Oats contain all nine essential amino acids necessary to make up a complete protein. However, oats don't have quite enough of the amino acid lysine to qualify as a complete protein.
By combining complementary proteins -- grains, like rice or bread, and plant-based protein sources, like peanuts, peanut butter or beans – you create a complete protein.
Dairy milk is also a source of complete, high-quality protein, which means every glass contains a full mix of essential amino acids. Most plant-based protein sources, like oats, are incomplete proteins and missing some of the essential amino acids our body needs.
However, oat is a little short on lysine. To have adequate amounts of all nine essential amino acids with oat alone, you will have to eat 1.8 cups of oats (276 grams) for an average person. That's about 7% more oat to compensate for the lack of lysine, compared to the protein requirement alone.
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.
Chickpeas are a good source of protein.
Like most other plant protein sources, chickpeas are not a complete protein and do not contain all nine essential amino acids. Chickpeas are rich in some essential amino acids, including lysine and arginine, but lack the sulfur-containing amino acids, methionine and cystine.
Incomplete Protein Foods. 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.
The casein in Greek yogurt is a complete protein because it contains all nine essential amino acids: methionine, lysine, isoleucine, histidine, valine, tryptophan, threonine, phenylalanine and leucine.
Seeds are low-calorie foods that are rich in fiber and heart-healthy Omega-3 fatty acids. Chia seeds are a complete source of protein that contain 2 g of protein per tablespoon.
Nut butter is also a source of protein, which is essential for building and repairing muscles. Although peanut butter is not a complete protein — meaning it does not contain all of the essential amino acids the body needs — it does count toward a person's daily protein intake.
Are Lentils a complete protein? No. According to the Cleveland Clinic, you should try to eat a variety of legumes, nuts, seeds and whole grains each day, which will allow you to get all the essential amino acids.
“Eggs are a great source of a complete protein,” according to McCune. “That means one egg contains six grams of protein and all the essential amino acids your body needs.
Surprisingly, potatoes offer a complete protein if you eat enough, over 10 per day. But you would ultimately encounter deficiencies in vitamins A, B12 and E, and calcium and selenium if you keep to just potatoes.
Almonds and garbanzo beans are both incomplete protein sources, meaning they don't contain all nine essential amino acids in sufficient amounts.
Unlike some plant proteins, quinoa is a complete protein, meaning that it contains all nine essential amino acids that our bodies cannot make on their own. Quinoa is also naturally gluten-free and can be eaten safely if one has gluten intolerance such as celiac disease.
Some plant proteins, such as those found in buckwheat, quinoa, and soy, are complete proteins as well. But the majority of plants contain just some of the essential amino acids.
Tofu, tempeh, and edamame
Soybeans are considered a whole source of protein. This means that they provide your body all the essential amino acids it needs.
Protein. Tuna is very high in protein. A can of tuna provides 42 grams of complete protein with all of the essential amino acids.
Complete proteins.
Eggs. Dairy products (milk, yogurt, or cheese, for example) Beef or pork. Soy products, such as tofu and edamame.
A Source of Incomplete Protein
Although sweet potatoes add some protein to your diet, plant-based protein foods are incomplete. This means that they do not provide all of the more than 20 essential amino acids your body needs on a daily basis.