Keto Claims: Can Diet Be a Form of Cancer Therapy?

An array of high fat, low-carbohydrate foods.

A ketogenic diet is one that is very low in carbohydrates and relatively high in fat. Researchers are exploring its role in cancer treatment.

In July 2018, researchers from Weill Cornell Medicine and Columbia University published the results of a laboratory study that combined a very low-carbohydrate diet with targeted drugs called PI3K inhibitors as a treatment for cancer. The researchers found that this diet, called ketogenic, improved how well the drugs worked in several types of cancer in mice.

The study attracted quite a bit of media attention, no doubt in part because the ketogenic diet is a popular topic among diet gurus. But for people with cancer, the study could be a source of confusion about what they should and should not be eating.

In an interview, Neil Iyengar describes the relationship between diet and cancer, including what role a ketogenic diet might play in prevention and treatment. Dr. Iyengar is a medical oncologist at Memorial Sloan Kettering who treats people with breast cancer and researches the relationship between obesity and cancer.

Nutrition and Cancer
The food you eat during and after cancer treatment can play an important role in your recovery. Check out Memorial Sloan Kettering's nutrition advice and recipes to help you feel your best.

What questions do your patients have about diet as it relates to cancer?

By the time people with breast cancer come to see a medical oncologist like me, they’ve already been diagnosed with cancer. Many have had surgery, and now they’re coming to talk about how to prevent the cancer from returning.

Oftentimes chemotherapy is a part of that conversation. Their main question is typically “What can I eat and what can’t I eat during chemo?” Many people believe that chemotherapy is going to obliterate their appetite. They think they’re going to waste away, so they need to eat as much as they can before chemo to prepare for this impending malnutrition.

But the data, especially in breast cancer, suggest the opposite. People are more likely to gain weight during adjuvant [postsurgery] chemotherapy for breast cancer. A lot of my patients are surprised when I tell them to watch their calorie intake. This is because we now have plenty of epidemiologic evidence showing that a 5 to 10% weight gain during or after adjuvant chemotherapy increases the risk of breast cancer relapse.

Read more about the link between fat and cancer.

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What do you think of the Weill Cornell–Columbia study that combined a ketogenic diet with drugs as a treatment for cancer?

I think that this study is incredibly interesting. We’ve known for a while that a common side effect of PI3K inhibitors is hyperglycemia, meaning high blood sugar. That’s a problem for people with diabetes or prediabetes, and it’s one of the reasons why we sometimes have to stop treatment. This study suggests that controlling that rise in blood sugar — either through a ketogenic diet or through medication — could be one way to make the drugs more effective.

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Tell us a little bit more about the cancer drugs used in this study. Why did the investigators choose to study them in combination with a ketogenic diet?

The idea behind giving someone PI3K inhibitors is that many cancers have mutations in the gene that codes for the PI3K enzyme. In fact, 70% of all cancers have mutations in the signaling pathway of which PI3K is a part. A key component of that pathway is insulin, a hormone that controls our blood sugar levels and has many other important functions. In the context of cancer cells, insulin can bind to a receptor on the surface of a cancer cell and stimulate growth-promoting pathways that include PI3K.

When a person takes a PI3K inhibitor, insulin signaling is disrupted in the body. Since the main function of insulin is to lower blood glucose levels, disruption of insulin signaling leads to elevated blood glucose. To counteract this rise in glucose, the body secretes more insulin.

The study investigators hypothesized that this insulin spike might negate the effect of blocking the PI3K enzyme with drugs. They took two approaches to prevent the spike: a ketogenic diet, which reduces the body’s glucose stores, and diabetes drugs that block insulin. Both approaches made PI3K inhibitors much more effective — at least in the mouse models they used. They concluded that a ketogenic diet improved responses to PI3K inhibitors by reducing the activation of insulin receptors in tumors.

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What should people with cancer know about the ketogenic diet, based on this study?

First of all, this study was done in mice, so we don’t know yet if people will respond the same way. Second, it’s important to note that a ketogenic diet by itself was not effective as a cancer treatment in this study. In fact, for some of the cancers they tested, it actually made the cancer worse.

That said, there could be other benefits of a ketogenic diet for some people. A ketogenic diet is a very low-carbohydrate diet that also tends to be low calorie. Therefore, over time it will lead to weight loss. That in turn will reduce obesity-related inflammation and other metabolic problems, which could reduce the risk of cancer forming and coming back. Other diets that induce weight loss may also be helpful in this regard.

But restrictive diets can be difficult to follow for long periods of time. A ketogenic diet is particularly difficult to follow for prolonged periods. Furthermore, yo-yo dieting can have harmful health effects. 

Ultimately, when it comes to diet, it depends on what works and is achievable for a particular person. Changing dietary behavior may be more effective than following a specific diet. In other words, if you can eat a healthy diet that is not overly restrictive, such as the American Cancer Society diet, this may be the most beneficial approach in the long run.

Ultimately, when it comes to diet, it depends on what works and is achievable for a particular person. Changing dietary behavior may be more effective than following a specific diet.
Neil M. Iyengar medical oncologist
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Are any trials combining cancer therapy with either a ketogenic diet or insulin-reducing drugs?

Several clinical trials are underway or are going to be launched soon. For example, researchers at Weill Cornell and Columbia are planning trials of a ketogenic diet with cancer therapy. We are also awaiting the results of a large global trial testing whether the diabetes drug metformin helps prevent breast cancer recurrence.

At MSK, we have a trial of a ketogenic diet for endometrial cancer, led by Vicky Makker. It is currently enrolling participants. We are in the planning phase of developing trials that combine diabetes drugs with cancer drugs like PI3K inhibitors.

In addition, MSK has one of the most active exercise oncology programs in the nation, led by Lee Jones. Under this program, we have several exercise trials that are currently ongoing. For example, we are testing different exercise regimens with chemotherapy for early-stage breast cancer in a study led by Jessica Scott. We will also soon launch a trial of precision exercise plans plus molecular and hormone-based cancer therapy for estrogen receptor-positive breast cancer.

This is a rapidly developing area of research. As a physician-researcher, I find it very exciting that I can offer these options to my patients. As we learn more about how diet and metabolic alterations affect cancer, I am sure that we will find new ways to prevent cancer and prolong survival after a cancer diagnosis, all while improving well-being and general health.

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Is melanoma a form of cancer that respond well to a ketogenic diet?!

Pascale, thank you for your question. The research is at an early stage and we don’t know which cancers it might help. It is important to understand that the research is investigating whether a ketogenic diet can make some cancer treatments more effective, not whether a ketogenic diet alone is an effective treatment. There is no evidence that dietary changes alone are an effective treatment for melanoma.

Keto should be implemented with lifestyle changes and exercise programs, mediation, acupuncture and many other integrative medicine treatments. Truly a comprehensive program seems most beneficial.

Would this diet help those with gene mutations on this pathway that predispose them to getting cancer?

Dear Jess,

We forwarded your question to Dr. Iyengar, who responded: “The study in mice was designed to address whether the keto diet improves response in cancers with PI3K mutations in conjunction with PI3K inhibitors. It is important to note that we are referring to mutations in tumor DNA, not mutations in the genes that predispose to cancer (in other words, the genes we inherit and pass down). We do not know if the keto diet is helpful for preventing cancer in individuals who have germline mutations that predispose to cancer. What we do know, is in individuals with mutations that predispose to cancer, obesity and metabolic diseases (like diabetes) are associated with earlier onset cancer. It is advisable for all individuals to maintain a healthy weight and healthy metabolic status by adhering to a balanced diet and exercise – and this is particularly important for individuals who are genetically at higher risk for developing cancer.” Thank you for your comment. 

Can the Keto diet help in the treatment of Prostate Cancer?

Dear Robert, the keto diet is being studied for a number of different kinds of cancer. It is too early to make recommendations based on what we know now. Thank you for your comment.

In 2013, I was diagnosed with colon cancer in the Sigmoid. I had Keyhole , In 2015 it reoccured.i then had a operation . I am presently in remission,seeing my Oncologist every 4 months. My blood markers are 2.2. I would like to be incontact for more advise on prevention of colon cancer reoccurring.
Thanking you
Yours truly
Dawn Morta

Dear Dawn, if you’d like to arrange a consultation to speak with someone at MSK about this, you can make an appointment online or call 800-525-2225. Thank you for your comment and best wishes to you.

A family member has colorectal stage 4 spread to the liver. Is the HAI pump still being used at MSK to treat the liver? I saw an article that is is being phased out.

Dear Donna, we’re very sorry to hear about your relative’s diagnosis. Due to changes in the plans for manufacture of both pumps and catheters (the tube that attaches the pump to the liver), we have an investigational protocol where we are investigating a new pump and catheter combination. This still provides access of pumps to appropriate patients. Some pumps using catheter combinations that have been evaluated previously are still available for placement as well. These options can be discussed with the treating physician and we continue to provide pumps to patients in which this treatment is recommended as the best option. If your family member would like to schedule a consultation to learn more, they can make an appointment online or call 800-525-2225. Thank you for your comment. 

The ketogenic diet is NOT a low calorie diet.

Is it true that cancer loves sugar and Cancer patients should avoid sugar? My cancer is adenocarcinoma of the stomach which has metastasized to the lymph nodes.

Dear Tim, we’re sorry to hear about your diagnosis. You can learn more about sugar and cancer from this blog post.

We recommend that you discuss any changes in diet with your medical team or with a dietitian who has experience in working with people who have cancer. Thank you for your comment and best wishes to you.

Hi Dr. Iyenger: First, thanks for answering many of the questions we cancer patients have about the Keto Diet. A couple of questions for you: 1. Does research suggest that a Keto diet will improve the efficacy of the drugs we metastatic patients are on, particularly those that target the PI3K pathways (i.e. will we get a longer duration of the drug before progression)? And is the benefit worth the offset of what the diet will do to our liver compounded with what the drugs are already doing to our liver? As I understand it, the Keto diet has two planks: what you eat (low carbs, lots of protein and healthy fats) and intermittent fasting. What does the research say about intermittent fasting alone in promoting drug efficacy? Is that something healthier stageiv cancer patients should be considering adding to their diet? Lastly, can you also weigh in on the latest research regarding Methionine and cutting back on or eliminating meat and eggs and how that may elongate treatments for those of us with metastatic cancers (obviously that would need a separate article). Thanks!

Dear Liz, the effect that a ketogenic diet may have on cancer drug efficacy is a new area of research and it is not possible to make recommendations as this time. Some of the first clinical trials of this approach are beginning now, but it is too soon to say whether this approach will be effective. We recommend you talk with your doctor about which diet is right for you. Thank you for your comment.

The article states that a Keto diet can actually make “cancers worse.” Please elaborate on this broad statement. I’m a MSK patient and currently NED after stage 3C Colorectal cancer. I, like many people, do Keto intermittently. If I thought there was ANY chance it may increase the chance of a recurrence, I would obviously not do it. So, please explain exactly what cancers you are referring to in the article when you say Keto could potentially make them worse. Or, at the very least, please cite the medical source that would back that up with specific cancer types.

Dear Katie, we recommend that you discuss any diets with your MSK care team. You may also want to ask your team for a referral to one of MSK’s dietitians. Thank you for your comment and best wishes to you.

Do you have any keto advice specific to people with breast cancer? For instance, my friend has HER2+ breast cancer and wants to do keto, but keto is meat-heavy and meat usually has estrogen. Her breast cancer is fueled by estrogen. So she is doing a plant-based keto diet, but I have found little help on the specific topic of treating HER2+ breast cancer patients with keto, ideally primarily plant-based. Any websites, dieticians, etc. you can recommend for this particular dilemma of treating breast cancer with a meat/estrogen free keto plan? Thanks!

Dear Alice, you can learn more about the connection between soy and breast cancer from this blog post. We recommend that your friend discuss any diets she is considering with her doctor and that she get a referral to a dietitian who has experience working with people who have cancer. Thank you for your comment and best wishes to you and your friend.