What are Proteins?
Proteins are an important substance in the body. The muscles, hair, eye, organs, and many hormones and enzymes are made of proteins. Proteins also help in repairing and maintaining the body tissues.
Proteins are made up of amino acids. There are 20 amino acids, out of which 11 are made by the body. The rest 9 are the essential amino acid that can be obtained from the diet.
These 9 amino acids are present in high-quality protein sources such as meat, egg, poultry, fish, and dairy products. Other sources of protein are:
- Nuts
- Bean
- Seeds
Proteins are ingested from the diet and digested into an amino acid or small peptides that can be absorbed by the intestine and transported in the blood.(1)
How Does Protein Get Digested?
Role of Enzymes in Protein Digestion
Protein digestion begins in the mouth when the food is chewed. The enzyme amylase and lipase are present in the saliva that breaks down carbohydrates and fats.
On reaching the stomach, it is broken down into smaller chains of amino acids by hydrochloric acid and an enzyme called protease.
Protease breaks down the peptides that join amino acids.
From the stomach, smaller chains of amino acids move to the small intestine. Enzymes and bicarbonate buffer are released by the pancreas that reduces the acidity of the digested food. This allows the enzymes to further break down the amino acid chains into individual amino acids. The enzymes involved here are trypsin, chymotrypsin, and carboxypeptidase.
Protein Absorption
The small intestine contains microvilli, and protein is also digested here. It is absorbed as tripeptides, dipeptides, or amino acids.
Microvilli are small, finger-like structures that increase the absorptive surface area of the intestine, which absorbs maximum amino acid and other nutrients.
Once absorbed, the amino acids are released into the bloodstream and are taken to cells in other parts of the body. They help in repairing tissue and building muscles.
It is transported to the liver by the hepatic portal vein and this is known as enterohepatic circulation. In the liver 50-66 % is used to synthesize protein, nitrogen-containing compounds. In some, it may be converted to energy. The liver regulates amino acid levels in the blood. The amino acid that does not stay in the liver is passed to the rest of the body to be utilized by other cells.
Protein absorption can be increased by choosing food containing all the nine essential amino acids, which include meat, fish, eggs, and dairy products.
Vegetarians can take food in combination to complete their protein requirement. They can include the following foods:
- Whole grains and legumes
- Nuts and whole grains
- Legumes with seeds
- Vegetables and nuts
- Vegetables and whole grains
The body can pool proteins from various foods to form a complete protein. So, variety is a key for vegetarians.
Along with choosing foods rich in protein, there are certain habits that can be adapted to make the most of the food eaten.
- Eat regularly
- Chew the food thoroughly
- Reduce stress
- Avoid intense exercise immediately after meals
- Manage any underlying condition that affects digestion
- Take probiotics
- Eat protein throughout the day rather than eating all the required amount once
Protein is the most important nutrient required by every part of the body. It is digested in the mouth, stomach, and intestine and is released into the bloodstream.
Its intake can be maximized by increasing the intake and adopting certain habits like chewing thoroughly before swallowing.
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