Dietary Protein and Protein Digestibility

Navita Bansal1 , Vinutha T1*, Dineshkumar R1, Rama Prashat G2, Suneha Goswami1 Ranjeet Ranjan kumar1, Vanchinathan S2, Nagesh C R1, Aruna Tyagi1 1Division of Biochemistry, ICAR-IARI, Pusa, New Delhi-110012 2 Division of Genetics, ICAR-IARI, Pusa, New Delhi-110012

2022-01-30 13:21:59

Credit: Vinutha T

Credit: Vinutha T

Protein is a crucial macronutrient and a key part of our diet which plays critical role in staying healthy and for growth. How the protein is essential for us it can be understood by the point that almost every tissue or part of the body including hair, skin, nails, muscles and bone contains protein. All the metabolic reactions in our body are catalyzed by enzymes and they are all proteinaceous in nature. So, this can be understood that protein diet is a necessity for all of us. There are twenty different amino acids which make up the protein molecule. Deficiency of protein can lead to severe problem like poor growth, development, poor health leading to malnutrition.

Malnutrition-Worldwide health problem

According to the World Health Organization (WHO), malnutrition can be briefly described  as deficiencies, excesses, or imbalances in a person's intake of energy and/or nutrients. Under nutrition can also be termed as malnutrition. Also overall maternal, infant and child nutrition play significant roles in the proper growth and development of a child. If protein needs are not fulfilled as per the body requirement, it may lead to poor health for example less growth and loss of muscles. Complete maternal nutrition during pregnancy is an important aspect that has to be taken care most importantly for a healthy child growth and development else it will lead to poor physical and mental growth and many other diseases. (Facts for life).

     Kwashiorkor and Marasmus-severe malnutrition diseases

Consuming diet devoid or having inadequate amount of protein for very long time can cause severe protein malnutrition disease known as Kwashiorkor with the symptoms of swollen belly,  loss of muscles mass, liver enlargement, weak immune response and possibly depigmentation of skin and hair.Another disease called Marasmus  also occurs due to continuous insufficient intake of protein and energy. Marasmus patients show symptoms of muscle wasting, with little or no edema, excessive tiredness, and deposition of subcutaneous fat.

Approximately 0.8 grams of protein per kilogram of body weight is required to meet the daily requirement of protein. For a person with 50 kg body weight must consume apprioximate 40 grams of protein daily. Consuming diet enriched with high quality protein in all the meals consumed throughout the day is highly recommended to avoid PEM (protein energy malnutrition) and to maintain good body and muscles growth. So, It is very much important to know about quality proteins (having good amount of essential amino acids) which our body is unable to synthesize it and what percentage of protein our body is getting after digestion.

Globally, The UNICEF/WHO/WB Joint Child Malnutrition Estimates (JME) group released new data for 2021. In 2020, globally, 149.2 million children under the age of 5 years of age were stunted, 45.4 million wasted, and 38.9 million overweight. India has although taken this problem very seriously long back as alarmed by several international health agency like -WHO that a large proportion of Indian population is suffering from severe malnutrition specially pregnant women and children. Our country is running several government nutrition schemes and programs to target this issue not only to solve malnutrition problem but also to enhance socio-economic growth of the country as it really causes a problem in achieving it.

We can easily get the high quality protein easily from dairy products including milk, cheese, pulses, sea food, eggs, meat, broccoli and protein supplements etc. Nutritionally, plant based proteins such as pulses are among the richest food sources of proteins having a protein content of 20-40% and a high content of the essential amino acid lysine, which is limiting in the cereals (Duranti, 2006).

Protein Digestibility-Parameter to know protein quality and important for health

Protein digestibility also known as PDCAAS (protein digestibility-corrected amino acid score) is based on both the amino acid requirements of humans and their ability to digest it. Based upon that PDCAAS rating chart, it is an important parameter to know about the quality of a protein. US FDA was the first organization to adopt this PDCAAS rating. In 1993 FAO and WHO recommended it as the preferred best method to assess the quality of a protein.

The quality of a protein also known as its nutritive or nutritional value is governed by a number of factors including amino acid composition, ratios of indispensable (essential) amino acids, susceptibility to hydrolysis during digestion, and the effects of processing but the basic parameters in determining the quality of a protein source are the essential amino acid (EAA) score and digestibility of proteins (Gilani et al., 2005). Digestion and absorption are considered as inherent parts of protein quality. A protein having a high amino acid score can be thought or predicted of being a good quality protein but in reality, it will be of poor quality if it is not digested and absorbed well (Joye. I, 2019).In this method of PDCAAS, at first, amino acid profile of a food protein is compared to a reference value and an amino acid score is determined by the ratio of the limiting amino acid content in the test protein to that of the reference protein. The amino acid score is then corrected by multiplying with digestibility (true digestibility, fecal digestibility or in vitro digestibility) of the protein to generate a PDCAAS value (Schaafsma, 2012; Hughes, 2011).Rhinehart (1975) studied various enzyme systems including, pepsin-trypsin, trypsin, trypsin-chymotrypsin as well as a combination of trypsin-chymotrypsin-peptidase and investigated the correlation between in vivo and in vitro protein digestibility (Hsu, 1977).

PDCAAS value of cow’s milk, eggs and casein is 1.0 which means that these proteins contains optimum amount of essential amino acids that we require. Similarly other foods or proteins are given PDCAAS values ranging from 0-1 depending upon their essential amino content they provide after digestion. So, depending upon PDCAAS value we can choose the food to eat. However protein quality and PDCAAS value is so much important but still the information to  common person is not upto the mark and more research and work has to be done in this area to reach to all the people.


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