Proteins from diet are important because they provide amino acids for the
- synthesis of body proteins in children when they are growing
- in adults for synthesis of new proteins to replace those being broken down
- in pregnant women for the requirement of the foetus and placenta
- for nursing mothers for synthesis of proteins in breast milk
Dietary proteins should be able to supply all the eight essential amino acids in the right proportions and quantities. In fact recent developments and investigations point to the fact that the earlier recommended essential amino acids are low and a higher intake is now recommended.
FAO and WHO recommend that human protein requirement should be determined by the N balance method. ICMR also feels that the nitrogen balance method is more accurate as it provides protein requirement based on physiological condition and the age of the individual. Another consideration is the quality of the habitual diet and the amino acid content in it and how well the amino acids are digested and absorbed in the body. Mostly it is egg protein that is taken as a reference point when comparing other proteins. Proteins from cereals, legumes and vegetables when taken individually are considered inferior to animal protein. However when cereals and legumes are taken in combination then they supplement each other and make good the loss of lysine in cereals and methionine which is found in low amounts in pulses. However as compared to egg protein the diet of cereals and legumes has a biological value of only 65% as compared to egg protein.
Some of the older methods of determining protein requirements were not very accurate and so the ICMR has adopted the following guidelines in fixing the protein requirement for Indians in different age groups. The guidelines are based on the 2007 recommendations of the FAO/WHO/UNU Committees.
- Nitrogen balance data obtained from normal, healthy well-nourished subjects should be used as the basis for fixing minimal N requirements.
- Daily protein requirement of different age groups should be expressed as g/kg/day
- The daily requirement of protein for individuals of different age groups is derived by a two-step process:
- First, the level of requirement per kg according to the age is chosen
- Second RDA is computed for a given age by multiplying the requirement per kg by the standard weight-for-the-age. For adolescents (10-18 years) and adults, the requirement is given as the same for both genders
- Yet another factor that determines the daily protein requirement depends on how much protein is absorbed and how much comes out as waste from the body. The essential or indispensable amino acid content from different sources like cereals, legumes, vegetables and milk are computed, their absorption studied and then the RDA is derived.
According to these methods of calculation the Nitrogen values, in terms of protein requirements stand at 0.66 g/kg/day for median requirement and 0.83 g/kg/day for safe requirement respectively.
Protein requirement for the elderly
There have been some suggestions that the elderly might require increased protein intake but there is no evidence to suggest any such thing in any studies. However, since protein and energy are inter-related elderly must make sure that they have enough calories intake to get the required proteins especially if they are active. However, if the elderly person does not have a good energy intake then there could be a need to reconsider protein ratio of the diet as protein amount could reduce with lower diet intake.
Protein requirement for pregnant and lactating mothers
Protein requirement for pregnant women has been assessed by the ICMR. They have concluded that there is additional requirement for proteins during pregnancy for the growth of the foetus and the expansion in maternal tissues. The ICMR has emphasised that though there is a need for additional proteins during pregnancy there is no requirements for any kind of supplements but can be made up from foods. They recommend that high quality protein foods such as milk or eggs must be consumed for additional requirement of protein during pregnancy. If the weight gain during pregnancy is 10kg then the mother would require 1, 7 and 23 g per day of extra proteins in 1st, 2nd, and 3rd trimesters of pregnancy respectively. Nursing mothers also require additional protein and the safe allowance would be19 grams per day during 1-6 months of breastfeeding and 13g from 6 to 12 months.
Recommended intake of protein for children and adults
Currently the recommended safe intake of protein according to Indian diet during 0-18 years in infants, children and adolescence is calculated on the basis of requirement for growth as well as maintenance. The values for boys and girls are similar up to the age of 10 years. The safe level of protein intake for girls between the ages of 11 and 18 is1.15 grams to 1.05 grams per kg of weight and the requirement reduces by 0.01gram at every increase of one year of age. For boys at the same age it is 1.16 to 1.09 gram of protein requirement per kg of weight.
For adults the recommended intake of protein has been calculated at 1.0 gram per kilogram of weight per day. The protein requirement has been calculated at average male weight of 60kg and female weight of 55kg. If a man weighs 60kg and a woman weighs 55kg then the protein requirement will be 60grams and 55 grams per day. For pregnant women an additional 23grams is recommended which makes it 78grams per day. Nursing mothers require additional protein of 19 grams when the baby is between 0-6months old which is 74grams per day and when the baby is between 6 to 12 months mother will require 13 additional grams of protein which comes to 68 grams per day.
For all ages the ICMR has based their protein values for Indians on per kg of standards weight. The same is recommended by the FAO/WHO/UNU 2007 Committee because that calculation is methodologically sound and based on International research data. However, ICMR has also taken into calculation that the Indian diets are predominantly plant based so the lower protein value is different from that of the FAO/WHO/UNU Committee. Indian protein requirement is based on a cereal-pulse-milk-vegetables diet keeping in mind the body weights of normal healthy Indians of different ages.
Protein Energy Interrelationship
Protein use and deposition by the body depends on adequate energy intake. The body requires adequate non-protein energy from carbohydrate and fat so that amino acid can be utilized for protein synthesis and for amino acid related functions in the body. This means if there is insufficient calorie intake, protein from the diet will also be unable to be utilised properly by the body.
-With References from ICMR Guidelines Doc.