The Building Blocks of Protein: Amino Acids
Proteins are composed of 20 different amino acids necessary for human health. The body produces 11 non-essential amino acids, but the remaining nine are essential and must be obtained from food. These essential amino acids are: Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, and Valine. Essential amino acids are vital for processes like tissue repair, hormone production, and immune function. A protein's classification as 'complete' or 'incomplete' is based on whether it provides all nine essential amino acids in adequate amounts.
Understanding Incomplete Proteins
What are incomplete proteins in the body? Incomplete proteins are food proteins that lack sufficient amounts of one or more essential amino acids. The deficient amino acid is called the 'limiting amino acid'. Most incomplete proteins come from plant-based sources, including legumes, nuts, seeds, grains, and many vegetables. However, some animal-based proteins, such as collagen, are also incomplete. Despite being 'incomplete' in terms of amino acids, these foods are often rich in other nutrients like fiber, vitamins, and minerals.
The Importance of Combining Incomplete Proteins
While it was previously thought that incomplete proteins needed to be combined at every meal, current understanding is that the body uses an amino acid pool. Consuming a variety of protein sources throughout the day ensures you get all the essential amino acids. This is why plant-based diets can easily provide all necessary amino acids by combining different plant foods over time. For example, combining legumes (high in lysine, low in methionine) with grains (low in lysine, high in methionine) helps create a complete amino acid profile. Classic complementary pairings include rice and beans, hummus and pita, or peanut butter on whole-grain toast.
Complete vs. Incomplete Proteins: A Comparison
Understanding the distinction between complete and incomplete proteins aids in dietary planning, although the goal remains to consume all nine essential amino acids from various sources.
| Feature | Complete Proteins | Incomplete Proteins |
|---|---|---|
| Essential Amino Acids | Contain all nine essential amino acids in adequate amounts. | Lack or are low in one or more essential amino acids. |
| Primary Sources | Animal products (meat, fish, eggs, dairy), soy, quinoa, buckwheat, hemp, chia. | Plant-based foods such as nuts, seeds, grains, and legumes. |
| Dietary Strategy | Provides all essential amino acids in a single food source, though a varied diet is still recommended. | Require intentional combination with other protein sources throughout the day for a complete amino acid profile. |
| Nutritional Profile | Often higher in certain nutrients like Vitamin B12 (animal sources), but can be higher in saturated fat. | Typically rich in other nutrients like fiber, vitamins, minerals, and antioxidants. |
The Role of Both Protein Types in the Body
Both complete and incomplete proteins are crucial for human nutrition. The body utilizes an amino acid pool from all protein sources for essential functions like muscle growth and repair, enzyme and hormone production, immune function, and tissue maintenance. A diverse diet ensures the body receives the necessary amino acids. For vegetarians and vegans, this involves consuming a variety of plant-based protein foods throughout the day.
Conclusion
Addressing what are incomplete proteins in the body? highlights that these protein sources are valuable components of a healthy diet, particularly for those on plant-based plans. By consuming a variety of incomplete proteins and understanding how they complement each other, individuals can easily obtain all essential amino acids. A balanced diet incorporating diverse protein sources provides the building blocks for optimal health. You can find more information on essential amino acids from sources like Harvard's T.H. Chan School of Public Health.
