Our dear mother Nature has provided us with various food options; all of which have a varied nutritional profile. Every nutrient has a specific role to play in our body. Amongst them, proteins have always intrigued us because of their functions, properties and usages.
Proteins are of prime importance in the structure and function of all living cells. As bricks join to make a wall, amino acids bind together to make proteins. 20 amino acids in all, out of which 8 are essential (need to be there in the diet) and rest are non-essential (our bodies can synthesize them). A protein which provides all 8 essential amino acids in the required amounts is called ‘A’ class protein. These are required the most during periods of growth (e.g. adolescence, pregnancy), physiological stress (e.g. any illness, pregnancy, surgery, burns, etc.). ‘A’ class proteins include proteins of animal origin like milk & its products, egg, meat, fish, chicken, etc.
Does that mean plant proteins are different from animal proteins?
Majorly yes. Animal proteins are superior to plant as they provide better quality protein, but vegetarians should not lose heart. They can also improve the quality of protein they take by making simple combinations like cereals with pulses or milk & milk products in the ratio of 3:1 e.g. Rice and Dal, Chapatti (made using wheat flour and chana flour), breakfast cereals with milk, Curd rice, khichri, etc. Vegetarian foods like pulses, soybean, quinoa and few millets if included in adequate amounts can help bridge the gap.
Role of protein in our body
- Body Building: This is the primary function of proteins i.e. tissue growth and maintenance. Proteins are present in all parts of our body be it muscles, bones, skin, blood, hair or other organs.
- As Enzymes: Enzymes are present in our body which are needed for digestion of the food we eat and for various reactions to occur inside our body. Most of these enzymes are proteins in nature. E.g. amylase, lipase.
- As Carriers: An important carrier of the body, haemoglobin (carries oxygen) is a protein in nature. Fats cannot be transported in the body unless bound to proteins.
- As Hormones: There are lots of hormones produced by the human body, most of which are protein in nature. E.g. Insulin
- As structural units: Lots of our organs are majorly made of proteins. E.g. liver: it has 50-60% of protein, muscles have 20% protein, keratin (which makes hair and skin), melanin (which gives colour to the skin) are all proteins.
The above list is non-exhaustive and we can see that apart from pumping our muscles; proteins are also essential for our general well being. Quantity of protein to be included in the diet depends on lots of factors: age, physical activity, physiological condition, etc.
Factors that affect protein requirement:
- Age: At certain periods of life when growth is rapid a person requires more dietary protein e.g. infancy (0-12 months), pre-school years, adolescence, etc.
- Current Nutritional Status: A person with a protein deficiency will have a higher protein requirement than a well-nourished one.
- Physical Activity: An increase in physical activity calls for increased protein intake.
- Weight and Height: For a normal weight person, a protein intake of 0.8g / kg body weight / day is required to fulfil the daily needs. E.g. a 60 kg person needs around 48 g protein daily.
- Physiological Condition: protein intake needs to be increased or decreased depending on certain physiological conditions. In pregnancy, lactation, recovery after a disease or injury, protein intake needs to be increased whereas, in diseases of liver or kidneys, protein intake needs to be decreased or monitored.
Sources of proteins
Milk and milk products, nuts and oilseeds (flax, sesame, sunflower, etc.), pulses and legumes, beans, egg, flesh foods like lean meat, fish, chicken, etc. Drumstick leaves are an exception being the only leafy greens rich in protein.
Protein intake more than required can be deleterious for health: Proteins are needed for numerous functions in our body. Once all these are fulfilled the excess needs to be removed. The liver processes this excess protein which is then removed via kidneys as part of the urine. Protein intake more than required thus burdens kidneys and liver. Also, a diet high in meat can contribute to high cholesterol levels or other diseases such as gout (gathiya). Rate of fractures, osteoporosis, bone pains and kidney stones is higher amongst people with excess animal protein consumption. Plant-based proteins do not have these effects on bones.
Deficiency of protein though rare can be life-threatening: Severe protein deficiency is seen majorly in growing children (in developing countries). This could affect their growth and can even be life-threatening. Mild protein deficiency can be seen in various diseases, pregnancy, lactation, etc.
A nutritionally balanced diet provides adequate protein. Approximately 12-14% of the day’s total calories should be derived from proteins. 2-3 servings of protein-rich foods are capable of meeting the daily needs of most adults. Protein supplements though might be needed by those with increased demands (illness, injury, physically active people, etc.).