BronzeWolf said:
This is true. But without meat, having a healthy diet is difficult, very difficult, and impossible even for some people. Without animal derivatives, I seriously doubt it's even feasible for more than a handful of people. The problem is just not subbing fat for fats, because animal fats differ greatly from plant fats, carbs for carbs, but most importantly, micronutrients like B, D and C vitamins and correct omega6

mega3 ratios for lectins and supplements. It just doesn't work that well.
IE while it's true that the brain sustains itself on anything we give it, the choices of what our food is actually made have a much great impact on how well the body uses that food
Agricultural nutrition IS NOT the same as hunter-gatherer nutrition. Not even close to an equivalent
When it comes to correct omega6

mega3 rations, people relying on meat and dairy products are struggly with this too. As an example in Norway there is a push for people to take Omega 3 supplements, and we are a fish loving society who thrives on eating more fish traditionally than not. It is true that you got more opportunities if you rely on animals, but when it comes to it being very difficult when not relying on meat is wrong on many fronts. You can get good proportions if you pay attention to what you eat at times. Yes the Omega 3 in flaxseeds (as an example) has to be converted inside the body before it becomes the active form such as in fish. However how expensive is it to buy and grind flaxseed? Its incredibly cheap. It is always very accessible and easy to find in your grocery store.
If you want to calculate additionally how much benefits you get for doing so, the anti inflammatory effects, and many other great documented health benefits. Despite Omega 3 in healthy fish being a more active one, the Omega 3 from flaxseed still is as functional despite the process taking a bit longer to adjust. What I am trying to say is that it doesn't have to be difficult or impossible to make sure your rations are balanced. Knowledge is the key, and many people lack this on all fronts.
Vegetarians, get their fix through dairy products when it comes to important things like B12 which hard to this age and day to just get from the soil and absord (like how animals do it). Being in my situation where I don't eat anything animal based, I have to rely on B12 supplements.
D Vitamins are not available in dairy products, except being fortified so of course that causes a complicated situation when you live in a country without much sun exposure. However the problem with D vitamins is also related to peoples unhealthy lazy habits of keeping away from the sun. There isn't that much sun exposure that is needed in order to get 10 000 IU of D3 (half an hour in the sun). If the sun isn't around the whole winter you either have to get Vitamin D from Fish, fortification or supplements. I personally take supplements for D Vitamin until the spring arrives.
However these fat soluble Vitamins do stay in the body for a while, so it is not necessary to repeatedly absorb these all the time. The same can be said with B vitamins.
When you speak unspecific about what B vitamins cause problems with vegetarians, I am sorry to say this then you don't know what you are talking about. If you eat a proper vegetarian diet with plants, grains, legumes and dairy you won't ever have any B vitamin deficiency. The problem here is those vegetarians who ate terribly even before they became vegetarian. They suddenly cut the "meat" source with the B vitamins, Iron and don't supplement it with vegetables, salads, legumes and grains. When you do such you are walking towards a dangerous path.
I know I can say this with confidence I speak with experience. I know plenty people who are incredibly stupid when going into a vegetarian/vegan diet, because they keep eating pasta and processed food expecting the body to keep functioning by itself. This is not a problem mainly with vegetarians/vegans, however when they get rid of their previous main source of certain minerals and vitamins (without finding alternatives) it is obvious that a malnutrition will start growing. Thinking of your health as an afterthought is terrible and everyones guilty of this.
However if they eat like how they are supposed to, which does not mean monitoring every single step what you eat. You will live a very functional life as a vegetarian (don't need any supplements either, unless the sun factor is terrible like high up north). It doesn't hurt to add additional supplements too (low risk with water soluble vitamins, like the extra benefits of Vitamin C), but people shouldn't be relying on it instead of eating a varied diet.
Why do you bring it up Vitamin C? There are no hardship in getting Vitamin C these days, due to fruit, berries being readily available during all seasons (the same with juice).
This post wasn't to bash everything you said. I respect your opinion and you seem to have a better knowledge of things than many people. However in terms of nutrition and when you speak out like this, it sounds to me like some speculation. A lot of things you say is true, but when you state boldly about vegetarians having a real hard time it is important to distinct and define what you mean with vegetarians and be specific with what nutritions they will be having a hard time with.