The keto diet has become one of the most talked about ways of eating out there.
Originally created decades ago to help control seizures, it’s now tried by millions hoping it might help with everything from losing weight to protecting the brain. Some scientists have even wondered whether it could help fight off cancer.
However, a brand-new study is throwing a bit of a curveball into that idea, showing that the exact same diet can actually do two completely opposite things depending on which part of the gut it’s affecting. Here’s what scientists actually found, and why it’s making people rethink what they thought they knew about this diet.
The same diet did two opposite things in the same body.
Researchers ran an experiment using mice that were genetically likely to develop tumours in their gut. When these mice were fed a keto style diet, something strange happened. The diet actually sped up tumour growth in one part of the small intestine, while at the same time slowing down tumour growth further along in the colon.
That’s a pretty striking result on its own, since you’d normally expect one diet to have a fairly consistent effect throughout the body. Finding two completely opposite outcomes happening at the same time, from the exact same diet, immediately raised a lot of questions for the research team.
It wasn’t ketones causing the effect, which surprised everyone.
For years, a lot of the credit for keto’s supposed benefits has gone to ketones, the little molecules your body makes when it’s burning fat instead of carbs for energy. Scientists had assumed these ketones were the main reason keto diets might help protect against certain cancers.
However, this new study found something completely different was going on. Whether the mice made more ketones or fewer of them didn’t actually change how their tumours grew at all. That ruled out ketones as the main driver, sending researchers looking elsewhere for an explanation.
The real cause turned out to be how cells burn fat.
Instead of ketones, the researchers traced the effect back to how cells in the gut actually break down and use dietary fat for energy. As gut cells processed all that extra fat from the keto diet, it switched on certain proteins that told nearby stem cells to start dividing more quickly.
That extra cell division can actually be useful in some situations, since it helps repair damaged tissue faster when something goes wrong. But it comes with a real downside too, since more actively dividing cells also means a higher chance that some of them could eventually turn cancerous.
Extra healing power comes with a hidden risk.
Having more active stem cells sounds like a good thing at first glance, since they’re the cells responsible for repairing your gut when it gets injured or irritated. A gut with more of these cells on standby can bounce back from damage more effectively.
The trade-off, though, is that busier, more active stem cells are also more likely to make mistakes as they divide, and some of those mistakes can eventually lead to tumours forming. It’s a case of the same process being helpful in one way and risky in another, all happening inside the same tissue.
This challenges what scientists previously believed about keto and cancer.
An earlier major study had suggested that ketones themselves were the reason keto diets seemed to offer some protection against colon cancer specifically. This new research tells a different story entirely, pointing instead to the fat itself, and how the body processes it, as the real reason behind that protective effect.
This distinction actually matters a lot for anyone taking ketone supplements hoping to get similar benefits without changing their whole diet. Since the effects seem to come from fat metabolism rather than ketones directly, simply boosting ketone levels through a supplement likely wouldn’t produce the same results seen in this study.
Diet and what happens inside your body aren’t always the same thing.
One of the researchers made a point of separating two ideas that often get lumped together, the diet itself and the biological process it triggers inside the body. In this case, it was specifically the high fat content of the diet driving these effects, not the ketones that diet happens to produce along the way.
This is a useful distinction for anyone trying to understand keto related headlines going forward. Just because a diet produces ketones doesn’t automatically mean those ketones are responsible for whatever effect is being observed, good or bad.
There’s still a lot researchers don’t understand.
One of the biggest remaining mysteries is exactly why two neighbouring parts of the intestine would respond so differently to the exact same diet in the first place. Right now, researchers don’t have a clear answer for why one section speeds up tumour growth while the other slows it down.
Figuring out the answer to that question is exactly what the research team plans to investigate next. Understanding why these two areas respond so differently could end up being just as important as the original discovery itself.
This research comes with some important limits that should be mentioned.
It’s worth being clear that this study was done entirely in mice that were specifically bred to be prone to developing intestinal tumours, not in ordinary people eating a keto diet for weight loss or general health. The closest matching condition in humans is a rare inherited disorder that majorly raises someone’s risk of developing intestinal tumours.
Because of this, researchers say more work is needed before anyone can say for certain whether the same pattern would play out in people. For now, this remains an important early clue rather than a final answer about how keto diets interact with cancer risk in humans.
