Comment · Thu, March 7, 2013 · Ceretropic
Creatine helps keep you alert
What they were answering
Vulpyne · 4 points
There is always genetic variance to this however. I too am one who has problems if I don't have meat in my diet (I've tried veggie and vegan). It turns out I don't need much (far, far less than the average American eats on average) but zero does cause problems for me.
I hope you don't take offense, but I've always been skeptical when people make this claim. It is a claim that a lot of people make, however there are (to the best of my knowledge) no reputable studies showing that any appreciable percentage of people require meat to survive and be healthy. There are also no nutrients that can only be obtained by eating meat in this day and age where we can synthesize whatever compounds we desire.
To the contrary, there are a lot of quite reputable people and organizations specifically saying that a vegan or vegetarian diet is appropriate. For example:
It is the position of the American Dietetic Association that appropriately planned vegetarian diets, including total vegetarian or vegan diets, are healthful, nutritionally adequate, and may provide health benefits in the prevention and treatment of certain diseases. Well-planned vegetarian diets are appropriate for individuals during all stages of the life cycle, including pregnancy, lactation, infancy, childhood, and adolescence, and for athletes. — http://www.ncbi.nlm.nih.gov/pubmed/19562864
I cannot speak as to whet…
u/MisterYouAreSoDumb · Ceretropic
There most certainly is a genetic variance in the ability to catalyze the amino acids L-arginine, glycine, and L-methionine. Expression of the L-Arginine:glycine amidinotransferase enzyme is what rate limits that ability for a person to naturally create creatine from their diet. Then there is also the Guanidinoacetate N-methyltransferase enzyme, which is also rate-limiting. This does not mean that one needs meat. It does mean that certain people need higher levels of L-arginine than others. This can manifest itself as having issues when cutting out all meat without supplementing for that amino acid.
So no, meat is not necessary for a human's diet. However, many of the amino acids in meat are needed by people with certain genetic variations. Those amino acids are also available in other food sources. So as long as that person's diet is sufficiently adding that in, there is no reason they cannot cut out all meat.