I'm not vegan anymore. I was, for a long time, until it became apparent that I had something of a fatty acid deficiency so I started eating (very carefully chosen sustainable) fish. I was already eating a ton of freshly ground flax almost every day and taking primrose oil supplements, but apparently I have a problem converting the ALA into DHA blahblahblah. I have very little interest in eating in such a way that I would have to supplement my diet in order for it to be adequate... I take a daily multi, sure... but I see supplements as supplementary, rather than THE source of certain nutrients.
ANYWAY, that said... all three of my pregnancies took place while I was vegan. My kids are WAY off the charts. My first was 9 pounds and 23 inches long at birth. My third was 10lb and 23". My middle child was smaller at birth (born early due to an abrupted placenta) but caught up to her big bro very quickly. My seven year old is still vegan. He refuses to eat eggs and dairy doesn't agree with him. My daughters get some local eggs and raw milk, but very little. Collectively, we've had ONE ear infection (my daughter when she stuck something in her ear), and we rarely get sick otherwise. Their whole lives, I have gotten nothing but "OH s/he looks so much older!" The only thing visibly off about my son (the only strict vegan in the bunch) is he has some dark circles under his eyes, that I suspect are from allergies, but we haven't found what it is he is allergic to (there is also the whole heredity thing- i have them too).
We don't eat soy, except the occasional box of tofu, and some shoyu every now and then. We don't eat fake meat (which counts as junk in my book). We shop at the crappiest (and sadly the only one within an hour's drive) grocery store ever, and manage to eat well enough. I don't find it particularly hard, never really bothered about combining proteins and all that, we just eat a very wide variety of fresh whole foods.
BUT... I have known a LOT of junk food vegans in my day. The worst were teenage girls whose parents weren't all that supportive of their choice, so they ended up eating way too many bag of chips and a soda meals. Even beyond that, it is REAL EASY to be a junk food vegan. It's hard to stare down that package of brand new vegan wonder food that mimics something you had to give up when you went vegan... and not buy it. Think back to when Soy Delish came out and we could all stop pretending that Rice Dream tasted anything like ice cream. Or when Tofutti started making a vegan thing that tasted just like a Kit Kat. Or Luna bars. Or vegan M&M's. Or Tofurkey Keilbasa. I don't eat that stuff anymore because it makes me feel like crap-o-la and it's expensive... But when a new vegan friendly food comes out, it just seems sortof special in a way that non-vegans just can't appreciate.
My opinion basically goes something like... an unhealthy diet is an unhealthy diet, period. A junk food vegan and a junk food omni eat almost identically, only vegans will eat the cheapo store brand accidently vegan chemically flavored bag of chocolate chip cookies rather than the Chips Ahoy. It's not a completely out of this world thing to say that many vegans aren't in it for their health but because of their ethical beliefs.
Simply being vegan or simply being omni isn't enough to garuntee your health either way.
My kids: http://www.homeschoolblogger.com/atlt