Elijah Ndung'u

Apr 11, 2023

Sources of Protein

The biggest difference between animal- and plant-based sources of protein is the presence of "complete" proteins. Complete proteins contain all nine essential amino acids. They include milk, pork, beef, eggs, poultry and fish. While the majority of these sources are animal products, soy foods, such as tofu, are plant-based alternatives. "Amino acid composition is the biggest thing," Bihuniak says. "Some [animal-based protein sources] tend to be higher in certain amino acids like leucine, which is important for muscle protein synthesis, but you can meet your needs with plant protein sources if you eat a variety." She adds that animal-based proteins can be easier to digest.

For decades, a long-held myth asserted that and had to combine specific foods if they wanted to form a complete protein. "When the rise of vegetarianism came out in the '60s and '70s, it was very much commonplace to discuss the idea of combining certain foods. So you had to have a piece of whole-grain bread with peanut butter to get your 'complete' food. You had to eat beans and rice to make a complete protein, and that carried on for a long time," Caspero says. "We recently found out that plant foods do contain all of the essential amino acids. They just contain limiting amounts of some of them." For example, broccoli contains a small amount of the essential amino acid lysine. Though you could get the recommended amount of essential amino acids from eating nothing but broccoli, that's hardly sustainable.

Generally, variety is more effective than zeroing in on one or two particular foods, no matter how much protein is in them. Recent research has also debunked a decades-long idea that vegetarians and vegans have to pair their protein sources in the same meal. "Let's say if we had broccoli in the morning, and then we had black beans for dinner, and black beans are very high in lysine, which within the broccoli is more limited. You're going to be able to get all of the essential lysine that you need just by eating naturally throughout the day," Caspero says.

Smith recommends to "consume a variety throughout the day every week. I think in general with nutrition people get focused on one or two foods that they may think is healthy or that they feel comfortable consuming, and really trying to choose a variety of foods will help with that ultimate balance and nutrition profile." If you eat only one or two plant-based sources of protein, you are likely limiting the amount of essential amino acids that your body needs.

Looking to pack your plate with more protein? It can be found in a variety of sources that you can incorporate into any meal of the day. Three ounces of roasted, skinless chicken breast is a leaner alternative to red meat, and has about 23 grams of protein, for example. The same amount of turkey breast contains similar levels of protein, and it's low in fat. Seafood options include shrimp, tuna, halibut and cod. Non-meat animal-based choices include egg whites and Greek yogurt, which can replace sugary cereals at breakfast.

Plenty of plant-based options can help vegetarians and vegans meet their protein needs. "I think the absolute biggest myth that I hear a lot is that you have to eat animal-based protein in order to get complete proteins," Caspero says. Bihuniak points to lentils, chickpeas, black beans, edamame, tofu, quinoa and nut butters (such as almond and cashew butters). Tofu and edamame are derived from soybeans and are rich in other nutrients, such as iron, calcium, folate, vitamin K and fiber.

Some vegetables, including spinach, Brussels sprouts, asparagus, artichokes, potatoes and sweet potatoes, contain small amounts of protein."Plant-based proteins are not only nutritionally amazing, but they also contain all these other benefits that you're just not going to be able to find in an animal-based protein," Caspero says. "Someone following a plant-based diet can consume adequate essential amino acids when they consume a variety of plant-based protein sources throughout the day. It just takes a bit more planning," Smith says. Spreading out your protein during the day has also been shown to be beneficial for muscle protein synthesis. Smith recommends swapping out a meat-centric meal for a plant-based meal every once and a while to get that variety.