Well, what if we told you that you are missing an important loop when it comes to protein intake? Forget how much you are eating. How much are you absorbing is the right question to think about? What if you aren’t absorbing even half of the protein you are eating. Protein absorption is dependent on many factors, identifying what hinders or slows down the absorption is a crucial step that is often ignored. Let’s check them out -
Enzymes - Protein digestion occurs when it is broken down into individual amino acids (the building blocks of proteins) for absorption in the body. This process is carried out by enzymes called proteases which play a critical role. To name a few, pepsin, chymotrypsin, trypsin, carboxypeptidase, elastase, lipase. For adequate protein digestion, it is necessary that the protein is available for the enzymes to act. This is achieved outside the body through the cooking of food (when it is not excessive) which makes the protein molecule more accessible to the action of digestive enzymes and within the body by the acid environment in the stomach.
PH balance - Gastric juice in the stomach starts protein digestion. Gastric juice mainly contains hydrochloric acid and pepsin. The acid plays a key role in digestion of proteins, by activating digestive enzymes and making ingested proteins unravel so that digestive enzymes break down the long chains of amino acids. Enzyme pepsin is only active within the pH range of 3.0 to 5.0 and requires the acid to maintain that pH. A low stomach acid disturbs this process and allows less protein to be further broken down into amino acids for absorption. In addition to this, water consumption dilutes the acid levels of food and in the stomach further reducing the efficacy of protein absorption.
Gut health - Protein absorption also happens in the 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. Spicy food, refried foods, consumption of foods that irritate your gut such as Junk or packaged foods, antacids (over-the-counter drugs), alcohol, stress damage these microvilli further affecting absorption.
Biological Value - Not all protein foods are equally absorbed. This is stated by the biological value of food which is the unit for measuring how much protein a certain source of food can provide. It is directly related to the efficacy of protein utilization. All animal and plant cells contain some protein but the amount of protein present in food varies widely. It is not just the amount of protein that needs to be considered – the quality of the protein is also important and that depends on the amino acids that are present. In general, proteins from animal sources have a higher biological value than proteins from plant sources. Animal sources of protein are meat, poultry, fish, eggs, milk, cheese and yoghurt. Plants, legumes, grains, nuts, seeds and vegetables provide low biological value proteins. For instance, the protein in chicken has a BV of 79. Eating 100g of chicken does not mean your body is getting 100g of protein; 100g of chicken provides about 20g of protein and the amount that will be absorbed will be—BV percentage (0.79) multiplied by 20—15.8g.
For quick reference, one lightly cooked egg has a BV of 100. One whole egg contains 6.29g of protein, which means that with a BV of 100 the entire 6.29g of protein is ingested, so eggs are an excellent source of protein. Whey protein, protein shakes, which contain about 24g protein, have a BV of 104. In the case of cow’s milk, 100ml has about 3.3g of protein and the BV is 91. A single egg white also contains 3g of protein, with a BV of 88; 100g of cooked rice (both white and brown), which has 4.6g of protein, has a BV of 74. In plant food, 100g of soy, which contains about 36g protein, has a BV of just 57. Also, soy protein doesn’t contain the essential amino acid methionine, which is why it must be combined with a grain like wheat or rice, which contains methionine, for the body to get all of the nine amino acids.