What Does Protein Do in the Body, and Why Do You Need It Every Day?

This article explains what protein is, the jobs it does, why a daily supply matters, how much Indian guidelines suggest and what happens when intake runs short. Lists of foods and personal targets live on other pages, linked below, so this one stays with the biology.

What is protein, in simple words?

Protein is a nutrient made of long chains of smaller units called amino acids, folded into precise shapes. Think of amino acids as letters and proteins as words: the same 20 letters, arranged in different orders and lengths, make tens of thousands of different proteins, each with its own job. When you eat dal or paneer, digestion breaks the food's protein back into amino acids, which travel in the blood and are reassembled into the proteins your own body needs. Protein also supplies energy, at about 4 kcal per gram.

What is protein called in Hindi?

In Hindi it is simply प्रोटीन (protein), the English word written in Devanagari, and that is the term doctors, food labels and school textbooks use. A coined formal word, प्रोभूजिन (probhujin), turns up occasionally in older Hindi texts, but it is rarely heard in speech. In daily conversation people often describe protein through its foods instead, such as dal, doodh, anda or paneer, which is a fair reminder that nobody eats protein on its own; it always arrives inside a food.

What are amino acids, and which ones are essential?

There are 20 amino acids that the body uses to build proteins, and 9 of them are essential, meaning the body cannot make them and must get them from food. The nine are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. The other 11 can be made from other compounds, though a few become conditionally essential during illness, rapid growth or injury. A food that supplies all nine in useful proportions is called a complete protein; one that runs short of one or more is called incomplete.

What does protein do in the body?

It does six broad jobs. It builds structure, forms enzymes, makes many hormones, defends against infection, carries substances around the blood and helps keep fluids where they belong. When other fuel runs short, it can also be burned for energy at about 4 kcal per gram, though that is a costly last resort: in starvation or a crash diet, the body breaks down working muscle to make glucose for the brain. Each job is described below. The common thread is that protein is not a single thing sitting in the body; it is thousands of specialised molecules that wear out and must be replaced, which is why intake matters every day and not only on gym days.

How does protein build muscle, skin, hair and bone?

Muscle fibres are made largely of two contractile proteins, actin and myosin, which slide past each other each time you move. Skin owes its strength and stretch to collagen and elastin. Hair and nails are made of keratin, a tough fibrous protein. Bone is not only calcium: collagen forms most of its organic matrix, a flexible scaffold onto which calcium and phosphate minerals are laid. All these tissues are constantly broken down and rebuilt, so the raw material has to keep coming. Growing children, pregnant women and anyone healing from an injury or surgery need more of it.

What do enzymes and hormones have to do with protein?

Almost every enzyme in the body is a protein. Enzymes speed up chemical reactions that would otherwise be far too slow for life: amylase in saliva starts digesting starch, pepsin in the stomach breaks down protein and lipase handles fat. Many hormones are proteins or shorter chains of amino acids called peptides. Insulin, which moves glucose from the blood into cells, is one; glucagon and growth hormone are others. Not every hormone is a protein, though: oestrogen, testosterone and cortisol are made from cholesterol.

How does protein protect against infection?

Antibodies, the molecules that recognise and neutralise viruses and bacteria, are proteins called immunoglobulins. So are many of the signalling molecules that coordinate the immune response, and immune cells divide quickly and need a steady supply of amino acids to do it. This is why people with very low protein intakes, especially undernourished children and frail older adults, tend to catch infections more often and recover more slowly. Eating protein beyond your needs does not make a healthy immune system stronger. The risk lies in not having enough.

How does protein carry oxygen and keep fluids balanced?

Haemoglobin, the protein inside red blood cells, picks up oxygen in the lungs and releases it in the tissues. Albumin, the most abundant protein in blood plasma, carries hormones, fatty acids and some medicines, and it holds water inside the blood vessels by osmotic pull. When albumin falls very low, as in severe protein malnutrition or some liver and kidney diseases, fluid leaks into the tissues and causes swelling, known as oedema.

Does the body store protein like it stores fat?

No. The body stores energy as fat in adipose tissue and as glycogen in the liver and muscles, but it keeps no dedicated reserve of spare protein. There is a small, fast-moving pool of free amino acids in the blood and tissues, and that is all. Each day the body breaks down and rebuilds a large amount of its own protein, recycling most of the amino acids, but some are lost and must be replaced from food. When intake falls short, the body takes what it needs from working tissue, mainly muscle. Protein cannot be banked on Sunday for use on Wednesday.

How much protein do you need each day?

The ICMR-NIN 2020 Nutrient Requirements for Indians set the adult recommended dietary allowance at about 0.83 g of protein per kg of body weight per day, roughly 50 g for a 60 kg adult. Needs rise in the second and third trimesters of pregnancy and during breastfeeding, for which ICMR-NIN adds a set amount on top. Many experts suggest 1.0 to 1.2 g per kg for healthy older adults to slow muscle loss, and sports nutrition bodies commonly suggest 1.2 to 2.0 g per kg for people in regular hard training. The protein calculator works out a personal figure.

What happens if you do not eat enough protein?

Mild shortfalls show up slowly and are easy to miss. Common signs include loss of muscle and strength, especially in older adults, wounds that take longer to heal, thinning hair, brittle or ridged nails and more frequent infections. Children may grow more slowly. Severe deficiency, seen mainly in undernourished children, causes oedema, skin changes and pale, sparse hair, a condition called kwashiorkor. Each of these signs has other possible causes too, including thyroid, iron and vitamin problems, so swelling, persistent hair loss or slow healing deserves a doctor's assessment rather than a guess about diet.

Does protein quality matter, and why pair dal with rice?

Yes. Protein quality depends on how many essential amino acids a food supplies and how well they are digested. Animal proteins such as milk, eggs, fish and meat are complete, and so is soy. Cereals such as rice and wheat run low in lysine, while most pulses run low in the sulphur amino acids, methionine and cysteine. Eaten together, each fills the other's gap, which is why dal-chawal, rajma with rice, khichdi and idli are nutritionally sound pairings. They need not share a bite or even a meal; what counts is the mix across the day.

Can you eat too much protein?

For healthy adults, intakes up to about 2 g per kg a day appear to be well tolerated in studies, and most Indians eat well below that. Very high intakes crowd out other foods, can be hard on digestion and rarely bring extra benefit. People with chronic kidney disease are a separate case: their protein intake is set by their kidney specialist and should not be raised on the strength of a gym plan. For the foods that actually supply protein, the guide to vegetarian protein sources has the practical list.

Where to learn how nutrients work together

Protein is one of the macronutrients, working alongside carbohydrate, fat, vitamins, minerals and water, and this overview of the types of nutrients sets it in context. If you want the whole picture in a structured way, NNWA's Introduction to Nutrition course is a beginner course of two to three weeks covering macronutrients, micronutrients, balanced plates and reading labels. It is priced at 2,999 rupees, down from 4,999, with EMI from 250 rupees a month, and awards an NNWA certificate.

The honest summary

Protein is the body's building material and much of its machinery: muscle, collagen and keratin, enzymes, insulin, antibodies, haemoglobin and albumin. It is made of 20 amino acids, 9 of which must come from food, and it cannot be stored, so a daily supply matters. Indian adults need about 0.83 g per kg a day, more in pregnancy, later life and hard training, and a mix of cereals and pulses takes care of quality.