I’m aware that the converstation has moved toward nutrition and a critique of “bro science,” but I have some thoughts on the original topic is anybody is interested.
I’ve always been interested in martial arts and I’ve been training intermittantly since my early teens. I started in Taekwon-do and switched to kickboxing in my later teens. I couldn’t compete in kickboxing due to a visual impairment and my interest dwindled over time. I discovered Judo and Brazilian Jiu-Jitsu while I was in university. I loved both, but I wasn’t able to train consistently due to a chronic RSI (from typing my thesis) and due to moving frequently for work after completing my doctorate. In 2017 I felt I was getting very out of shape and I decided to return to jiu-jitsu. My work situation has been stable since then and I’ve been able to train consistently. I earned my purple belt this year.
The BJJ gym also offers boxing classes, which I atttend regularly. I’m much less experienced in boxing than I am in jiu-jitsu and submission grappling and I have a lot of habits from kickboxing and grappling which are problematic in boxing, but I do train.
Honestly, I think it’s very unlikely that you’ll injure your hands in boxing. Most of the time in training you’ll be hitting pads with gloves and wrapped hands, working on movement/footwork, etc. Unless you’re doing something really stupid (like hitting a heavy bag without wraps & gloves), I think you should be ok. Obviously, broken hands are a common occurrence in full contact competition, but in training the risk would seem very low to me.
Grappling with a jacket (BJJ, Judo, Sambo) absolutely carries a risk of finger injury, however that risk can be greatly reduced by avoiding situations which are particularly stressful on the fingers. There are some specific techniques and styles of play which are notoriously hard on the fingers, and some practitioners have severely damaged fingers. However, simply being willing to release your grip and take another, rather than trying to deathgrip while your partner/opponent tries to forcibly break your grip, goes a long way to keeping your fingers safe. My fingers are fine, I just have some calloused skin on my knuckles from friction against the cloth.
Without the jacket (NoGi BJJ, Submission Grappling), the risk of finger injury is much lower. Any activity carries a risk of acute injury, but the long term, attritional damage that some Gi-focused practitioners experience is unlikely. Also, keep in mind that any physical activity carries a risk of injury, particularly as we get older.