The debate over how much protein one needs is never ending. With experts giving diverse theories on how much is enough and how much is too much, you find yourself questioning your understanding often. The very first thought that hits our mind when we experience a plateau or see slow results is “Am I hitting the right quantity of the protein” and try to intake more protein. Various nutrition bodies recommend 0.8 to 1.2-1.8 grams of protein per kg body weight as daily protein intake while fitness experts’ recommends of 2.2 to 4.4 grams per kg body weight.
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 which 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 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 a food which is the unit for measuring how much protein a certain source of food can provide. It is directly related to efficacy of protein utilisation. 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 yogurt. 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.
As the limiting amino acid tends to be different in different vegetable proteins, combination of vegetable sources of proteins in the same meal (e.g. legumes or pulses with cereals), can result in a mix of higher biological value.
- Protein per meal – Skeletal muscle protein synthesis is maximized by 25 to 35 grams of high-quality protein during a meal,” says Doug Paddon-Jones, Ph.D., a professor of nutrition and metabolism at the University of Texas Medical Branch. The magic quantity of protein your muscles are capable of absorbing during a meal seems to be about 25 to 35 grams, anything above this amount is believed to be oxidized for energy or converted to waste. However, these findings are specific to the provision of fast-digesting proteins (E.g. Egg, Whey) without the addition of other macronutrients. Consumption of slower-acting protein sources (such as lean meat, dairy, beans), particularly when consumed in combination with other macronutrients, would delay absorption and thus conceivably enhance the utilization of amino acids. A paper published in the journal of The International Society of Sports Nutrition concluded that to maximize anabolism (metabolism that supports the ‘build up’ process which helps combine simple molecules to make complex molecules in the body) one should consume 0.4 g/kg/meal protein over a minimum of four meals in order to reach a minimum of 1.6 g/kg/day. Using the upper daily intake of 2.2 g/kg/day reported in the literature spread out over the same four meals would necessitate a maximum of 0.55 g/kg/meal.
- Vitamin Presence – Vitamin B6 helps enzymes break down protein and carry the broken down amino acids to the bloodstream. Moreover, it is essential to regulate the amino acid balance in your body and get the most from your protein intake. It acts as a coenzyme which is required to metabolise amino acids. The coenzyme participates in reactions that allow a cell to synthesize nonessential amino acids (the ones that are formed within the body). Surprisingly, it is used in more than sixty different enzyme systems which are involved in the protein metabolism.