Is Starving Cancer Possible?
This is an important question that many people ask when faced with a cancer diagnosis. I first heard this over 20 years ago, when I was doing my clinical dietetic internship. The standard answer at the time was “no, you can’t starve your cancer without starving yourself.”
But at that time the link to obesity and cancer was not as well established as it is now. No one talked about insulin receptors on cancer cells, and weight loss in a cancer patient was feared and not promoted. In fact, gaining an “extra 10 lbs” in case you lost weight during treatment was seen as a good preemptive strategy. But, times have changed and now there are some indications that you can starve cancer.
How Do I Starve Cancer?
There are three ways to starve cancer;
To read more about ketogenic diet and low methionine diets, use the links above. To find out more about starving cancer with intermittent fasting, you can keep reading and use this Table Of Contents to navigate the post
What is Fasting?
It is refraining from certain or all food or drink for a period of time. You are likely familiar with it as part of religious practice and in some cultures it is a form of prayer but it also has a long history as a medical intervention.
What is Intermittent Fasting?
Intermittent fasting is a method in which you alternate between fasting and not fasting. For example a popular form of fasting at the moment is called the 5:2 diet. On this program you eat normally, five days a week and fast for 2 days. The “alternate daily fasting” or ADF approach is another popular intermittent fasting regime. As the name implies you fast every other day, and eat normally the days between fasts.
There are also some intermittent fasts in which you eat for only part of the day, then stop eating at a specific time. For example, you can be allowed to eat breakfast and lunch and snack and then nothing after 3pm. It can also be eating a normal dinner then fasting through the night and breakfast and breaking the fast at noon. Read more about the different fasting methods in my blog post called Intermittent Fasting for Women Over 40.
Starving Cancer in Humans
I would like to divide this topic into two important categories; intermittent fasting for cancer treatment and intermittent fasting for cancer prevention. I’ll further divide in-treatment to intermittent fasting for chemotherapy and intermittent fasting for radiation.
Intermittent Fasting for Chemotherapy
This table summarizes 4 studies on humans that use intermittent fasting during chemotherapy cancer treatment.
As you can see, the human trials are rather small at the moment. While they fall short of showing that fasting improves cancer outcomes – like reduced recurrence rates or longer survival. What these studies do show is;
- Intermittent fasting is safe and feasible with few side effects
- Intermittent fasting appears to reduce side-effects of chemotherapy
- Intermittent fasting appears to make cancer cells more vulnerable to treatment
How Does Intermittent Fasting Help During Chemotherapy Treatment?
There are a couple of theories put forth which help us understand how intermittent fasting helps during cancer treatment which are (Safdie, 2009 and Dorff, 2016);
- Fasting reduces the anabolic hormones insulin and insulin-link growth factor (IGF-1) and up-regulates several stress resistance proteins. These changes make normal healthy cells more resistance to chemotherapy and oxidative stress.
- When normal healthy cells are stressed from fasting, they switch into protection mode and the usual cell life cycle is stopped. Cancer cells, lack the ability to stop their cell life cycle and are therefore vulnerable to the chemotherapy. In this way, the normal cells are spared and less side effects occur and the chemotherapy can be more targeted to the cancer cells.
- There is reduced DNA damage to blood stem cells, which allows these cells to continue to produce new white blood cells. The white blood cell count can therefore be maintained within normal limits, allowing patients to receive their full dose of chemotherapy on time.
Intermittent Fasting and Radiation Treatment
In a review article, researchers examined fasting as well as ketogenic diet and calorie restriction during radiation. They noted that these three starvation methods can protect healthy cells from radiation damage as they can adapt more efficiently to glucose starvation than cancer cells. This protection is called “differential stress resistance”. They noted that normal cells, unlike cancer cells, can use ketones for energy. Although, this is not true for all cancer subtypes in which cell and animal studies show that some breast cancers, acute myeloid leukemia and melanoma among others can use ketones (Icard, 2020).
Ketones are produced by the body either during fasting or ketogenic diet, when the body has used up its stored form of glucose, it then burns fat for fuel which produces ketones. When your body produces ketones for energy, you are ‘in ketosis’.
After examining 26 published studies, the researchers concluded that intermittent fasting before radiation treatment may improve tumor response to radiation and repeating fasting may increase the efficiency of radiation and may protect healthy tissues. This would be especially relevant for tumors that show a high update of glucose on a PET scan (Icard, 2020).
Are there Risks to Fasting During Cancer Treatment?
The studies that were done on intermittent fasting during cancer treatment (outlined in the chart above) were all careful to choose their participants. For example, people who had unintentional weight loss or whose weight was below normal were not allowed in the studies. This was done as intermittent fasting diets are known to promote weight loss (which is why there are so popular). The risks of intermittent fasting during cancer treatment include:
- Sarcopenia (reduced muscle mass)
- Delaying wound healing
- Impaired immune function
In addition, it’s not known if the chemotherapy or radiation dose should be reduced if the patient fasts. Since these studies have shown that fasting creates a better target of the cancer cells, it’s possible you need less chemotherapy or radiation because of this. Also, it’s not known yet, which cancers, which fasting regimens and which treatments provide the best outcomes.
It’s important to point out that even if an individual is overweight or obese, it doesn’t mean that they don’t have sarcopenia. So, while you might think since you are overweight, and losing weight while fasting for chemotherapy, is low risk, it’s important to be assessed for muscle mass. The most common way to do this is with a hand grip measurement. Maintaining your muscle mass throughout cancer treatment is important as sarcopenia can affect your survival from cancer (Shachar, 2016).
There are currently nine studies recruiting or underway that will examine intermittent fasting and cancer from countries all around the world (Germany, Ireland, Australia, Sweeden, Pakistan, China, Holland and U.S.A.) I’ll continue to watch this research and update by Cancer Bites diet blog, so be sure to sign up so that you can get the updates when I publish my next blog.
How to Starve Cancer for Prevention?
I was able to find two epidemiological studies that examined this question. I will share those with you, but first, I want to share some other pieces to this puzzle, which helps you to understand the mechanism by which intermittent fasting could be a tool to prevent cancer. Let’s examine these first, starting with body weight, then I’ll share the two studies.
Body Weight and Cancer Risk
Being overweight, or having a larger waist circumference are both risk factors for cancer. So if intermittent fasting can help you lose weight, there is likely a lowered risk of developing a first cancer or a recurrence. The American Institute for Cancer Research (AICR) recommends that you be as lean as possible without being underweight. This target would be difficult to attain without a conscientious effort at weight management. Intermittent fasting has been shown to be as successful as traditional calorie restrictive diets for weight loss, but may be easier to stick with long term (Rynders, 2019).
Inflammation and Cancer
Inflammation has long been linked to cancer. While short term (acute) inflammation is normal and healthy, long term (chronic) inflammation creates an environment inside your body that encourages the growth of cancer cells. Intermittent fasting has been shown to reduce blood levels of inflammation (Antoni, 2018, Malinowski, 2019). Researchers examined the food records and blood results of 1,034 women who participated in the NHANES survey in 2009-2010. Specifically, they looked at the number of meals they ate in a day, whether the bulk of the calories were consumed in the day or evening and the length of their overnight fast. They measured their blood levels of inflammation with a test called C-Reactive protein (CRP). What they discovered was that;
- Eating calories during the day was less inflammatory
- Each 10% increase in proportion of calories in the evening was associated with a 3% rise in CRP
- Eating more frequently was less inflammatory
- Eating one additional meal or snack per day was associated with an 8% reduction in CRP
- A longer overnight fast was less inflammatory
- Eating less than 30% of calories in the evening and a longer overnight fast meant an 8% reduction in CRP
They concluded that reducing evening energy intake, eating more frequently and fasting for longer overnight (when fasting is initiated early in the evening) may reduce systemic inflammation in the body which could reduce breast cancer and chronic disease risk (Marinac, 2015). Time restricted feeding is a form of intermittent fasting that limits your eating window and lengthens your fasting window and could help to achieve reduced inflammation.
Circadian Rhythms and Cancer
Your circadian rhythm is the bodies response to light and dark. When it gets dark out, this is detected by the master clock in your brain (the Suprachiasmatic nucleus/SCN) and the body responds by producing melatonin. Disruptions to the circadian clock causes unhealthy levels of hormones, microbiota and gene expression and these are linked to a variety of chronic diseases including heart disease, diabetes and cancer (Gibson, 2009). We see this in higher rates of cancer in shift workers, in one study, breast cancer rates were twice as high in shift workers (Sziela, 2020).
To help align your circadian rhythm, you can sync your master regulator in the brain with the peripheral regulators in the GI tract. To do this, you need to eat when it is light and stop eating when it’s dark and have a regular eating and sleeping pattern. Following an intermittent fasting pattern that shortens your eating window is a good way to accomplish this. Even making sure you eat within 12 hours is a good first step.
Blood Sugars and Cancer
Blood sugar, insulin, insulin resistance, IGF-1 (Insulin like growth factor-1) are strongly associated with most cancers (Johnson, 2010). Cancer cells have insulin receptors, meaning that insulin will promote their growth, in addition, cancer cells are avid glucose consumers. Intermittent fasting has been shown to lower glucose, HgbA1c, insulin and insulin resistance. Longer overnight fasts were shown to reduce HgbA1c, blood sugar, circulating and insulin sensitivity (Marinac, 2015, Marinac, 2016, Halberg, 2015)
Sleep and Cancer
Sleep is a critical time for our immune system, which is in turn important for cancer protection. In a study of healthy individuals who tracked their eating and sleeping patterns, researchers discovered that on average people ate within a 15 hour window, that eating and sleeping schedules were so erratic, they called it “metabolic jet leg”. When asked to eat within a 10-12 hour eating window and to minimize the weekend/weekday differences to only 1 hour, participants lost weight and reported improved sleep (Gill, 2015).
Another study confirms this finding. They found that prolonging the nightly fast and eating more frequently were associated with a significantly longer sleep duration (Marinac, 2016).
In addition to this evidence that fasting can improve body weight, inflammation, circadian rhythms, blood sugars and sleep, all things that can impact cancer risk, we have evidence directly linking fasting to cancer protection.
Evidence of Fasting and Cancer Protection
In an analysis, 2413 women with breast cancer recorded their food intake and timing. Researchers from the University of California reported that fasting less than 13 hours per night was associated with a 36% increased risk of recurrence of their breast cancer (Marinac, 2016).
In a study done in Spain, over 1,826 men and women with prostate and breast cancer and 2,000 controls were asked questions about what and when they eat as well as their sleep and chronotype (whether they are early birds or night owls). When the data from the cancer patients was analyzed and compared to the controls without cancer, researchers saw that timing of meals matters. In fact:
- If they ate dinner by 9:00 pm compared to after 10;00 pm they had 35% lower risk of developing breast or prostate cancer
- If they had two or more hours between finishing dinner and bedtime they had a 26% lower risk of prostate cancer and a 16% lower risk of breast cancer
Breast and prostate cancers are described as the two most common night-shift related cancers (Kogevinas, 2018). This data would support time restricted feeding that limits eating too late as cancer protective.
Autophagy in Cancer
Autophagy is ‘self-eating’ (auto=self, phagy = eating). It’s a way for the body to recycle damaged proteins. The process of autophagy increases with fasting and it credited with many beneficial metabolic changes (de Cabo, 2019). However, there is research from Eileen White from Rutgers Cancer Institute using genetically engineered mice that has found that in the presence of cancer, autophagy favours the cancer. This would mean that fasting would not be beneficial for someone with cancer, outside of the chemotherapy and radiation scenarios described above (White, E, 2020 and Paillet-Perez, 2019).
Fasting has a couple of things going for it; it’s easier to follow then traditional continuous calorie restriction diets and in addition to weight loss, you have improved metabolic changes (Harvie, 2014 presentation). Intermittent fasting appears to help reduce the toxicity of both chemotherapy and radiation, but is not without its risks, so you must work with your oncology dietitian and the rest of your team to determine if fasting during chemotherapy and radiation treatment is right for you. Outside of treatment, fasting and autophagy might be detrimental.
When it comes to preventing cancer with intermittent fasting, the research is early but promising.
When I work with a client that is interested in reducing cancer risk, I teach the 3 Keys to Cancer Risk Reduction, namely
- Support the immune system
- Reduce chronic inflammation
- Choose foods that act directly against cancer cells
Intermittent fasting supports the first two of these three keys and it is therefore consistent with a cancer prevention strategy. As noted by researchers from Philadelphia, the type of dietary manipulation you do may be unique for you and your cancer subtype (Simone, 2013)
If intermittent fasting is something you would like to try and would like to work with a professional, then I am happy provide you private virtual sessions that will incorporate intermittent fasting along with my 3 keys to cancer risk reduction.
To read more about Intermittent Fasting and Starving Cancer Check out these Cancer Bites Diet blog posts
To watch a webinar where I present information on intermittent fasting and answer questions watch Intermittent Fasting – A Guide for Dietitians and earn 1 CEU.
References for How to Starve Cancer
Antoni, R., Robertson, T., Robertson, M., & Johnston, J. (2018). A pilot feasibility study exploring the effects of a moderate time-restricted feeding intervention on energy intake, adiposity and metabolic physiology in free-living human subjects. Journal of Nutritional Science, 7, E22. doi:10.1017/jns.2018.13
Bauersfeld SP, Kessler CS, Wischnewsky M, et al. The effects of short-term fasting on quality of life and tolerance to chemotherapy in patients with breast and ovarian cancer: a randomized cross-over pilot study. BMC Cancer. 2018;18(1):476. Published 2018 Apr 27. doi:10.1186/s12885-018-4353-2
de Groot S, Vreeswijk MP, Welters MJ, et al. The effects of short-term fasting on tolerance to (neo) adjuvant chemotherapy in HER2-negative breast cancer patients: a randomized pilot study. BMC Cancer. 2015;15:652. Published 2015 Oct 5. doi:10.1186/s12885-015-1663-5
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Harvie, M Does Intermittent Energy Restriction Play a Role in Prevention and Treatment of Cancer? Genesis Breast Cancer Prevention Centre. Presentation at AICR conference Oct 29-31, 2014. pdf presentation.
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Szkiela M, Kusideł E, Makowiec-Dąbrowska T, Kaleta D. Night Shift Work-A Risk Factor for Breast Cancer. Int J Environ Res Public Health. 2020;17(2):659. Published 2020 Jan 20. doi:10.3390/ijerph17020659
White, E and Attia, P. Autophagy, fasting, and promising new cancer therapies. The Drive, episode 114.