Editor’s Note: While 2019 brings all the promise that every new year brings, there’s a good chance that someone you know will be facing a new or ongoing journey with cancer this year, or knows someone else who will. The good news is that precision medicine and our ability to know of the molecular signatures and metabolic processes of cancer on an individual level are making new treatments possible. Precision nutrition is one of the emerging tools that we can bring to the cancer fight. Cancer researcher Emily Poulin walks us through what we know about nutrient restriction as an adjuvant cancer therapy in this New Year’s LIFE Blogathon post.

Chemotherapy and radiation have remained mainstay weapons in the in anti-cancer therapy arsenal since they were first used to treat cancer patients. However, the toxic effects of chemotherapy and radiation, including nausea, hair loss and fatigue, are all too familiar. These side effects can make the use of these therapies extremely difficult for some patients.

Chemotherapy and radiation work by killing cells that multiply quickly. Since cancer cells tend to divide and multiply faster than normal cells, these treatments tend to mostly target cancer cells. However, chemotherapy and radiation cannot differentiate between normal and cancer cells. They kill normal cells, particularly quickly dividing and metabolically active cells, as well. It is the toxic effects on normal cells that result in the side effects we associate with these treatments.

Chemotherapy drugs in oral and injection forms. Credit: fluxfoto.

Although new cancer therapies are constantly being researched and developed, there are still certain cancers for which chemotherapy and radiation are the most effective therapeutic options. Therefore, it is critical for these patients that we work to make these therapies more effective long term, while reducing the toxic side effects.

One of the ways in which researchers are approaching this problem is by investigating how intermittent fasting and calorie restriction affect chemotherapy efficacy. Fasting is the absence of caloric intake for a given amount of time (anywhere from 12 hours to multiple days), while calorie restriction is a reduction in total daily caloric intake. In animal models, fasting has been reported to improve the anti-tumor effects of chemotherapy, reduce chemotherapy-associated side effects and even reduce tumor size.

The rationale behind why fasting may work to increase the effectiveness of chemotherapy has to do with the way that cancer cells are programmed. Cancer cells are essentially normal cells of the body that have “gone bad”. The accumulation of genetic mutations in a normal cell leads to transformation into a cancer cell, which is reprogrammed to divide often, grow faster and resist cell death.

Fasting results in reduced levels of cellular energy. Our bodies break down the food we eat and convert it into energy. At the cellular level, energy is packaged into molecules called ATP. The consumption of ATP is critical for all cellular functions, including survival. When cellular energy becomes limited during fasting conditions, normal cells enter a dormant mode and cease to divide until energy is once again available.

In contrast, because of their reprogramming, cancer cells do not generate energy in the same way as normal cells and do not restrict growth and proliferation during a fasting period. This creates an environment whereby following chemotherapy treatment, normal cells that proliferate less often are more protected against chemotherapeutic drugs, while cancer cells that continue to proliferate are further targeted by the chemotherapy. This effect is called differential stress resistance. Because they have become dormant and cease to proliferate, normal cells are less likely to be killed by the chemotherapy drugs, illustrating why the side effects of chemotherapy are improved following starvation.

The effects of fasting on chemotherapy have to date been largely studied in preclinical models (cancer cell lines and animal models). Some human clinical trials suggest that short-term fasting during chemotherapy improves patient quality of life and the side effects of chemotherapy. However, to determine whether these and other effects observed in preclinical models translate to humans on a broad scale, further trials are ongoing.

Dr. Nicole Simone (Jefferson Hospital) is working on bridging this gap between animal models and human cancer patients. She has three open clinical trials investigating the effects of intermittent fasting and caloric restriction in the context of cancer therapy. Her first clinical trial investigating intermittent fasting enrolled breast cancer patients who started a 10-week diet two weeks before radiation therapy. Importantly, patients reported improved skin toxicity, fatigue and quality of life scores when dieting before and during radiation therapy, suggesting that the changes in diet were having a positive effect. The diet consisted of daily calorie restriction, or a restriction of normal caloric intake by 25%.

Simone says, “Most of us cancer doctors are taught to treat the cancer, treat the cancer, treat the cancer. We don’t often stop to talk about other things with the patient. But what I notice is that all patients faced with a diagnosis of cancer come back asking, ‘What else can I do?’ This should be a teachable moment. Why aren’t we telling people what to eat?”

Young cancer survivor doing yoga in the park drinking water.
Exercise, hydration, healthy eating and stress management are important components of effective cancer therapy. Credit: Dragon Images.

New investigations into the role of fasting and nutrition on the effectiveness of chemotherapy and radiation may soon demonstrate that simple lifestyle changes may give new life to chemotherapy and radiation, two of the first cancer therapies that have been saving lives for close to a century.

Editor’s Note: If you are facing a cancer diagnosis or being treated for cancer, talk to your doctor about whether intermittent fasting would be safe for you to try. Safe ways to approach fasting and determine whether it helps you feel better during cancer therapy might include moderate time-restricted feeding (with an overnight or pre-chemo fast of 12 to 14 hours). You’ll need to work with your doctor or a dietitian at your cancer clinic to make sure you are eating in a way that complements your therapy and the metabolic processes of the cancer you are fighting. In general, you should maintain a healthy, balanced diet during cancer therapy and avoid added sugar and processed foods.