Proteins are considered macronutrients and consist of one or more long chains of amino acids. For our body to use these amino acids, our digestive system first needs to break down the complex protein into single amino acids that can be utilized by the system.
This section examines proteins and amino acids in greater detail and should provide the reader with a well rounded understanding of their functions and areas where potential absorption issues may arise.
Why We Need Protein
Our bodies require protein for a variety of essential functions. Without proteins, our bodies would break down and most function would be lost.
Even though some amino acids (most basic form of protein) can be produced in the body, 9 out of a total of 20 need to be obtained from diet. Therefore, these 9 are called the 9 essential amino acids.
The 9 essential amino acids include:
- Histidine (important for cell replication and division)
- Isoleucine (promotes muscle recovery, forms hemoglobin, assists in regulation of blood sugar levels, and involved in blood-clot formation)
- Leucine (stimulates release of insulin, protects muscles, increase energy production, promotes tissue healing and skin repair)
- Lysine (assists in prevention of herpes infections)
- Methionine (metabolic function, breakdown of fat, removal of heavy metals and primary source of sulfur)
- Phenylalanine (converted to tyrosine, which is used to create proteins, thyroid hormones and brain chemicals)
- Threonine (aids in formation of collagen and elastin)
- Tryptophan (used in production of niacin, essential for normal nerve and brain function and production of serotonin)
- Valine (required for muscle metabolism, maintenance of nitrogen balance, and repair/growth of tissue)
As you can see, these essential amino acids serve a variety of very different roles within our bodies. However, in addition to those, there are 11 other amino acids that a healthy body is able to produce on its own. We won’t be going over these 11; however, let’s briefly look at the main roles that amino acids play in our bodies in general:
- Growth and repair of tissues (muscles, organs, etc)
- Production of enzymes (all enzymes are actually proteins)
- Production of some hormones
- To carry oxygen through the bloodstream
- Production of antibodies (antibodies are proteins)
- Maintenance of blood pH
- Proteins are our neurotransmitters
- For use as a secondary source of energy (in the absence of carbohydrate and lipid supply)
In summary, proteins are crucial for regular functioning of our bodies. If something in our body or diet prevents us from obtaining our requirements, a myriad of health issues may arise. However, based on the complexity of some of these issues and variance among individuals, it is nearly impossible to make specific recommendations. The least you can do is understand the value of protein and acknowledge their significance for various functions.
The Process of Protein Digestion and Absorption
In the stomach, hydrochloric acid denatures proteins. This destroys foreign DNA and allows them to be assimilated by our bodies unique requirements. Additionally, an enzyme called pepsin gets to work digesting the larger proteins into smaller polypeptides.
Once the food reaches the small intestines, a myriad of other enzymes join the effort. This includes trypsin and chymotrypsin, which continue the work of pepsin by aiding breakdown to polypeptides. The process in the small intestine takes things further, and enzymes are used to break down these polypeptides into even shorter peptides and individual amino acids. Once this fundamental breakdown occurs, the gut lining absorbs the individual amino acids and passes them into the bloodstream for delivery to the liver.
Once the liver receives the amino acids, they are kept here for storage until required by the body. Thus, the liver acts as a storage organ for the majority of individual amino acids.
The Relative Ease of Absorbing and Acquiring Enough Protein
The absorption of proteins is fairly straightforward and typically happens quite efficiently. However, the quality of the protein consumed will play a large role in determining the amount of usable amino acids obtained.
The highest quality proteins have two qualities: they are easily digestible, and they have a good profile of essential amino acids. And the best protein source of all the food out there is eggs; however, milk, meat and fish come quite close as well.
Generally, animal products are typically considered the best choice for obtaining the required proteins. This, however, doesn’t necessarily mean that individuals abstaining from the consumption of animal products can’t get their requirements. For these individuals, it is essential to combine complementary protein choices in order to get a good profile of the essential amino acids. And there are tons of resources available on the internet for guidance in this area.
Additionally, even for those who eat animal products, some amino acids can be “limiting”. This basically means that the diet may not contain enough of them in proportion of total protein consumption. As a result, the lack of these amino acids becomes restricting on overall functioning. The most commonly discussed “limiting” amino acids are lysine, threonine, and methionine. And the best way to ensure you get enough of them, is by simply eating lots of leafy green vegetables or legumes.
One other thing to note is that proteins are typically spared from use as energy, if dietary intake of nutrients is adequate. This allows amino acids to be stored away and only be used for the roles they are required for.
If nutrient intake is inadequate, our body starts to use these stored amino acids for the simple purpose of energy production. This can deplete our reserves and potentially make us deficient in certain amino acids. As a result, we may see health issues arise, not from the fact that we are not obtaining enough amino acids, but simply due to the fact we are not obtaining enough nutrients to meet our energy requirements.
How Proteins Become Allergens
Most food allergies are the direct result of proteins that escape the digestion process but are still absorbed by the microvilli. These proteins still have their foreign DNA intact and as a result, cause a negative reaction in our bodies.
The signs of an allergy typically occur anywhere within a few minutes and several hours. The most common foods to cause allergies are typically ones that are exceptionally high in protein and as a result, have a greater potential to escape digestion. This includes foods such as milk, eggs, peanuts, wheat, soy-beans, fish and shellfish.
This section walked through the process of protein absorption, discussed how easy it is to get enough of them and introduced their potential to become allergens. Key points include:
- Proteins are macronutrients consisting of one or more long chains of amino acids, 9 of which are called essential amino acids and must be obtained from diet
- Amino acids play many crucial functions throughout the body and without them our health would drastically decline
- In order to be observed by our bodies, the must be first denatured by hydrochloric acid and then broken down to polypeptides by various enzymes
- Though our stomach and small intestine play the biggest roles in the breakdown of proteins, the liver is responsible for storage
- High quality proteins are those which are easily digestible while also having a good profile of essential amino acids
- Animal products (especially eggs) are the best sources of protein, but obtaining them from plant food as long as balance is achieved
- Limiting amino acids are those most likely to be inadequate in a typical diet and eating leafy greens is the easiest way to obtain enough of them
- Amino acids are not typically used for energy production and this stays true as long as energy requirements are met by other nutrients
- Proteins commonly become allergens if they enter the blood stream with their DNA intact, causing our bodies to treat them as pathogens