Its the same with any other kind of food-related lifestyle you chose to follow. Vegan food can be good for you because you tend to eat a lot of fruit and veg and that is good for you. But you can still be vegan and have a bad diet if you eat loads of fizzy drinks and sweets. But being vegan, people tend to be more interested in food and health, so tend to make better food choices.
And don’t forget that a vegan diet is better for the planet too!
Generally speaking, it uses up less resources and makes less CO2 (the gas that causes climate change) to grow plants, than it does to raise animals for food.
So, swap that beefburger for a falafel burger, and save the planet!