Keto Causes Cancer? Here's What the Headlines Aren't Telling You.

Keto Causes Cancer? Here's What the Headlines Aren't Telling You.

A study from MIT has people questioning the ketogenic diet. But what the researchers actually discovered is a lot more interesting than the headlines suggest.

Well, here we go again.

Another study about the ketogenic diet, and another round of headlines suggesting that something millions of people have used to improve their health might actually be killing them.

This time, the concern is cancer.

Researchers from MIT published a study in Nature suggesting that a ketogenic diet could increase the risk of certain intestinal tumors.

And naturally, that gets people's attention.

Especially those of us who have followed some version of a ketogenic or low-carbohydrate lifestyle for years.

But before you throw out your eggs, steak, and avocado, there's something you need to understand.

The study didn't find that keto causes cancer in humans.

And that's only the beginning…

What the Researchers ACTUALLY Found

The MIT researchers studied mice that were genetically predisposed to developing intestinal tumors.

That's important.

These weren't ordinary, healthy mice that suddenly developed cancer because somebody took away their carbohydrates.

They were mice that already had a genetic susceptibility to tumor development.

The researchers divided them into groups receiving different diets, including a ketogenic diet, a standard control diet, and a high-fat, high-calorie diet.

And here's where things got interesting.

The mice eating the ketogenic diet developed more tumors in their small intestines than mice eating the control diet.

In some cases, their tumor rates were comparable to or higher than mice eating the high-fat, high-calorie diet.

The researchers also found increased tumor burden and shorter survival in their cancer-prone mouse models.

Sounds pretty bad, doesn't it?

But keep reading, because there's another part of this study that hasn't gotten nearly as much attention.

The Same Diet Actually Reduced Tumors Somewhere Else

While the ketogenic diet promoted tumor development in the small intestine, the researchers observed something completely different in the colon.

The mice eating keto developed fewer colon tumors.

Same animals.

Same diet.

Two different parts of the digestive system.

And two completely different responses.

Think about that for a minute.

If someone wanted to make the ketogenic diet look dangerous, they could point to the small intestine findings.

If someone wanted to make keto look protective against cancer, they could point to the colon findings.

And technically, both would be describing results from the same research.

This is exactly why I get frustrated with the way nutrition studies are presented to the public.

People want a simple answer.

Is keto good or bad?

Is fat healthy or unhealthy?

Does this food cause cancer or prevent it?

But the human body doesn't operate in those neat little categories.

And apparently, neither does the body of a mouse.

Here's the Part That Really Caught My Attention

For years, there's been interest in the possibility that ketogenic diets might help fight certain cancers.

The basic idea is that many cancer cells rely heavily on glucose for energy.

Reduce the carbohydrates, lower circulating glucose and insulin, and perhaps you can make the environment less favorable for some tumors.

That's an interesting theory, and researchers have been investigating it.

But it's also been oversimplified.

Not every cancer behaves the same way, and not every cancer cell depends on glucose to the same degree.

Some tumors can use other fuels.

Now here's what the MIT researchers discovered.

The increased tumor development wasn't being driven by ketones themselves.

It was associated with the way cells in the small intestine were processing and burning dietary fat.

That process, called fatty acid oxidation, activated signaling pathways that encouraged intestinal stem cells to multiply.

Normally, stem cells help repair and maintain the intestinal lining.

That's a good thing.

But in animals already genetically prone to intestinal tumors, stimulating that process appeared to create more opportunities for abnormal growth.

And importantly, the researchers found that manipulating ketone production didn't eliminate the effect.

In other words, simply producing more ketones wasn't what caused the tumors to grow.

The high-fat dietary environment and how those intestinal cells used fat were central to the findings.

That's a pretty significant difference.

Does This Mean Eating Fat Causes Cancer?

No.

And I wouldn't make that conclusion any more than I'd claim this study proves keto prevents colon cancer in humans.

Here's the deal.

We need to recognize what this research can tell us and what it can't.

First, this was an animal study.

Mice are useful for studying biological mechanisms, but they're not little humans running around on four legs.

Their metabolism, genetics, and responses to dietary changes can be different from ours.

Second, these mice were genetically predisposed to intestinal tumors.

That doesn't mean the results are meaningless.

It means we need to be especially careful about applying them to the general population.

Third, the researchers investigated a ketogenic diet with a very high proportion of dietary fat.

That isn't necessarily the same thing as someone eating a moderate-protein, real-food, lower-carbohydrate diet built around meat, eggs, vegetables, and reasonable amounts of healthy fats.

And finally, we don't yet know whether these same effects occur in people, which types or amounts of dietary fat might matter most, or whether particular individuals are more susceptible.

Those are questions that need answers.

Not guesses.

But Keto Supporters Need to Hear This Too

I'm going to say something that might irritate a few people in the keto community.

Being in ketosis doesn't automatically mean everything you're doing is healthy.

I've seen people become so obsessed with ketone numbers that they forget why they started eating differently in the first place.

They're dumping butter into their coffee, adding fat to everything they eat, and treating carbohydrates like they're radioactive.

Meanwhile, they're barely eating vegetables, ignoring fiber, and assuming that because they're producing ketones, they're improving their health.

That's not how this works.

There's a difference between using ketosis as a metabolic tool and making ketosis the entire goal of your diet.

You can reduce refined carbohydrates and added sugar without believing that every gram of carbohydrate is harmful.

You can eat healthy fats without eating sticks of butter and feeling obligated to consume as much fat as physically possible

And you can enjoy the benefits of a lower-carbohydrate lifestyle without pretending the research is settled on every long-term outcome.

I've always believed that real food should be the foundation.

Not a particular ketone reading.

Not a magical macronutrient ratio.

And DEFINITELY not some packaged product that says KETO in giant letters across the front while the ingredient list looks like a chemistry experiment.

So What Should You Actually Do?

If you're following a ketogenic or low-carbohydrate diet and it's helping you improve your metabolic health, this study alone isn't a reason to abandon everything that's working.

But it is a good reminder to pay attention to the bigger picture.

Eat adequate protein.

Include vegetables and other fiber-rich whole foods that fit your dietary needs.

Get your fats from a variety of minimally processed sources rather than treating added fat as something you need to maximize.

Pay attention to your metabolic health, blood pressure, blood panel markers, energy, and how you feel over time.

And remember that metabolic flexibility or what I call Fuel Freedom matters.

Your body is designed to use different fuels depending on what's available and what you're asking it to do.

You don't need to spend every waking moment chasing the highest possible ketone reading.

If you have a hereditary cancer syndrome, an intestinal tumor history, or you're being treated for cancer, dietary decisions deserve individualized medical guidance. This research definitlely doesn't establish keto as a cancer treatment.

My Bottom Line

I don't think this study proves that keto causes cancer.

I also don't think it should be dismissed simply because the findings are uncomfortable for people who love the ketogenic diet.

That's not how science should work.

What it demonstrates is that the same dietary approach can produce very different biological effects depending on the tissue involved and the circumstances of the individual.

And that's something we should take seriously.

For me, this doesn't change the fundamentals.

Eat real food.

Reduce ultra-processed junk.

Get enough protein.

Don't be afraid of healthy fats, but don't assume unlimited amounts are automatically better.

Take care of your metabolic health.

And stop expecting a single dietary strategy to solve every health problem known to man.

I lost 85 pounds changing how I ate, and I still believe reducing the junk in our diets is one of the most important things we can do for our health.

But I didn't make those changes because I wanted to worship a ketone meter.

I made them because I wanted to be healthier.

There's a difference.

A diet is supposed to be a tool that helps you live a healthier life. Not a religion you have to defend every time a new study comes out.

And that's probably the most important lesson from this research.

Research and Sources

MIT — Ketogenic Diets May Increase Cancer Risk in the Small Intestine (July 15, 2026)

https://news.mit.edu/2026/ketogenic-diets-may-increase-cancer-risk-small-intestine-0715

Nature — Ketogenic Diet Mediates Intestinal Tumorigenesis Through Lipids Not Ketones (July 15, 2026)

https://www.nature.com/articles/s41586-026-10779-y

ScienceDaily — MIT Scientists Find a Hidden Cancer Risk of the Keto Diet (October 5, 2026)

https://www.sciencedaily.com/releases/2026/10/261002080037.htm

I put 3 videos from last week that you may be interested in down below if you missed them. The first is about prediabetes and how it starts a lot earlier than you think. The second is the one plate that can reverse your fatty liver. The third? My recipe of the week for a low carb viral “Dorito” casserole

Stay healthy,
Victor
Primal Nutrition / Southern Keto

P.S.

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Let’s make this your healthiest chapter yet.