Remember way back in the 1980s and ’90s when fat was the enemy and doctors and nutritionists espoused the virtues of a high-carb, low-fat diet? When a plain baked potato was considered a healthy lunch and eggs, bacon and butter were bad? The food industry jumped on the bandwagon, stripping products of fat and cramming them full of sugar to keep them palatable just so they could label them as low-fat and thus boost sales.
By the early 2000s, though, that approach had turned completely on its head. The Atkins Diet, which promotes high protein and fat and low carbohydrate consumption, is often credited with leading the way toward the low-carb revolution. It gave way to the paleo diet movement, where people eat like our hunter-gatherer ancestors. And other fad diets have come and gone in between, each branding carbs and sugar as the enemy.
More recently, the ketogenic or keto diet has lately garnered much attention for its intensive weight loss benefits and potential in fueling endurance athletic activities. People following this diet eat no more than 10 percent of their calories from carbohydrates, about 20 percent from protein and the remaining 70 percent from healthy fats. Maintaining this ratio of macronutrients for a period of time (typically between two and seven days) causes your body to go into ketosis, a state in which the liver produces ketones — compounds derived from fatty acids produced by the liver as a byproduct of breaking down fat for fuel. The idea is that by depriving your body of carbohydrates, which it can more easily burn for energy, you force it into a fat-burning mode that torches reserved fat stores and bingo, you lose weight or can run, swim or bike nearly endlessly on minimal food.
But other things also happen in the body and the brain when ketones are present. For one, it can quell seizures in epileptics. Angela Poff, a research associate in the Department of Molecular Pharmacology and Physiology at the University of South Florida in Tampa, says “it had been known for a really long time that fasting or starvation could basically cure seizures, at least for the time you could continue to fast.” To extend the timeline of benefit, “physicians developed a diet that they felt would mimic the metabolic state of fasting, which is essentially a very high-fat diet,” called the ketogenic diet. Today, “it’s a standard of care therapy for refractory epilepsy, meaning seizures that don’t respond to the typical anti-epileptic medication,” Poff says.
Around the time the ketogenic diet was being developed, the work of a German biochemist named Otto Warburg began to uncover a potential application for this diet in the treatment of cancer. Warburg observed that cancer cells typically derive energy from different sources than healthy cells. Poff explains: “In general, most cancers have a higher reliance on glucose (sugar) than a normal cell, and so the idea was if you use this diet that lowers glucose, it might be helpful” in killing off the cancer by depriving it of its preferred fuel source. This so-called Warburg Effect suggests that following a ketogenic diet could slow the growth of cancer or even cure it outright. But so far, those concepts haven’t been fully proven.
That said, some studies have supported the notion that the assumption is true, at least in some cancers, but Poff is careful to add that much more research needs to be done before we fully understand how it all works. “Most of the work in this field is still pre-clinical, meaning it’s been conducted in animal models. It’s been done in various cancer types, but most of the work has been done in brain cancer specifically. But there’s very little clinical data all around. There’s some case reports and very small preliminary clinical studies in small groups of patients, usually very late-stage patients with various types of cancers. So in the clinical realm, which is the most important in telling us whether this is going to be useful, we have a long way to go.”
Over the past few years, as the general public has become more aware of the ketogenic diet and its potential to help people lose weight — which in itself could reduce risk of developing cancer, as adipose tissue is metabolically active and obesity has been linked to a higher risk of developing many types of cancer, including breast cancer — more researchers are looking at whether it may offer a key to help control certain types of cancer. Several recent studies have suggested that yes, in certain instances following a ketogenic diet could slow the growth of some forms of cancer.
For example, a 2015 study in the journal PLoS One found that the growth of neuroblastoma xenografts — neuroblastoma is a form of pediatric brain cancer and to study how it behaves, grafts are implanted into mouse models — were significantly reduced by following a ketogenic diet consisting of a 2 to 1 ratio of fat to carbohydrate plus protein when combined with calorie restriction. However, restricting calories isn’t right for all cancer patients, particularly those who have developed cachexia, a wasting syndrome that’s common in certain cancers, including lung cancer. A 2018 study, also conducted in mice, found that using an infant formula with a ketogenic composition was effective in slowing the growth of colorectal cancer and actually helped prevent cancer cachexia. These mixed results indicate that the science is still murky.
Plus, following a ketogenic diet is probably not a good fit for every type of cancer and not a good fit for all people. A 2017 study found that a genetic mutation that’s common in melanoma actually uses ketones to grow faster. And a review of the available clinical data published in 2018 in the journal Aging noted that a keto diet has shown a pro-tumor effect in some studies conducted in prostate cancer and kidney cancer as well. It’s unclear why some tumors shrink in the presence of ketones while others are able to use these compounds to fuel growth, but research is ongoing to help unlock the secret.
For breast cancer specifically, several studies have shown an anti-tumor effect when a keto diet is used. However, there haven’t been many studies done, and although Poff says she’s “very encouraged by the research that’s out there, it’s by no means conclusive and there’s a lot more research that needs to be done.”
To further complicate matters, many women who’ve dealt with breast cancer are told to follow a low-fat diet as a means of reducing their risk of occurrence. A secondary analysis of the Women’s Health Initiative — a large-scale study looking at the relationship between diet and lifestyle factors and post-menopausal women’s health — found that post-menopausal women who followed a low-fat diet after being diagnosed with breast cancer were less likely to die of any cause over the next 10 years versus women who ate a higher-fat diet.
It can be difficult to understand what the best approach is if you’ve had or are worried about developing breast cancer. As the American Cancer Society notes, although some epidemiological studies have indicated that “people who live in countries with higher amounts of fat in their diet have higher rates of breast, prostate, colon, and other cancers,” it’s not clear if dietary fat is a causal factor. “At this time, there is not much proof that the total amount of fat a person eats affects cancer risk.”
But for Thomas Seyfried, professor of biology at Boston College, the results in animal studies and limited testing in humans aren’t just promising, they’re revolutionary. Though his stance is considered controversial to some oncology experts, he’s adamant that treating cancer as a metabolic rather than a genetic disease (meaning to target how the cells fuel themselves rather than genetic mutations within them) will lead to a vast reduction in the number of deaths from cancer. He’s been working to develop a treatment protocol that might one day find its way to a treatment center near you.
“It’s called ketogenic metabolic therapy,” and he says in this context, “the ketogenic diet shouldn’t be considered a diet like green salads or other such stuff. It’s essentially medicine, and the process primarily tries to remove one of the driving fuels for the disease, which is glucose, and transition the whole body over to ketones, which the tumor cells can’t use as a fuel. So it’s very simple,” he says. The approach was outlined in a 2017 paper that Seyfried believes will serve as the “blueprint for the destruction of cancer” once all the particulars have been worked out.
“It’s a cocktail of drugs and procedures and foods and they all work synergistically to gradually eliminate the tumor while maintaining the health and vitality of our normal organs. The whole goal of this metabolic therapy, which involves the ketogenic diet, is to gradually degrade and eliminate tumor cells without toxicity so the patient emerges from the therapy healthier than when they started,” he says.
The approach is still new and has only been tested in limited settings. Seyfried’s team continues to research which patients are best suited to the treatment and when and how drugs and the other elements of the therapy should be administered for the best outcome. But he’s enthusiastic that this approach will fundamentally alter the way cancer will be treated in the future.
In the meantime, if you’re interested in trying a ketogenic diet as part of your treatment for breast cancer or to reduce your risk of recurrence or developing it, be sure to talk with your doctor first. Some doctors and nutritionists worry that the diet’s reliance on red meat and animal products may actually elevate your risk of colon cancer. There’s also limited data on how the diet impacts health long term. Because it’s quite restrictive, it can also be challenging to maintain this approach to food over the long haul. And it could end up being a pointless exercise in deprivation; as the American Institute for Cancer Research notes, “currently, no major cancer health organizations, including AICR, recommend the ketogenic diet for cancer patients — or for cancer prevention.”
If you have breast cancer or another disease, Poff says it’s absolutely critical that you communicate with your doctor about any changes you make to your diet. Although most people have no real problem adapting to a really low-carb diet, she says it can be dangerous for people with metabolic diseases that prevent the normal metabolism of fat, and people with any sort of liver disease should only proceed under the care of a physician.
“I think it’s really important anytime anyone completely makes such a huge diet change that they’re being overseen by their doctor and keeping an eye on their blood lipids (fats in the blood) and blood parameters. While the data that’s out there about keto in the healthy population shows that, for the most part, people respond very favorably in terms of their biomarkers improving, there’s some small groups of people who have concerning changes in their biomarkers as well. So, we’re not all the same by any means, and it’s possible” that a keto diet will not provide benefits for you.
And for cancer patients, she urges caution. “It’s absolutely critical for a cancer patient, if they wanted to do something like this, that they work very closely with their oncologist and a ketogenic diet-trained dietitian.”
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Update 04/24/19: This story was originally published on April 2, 2018, and has been updated with new information.