In a paper published in the journal, PLoS ONE, scientists at Wageningen University in The Netherlands proposed that eating mealworms is a more sensible way of acquiring protein in the diet than eating chicken, pork or cattle. Per the article:
Compared to a kilogram of edible protein in meat from cows, chickens or pigs, production of the same amount of mealworm protein emits fewer greenhouse gases and requires much less land to grow. The findings support the argument that environmentally conscious eaters may do well to include beetle larvae in their diets. "This study demonstrates that mealworms should be considered a more sustainable source of edible protein," the team writes in a paper published yesterday in the journal PLoS ONE...Among the things that the worm-like larvae have going for them, they don't emit methane. Also, they are prolific. Depending on the species, females release up to 1,500 eggs over a lifetime. Larvae develop quickly and they convert their food into protein efficiently, at a similar rate to chicken but better than pigs and cattle.
I'm an animal lover too.
The only real worry for vegans is that they get enough vitamin B12, so be sure to take your supplements. Some supplements are made from krill, which is OK, except that if we harvest too much krill, then the whales that eat krill will go hungry and suffer. With our massive overpopulation, there is absolutely NO ethical way to eat anything on this planet without impacting wildlife -- all farmland takes up space that used to be habitat for wildlife. So I don't worry about meat-eating or veganism -- I'm concentrating my resources on getting the population down.
I'm happy with people being vegans. It's not sarcastically that I suggest the more vegans there are, the more meat there is for me. However, I think the primary drawback from veganism is that for everyone to follow through on such a restrictive diet it would wreak environmental havoc. Lierre Keith (despite some of her other dodgy views) does a really wonderful job of spelling-out how this is so in her book "The Vegetarian Myth".
Also, there are anthropological reasons to avoid veganism as outlined here. Also, Denise Minger is an excellent former-vegan nutrition expert who goes into quite a lot of scientific depth explaining how veganism, while initially very helpful, eventually does degrade the body.
There's a good paper Diet, Energy and Global Warming which assessed the impact of various diets on global warming. It concluded that a vegan diet has the lowest impact, which makes sense because you're eating lower on the food chain.
Vegetarian diets than include dairy, generally contribute more to global warming than a diet that doesn't use large animals, i.e. including chicken. However including chicken is more environmentally costly than a vegan diet, according to the paper.
I've read similar conclusions by researchers elsewhere.
Jack Norris is a vegan RD (registered dietician) who maintains an excellent website, http://veganhealth.org He's science-based, vegan himself and he helps many vegans with nutrition issues for free. He lists nutrients that vegans should be concerned with - a different list from yours.
I eat a vegan diet, a very unusual one since I can't eat grains, legumes or many common foods bc of allergies. I wrote a nutrients tracking program and I use it routinely to see what my diet might be lacking. Even with so many food restrictions, I still do very well, by dint of eating lots and lots of vegetables.
With Vitamin A, even a very lowfat vegan diet, if it has plenty of whole foods, will have about 10% fat. This is enough so far as I know. Getting Vitamin A via beta carotene prevents getting too much of it.
Vitamin D: It's difficult for anyone, vegan or non-vegan, to get much vitamin D from unprocessed food. For most people, most of their dietary Vitamin D comes from foods fortified with vitamin D. In the U.S., milk is required to be fortified with Vit. D. But some vegan foods like breakfast cereals are also fortified with Vit. D. Despite this, Vit. D deficiency is common, especially in the high latitudes. At high latitudes, autoimmune diseases and breast cancers are more common I've heard, and it's been theorized that this is because of Vit. D deficiency. Many people, not just dark-skinned people or vegans, should check their vit. D status.
There are vegan sources of vit. D. Jack Norris mentions yeast (if you count that as vegan). Also (some) mushrooms like shiitake apparently make vit. D when they're dried in the sun, just like people do! Personally, I just take a vit. D supplement.
Protein: This is an old anti-vegan canard. Most people on a nonvegan diet get way more than the RDA of protein, and a reasonably good vegan diet should provide plenty of protein. I have no problem getting enough protein from the vegetables I eat, and I used to lift weights on a vegan diet and I got quite muscular. In the U.S. people for some reason worry about getting enough protein, perhaps an idea propagated by the meat and dairy industries, but usually it's the wrong thing to worry about.
The requirements for essential amino acids are quite low. Jack Norris has an article about protein, he does say that the amino acid lysine is something vegans have to be careful to get enough of. I get plenty of lysine, maybe because I eat quinoa. The only essential amino acids that my program sometimes shows I need more of, are the sulfur-containing amino acids Met and Cys, I lump them together. I get Met and Cys mostly from quinoa and amaranth, which are vegan foods with complete protein.
That said, vegans in my experience often are cavalier about possible nutrient deficiencies. Some vegans have a B12 denialism where they believe they get enough B12 from a vegan diet. The body stores B12, so vegans may not have problems from B12 deficiency for years, but when neurological damage from B12 deficiency shows up, it can be permanent! B12 deficiency is nothing to mess around with. Symptoms of mild B12 deficiency, like elevated homocysteine, are apparently shockingly common among vegans.
But anyone on any diet can get a nutrient deficiency. Vegans are also less likely to be overweight. It's refreshing at vegan gatherings that so many people aren't fat! Vegans also eat more fruits and vegetables, and none of the potentially damaging foods like meat and cholesterol, and they generally eat less fat and less saturated fat. The vegan Dr. Michael Klaper did a vegan health study. He found many benefits to being vegan but risks from possible nutrient deficiencies. The Vegan Health Study doesn't seem to be online any more, but there's a summary, with Dr. Klaper's recommendations for a healthy vegan diet.
I don't think worms are conscious, so eating them doesn't bother me ethically. I just think it's gross :)
Why wouldn't yeast be vegan? Isn't it a fungus?
ps Just like Popeye says, spinach is a miracle food - if you look in the USDA nutrients database it has lots of lots of nutrients.
Also, vegan diets usually don't have the "Adequate Intake" of choline as defined in the U.S. Whether this is really a problem isn't clear, since more research is needed on choline requirements and the effects of a deficiency. But a researcher called Dr. Zeisel was going around warning that pregnant vegans really should take a choline supplement, because choline deficiency can cause neural tube defects in the babies.
Choline is a little-known nutrient and choline content isn't in the USDA Nutrients database, for many foods.
I don't care if people choose to eat vegan, although veganism is NOT the magic solution to our environmental problems.
What I DO object to, though, are unsubstantiated statements like "potentially damaging foods like meat". Damaging in what way? Not to our bodies: we are genetically evolved to eat meat (look at the cave paintings in Lascaux, for example). Damaging to the environment? Only in the sense that, as we are far above what our sustainable population should be, we are taking land out of natural habitat to sustain agriculture, but that applies equally, if not more, to farmland used to grow grain, corn, soybeans, and vegetables.
As far as the dangers of fat, that's a line fed to us by scientists who had a political agenda. New evidence is coming out that if carbs are reduced, then the body stores less visceral fat, and it's visceral fat that causes cardio-metabolic syndrome. Interestingly, cardio-metabolic syndrome was unheard of among Inuit eating their native diet, consisting entirely of meat, nor among the Plains Indians, who relied on bison. In addition, if carbs are limited, the body requires very little vitamin C, which evolutionarily makes sense, since the aborigines of Europe and the far North did not have access to vitamin C bearing fruits.
What I'm trying to say is that nutrition is a VERY complex science, and VERY little is known about it, and it changes daily anyway. We humans were evolved to be opportunistic omnivores, and pretty much NO food is off limits to us. Vegans do not live any longer or any healthier than others (wish I could remember where I read that -- I have a trash-can memory -- lots of stuff goes in, but it's all jumbled up). If you want to eat an extreme diet, go for it, but don't be so sure of your proselytism. You MIGHT just be mistaken.
And my final word is that in nature, red in tooth and claw (quote from somewhere!), animals ARE killed and eaten by others. It's actually more merciful for a range-raised animal to be shot through the head and die quickly than to become weak and fragile and die of agonizing illness or old age, like we do (I'd prefer the bullet to the head myself) (but I'm lucky -- I have insulin-dependent diabetes, and when I want to go, I'll just stop my insulin). If we really want to be kind to "sentient" animals (the meaning of the word "sentient" has changed during my lifetime), we won't cause them undue suffering, but raising them properly, and killing them mercifully and then eating them is NOT unethical in my book.
There's a lot of evidence that vegetarians are healthier, and correlations of eating red meat with cancer, etc. etc. Like this for example: http://www.ncbi.nlm.nih.gov/pubmed/23169929
Very easy to find on Medline. In any case I didn't post to get into a war with low-carbers, if that's what you want to do, do it. I was replying to an earlier post that claimed all sorts of problems from a vegan diet.