I do eat meat. That said, a vegan diet can absolutely be healthy.
For post-menopausal women, perhaps.
Also, while there may not be many vegans who are at the oldest ages in the world (for the most part, veganism is relatively new way of eating), most of the oldest folks in the world are vegetarian. Though they typically eat dairy. A heathy diet can take many different forms. I agree that being vegetarian (or more-so vegan) involves making sure you cover the nutrients, protiens you need.
I spent a good deal of my life as a "vegan" or hardcore vegetarian. That lifestyle didn't prepare me as well as I would have liked to bear children. Frankly, as a girl I wasn't very healthy, despite growing up on "wholesome" foods and having vitamins and other supplements from time to time. At least there weren't so many pesticides in the food back then, but at the same time, the people who raised me didn't know to soak grains and legumes, which makes a good deal of difference in digestibility. Certain nutrients go into you better with the animal based, fat soluble vitamins.
I was really impressed at how well I did during my 4th pregnancy, which was the first one that I had with a good animal based diet. I was getting a lot more nutrients, I believe, and that's why she was so hardy. She had a big healthy placenta, she just in general seems to glow with good health in a particular way that makes her stand out compared to her older siblings at her age. The older kids are doing really well though, too. Once we made the switch to a higher fat and meaty diet they really seemed to get healthier, too. Children must have a high fat diet, and animal fats really are irreplaceably valuable.
I don't really understand why many meat-eating folks seem to care so much about whether someone eats meat or not. I'd think if someone actually cared, soda and frozen tater-tots would be a bigger concern.
As a mother, I found I had specific concerns about the impact of vegan diets on maternal and child health. A lack of an abundance of fatty acids can be very detrimental. The proteins also seem to be very important, but at least plant seeds and nuts can be treated with sprouting and fermentation to help release the amino acids and other nutrients in a useful form.
