Updated: Mar 14, 2022
Ever wondered what type of special nutrient (material) must have been used in building our body tissues like muscles, bones, skin, hair, nails, etc., or has been responsible for our growth & maintenance, what about immunity and energy?
Well, the answer is PROTEIN!
So, what is Protein?
Protein has been recognised as a fundamental element of every cell of the body. Basically, proteins are complex compounds that are used for -
Growth & maintenance - growth means cell division or multiplication for the production of new tissues and those tissues come together and form an organ, and many organs coming together forms an organ system. Also, proteins are important for the maintenance of tissues as normal wear and tear happen. At times of stress, injury, surgery, tissue repair needs protein.
Synthesis of essential components - Proteins help in the formation of important components like all enzymes, certain hormones, immune components, substances that are needed for blood clots, proteins of muscle that play a role in contraction and relaxation of the Heart etc.
Supply of energy - Protein is used as a source of energy and gives around 4.0 Kcal/gram.
Regulation of body processes - Protein plays a vital role in helping to maintain blood pH levels (7.4) required for the proper function of cellular processes in the human body.
What are the classifications of Protein?
Proteins have similar compounds like Fats and Carbohydrates, (i.e Carbon, Hydrogen & Oxygen), but they differ from Fats and Carbohydrates and have additional Compound - Nitrogen. Nitrogen constitutes 16% of the protein.
Proteins are made up of Amino Acids (Building blocks). There are 20 such Amino acids and are further classified as
Essential Amino Acids (Indispensable) - these are the Amino Acids that cannot be synthesised by the Human Body and so they have to be supplied through a Proper Diet.
Non-Essential Amino Acid (Dispensable) - these Amino Acids can be synthesised by the human body in sufficient amounts.
Where do we get our protein from?
There is a common misconception that Proteins are only found in animal products but let's have a look at the Sources:
Plant Sources - yes, indeed plant sources like pulses (legumes), beans, peas, soy, nuts, nuts & oilseed, cereals, millets like Jowar, Bajra etc, do have protein
Animal Sources - Milk & Milk products like curd, paneer, cheese, khoya, mawa, milk powders, meat, chicken, eggs, fish, pork, beef & lamb.
Another huge misconception is that some of the plant sources are missing some of the amino acids, which really isn't true at all. All foods and animal products have all 20 Amino acids, but the distribution is different.
Let's say I had sprouts and I want to know how Protein would break down inside my body and get absorbed. In order to get absorbed, proteins have to be broken down into amino acids. Protein is first broken in the mouth by mechanical digestion into smaller pieces and then moved to the stomach where the actual digestion begins, the first thing that needs to happen is that the protein needs to be denatured (i.e. broken apart) by hydrochloric acid in the stomach which uncoils the protein structures and an enzyme named, pepsin which attacks the bonds holding the protein structures together and breaks it up into smaller chains of polypeptide (fun fact: pepsin itself is a protein). These polypeptides and a few loose strands move into the small intestine, where the gastric acid from the stomach is neutralised by more alkaline juices delivered from the pancreas. The polypeptide strands are further broken down into dipeptides, tripeptides and single amino acids. The final step is accomplished by the cells of the intestinal walls, where the dipeptides and tripeptides are split by the enzymes on the surface of these walls into single amino acids, which now have to be delivered into the bloodstream for various uses.
What are our actual protein requirements?
The Recommended Dietary Allowance (RDA) for protein is 0.8g/kg body weight of protein per day. So let us say if you weigh 60 kgs, so 60 x 0.8 = 48g will be your protein requirement per day.
The Estimated Average Requirement (EAR) for protein in adults is 0.66g/kg body weight per day, and a little higher for infants and children (ranging from 1g/kg for infants up to 12 months to 0.73g/kg for teenagers).
Protein for Elderly - Intakes of 1.2–2g/kg body weight per day may help prevent sarcopenia (the loss of muscle mass and strength with age). These increased amounts of protein stimulate muscle growth and maintenance up to a point.
The Acceptable Macronutrient Distribution Range (AMDR) for protein is given as 10–35% of total calories consumed per day.
How much Protein is required for Muscle building?
It is said that athletes should consume a higher amount of protein intake to maintain optimum physical performance but as per the Institute of Medicine of the National Academies 2006, the evidence of additional protein for athletes is lacking for healthy adults who undertake resistance or endurance exercise.
However, the International Society of Sports Nutrition, states that a higher protein requirement of 1.4 – 2 g/kg/day for athletes is acceptable for those wishing to build or maintain muscle mass. The American College of Sports Medicine also suggests a value in the range of 1.2 – 2 g/kg/day.
Another important fact that many of us aren’t aware of is that ingestion of protein along with carbohydrates post-workout have been known to stimulate muscle growth and repair, by both the International Society for Sports Nutrition and the International Olympic Committee.
What happens when too much protein is consumed?
Consuming higher amounts of any nutrients often comes with risks that we never think of. Unlike carbohydrates, which are stored as glycogen in the muscles & liver or unlike excess fat stored in the various fat depots, any protein consumed in excess of the body's requirement doesn’t have any particular place to be stored. So what happens to those amino acids circulating in the blood if they aren't being used?
Excess protein is often stored as fat then or converted into glucose. Yes, fat it is, especially in the liver where it can also cause insulin resistance. There was a 2016 study that stated that “High dietary protein intake is associated with an increased body weight and total death risk”, super scary so we need to monitor our protein intake well. Even if that excess protein gets excreted out in our urine, it puts extra load on our kidneys.
What is the relationship between Protein and High blood glucose?
Insulin is a hormone necessary for the use & storage of body fuels (carbohydrate, protein, and fat). It acts as a key. It unlocks cells to let in glucose from the blood to make energy. Sometimes this lock and key process does not work, even when the body produces more insulin.
Let us understand if excess protein can cause insulin resistance?
Not only carbohydrate and fat metabolism but also protein metabolism is related to
insulin resistance. The addition of Branch Chained Amino Acids (BCAA) to high-fat diets, such as in red meats and dairy, contributes to the development of insulin resistance, impaired glucose homeostasis that can occur independent of body weight.
Let us have a look at how excess protein actually causes insulin resistance.
Excess BCAA in the liver leads to the conversion of carbohydrates to fatty acids, and this process is called, DNL (De novo lipogenesis, it is the biochemical process of synthesising fatty acids from acetyl‐CoA subunits that are produced from a number of different pathways within the cell). Because of this DNL, there is an increase in levels of fatty acids which further causes exhaustion of lipid export machinery which leads to intrahepatic lipid deposition (fat storage) & steatosis (too much fat build up in your liver) and this excess of fat in the liver leads to insulin resistance.
Thus insulin resistance, in turn, causes the building up of glucose in the blood also known as hyperglycemia.
Last but not least, we are going to see which protein source is better as per the American Heart Association guidelines (Hint: it's plant-based).
Plant proteins are far healthier because they pack more nutrients into fewer calories as compared to animal proteins, they also have one important thing that animal proteins lack and i.e. fibre.
Animal protein sources like red meat & processed meats like ham, bacon & hot dogs are often higher in saturated fat and sodium (contribute to cardiovascular disease)
Eat a wide variety of fruits & vegetables, pick whole grains instead of refined grains.
Choose healthy sources of protein mostly from plants, some from fish and seafood, if opting for meat or poultry, pick lean cuts and avoid processed forms.
Low-fat or fat-free dairy products instead of full-fat dairy products could be a better choice.
Choose liquid plant oils rather than tropical oils (coconut, palm, and palm kernel), animal fats (eg, butter and lard), and partially hydrogenated fats.