The heart disease part is basically what I said about the saturated fat.
The diabetes and cancer risks are generally tougher to track. There are other factors at play that are had to control for. For example, you could grill your red meat and increase cancer risk from that (just like other grilled meats). Processed red meat is also usually included in these studies and that has known cancer and diabetes risks (just like other processed foods).
Many of these are high level observational studies which are unable to fully account for all the factors (because we still don't know all the factors). We can show correlation, but there are things like consumption varying by age group, people earing red meat are more likely to be eating other saturated fats as well. People choosing healthy diets are also making other changes than just not eating red meat.
There have been some smaller studies about stuff related to this. Things like plant based diets reducing high risk interorgan fat. So it may not be the red meat itself, but rather the impact of the red meat on things like that interorgan fat. Or how more red meat in a diet can impact gut bacteria, which we are just learning about how important these gut bacteria are. So it's one factor that can influence that.
At this point, I'm not convinced that we know enough of the factors and mechanisms to say the risk is fully linear at the low end of consumption. I do believe it increases as consumption increases, but only beyond a certain point and likely in some logarithmic way.
https://nutritionfacts.org/video/why-is-meat-a-risk-factor-f...
See also the sources under this one:
https://nutritionfacts.org/video/the-health-risks-vs-benefit...
I’m vegan, but for animal welfare reasons, so this discussion is mostly academic for me. I follow this guy for suggestions on what food I should eat as a vegan, but I’ve noticed he has a lot to say about the risks of meat consumption and he seems to be qualified and have relatively straightforward motivations (I think he lost his mother to cancer or something and says he just wants to find the truth). Everyone is flawed and as you say science is still investigating a lot, and we can’t do double blind or placebo trials with much of this stuff. But I’d be curious what you think of the studies!
Based on the evidence available, my opinion for my own life is that moderate intake appears to have little to no risk if other mitigations are in place (cooking practices for lower AGEs, other healthy diet like saturated fat and sugar intake regulation, etc). I also believe that there are a number of non-diet related factors that influence if a diet is "healthy" for a specific individual, including activity level, genetics, family/cultural histories, etc. To me, the data doesn't support either of the extreme statements - that red meat is bad, or that red meat is good. There are so many factors at play that the best we can do is say that here are some potential positives, and here are some potential negatives.
