs if the first is not effective.
To move toward that goal, they say they needed to first test two hypotheses: that their non-toxic combination interventions would work in mice, and that it would look promising for human clinical trials. In this new study, they said that they've demonstrated both.
Source: Nature Communications
Longo. V. D., et al
"Synergistic effect of fasting-mimicking diet and vitamin C against KRAS mutated cancers"