Americans where the first who were interested on a diet based on plants, and that idea was quickly accepted by the other people – reducing fats in our diet and intake more cereals fruits and vegetables.
Before 20 or 30 years the major concern for vegetarians was did they intake enough proteins and if proteins are complete or just incomplete. Today we know that proteins in vegetables and cereals don’t have a lack of amino acid, only some of theme contain less and other more. For example bread, who has long been considered a violator of any diet, is rich whit amino acetic metonimia, but has low level of lutein. From the other side leguminous vegetable is rich with leutin but contain low level of metonimia. So if you eat leguminous vegetable and bread you will take the complete amount of proteins, but you don’t have to combine proteins in the same meals. You may take food in brake 3-4 hours and their amino acid steal will connect in a useful way. One important think you should remember is to eat а variety of foods who will for sure absorb all amino acid you need.
In different cuisines across the world are made different combination of food. Early, before biochemistry was developed, cooks combine lentils and rice, beans with black bread or corn bread, corn and beans. Most of diets in the world make proper combination of amino acid and proteins, so there is no need of concern for amount of proteins.
Strict vegetarians have no need to bee concern about less amount of some special vitamins. Problem may be only vitamins B12 and D, because they only exist in animal products. Even if there is leak of B12 can cause amnesia or some changes in the nervous system. Steal don’t exist profs that vegetarians may develop some of this symptoms. However if you don’t eat any meat, milk products, or even eggs, you will need to take vitamins or eat some reinforced food, like milk from soybeans and cereals.
Does people who are longer time vegetarians already live healthier life. They are exposed on smaller risks from heart, diabetes and some types of cancer (especially cancer on breast and lungs). There blood pressure, and level of cholesterol is lower. And they also safer less from weight and have much lower problems with digestive system.