When you become a vegan, or "strict vegetarian," you may want to pay closer attention to the types of protein sources you eat. Plant based foods are incomplete proteins. That doesn't mean they don't contain enough protein, it means they don't contain all the essential amino acids.
A Little Amino Acid Chemistry
Let's talk about amino acids for a minute. Amino acids are the building blocks of protein. Your body needs them to make the protein structures that build and maintain the tissues in your body. There are many different amino acids; they all have similar structures, but are differentiated by their side chains. All proteins, no matter what food they come from, are made up of amino acids. But the number and order of the amino acids that make up a cow's rump or a navy bean are different from the arrangements of amino acids that make up all the tissues of your body. So when you eat round steak or baked beans (or anything that contains any protein at all, even a tiny amount), your digestive system breaks it down into amino acids that are absorbed into your blood stream. From there, the amino acids are used to build the proteins that make up your muscles, organs and lots of other tissues.
Back to Essential Amino Acids
Not all amino acids are essential. Your body can make many amino acids from the leftover bits of old amino acids and a few other raw materials found in the body, but there are some amino acids that the human body can't manufacture. These amino acids are called the essential amino acids because you have to consume them. These are the essential amino acids:
• Histidine
• Isoleucine
• Leucine
• Lysine
• Methionine
• Phenylalanine
• Threonine
• Tryptophan
• Valine
Animal proteins all contain every single one of these essential amino acids so they're called complete proteins. If you're an ovo-lacto vegetarian (you eat eggs or dairy products) you're getting complete proteins when you eat the eggs or dairy products.
Plant proteins are a little different. Each plant that you eat has a different amino acid profile. For example, grains and cereals are extremely low in lysine. So low that they can't even be considered a source of lysine. So if you only eat grains and cereals, you won't get enough lysine and that's bad. However, legumes such as peanuts, peas, dry beans and lentils contain a lot of lysine. All the lysine you really need. On the flip side, legumes aren't good sources of tryptophan, methionine and cystine, but those amino acids are found in grains and cereals. So as long as you eat some grains and some legumes, you'll get some of each type of essential amino acid.
Grains and legumes are called complementary proteins because when you combine them, you get all of essential amino acids. Nuts and seeds are also complementary to legumes because they contain tryptophan, methionine and cystine.
You don't need to eat complementary proteins together at every meal. As long as you get a variety of proteins throughout the day, you'll get ample amounts of each amino acid. But, just in case you're interested, here are some ways to combine your complementary proteins.
Soy is the one plant protein that contains all the essential amino acids. It's also a good source of healthy fats and phytochemicals (plant chemicals that may be good for you). It's usually served as tempeh or tofu, and soy milk is a popular replacement for milk.
Grains and legumes:
• Black beans and rice (brown rice is better for you than white rice)
• Pasta and peas
• Whole wheat bread and peanut butter
• Bean soup and crackers
Nuts and seeds plus legumes:
• Roasted nuts, seeds and peanuts
• Hummus (chickpeas and tahini)
Lentils and almonds
If you take a trip back to your old science class, you might remember that protein is made up of smaller components called amino acids, 12 of which are manufactured by the human body. Another nine, called essential amino acids, must be obtained from food. A complete protein is a protein that contains all of the essential amino acids. Animal proteins are complete, including red meat, poultry, seafood, eggs, and dairy, so what's a vegetarian or vegan to do? There are a few nonanimal sources that offer complete proteins, so it's important to get your fill of soybeans, blue green algae, hempseed, buckwheat, and quinoa if you're diet is meat-, milk-, or egg-free.
Then there are foods known as incomplete proteins, including beans, whole grains, nuts, seeds, peas, and corn. Combine two or more incomplete proteins and boom — you've got a complete protein. Enjoy them together in one meal or the combination can be consumed over the same day, such as black bean soup for lunch and brown rice with dinner. Here are some other food combinations that work:
• Beans with whole grains: hummus (contains chickpeas and tahini, which is made from sesame seeds) and pita bread, red beans and rice, chickpea and quinoa veggie burgers on a whole-wheat bun, split pea soup with whole-grain bread, lentil barley soup, black beans and polenta, and tortillas with refried beans
• Nuts or seeds with whole grains: sunflower seed butter on crackers, almond butter on toast, peanut noodles
Beans with seeds or nuts: hummus, salad topped with sunflower seeds and chickpeas
• Isoleucine (Ile) - for muscle production, maintenance and recovery after workout. Involved in hemoglobin formation, blood sugar levels, blood clot formation and energy.
• Leucine (Leu) - growth hormone production, tissue production and repair, prevents muscle wasting, used in treating conditions such as Parkinson’s disease.
• Lysine (Lys) - calcium absorption, bone development, nitrogen maintenance, tissue repair, hormone production, antibody production.
• Methionine (Met) - fat emulsification, digestion, antioxidant (cancer prevention), arterial plaque prevention (heart health), and heavy metal removal.
• Phenylalanine (Phe) - tyrosine synthesis and the neurochemicals dopamine and norepinephrine. Supports learning and memory, brain processes and mood elevation.
• Threonine (Thr) monitors bodily proteins for maintaining or recycling processes.
• Tryptophan (Trp) - niacin production, serotonin production, pain management, sleep and mood regulation.
• Valine (Val) helps muscle production, recovery, energy, endurance; balances nitrogen levels; used in treatment of alcohol related brain damage.
Histidine (His) - the 'growth amino' essential for young children. Lack of histidine is associated with impaired speech and growth. Abundant in spirulina, seaweed, sesame, soy, rice and legumes.