Plants contain all the essential amino acids and any single starch or vegetable has levels that exceed Rose’s Recommended Requirements (the values present in your dietetic books).
It is impossible to design an amino acid deficient pure vegetarian diet that is based around any single or combination of unprocessed starches and/or vegetables (assuming calorie needs are met).
It is unnecessary (and in some ways harmful) to combine various vegetable foods to make the amino acid pattern look more like meat.
Dairy – consuming vegetarians commonly develop an iron deficiency because of multiple effects of milk on iron metabolism.
Vegetarians do need B12 – but the risk of deficiency approaches zero on a pure vegetarian diet.
This is the only scientifically valid criticism of a pure vegetarian diet.
Plants are loaded with iron and people on plant-based diets, like the Chinese, have iron intakes that exceed Americans – furthermore, the iron is well absorbed and utilized; so that iron deficiency anemia is rare in pure vegetarians. Dairy-consuming vegetarians commonly develop an iron deficiency because of multiple effects of milk on iron metabolism.
Calcium deficiency due to a low calcium diet is unreported in humans. I gather from your warnings about getting too much protein you are already aware of the adverse effects of animal protein on bone health (osteoporosis). A pure vegetarian diet has sufficient calcium and avoids the acid load and calcium losing kidney effects from meat proteins.
Worldwide osteoporosis is found commonly among people who eat a high animal protein diet (as well as a high calcium diet). This disease is rare in places where people consume no dairy (Africa/Asia) and little meat.
Vitamin D is a hormone provided by the action of sunlight on plant sterols found in the skin.
I have never heard of nor seen Rose’s Recommended Requirements cited in dietetic books or literature. The National Academy of Sciences sets Recommended Dietary Allowances in the United States. The latest RDA’s were published in 1989 and include estimates of amino acid requirements “based on nitrogen balance sufficient to support adequate lean tissue gain” for all age groups (Pineda et al 1981. The World Health Organization (WHO) also sets nutrient and amino acid requirements.
While plant-based foods contain some of all amino acids, essential and non-essential, all single plant foods are an incomplete source of protein other than soybeans. That is why a variety of plant foods should be eaten, in particular with other plant foods not lacking in the same amino acid. Otherwise, eating single starch or vegetable food over a day can negatively affect protein synthesis in the body. Synthesis of lean muscle tissue goes on continuously within the body and is dependent upon new dietary sources of specific amino acids. In fact, eating just brown rice and no other foods actually caused death in some persons (Zen Macrobiotic diet).
I know of no research that states it is harmful to eat any combination of vegetable foods at the same time. After all, this body has genetic material that is thousands of years old and is based on foods available to a foraging cave person who ate whatever edible food they came in contact with, including meat.
The form of iron in plant materials is nonheme (2%) which is not as absorbable as heme iron (23%) found in meat. There are other factors such as cast iron cookware and the presence of foods high in vitamin C that increase iron absorption. I would recommend a diet of only plant foods for children even though iron deficiency anemia is the number one nutritional deficiency of children in the United States.
I do not know what the iron status is of people in China specifically. I do know that one area of China (Linxian) has the highest incidence of stomach and esophageal cancer in the world which after a controlled experiment (30,000 people) showed a significant decrease in cancers after supplementing their Chinese diet with a multivitamin and antioxidants which are mostly found in fruits and vegetables.
Calcium deficiency in humans is due to a low calcium diet or increased calcium loses. Phosphorus does increase calcium loss and phosphorus is found in meat and carbonated beverages. But unless one ate excess meat as in high protein, low carbohydrate diets, calcium loss is not considered significant.
Osteoporosis in postmenopausal women is attributed to decreased estrogen production, inadequate dietary calcium, and insufficient weight-bearing exercise.
Vitamin D can be made by cholesterol in the skin that is exposed to sunlight. Increased sun exposure, however, can increase a person’s susceptibility to skin cancer. Fortified milk is the best source of vitamin D other than fish oils, dairy fats, egg yolks and liver – most sources of saturated fats which are also undesirable.
A vegetarian diet can provide adequate amino acids, vitamins, and minerals provided that a person makes good food choices.