Importance of proteins- the building blocks of our body

The word protein comes from a Greek word meaning “Primary or holding first place”, which is an appropriate name for an essential life-forming and life-sustaining substance of all organisms. 

Functions of proteins:

• As the name suggests, proteins are essential for growth and development. They help build tissues and also essential for tissue repair.
• Proteins are the main constituents of muscles, organs and endocrine glands.  Also, they are the major and indispensable constituents of skin, hair, nails, bones, blood, etc.  In short, every living cell of our body contains protein and hence protein is required for growth and maintenance of every cell in our body.

• Proteins are necessary for the regulation of various body processes.  Antibodies, which are part and parcel of the immune system, and also the various enzymes secreted in our body are protein in nature.  Hemoglobin, the important constituent of blood is also a protein. Plasma proteins such as albumin and globulin help in maintaining osmotic pressure and hence are essential for maintaining the water balance in our body.

• Dietary proteins are essential for the growth of foetus during pregnancy and also for the production of milk proteins during lactation.
• Proteins are also essential for the formation of nucleic acids, i.e., DNA and RNA that carry the genetic code.
• Proteins are responsible for the transport of nutrients across the cell membranes.

The end product of protein digestion is amino acid. Amino acids are the structural and functional units of proteins.

According to National Institute of Nutrition, Hyderabad, proteins should supply 10% to 15% of energy requirements. One gram of protein gives 4 kcal.

Classification of proteins:

Proteins are classified into complete and incomplete proteins.

Complete proteins have all the essential amino acids in sufficient quantities to meet the body’s needs. Animal origin proteins such as milk, meat, egg and fish are complete proteins. The quality of proteins in such sources is much superior.

Incomplete proteins are deficient in one or more essential amino acids and hence they need to be supplemented with other proteins. Proteins from plant sources such as vegetables, fruits, cereals, pulses, nuts and oil seeds are incomplete proteins. But if two different incomplete proteins are combined together, the resulting protein may be of better quality. For e.g., khichdi prepared using moong dhal/toor dhal and rice may be of better quality than rice or dal cooked separately. In the same way, dal and a vegetable can be combined to produce better quality protein dishes. For e.g., kootu is a South Indian dish which is prepared using a combination of dal, vegetables and coconut.

Sources of proteins:

Rich sources: Egg, milk, cheese, paneer, curd, meat, fish, poultry, pulses and legumes.

In legumes, soybean has the highest protein content, about 43.2 gms/100 gms. Also, soy protein has a high biological value and is the only protein of plant origin that is a complete protein. Vegetarians and vegans can opt for soy protein products such as soybean milk, tofu, etc., to meet their protein requirements apart from pulses and legumes.

There have been lots of controversial reports about the possible link between consumption of soy protein and the risk of breast cancer. It was thought that the presence of isoflavone, a plant estrogen found in soybean, could mimic estrogen. Increased levels of estrogen have been linked to certain types of breast cancer. But, human studies have shown that there has been little or no effect on the risk of breast cancer due to the consumption of soybean protein. Experts advise a moderate consumption of soy proteins and avoid taking soy protein supplements as they contain very high concentrations of isoflavones.

Good sources: Cereals such as wheat, rice, millets and their products; beans and peas; and few green leafy vegetables like amaranth, chickpea leaves, August tree leaves, etc.

What are essential amino acids?

There are 22 amino acids that are vital for human life and health, out of which 9 of them cannot be synthesized by our body. These 9 amino acids that cannot be synthesized by our body and hence have to be supplied through diet are called essential amino acids.

Recommended Dietary Intake of Proteins:

According to the latest (2020) ICMR guidelines, 0.83 gm of protein/kg of body weight is recommended for healthy Indian adults.

Age group	Body weight (kg)	Protein requirement (gms)
Adult man	65	54
Adult woman Pregnant woman Lactation (0-6 months) ” (7-12 months)	55 55 + 10	45.7 +9.5 in the 2nd trimester +22 in the 3rd trimester +16.9 +13.2

Source: Nutrient Requirements for Indians (2020), National Institute of Nutrition, Hyderabad, ICMR

Protein consumption in India:

Our Indian diet comprises a sufficient amount of proteins. Every region in India includes proteins in some form or another.  Dal is an indispensable ingredient in cuisines throughout India. Milk in various forms such as milk, curds, ghee, butter and cottage cheese (paneer) forms an essential component in the diets, pan India.

Red gram dal is consumed throughout India in the form of dhal in Northern, Eastern and Western parts of India and as sambhar in Southern India. There are different varieties of dals cultivated in India as red gram dhal (thuar dal), green gram dhal (moong dal), masoor dhal, urud dal, channa dal, etc.  Whole pulses (legumes) are even a better source of proteins with an additional benefit of high fibre in them. 

In Maharashtra, legumes form part of their staple diet.  The dish üsal”, a specialty of Maharashtra, is made out of different varieties of legumes cooked in an onion-ginger-garlic and tomato-based gravy, where typical spice powders indigenous to the specific region are added.

In the case of non-vegetarians, proteins are consumed in the form of eggs, meat and fish. Fish is the staple food in the coastal regions of India, mainly Kerala, Konkan and West Bengal.

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Reference: 
Nutrition & Dietetics – Shubangini A. Joshi
Fundamentals of Food, Nutrition and Diet Therapy - S.R. Mudambi & M.V. Rajagopal
https://www.cancer.org/latest-news/soy-and-cancer-risk-our-experts-advice.html

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