We have to do it. Some of us have to do it in different ways. Doing small things where you can is all well and good but literally none of us are making a single impact in capitalism by making different choices about how we're forced to participate in it. Focus on tearing it down together rather than picking apart individual choices because those individual choices still result in participating in capitalism.
That literally happened to me(vegetarian) and my nutritional levels dropped too. My doctor forced me back into eating at least some kind of red meat and fish, at least one of them each week. I tried my best to have a balanced diet while vegetarian, but it didn't help apparently.
Edit: By the way i'm perfectly aware that mine is a rare situation and don't apply to everyone. Try going vegan/vegetarian if you can. I'm eating the minimum amount of meat just to keep myself healthy. If you don't feel like it, try reducing the amount of meat consumption. Every little bit helps. If you don't want to go vegan, don't go vegan, you're not forced to, and people who are trying to guilt-trip you have online poisoning.