Cancer is the second leading cause of death in the United States (1).
Researchers estimated that 606,520 Americans would die from cancer in 2020. That means more than 1,600 deaths a day, on average (1).
Cancer is most commonly treated with a combination of surgery, chemotherapy, and radiation.
Many different diet strategies have been studied, but none has been particularly effective.
Important note: You should never, ever delay or avoid conventional medical treatment of cancer in favor of an alternative treatment such as the ketogenic diet. You should discuss all treatment options with your healthcare provider.
It involves significantly reducing your intake of carbs and replacing them with fat and protein. This change leads to a metabolic state called ketosis.
After several days, fat becomes your body’s primary energy source.
This causes a substantial increase in the levels of compounds called ketones in your blood (
In general, a ketogenic diet provides 70% of calories as fat, with 20% of calories from protein and 10% of calories from carbs (
There are many versions of the ketogenic diet, though. Some versions are even higher in fat.
The ketogenic diet is a very low carb, high fat diet. Fat intake may be 70% of total calorie intake, if not higher.
Many cancer therapies are designed to target the biological differences between cancer cells and normal cells.
Basically, this is claimed to “starve” the cancer cells of fuel.
As in all living cells, the long-term effect of this “starvation” may be that the cancer cells will grow more slowly, decrease in size, or possibly even die.
A ketogenic diet can lower blood sugar levels. This may help reduce tumor growth and even starve cancer cells of energy.
Several other processes may explain how a ketogenic diet can aid cancer treatment.
Firstly, reducing carbs can quickly lower calorie intake, reducing the energy available to the cells in your body.
In turn, this may slow tumor growth and the cancer’s progression.
In addition, ketogenic diets can provide other benefits.
Cancer cells can’t use ketones as fuel. Research in animals shows that ketones may reduce tumor size and growth (10).
Beyond lowering blood sugar, the ketogenic diet may also help treat cancer via other mechanisms. These include lowering calories, reducing insulin levels, and increasing ketones.
Researchers have studied the ketogenic diet as an alternative cancer therapy for decades.
Until recently, most of these studies were done in animals.
One study of mice with metastatic cancer tested a ketogenic diet with or without oxygen therapy. When compared with a standard diet, the ketogenic diet resulted in a significant decrease in tumor growth (
The ketogenic diet also increased mean survival time by 56.7% (the equivalent of around 17 days). This number increased to 77.9% (or around 24 days) when combined with oxygen therapy (
Another study found that using a very low carb diet to restrict glucose levels prevented the growth of squamous cell carcinoma tumors in mice with lung cancer or esophageal cancer. Study subjects received only 0.1% of their calories from carbs (12).
The diet was even more effective at preventing tumor growth when it was combined with the diabetes drug canagliflozin.
The ketogenic diet alone didn’t help to shrink existing tumors, and neither did the chemotherapy drug cisplatin. However, combining these two methods was effective at helping to shrink tumors (12).
In some cases, following the ketogenic diet made the anticancer drugs phosphoinositide 3-kinase inhibitors (PI3K inhibitors) work more effectively. This effect was partly attributed to the fact that the ketogenic diet reduces insulin levels (
In animals, the ketogenic diet seems to be a promising alternative treatment for cancer.
Despite the promising evidence in animals, research in humans is only just emerging and largely limited to case studies.
Currently, the limited research seems to show that a ketogenic diet may reduce tumor size and the progression rate of certain cancers (16).
Brain cancer studies
A 2010 case study marked the first time that research was published on the effects of treating a glioblastoma with a combination of standard therapy and a restricted ketogenic diet.
The case study followed a 65-year-old woman. Following surgery, she received a very low calorie ketogenic diet. During this time, the tumor’s progression slowed.
However, 10 weeks after returning to a normal diet, she experienced a significant increase in tumor growth (17).
Results from later research are also promising. Almost all of the later research has concluded that a ketogenic diet leads to reduced glucose levels.
In another study, 3 out of 5 people with a glioma experienced complete remission after adopting a ketogenic diet combined with radiation or chemotherapy.
The other two participants, though, experienced a progression in the disease after they stopped the ketogenic diet (
Similar case reports from 1995 examined the reactions to a ketogenic diet in two girls who were undergoing treatment for advanced brain cancer.
Researchers found that glucose uptake was decreased in the tumors of both girls.
One of the girls reported improved quality of life and remained on the diet for 12 months. During that time, her disease showed no further progression (
Studies of other cancers
Some participants in the study followed the high fiber, low fat American Cancer Society (ACS) diet instead. The women who followed the ketogenic diet were more likely to report that they could readily complete activities such as climbing stairs or moving a table (
They also experienced other benefits, such as increased energy and decreased cravings for starchy foods and “fast food fats” like pizza (
The ketogenic diet may also help improve the body composition of people with various types of cancer.
In a study of 81 people, researchers observed benefits such as reduced fat mass in people with rectal or breast cancer and the preservation of skeletal muscle mass.
Study participants experienced these benefits even though they were also undergoing radiation therapy, chemotherapy, or a combination of both. These standard cancer treatments have been known to negatively affect body composition and appetite (25).
One quality-of-life study investigated the effects of a ketogenic diet in 16 people with advanced cancer.
Several people dropped out of the study because they didn’t enjoy the diet or due to personal reasons. Two people died early.
Out of the 16 participants, 5 remained on the ketogenic diet for the entire 3-month study period. They reported improved emotional well-being and reduced insomnia, without any negative side effects caused by the diet.
Some parameters, such as fatigue and pain, remained the same or worsened over time. Because the study participants all had advanced disease, this outcome was expected (26).
Although the ketogenic diet showed benefits for quality of life, the relatively low compliance rate indicates that it may be hard to get people to stick with the diet.
A few small studies and case reports in humans suggest that a ketogenic diet may help slow the progression of cancer. However, a lot more research is needed.
Some mechanisms suggest that a ketogenic diet may help prevent the development of cancer in the first place.
Primarily, it may reduce several of the main risk factors for cancer.
May decrease IGF-1 levels
Insulin-like growth factor 1 (IGF-1) is a hormone that’s important for cell development. It also reduces programmed cell death.
This hormone plays a role in the development and progression of cancer (27).
The ketogenic diet reduces IGF-1 levels, thereby decreasing the direct effects insulin has on cell growth (
This may reduce tumor growth and cancer risk over the long term (
Can help blood sugar levels and management of diabetes
Some people may find it challenging to adhere to the diet over a long period of time, though. More studies on the long-term safety of the diet are also needed.
May decrease obesity
Obesity is also a risk factor for cancer (34).
The ketogenic diet reduces IGF-1 levels, blood sugar levels, and the risk of diabetes and obesity. These factors may lead to a reduced risk of developing cancer in the first place.
It’s important to note that no major cancer group recommends the ketogenic diet for either cancer prevention or cancer treatment, despite the promising research.
The ketogenic diet has its benefits, but it comes with risks, too.
The diet is very limiting in terms of foods known to prevent cancer, such as whole grains, fruits, and some vegetables.
It can also be challenging for those undergoing traditional cancer therapies to consume enough calories while on the diet. Low carb diets, such as ketogenic diets, often result in weight loss (16,
Compliance is poor, which makes the diet challenging for people with cancer. The restrictive nature of the diet can sometimes be too much for a person with cancer, especially when food can be a source of comfort (16, 38).
The diet isn’t appropriate for everyone and could even cause harm. If you’d like to explore the ketogenic diet, speak with a medical professional first. They can help you decide whether the diet’s right for you in the first place and work with you along the way.
A ketogenic diet provides many benefits for health.
According to animal studies and some preliminary research in humans, it may also help treat or prevent cancer.
However, it’s important to keep in mind that the current research is still emerging.
You should never, ever avoid conventional cancer treatment in favor of an alternative treatment like the ketogenic diet.
Your best bet is still to follow the advice of your oncologist. Mainstream medical treatments are very effective at treating many common types of cancer.
That said, perhaps a ketogenic diet could be a good choice as an adjuvant therapy, meaning that it’s used in addition to the conventional treatments.