The Keto Diet Fad and Cancer

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The Keto Diet Fad and Cancer about undefined

Do you remember those “easy button” commercials for an office supply store from several years back? Any time someone had a problem all they had to do was press that button and the perfect solution would fall from the sky into their lap.

We all crave a simple, one-stop, comprehensive answer to our problems– and health challenges are no different. American culture has long leaned toward favoring the health quick-fix which is why drug companies touting fancy little pills do so well.

But the reality is our health needs are a lot more complex, and there’s no single answer that works for everyone. This is particularly true when it comes to diet. Our modern world wants an easy answer for staying thin with boundless energy and multi-faceted protection against diseases like cancer.

Yet no two people are alike, and the benefits of diets quickly get muddled once they become fads – sometimes to a dangerous degree. Take the keto diet, for example…

Fueling America’s “carbophobia”

The low-carbohydrate ketogenic diet is currently the most popular diet in the United States. It’s hardly surprising, since one of the most appealing aspects of the diet is its encouragement to eat fat. After decades of the diet industry telling us to ignore our primal desire to bulk up on satiating fat sources like cheese, butter, and bacon, this comes as welcome news.

The keto diet becomes even more attractive as carbohydrates like whole grains, legumes, fruit, and starchy vegetables get pushed to the back burner – or back of the cupboard, even those once considered healthy. Meat is favored instead, covered in cheese and butter. The weight-loss angle of the keto diet is that by minimizing carbs and the glucose they create, your body will burn fat instead of glucose for energy.

What is the keto diet anyway? 

The goal with a ketogenic diet is to get 70 percent of your calories from fat sources, less than 20 percent from protein, and less than ten percent from carbohydrates. The goal is also to get your body to enter a state of ketosis, where it primarily uses fat for energy instead of carbohydrates. The idea of ketosis is that if your carb levels are low, fats get converted into ketones that fuel your body.

Along with shaving off the pounds, the keto diet is said to minimize hunger, keep diabetes in check, improve blood pressure and even treat certain kinds of epilepsy. Throw in a boost to concentration, and what’s not to love?

Full disclosure: I have strongly advocated a low or no-carb diet as a cancer treatment because substantial evidence at the cellular level indicates cancer needs glucose to thrive, and of course the carbs we eat are our main source of blood glucose.

In subsequent years it’s turned out that this does not work against some types of cancer, although I still think it’s a useful weapon to fight the disease. Towards the end of this article I’ll give you my current take on how to keep from feeding your cancer with glucose.

I’d also like to note that the benefit of a keto diet for epileptics is actually accepted as a third-line treatment to drug-resistant pediatric epilepsy, yet keto proponents seem to take this fact and conflate it into the confounding idea that keto is good for everyone.

Now, properly and carefully managed, a keto eating plan can help specific individuals with specific health problems such as obesity, but when it comes to preventing or treating cancer the physiology is complicated, and you need to know a lot more than you’re likely to learn from marketers pushing keto as a weight-loss solution.

Surprise: Cancer can live on fats, too 

A ketogenic diet is not only restrictive, it’s nutritionally sparse. Consider this: to enter ketosis and burn that unwanted fat, an adult male must eat fewer than 20 to 50 grams of carbs. Given that a medium-size apple has 25 grams of carbohydrates and a single, thick slice of bread has 21 grams of carbs, it’s very easy to cross that threshold in a single snack session.

At present, companies that market ketogenic meals are populating news feeds with reports of extraordinary effects in cancer patients. They argue that since cancer feeds on sugar, you’re better off avoiding carbohydrates that turn into sugar in the body. This is true as far as it goes.

But the truth is, all cells feed on sugar. I’m all for avoiding processed sugars, but avoiding healthy carbohydrates not only weakens cancer cells, it weakens healthy cells—like your immune cells– as well. I would number certain fruits and whole grains among the healthy carbs.

What’s more, the research I’ve seen shows that cancer also feeds on ketones after all. The original theory of the keto treatment for cancer is that cancer can ONLY feed on glucose. But cancers vary and this is not quite true.

Ketones shown to fuel breast cancer 

In one experiment, scientists dripped ketones on breast cancer cells in a petri dish and the result was a much more aggressive cancer which possessed the kind of genes associated with significantly lower survival rates.

On top of that, cancer researchers are currently considering a way to develop ketone-blocking drugs that completely halt ketone production to further prevent cancer growth-– very much the opposite of what the keto diet tries to achieve. To be honest, I don’t know much about this research, but it’s concerning.

You also have to consider decades of research into diet and cancer risk. Numerous studies confirm that high-fat diets like the keto diet increase risk for breast cancer and prostate cancer, to name just two.

And though people might argue that losing weight through the keto diet lowers your overall risk of health complications like cancer, the truth is likely more complicated.  Yes, maintaining a health weight does protect you against cancer. But eating high amounts of fat, especially saturated fats from animal products, while foregoing healthy carbs, may increase your risk.

For what it’s worth, to date there is no clinical study that shows any kind of measurable benefit from a ketogenic diet when you’re dealing with cancer.

So what about keto and weight loss? 

The keto diet will help you lose weight, at least for the short term. But after two to six months, the advantage of cutting out those carbs disappears when compared to other diets. By then, your body adjusts to the carbohydrate loss and burns less fat. Not to mention that the diet is hard to endure over the long run.

I’ve tried the super-low-carb diet myself and it’s nearly impossible to stick with.

It’s also interesting to note that when scientists compared the keto diet to other diets, long-term weight loss remained the same. There are probably a lot of compliance issues here. People with weight problems tend to have trouble sticking with ANY diet, and go from one diet to the next hoping to find one that works for them.

Still – and, again, for what it’s worth – keto seems to be no better than anything else for weight loss. And although the keto diet does appear to help people with Type 2 diabetes better control their blood sugar levels, that advantage likewise disappears after a few months.

When you give up carbs almost completely, the tendency is to turn to meat – you have to eat something – and extremely high meat consumption is at least dubious (I don’t believe it’s been proven dangerous).

Put it this way: you can sum up the problem as “operator error.” You can follow keto rules and eat a salad with chicken and olive oil dressing. Or you can eat bacon and diet soda – or any kind of processed food for that matter, if it’s low in carbs. The latter is decidedly not helpful in your fight against cancer.

The more healthy type of keto diet, in which you eat massive amounts of vegetables, is almost impossible to comply with long term.

There’s also a common misconception that you can’t eat too much protein, which leads people to opt for three steaks a week. But beware: the amino acids in animal protein can be converted into glucose in your body, which has the same effect as eating carbs!

So what should a cancer patient do? 

I think the problem is that when diets become fads, people overlook the fact that everyone’s body and health needs are unique. And the bandwagon is never the best place to be when you’re trying to fight or prevent cancer.

So what’s my advice for the cancer patient?  Sugar and most other high-density sweeteners should be out. That includes honey, even though it contains health-giving nutrients.

Ditto for most other “white carbs” – potatoes, rice, refined white flour and products made from it such as pasta, bread or cereals.  These are high-glycemic foods that are quickly converted to blood sugar. And even though, yes, cancer can learn to live on fat, its strong preference is for glucose.  You’re supercharging cancer when you consume high-glycemic products.

After nearly 20 years of researching and writing about cancer, I’m confident of this advice.

I do think the cancer patient can safely eat moderate amounts of fruit – and should. Likewise moderate amounts of whole grains like oatmeal sound healthy to me. There is not a lot of scientific evidence on exactly how much a cancer patient is going to benefit from this approach, however.

We do know that the evidence is you need some carbs, and the fruits and whole grains are the healthiest choices. And they have the advantage of being rich in a vast range of nutrients – which sugar, potatoes, white bread and rice are definitely not. AND this is a diet you can live with, while the hardcore, pure keto diet probably isn’t.

Avoid all processed foods. They usually have added sugar and dubious chemical food additives. Get in the habit of reading package labels. If the list of ingredients includes sugar or chemicals you’ve never heard of and probably can’t pronounce, then don’t buy it. An MD and nutrition expert I respect says don’t buy any packaged good that contains more than five ingredients. I wouldn’t make that a rule but it’s a useful guideline.

I hope it goes without saying that all your foods should be organic.

I believe the best option for the cancer patient is to seek the help of an alternative or integrative cancer doctor who is receptive to nutrition (not all of them are). Ask him or her to not only help you come up with an eating plan to beat your cancer, but one you can stick with for life.

Because that’s what you’re going to have to do if you want that life to be a long one.

Best regards,

Lee Euler,


  1. Greger, Michael. “How Not to Diet: The Groundbreaking Science of Healthy, Permanent Weight Loss.” Flatiron Books, New York, 2019.
  2. “Is the keto diet healthy? A cancer doctor explains why he's been on keto for 6 years.” By Kristin Kirkpatrick.18 December 2019 for Today.
  3. “Ketones and lactate increase cancer cell “stemness,” driving recurrence, metastasis and poor clinical outcome in breast cancer: achieving personalized medicine via metabolo-genomics.” Martinez-Outschoorn U.E. Prisco M., et al. Cell Cycle. 2011(8):1271-86.
  4. “Response to commentary by Champ and Klement: is a ketogenic diet the solution for the hyperglycemia problem in glioblastoma therapy?” By Mayer A., Vaupel P., et al. StrahlentherOnkol. 2015:191(3):283-4.
  5. “What Is the Keto Diet and Does It Work?” By Dawn MacKeen, published Jan. 2, 2020 for The New York Times.

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