Common examples of the limiting amino acids in plant-based proteins include lysine, methionine, isoleucine, threonine and tryptophan. Of these, lysine appears to be to be most commonly absent, particularly from cereal grains [46].
There are a few vegetarian sources that contain all 9 essential amino acids, including eggs and dairy (for those lacto-ovo vegetarians), as well as quinoa, buckwheat, hemp seeds, chia seeds, and spirulina.
Amino Acid Adequacy in Vegetarian Diets
The claim that certain plant foods are “missing” specific amino acids is demonstrably false. All plant foods contain all 20 amino acids, including the 9 indispensable amino acids [33].
A meatless diet can be healthy, but vegetarians -- especially vegans -- need to make sure they're getting enough vitamin B12, calcium, iron, and zinc. The Academy of Nutrition and Dietetics warns of the risk of vitamin B12 deficiencies in vegetarians and vegans. Vitamin B12 is found naturally only in animal products.
Lysine is the limiting amino acid (the amino acid in shortest supply) in vegan diets. If you're eating a plant-based diet, the amino acid lysine is more important than total protein, according to Norris, because if you eat enough lysine, chances are you're getting enough total protein.
Plant proteins have a reduced content of essential amino acids in comparison to animal proteins. A significant reduction of limiting amino acids (methionine, lysine, tryptophan) means lower protein synthesis.
The nutrients of concern in the diet of vegetarians include vitamin B(12), vitamin D, ω-3 fatty acids, calcium, iron, and zinc. Although a vegetarian diet can meet current recommendations for all of these nutrients, the use of supplements and fortified foods provides a useful shield against deficiency.
The main foods which provide vitamin B12 are derived from animals, such as dairy products and eggs. For people not eating any animal products, yeast extract and other fortified/supplemented foods such as breakfast cereals, soya milks, soya/veggie burgers, and vegetable margarines are all good sources.
Foods that contain all nine essential amino acids are called complete proteins. These foods include beef, poultry, fish, eggs, dairy, soy, quinoa and buckwheat. Foods that contain some but not all the essential amino acids are called incomplete proteins. These foods include nuts, seeds, beans and some grains.
Avocados don't contain all the amino acids used by your body to build protein-based structures, but they contain all the essential ones. Essential amino acids must be obtained from the diet, whereas your body can make the non-essential types.
While naturally low in saturated fat, chickpeas are nutrient-dense. They provide nearly 20 grams of protein in a ½-cup serving. However, chickpeas aren't a complete protein because they don't provide adequate amounts of the nine essential amino acids. To make them a complete protein, eat them with wheat, oats or rice.
According to Harvard Health Publishing, all animal-based foods, including meat, dairy, and eggs, contain complete protein. The majority of plant-based protein sources, such as whole grains, legumes, seeds and nuts, spinach, broccoli, and mushrooms, are incomplete.
You may feel tired and weak if you cut meat out of your diet. That's because you're missing an important source of protein and iron, both of which give you energy. The body absorbs more iron from meat than other foods, but it's not your only choice.
Many vegetarians, for example, avoid meat because they do not want animals killed or harmed. These individuals may also object to the treatment of animals raised on industrial farms. The environment is an additional concern for some vegetarians.
Dr. Ellis Hunnes says cutting out meat may actually cause acne and other skin problems to worsen at first while your body adjusts to your new way of eating and your hormones begin to self-regulate. The key, she suggests, is to be patient and allow your body a grace period.
Meeting nutritional needs on a vegetarian diet
Essential nutrients that are harder to obtain in a vegetarian diet, if not carefully planned – include protein, some minerals (especially iron, calcium and zinc), vitamin B12 and vitamin D.
Vitamin B12 deficiency due to a strictly vegetarian diet in adolescence.
What vegan foods are high in amino acids? Soybeans and their products (tofu, tempeh) are considered whole protein sources, providing the body with all the essential amino acids. Oats, nuts, seeds, and legumes are also high in amino acids.
Beans, lentils and chickpeas have essential amino acids that brown rice lacks. Simply pairing rice and beans will give you a vegan-friendly meal with complete proteins.
The best part about hummus protein is that it provides your body with all nine essential amino acids that are able to produce complete protein – this makes it a much better choice than other sources. You can up the amount you get when you eat humus by pairing it with food that is also high in protein, such as: Broccoli.