[epistasis]

Why would meat cause a decrease in incidence for older folks but a higher incidence for younger folks?

Additionally, the risks you quantify for general cancer incidence are at the bottom odds ratios listed at the end for early-onset. Speculating that ultra-endurance athletes eat tons of meat, without any evidence, seems quite misplaced.

[recallingmemory]

2025 study on the diet quality of ultra-marathon runners: https://pmc.ncbi.nlm.nih.gov/articles/PMC11820624/

From the discussion section, "It is important to note that inadequate intake in the athletes of the present study may carry significant negative health implications. Insufficient consumption of fruits and wholegrains has been linked to the development of chronic diseases, including CVD, cancer, T2D, and hypertension. Additionally, high intake of sodium, saturated fat and discretionary food items are correlated with higher incidence of obesity, T2D, CVD, dementia, and cancer. Paradoxically, despite exceeding the WHO guidelines for physical activity by a substantial margin, these athletes are not meeting dietary recommendations essential for long-term health, highlighting the potential risks posed by these inadequacies."

[epistasis]

Interestingly no mention of meat there.

Low fiber is quite interesting though, even if it alone doesn't quite explain the massive increase in risk that is observed, at least as I understand it. Correlation between low fiber and high meat consumption would be interesting to investigate as well.