Complete Proteins: What They Are and How to Combine Incomplete Proteins for Optimal Nutrition

Protein is an essential macronutrient that plays a crucial role in providing energy, supporting tissue growth and repair, and aiding the production of hormones and enzymes in the body, among many other vital functions. While many foods offer protein, only some are classified as complete proteins. This article explains what complete proteins are, why they matter, and how you can combine incomplete proteins to ensure you get all the essential nutrients your body needs.

What Defines a Complete Protein?

Proteins consist of amino acids, which are the fundamental building blocks. There are 20 different amino acids in total, of which the body can produce 11. However, the remaining nine essential amino acids cannot be synthesized by the body and must be obtained through the foods we eat.

A protein is considered complete when it includes all nine of the essential amino acids: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.

The Difference Between Complete and Incomplete Proteins

Complete proteins provide all nine essential amino acids, while incomplete proteins offer only a selection of them. The term "incomplete" might sound negative, but rest assured: foods that lack the full set of essential amino acids are not unhealthy or bad for you. This classification simply serves as a way to distinguish between different types of proteins.

Examples of incomplete proteins found in plant-based foods include:

• Nuts
• Seeds
• Various whole grains (excluding those already mentioned)
• Legumes such as lentils, peas, and beans

While these foods may not contain all nine essential amino acids, they remain highly nutritious choices. The good news is that by combining certain incomplete protein foods, you can fill in the missing amino acids and complete your protein intake.

Sources of Complete Protein Foods

To maximize the health benefits of protein, it's ideal to consume all nine essential amino acids every day. Eating complete protein foods ensures you get all nine at once. But what should you eat?

Complete Protein Foods from Animal Sources

Animal-derived protein foods are guaranteed to provide all nine essential amino acids. Some examples of common animal-based complete proteins include:

• Fish
• Poultry
• Eggs
• Beef
• Pork
• Dairy

Complete Protein Sources from Plants

As plant-based diets continue to grow in popularity, there’s increasing interest in plant-derived complete proteins. These can be found in whole soy products, certain grains, and more. Here are some common plant-based complete proteins:

• Tempeh
• Miso
• Tofu
• Edamame
• Quinoa
• Hemp seeds
• Chia seeds
• Buckwheat
• Amaranth
• Nutritional yeast
• Blue-green algae, like spirulina

Should Vegans Combine Incomplete Proteins?

If you follow a plant-based diet or sometimes go without animal-based protein, it’s important to consider the type of protein you consume—whether it's complete or incomplete. The good news is that you can easily combine incomplete protein sources to ensure you’re getting all nine essential amino acids each day.

Experts have differing opinions on how to best combine incomplete proteins. Some argue that it’s unnecessary to worry about the specifics; as long as you’re eating a variety of plant-based proteins throughout your day and week, you’ll naturally get all the amino acids you need. (Many plant-based eaters follow this approach and experience no signs of protein deficiencies.) Others suggest pairing incomplete proteins together within a meal to create a complete protein.

How Can Vegetarians Combine Protein?

Vegetarians can increase their protein intake and discover tasty complementary pairings in the process! For instance, dairy, fruits, soybeans, and nuts all make great vegetarian-friendly food options that pair well in numerous dishes. For a protein-packed breakfast, consider a bowl of Greek yogurt topped with high-protein fruits (like blackberries or raspberries) to meet the daily recommended intake. You don’t have to rely on animal-based protein to get your nutrients!

Complementary Protein Pairings

Here are some simple and flavorful ways to combine incomplete protein sources, resulting in a complete essential amino acid profile.

Whole Grains With Beans or Legumes

Combining whole grains (like rice, crackers, or bread) with legumes or beans is a fantastic way to pair incomplete proteins. Here are a few tasty examples:

• Black beans paired with rice
• Rice baked with peas
• Rice salad with chickpeas
• Pita bread served with homemade hummus

Whole Grains Combined With Nuts or Seeds

Similarly, pairing whole grains with nuts or seeds creates a complete protein source. Some family favorites include:

• A peanut butter sandwich on whole-grain bread
• Oatmeal with a topping of nut butter
• Energy balls made with nut butter and oats
• Oatmeal and nut bars
• Pasta with pine nuts

Beans or Legumes Combined With Nuts or Seeds

Another great way to achieve complete proteins is by pairing beans and legumes with nuts or seeds. Some healthy combinations include:

• A mixed bean salad with crushed walnuts
• Hummus topped with pepitas (pumpkin seeds)
• Bean chili served with pesto
• Lentil soup garnished with walnuts

How Much Protein Should We Consume Each Day?

The recommended protein intake for most people is about 0.8 grams of protein per kilogram of body weight daily. However, individual needs may vary, so it’s best to consult a dietitian or healthcare provider for more personalized advice.

While the high-protein diet trend persists, most people in the U.S. are consuming more protein than necessary, so protein overload isn’t required. Additionally, although the precise amount is debated, our bodies can only absorb between 25 and 40 grams of protein in one sitting. This highlights the importance of maintaining the right balance—neither too much nor too little.