My family has a genetic quirk where we don't produce enough cholesterol naturally. My dad is the healthiest, and he eats the largest amount of cholesterol (his doctor commented on his absolutely perfect heart, asking if he was a raw food vegan or something. Dad listed his primary foods: red meat, potatoes, pork, rye bread, sauerkraut, pasta, and salads with blue cheese dressing). Just to stay healthy, we need to supplement. I'm also estrogen-sensitive, so I don't eat soy.
I tried giving up meat for Lent once, still noshing on eggs, cheese, and high protein nuts, and it didn't matter. My hair started falling out in clumps and my doctor ordered me back on my high meat diet. That, and the side effects of very low cholesterol are awful: chronic fatigue, strokes, heart failure, depression, anxiety, and suicidal urges. My grandfather's death was probably caused by dangerously low cholesterol (heart failure, not suicide).
So... while this condition is somewhat rare, being a vegan or vegetarian is definitely not healthy for everyone. It comes down to knowing your individual body and it's quirks - there is no one diet that is perfectly healthy for everyone alive.
