Nutrition Series: Protein in a nutshell

What is a protein?

Protein is a highly complex substance that is present in all living organisms. Proteins are of great nutritional value and are directly involved in the chemical processes essential for life. The importance of proteins was recognized by chemists in the early 19th century, including Swedish chemist Jöns Jacob Berzelius, who in 1838 coined the term protein, a word derived from the Greek prōteios, meaning “holding first place.” ¹

Importantly, protein makes up about 20% of our body weight and is a primary component of our muscles, hair, nails, skin, eyes and internal organs. Protein molecules are composed of carbon, oxygen, hydrogen, and nitrogen². Interestingly, proteins consist of smaller molecules called amino acids, which link together like beads on a string. These linked amino acids form long protein chains, which then fold into complex shapes. There are about 20 different amino acids that occur naturally in proteins.³ Proteins differ from one another primarily in their sequence of amino acids, which is dictated by the nucleotide sequence of their genes.⁴

Types of amino acids⁵

Amino acids are classified into three groups:

• Essential amino acids
• Nonessential amino acids
• Conditionally essential amino acids

Essential amino acids

Essential amino acids cannot be made by the body. As a result, they must come from food.

The 9 essential amino acids are: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.

Nonessential amino acids

Nonessential means that our bodies can produce the amino acid, even if we do not get it from the food we eat. Nonessential amino acids include alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, and tyrosine.

Conditionally essential amino acids

Conditionally essential amino acids are usually not essential, except in times of illness and stress. Conditionally essential amino acids include: arginine, cysteine, glutamine, tyrosine, glycine, proline, and serine.

Functions of proteins⁶

1. Growth and maintenance of tissues
2. Catalysis of biochemical reactions – Enzymes are proteins that allow key chemical reactions to take place within your body
3. Acting as messengers – Some proteins are hormones, which are chemical messengers that aid communication between your cells, tissues and organs
4. Providing structure – A class of proteins known as fibrous proteins provide various parts of your body with structure, strength, and elasticity
5. Maintaining proper pH – Proteins act as a buffer system, helping your body maintain proper pH values in the blood and other bodily fluids
6. Balancing fluids- Albumin and globulin are proteins in your blood that help maintain your body’s fluid balance by attracting and retaining water
7. Supporting immune function – Proteins form antibodies to protect your body from foreign invaders such as bacteria and viruses
8. Transporting and storing nutrients – Hemoglobin is a protein that carries oxygen while ferritin is a protein that stores iron
9. Providing energy – Normally, protein supplies your body with very little of its energy, however in a state of fasting (18–48 hours of no food intake), your body breaks down skeletal muscle so that the amino acids can supply you with energy

Benefits of Protein⁷

Protein is not only important for building lean muscle tissue, it’s also critical for organ function. In fact, a lot of your organs, cells and tissues require protein for proper regeneration. Here is a breakdown of the benefits of proper protein intake:

1. Boosts muscle mass
2. Helps with weight loss
3. Boosts mood
4. Maintains healthy blood sugar levels
5. Supports bone health
6. Supports cardiovascular health
7. Promotes healthy brain function

Digestion and absorption of proteins⁸

Once a protein reaches your stomach, hydrochloric acid and enzymes called proteases break it down into smaller chains of amino acids. From your stomach, these smaller chains of amino acids move into your small intestine. As this happens, your pancreas releases enzymes and a bicarbonate buffer that reduces the acidity of digested food. This reduction allows more enzymes to work on further breaking down amino acid chains into individual amino acids.

Protein absorption also happens in your small intestine, which contains microvilli. These are small, finger-like structures that increase the absorptive surface area of your small intestine. This allows for maximum absorption of amino acids and other nutrients. Once they’ve been absorbed, amino acids are released into your bloodstream, which takes them to cells in other parts of your body so they can start repairing tissue and building muscle.

How Much Protein Do I Need?

The National Academy of Medicine recommends that adults get a minimum of 0.8 grams of protein for every kilogram of body weight per day, or just over 7 grams for every 20 pounds of body weight⁹.

• For a 140-pound person, that means about 50 grams of protein each day
• For a 200-pound person, that means about 70 grams of protein each day

Here are some of the best protein-rich foods for a healthy diet:¹⁰

• Grass-fed beef
• Organic chicken breast
• Wild-caught salmon
• Eggs, goat cheese
• Yogurt, kefir
• White and black beans
• Lentils
• Natto
• Almonds
• Whey protein powder
• Hemp seed protein powder

Check out Part 2 of our nutrition series: What you need to know about carbohydrates
Check out part 3 of our nutrition series: Facts about Fat

References:

1. https://www.britannica.com/science/protein ↩︎
2. Staying healthy with nutrition, Elson M. Haas, MD ↩︎
3. https://www.britannica.com/science/protein ↩︎
4. https://en.wikipedia.org/wiki/Protein ↩︎
5. https://medlineplus.gov/ency/article/002222.htm ↩︎
6. https://www.healthline.com/nutrition/functions-of-protein ↩︎
7. https://draxe.com/nutrition/how-many-grams-of-protein-per-day/ ↩︎
8. https://www.healthline.com/health/protein-digestion#enzymes ↩︎
9. https://www.hsph.harvard.edu/nutritionsource/what-should-you-eat/protein/ ↩︎
10. https://draxe.com/nutrition/how-many-grams-of-protein-per-day/ ↩︎