More likely relates to diet. There was a recent WashU study directly linking high fructose diets to increased cancer. Cancer cells are vigorously growing, needs lots of available fuel, a diet full of corn syrup fuels both fat and cancer.
> How much fruit do you have to eat before it becomes harmful?
Unclear. The aforementioned study fed mice sugar water [1], and cautions against extending its findings to fruit as "natural fructose obtained from plants typically confers metabolic benefits due to its slower absorption rate and the presence of beneficial plant fiber and antioxidants."
It does mention, however, that "human physiology...confronts challenges when metabolizing fructose beyond 25g/day." That's like a cup of grapes, a medium pear or half a mango [2].
I've stopped eating fruit (and carrots, which have fruit-like levels of sugar) with the exception of tart (i.e., less sugary) cherries out of a desire to limit my fructose intake. I was eating raspberries, too, which are much lower in sugar than most fruit, but stopped because of their high levels of oxalic acid, but I do expect to restart raspberries in a few years because I expect my ability to tolerate oxalic acid in my diet to improve slowly over the next few years. (In contrast, high-fructose foods including most fruit are probably gone for good.)
Of course, I'm not asserting that everyone should do as I am doing. There is substantial variation between individuals here.
> AIUI cancer cells are also metabolically inflexible; they like glucose, not ketones
Is there a selection effect at play? As in, a person with high serum glucose levels will tend to have cancer that likes glucose? That would imply the solution isn't ketones per se, but changing the fuel from whatever the cancer grew up with.
iirc the talk I learned this from said there's simply not many cancer variants that don't need abundant glucose to grow tumors. That the whole defect stems from hijacking the energy side to fuel uncontrolled growth, and it needs glucose.
Yeah I see this take all the time and it's dangerous, it might have an element of truth but it's definitely dangerously simplistic. You can find advocates of low fat high carb diets also claiming that very low fat intakes improve cancer survivability.
You're absolutely right it's dangerous. It's likely that I gave myself cancer by adopting this 'simplistic truth'.
A decade ago I read about the keto diet and thought "why not?". Lots of positive stories about dropping weight fast, getting mental clarity and starving cancer.
A few years later, I was diagnosed with a rare Leukaemia (with a distinctive BRAF mutation).
I was too young to have a cancer so I thought... maybe this keto thing is not so good after all?
Cue to several Pubmed rabbit holes, where I find studies suggesting that one of the ketones (acetoacetate) promotes tumor growth in BRAF-related cancers (melanoma, colorectal, hairy cell leukemia, and others).
Well, that was the moment I stopped doing stupid 'hacks' with my body and strictly adhere to the 'common sense diet' - ie eating like my grandpa did.
While I can't confirm 100% that my cancer was triggered by the keto diet, I have a strong suspicion it did.
So yeah, before going online and stating grandiose things like "cancer starve on ketones, they need glucose" let's all acknowledge that we humans know very little about what's going on with cancer, and the potential adaptations it can do.
It also doesn't pass the smell test for me because some of the most long-lived, relatively cancer-resistent populations like the Japanese eat carb based diets. That's hard to explain if it really is just a case of replacing glucose in the fuel mixture with fat and ketones.
+1 for the 'grandpa diet', I also feel best eating normally
