Like any Vegan is going to believe this or that I care, but maybe they’ll be a lot less annoying about telling you that they don’t eat meat.

You lose IQ points being a vegan. I already knew this before I read about the study when my ex told me she was vegan. That was enough for me to know the lower IQ part.
Here are some excerpt and the rest of the story if you care to read:
On the one hand, recent concern about the nutritional gaps in plant-based diets has led to a number of alarming headlines, including a warning that they can stunt brain development and cause irreversible damage to a person’s nervous system. Back in 2016, the German Society for Nutrition went so far as to categorically state that – for children, pregnant or nursing women, and adolescents – vegan diets are not recommended, which has been backed up by a 2018 review of the research. After the Royal Academy of Medicine in Belgium decided a vegan diet was “unsuitable” for children, parents who force a vegan diet on their offspring in Belgium could even one day find themselves in prison.
Ideally, to test the impact of the vegan diet on the brain, you would take a randomly selected group of people, ask half to stop eating animal products – then see what happens. But there isn’t a single study like this.
There are several important brain nutrients that simply do not exist in plants or fungi
Instead, the only research that comes close involved the reverse. It was conducted on 555 Kenyan schoolchildren, who were fed one of three different types of soup – one with meat, one with milk, and one with oil – or no soup at all, as a snack over seven school terms. They were tested before and after, to see how their intelligence compared. Because of their economic circumstances, the majority of the children were de facto vegetarians at the start of the study.
Surprisingly, the children who were given the soup containing meat each day seemed to have a significant edge. By the end of the study, they outperformed all the other children on a test for non-verbal reasoning. Along with the children who received soup with added oil, they also did the best on a test of arithmetic ability. Of course, more research is needed to verify if this effect is real, and if it would also apply to adults in developed countries, too. But it does raise intriguing questions about whether veganism could be holding some people back.

