As a general rule, high-quality vegetarian diets—regardless of type (i.e., lacto-ovo vegetarian, pesco-vegetarian, or vegan) —can provide ample amounts of protein as well as a good balance of amino acids. However, ample protein intake is not automatically guaranteed on a vegetarian diet, and this lack of a guarantee is reflected in research results from the National Health and Nutrition Examination Survey (NHANES) from 2003-2010. In this study, a little under half of all persons who identified themselves as vegetarians had adequate protein intake, and the remainder did not.
From our perspective at WHFoods, there are no insurmountable difficulties in consuming sufficient protein or a good amino acid balance from plant foods alone. There are simply too many plant foods that can serve as substantial contributors of protein to a meal plan. But obtaining adequate protein on a vegetarian diet does require that you pay attention to your food selections. We would like to provide some detailed examples here, involving the exclusive use of plant foods to supply the protein that you need.
Our daily recommended minimum protein level at WHFoods is 50 grams. Over half of that amount could come from a single cup of cooked soybeans. One third could come from 4 ounces of tofu or tempeh, or one cup of virtually any food from our Beans & Legumes group (including lentils, dried peas, pinto beans, kidney beans, black, navy, lima and garbanzo beans). Most of the nuts and seeds on our website provide about 3-7 grams of protein, as do most of our grains. And from our vegetables, you will average about 1-2 grams per serving. In fact, virtually all of the plant foods profiled on our website provide some amount of protein. (Fruits are the weakest food group in this regard. Foods in this group seldom provide more than 1.5 grams of protein, and often provide less than 1 gram.)
Let's say that on a given day, you consumed our Black Bean Chili at lunch and our Asian-Flavored Broccoli with Tofu at dinner. That combination alone would provide you with 42 grams of protein, and one serving of our Spicy Vegetable Tart would put you over the 50 gram level.
Or another example: let's say you start out your day with our 10-Minute Energizing Oatmeal, enjoy our Curried Lentils for lunch, and move on to our Spicy Healthy Sautéed Tofu at dinner. That combination will take care of 44 of the protein grams that you need, leaving on 6 grams to be provided by, let's say, a single serving of green peas.
Without question, it would be easier to achieve these same protein results on a pesco-vegetarian diet, since one serving of most fish can provide approximately 20-30 grams of protein. On a lacto-ovo vegetarian, meeting protein requirements might also be slightly easier (but not all that much), since a serving of milk, yogurt, cheese, or eggs can typically provide 4-8 grams of protein. But even on a meal plan composed exclusively of plant foods, getting enough protein is very do-able, provided that an effort is made throughout the course of the day to include protein-rich choices on a meal-by-meal and snack-by-snack basis.
How much of a problem is protein on a vegetarian diet? For someone who assumes that sufficient protein is guaranteed on a vegetarian diet, with sufficient intake requiring no special thinking or planning, protein can indeed be a problem. But for someone who would like to consume plant foods only, and who is willing to consider protein-richness as a criterion when selecting foods, adequate protein intake is a problem that can not only be solved, but solved in such a way as to bring about a delicious-tasting meal plan as well as many health benefits.
For more information on the subject of vegetarian diets, please see our overview article "A Practical Look at Vegetarian Diets" as well as the following Q+As.
To see the research articles we reviewed in the writing of these articles, see here.