Another reason why we may need more B6 when we aren't eating any meat is that b6 is needed to manufacture carnitine. If there is no carnitine coming from diet, the body can make it. In fact, most of us make at least half of what we need, even when we do get some from meat. But it would make sense that with zero meat, we'd need to make up the difference, and that would presumably mean a higher requirement for b6, too.

I really feel like flexitarianism is a very healthy way to eat, to keep both brain and body healthy, but I think it works best when it includes a small amount of meat such as fish or chicken (2 or 3 oz per day for example) at least a few days out of the week, and/or supplements used in a judicious way.

I think most of us are eating more meat than is good for us, and that an excess of protein can be detrimental in the long run, like our sugar overconsumption is. But I feel like taking a middle road of reducing the balance of meat in favor of increasing whole grains, fruits, and fresh veggies would be the most beneficial for most of us.