Comment by adrian_b

For a vegan who has a sedentary lifestyle, the problem is not getting appropriate amounts of amino-acids from the food, but getting them without eating so much as to cause a rapid gain of weight.

Lean meat provides proteins with very little of anything else, so it is extremely easy to choose a menu providing enough proteins but not too much energy.

Among vegetable products, only the seeds contain decent amount of proteins (this includes the cereals and the legumes), but all seeds contain much more of either carbohydrates or fats than proteins.

There are vegetable protein extracts aimed at vegans, but I do not consider those as an acceptable solution, because they are several times more expensive than meat, so it is likely that their environmental impact, due to the consumption of energy and chemicals for the protein extraction is greater than that of meat. Chicken meat is only about twice more expensive than legumes like peas, lentils or beans, so it is not easy to find a method of protein extraction from vegetables that can compete with that.

In Europe, where I live, there exists only one method that I am aware of that can be used to obtain enough proteins in a vegan diet with no more than 2000 kcal/day, when paying no more than for a chicken meat-based diet, which is to get more than half of the proteins from wheat flour from which the starch is removed at home by washing the dough made of it.

Any vegan diet that does not use some method of protein extraction would lead to a daily intake of around 3000 kcal when providing enough proteins for a healthy male, which is acceptable only for someone who does heavy physical work, but not for someone who works by sitting in the front of a computer.

Regarding the amino-acid balance, 167 g/day of lentils can provide enough of each essential amino-acid for a 75-kg human, with the exception of methionine. Similarly 500 g/day of wheat flour can provide enough of each essential amino-acid for a 75-kg human, with the exception of lysine.

If only wheat flour would be the source of proteins 1000 g per day would be needed to provide all essential amino-acids, but that alone would provide about 3500 kcal. If only lentils would be the source of proteins, about 600 g per day would be needed to provide all essential amino-acids, but that alone would provide about 1900 kcal (and eating so much lentils per day would be more expensive than eating chicken meat).

Combining wheat flour with lentils can satisfy the amino-acid requirements with much more reasonable quantities, but the daily intake of calories remains too high, unless most of the starch (i.e. about 75% of the starch) is removed from the wheat flour.