Dietary fiber is well established to reduce the risk of Colorectal cancer [1]. If there's one thing that's seriously missing from an ultra-processed diet it's fiber.

Almost certainly multifactorial though.

1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3926973/

there is also an extraordinary amount of plastic and chemicals getting absorbed by nearly all food, as per a study last week:

https://edition.cnn.com/2024/09/16/health/food-packaging-che...

> [.. &] alcohol consumption, and tobacco use were the main risk factors for major early-onset cancers

This would be a good explanation for any decline in early onset cancer given that a 40 year old could not have been binge drinking and smoking at their height in 1970s UK.

As a small data set, my mother and grandparents all smoked like there was no tomorrow and drank plenty, but never had any cancer issues. Though my mother and grandfather both had COPD, my mother in particular spent the last few years of her too-short life (late 60s) basically drowning because she couldn't expel the CO2.

Prepared and ultra-processed foods, gut feel, seem to be a huge problem in many ways. A buddy of mine, his girlfriend is a big health nut and her rule of thumb is: Don't eat anything that has more than 4 ingredients or comes in a bag, and that seems like a good idea to me.

> What's the mechanism of this?

It doesn’t necessarily have an easy to understand soundbite explanation. Biology is like spagetti code. Everything depends on everything in difficult to comprehend ways.

Cancer is caused by bad-luck random cell division creating a bad cell

That is only the first necessary step towards cancer. Our bodies have various mechanisms to kill suspicious cells before they start being a systemic problem. Apoptosis, or the immune system attacking them if they can be recognized. These mechanisms are pretty efficient; in the animal world, animals with really strong immune systems, like bats, very rarely get cancer. And most of our current progress against cancer involves ... very careful stimulation of the immune system against targets specific for that particular patient's tumor.

Physical activity can probably influence these anti-cancer mechanisms, as does aging etc.

The simplest explanation is that physical activity increases blood circulation and lung ventilation, which (as long as one is not exercising in a polluted environment) helps the liver and kidneys process and excrete various toxins at a greater rate. It also reduces body fat, which can store fat-soluble toxins.

There's also a high likelihood that people who get regular exercise are also eating healthier food that hasn't been highly processed and loaded up with pesticide residue, biocides that slow fungal and bacterial growth, animal growth hormones, etc.

The fundamental equation is something like:

(body load of toxins) = (ingestion rate) - (excretion rate)

A significant risk factor for some cancers is chronic inflammation. Physical activity can help with that directly, but also indirectly as it can help reduce weight (diet is more important there). Reducing/eliminating chronic inflammation is generally a good thing anyways for other health concerns besides just cancer.

A cutting edge theory is that exercise can interfere's with cancer's metabolism (Warburg Effect) and helps to regulate lactate levels which chronically dis-regulated will promote cancer.

"Specifically, we posit that in carcinogenesis aberrant cell signaling due to exaggerated and continually high lactate levels yields an (inappropriate) positive feedback loop"

[1] https://academic.oup.com/carcin/article/38/2/119/2709442

Here’s a meta-study on the mechanisms for the benefits of moderate exercise, and it includes a sizeable list of different chemical changes in the body that exercise promotes: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9923435/

Recent science suggests that the body adjusts to burn approximately the same amount of calories per day, given a consistent amount of activity, regardless of how much activity there actually is. So, a person with an active lifestyle will burn approximately the average 2,000 calories, but a person at rest will also burn about the same number.

I'm oversimplifying massively, but essentially, the theory is that if you don't give your body an outlet to burn with, it will burn the calories on things that aren't good for you. Eg, increasing inflammation.

It wouldn't surprise me if some of these effects are contributing factors.

Source: https://youtu.be/vSSkDos2hzo?si=CrPh2_vLRqHG0Z3i

Exercise induces stress which triggers a systemic hormetic response. That response makes cells more resistant to random errors. Additionally, that stress can trigger apoptosis in senescent or unhealthy cells.

I never found a reason BUT my personal opinion is:

Probably putting some "stress" on the cells is beneficial, is like forcing them to work a little once in a while instead of letting them function in the "just survive" mode.

Maybe blood circulation? It may clean toxins from where the blood may flow slower?

That's my headcanon

Higher fitness -> higher chance the immune system will kill the rogue cells on its own.

well there’s the obvious pathway that people who exercise regularly tend to have fewer number of cells than those who don’t

e: okay, not the pathway - but we do know that additional weight increases cancer risk

All the studies say glyphosate is safe. But, glyphosate use really ramped up in the 90s with "round up ready" GMOs being created in 1996. It is even sprayed pre-harvest to uniformly dry grains for harvest.

Who knows if glyphosate is causing cancer. I think there is strong evidence that it is the cause of the rise of celiac disease cases.

Isn't tobacco and alcohol at a high time low in the younger generations?

> tobacco use

What's the worst part of a cigarette, the fact that it has tobacco, or the fact that it has like 100 different cancer causing toxins?

Sugar

If I had to guess I'd think microplastics[1] because we actively consume them and they're found in our tissues and they didn't really exist before the 50s/60s.

But I haven't seen any research showing correlations in real human beings yet.

[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10340669/

PFAS are big in media right now but likely not the main cause.

That's the kind which scares me the most given how quickly it can grow and spread without any symptoms. Feel really fortunate to live in a country where screening starts at thirty years. Back home I would have to be well into my fifties.

There is some correlation between COVID exhausting certain white blood cells that fight cancer:

https://www.nature.com/articles/s41423-021-00750-4

It’s almost certainly much too early to have any data on the relationship between the pandemic and cancer. Cancer causing factors may take decades to turn into detectable cancers, and even if the data were available, publishing them can take a couple of years on top.

The study in question looks at data from before the pandemic: "Global trends in incidence, death, burden and risk factors of early-onset cancer from 1990 to 2019"

yes and then there is the elephant in the room nobody talks about: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10184721/

The pseudouridine in the current generation of mRNA vaccines has also been demonstrated to promote cancer growth: https://www.sciencedirect.com/science/article/abs/pii/S01418...

<in a snarly medical tyranny voice> NIE, you will have zeh vackzine!

Jokes aside though, how is it that hard for people to connect the dots of what happened after "covid"? I guess because there are many other causes for cancer that have also increased since 2019 (poorer sleep quality, worse diets, depression, social isolation). But then again, forcibly injecting something with known carcinogens, into your blood that has since caused athletes and children to immediately collapse and die (or later on from myocarditis) should be overwhelming evidence of something akin to genocide.

You should at least post a link to some source when spreading these rumors.

Those darn cellphones!

The study covers the period 1990-2019, before the mRNA COVID-19 vaccines were developed.

Obviously. It is the only recent nationwide (worldwide actually) environmental change. Might also ask about the plethora of athletes dropping dead or falling extremely ill on the playing field.