Putting a controversial claim for keto-style diets under the microscope 05/03/2018
Why is our report illustrated with an image of an early hunter-gatherer?
Our choice relates to a metabolic state that gets triggered in calorie-deprived humans.
And periods of calorie deprivation are common in hunter-gather populations, whether of the distant past or the present.
When we’re lacking sufficient calories, we shift into a metabolic state called “ketogenesis”.
During ketogenesis, the body releases and burns stored fats to replace missing dietary carbs, which are its usual fuel.
Ketogenic diets are touted for quick weight loss — a benefit for which there’s some evidence — and are an approved therapy for certain cases of epilepsy in children.
You can place your body into a ketogenic state by cutting way back on carbs and sharply upping your fat intake.
Emerging evidence suggests that ketogenic diets might work to discourage and/or hinder the growth of a significant proportion of human cancers.
But new research suggests that ketogenic diets may actually promote the growth of certain types of tumors, including some common ones.
Ketogenic diets versus cancer: Broad strategy or selective tool?
Many tumors rely heavily on sugar to fuel their survival and growth — with exceptions, as we’ll see.
That fact has fueled hopes that ketogenic and other very-low-carb diets could reduce the risk for common cancers or hamper their ability to spread (metastasize).
A low-carb diet will also lower levels of insulin levels, which is an anabolic (growth-promoting) hormone that stimulates proliferation of cells, including cancerous ones.
But the picture is quite a bit more complex. In fact, emerging evidence suggests that ketogenic diets may actually promote certain kinds of cancer.
Before we delve deeper, let’s review the basics about ketogenic diets.
Ketogenic diets: Weight loss and anti-cancer versions
Ketogenic diets designed for weight loss typically derive 60-75% of their calories from fats, 15-30% of their calories from protein, and 5-10% of their calories from carbohydrates.
In contrast, a ketogenic diet designed for therapeutic use against cancer may derive up to 90% of its calories from fats, less than 15% of its calories from protein, and no more than 5% of its calories from carbohydrates.
The US Dietary Guidelines for 2015-2020 don’t spell out specific proportions of fat, carbs, and protein, but say that a “healthy eating style” derives up to 35% of daily calories from fat.
In other words, the standard ketogenic diet derives about 70% more of its calories from fat versus the 35% maximum recommended by the USDA Dietary Guidelines, while a cancer-oriented ketogenic diet calls for more than twice as many calories from fat (about 115% more).
We should clarify that carbohydrates include sugars and readily digested starches, while indigestible starches are considered fibers.
(Carbohydrates known as “resistant starches” — which predominate in many beans — occupy the middle ground. They tend to stabilize blood sugar levels in response to a meal, and in some cases, that beneficial effect that can last up to 24 hours.)
When blood sugar (glucose) levels fall low enough, your liver cells release fatty acids and convert them into so-called “ketone bodies” which your cells can then oxidize or “burn” as an alternate source of energy.
To shift from a normal metabolic state to a ketogenic state, most people need to limit dietary carbohydrates to less than 80 grams (just under 3 ounces) daily and dietary protein to no more than 1.2 grams per kg (2.2 pounds) of lean body mass (i.e., muscle and connective tissue).
As the body gradually adapts to burning ketones instead of sugar (glucose), the liver hormone that’s essential to ketone production (FGF21) becomes more efficient.
Ketogenic diets: Potential anti-cancer ally may promote some tumors
As we said, it’s something of a myth that all cancers depend on sugar to survive and thrive.
Some animal and human research suggests that ketogenic diets can sometimes reduce tumor size and growth.
But it’s not clear whether that beneficial effect would persist, because there’s growing evidence that the cells in some normally sugar-fueled cancers can live and grow on a diet of ketones if carbs are in short supply.
Of course, it’s also something of a challenge to stick to a ketogenic diet — much less the even lower-carb, higher-fat version some recommend for cancer control.
And according to a recent study, ketogenic diets may activate a mutation in certain kinds of cancer cells — a change that enhances growth.
The unfortunate news comes from an international team that included Chinese scientists as well as American researchers from Atlanta’s Emory University and New York’s Memorial Sloan Kettering Cancer Center.
They set out to examine the effects of diet on a mutation to a gene called BRAF — known as the BRAF V600E mutation — that’s found in some cancers (Xia S et al. 2017).
The BRAF V600E mutation occurs in more than half of all melanomas (dangerous skin cancers), 10% of colorectal cancers, five percent of multiple myelomas, and all hairy cell leukemias.
The international team found that a ketone generated by ketogenic diets, called acetoacetate, promotes the growth of melanomas and other tumors that carry the BRAF V600E mutation.
Worse yet, tumors bearing the BRAF V600E mutation promote production of acetoacetate, and acetoacetate stimulates occurance of the BRAF V600E mutation in other cancer cells.
The Chinese-American team concluded that, “… the selective effect of [very high levels of] dietary fat on BRAF V600E tumor growth is mediated through elevated ketogenesis and consequently increased circulating levels of acetoacetate.”
And as they wrote, their findings could enable “… the design of conceptualized ‘precision diets’ that may prevent or delay tumor progression based on an individual's specific oncogenic mutation profile.”
Not all cancers, diets, or persons are created equal
It remains possible — although unproven — that ketogenic diets can slow or stop tumor growth in a substantial proportion of human cancers, and/or help prevent them.
If you know you’re at higher risk for cancers that can bear the BRAF V600E mutation — melanomas, colorectal, multiple myeloma, hairy cell leukemia, and possibly more — work with your medical practitioner to get your tumor tested for this mutation.
If your tumor bears the mutation, it might make sense to avoid putting your body into a ketogenic state.
Just consume a substantial amount of carbs, so your body won’t turn to dietary fat to produce energy — and won’t have as much dietary fat available to convert into ketones.
It would be wise to seek help from a nutrition-savvy physician or well-credentialed nutritionist to devise a diet that provides enough carbs, fats, and protein, but doesn’t encourage ketogenesis.
Conversely, if your tumor does not bear that mutation, it may make very good sense to strictly limit your intake of carbs, especially sugars.
Ketonic diets seem more credible than some alternative therapies
The Internet is rife with websites claiming to offer alternative cancer cures.
While some sites seem sincere, it takes real research to separate the wheat from the chaff.
To date, none of the most commonly prescribed alternative anti-cancer plans possess any significant evidence of efficacy.
These are some commonly touted plans:
- German physician Max Gerson, M.D., (1881 – 1959) recommended a vegetarian diet featuring copious amounts of orange juice, plus various supplements, as well as enemas employing coffee, castor oil, hydrogen peroxide, and/or ozone.
- Prominent German biochemist Johanna Budwig, Ph.D., (1908 – 2003) advised a diet high in flaxseed oil, cottage cheese, fruits, vegetables, and fiber, which avoids meat, shellfish, sugar, processed foods, drugs or supplements, and animal or plant fats (other than flaxseed oil).
- American physician Stanislaw Burzynski, M.D., offers a “personalized cancer therapy” which can include a variety of pharmaceutical drugs, but features a blend of amino acids and amino acid derivatives he calls “antineoplastons”.
Although some dietary aspects of the Gerson and Budwig plans make sense, these plans lack good evidence of efficacy.
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