Nutrition Meets Food Science

Good Sources of Dietary Proteins

Proteins are essential nutrients for all animals including humans for the growth and maintenance of body. Proteins are found in all cells of our body. It is the major structural components including muscle, bones, various body organs, hair and skin. It is found in virtually every part of body or tissue. They are also present in membranes and in enzymes and for formation of blood. Proteins are composed of amino acids which are precursors of nucleic acid, co-enzymes, hormones, immune response, cellular repair and other molecules essential for life.

Daily requirement of proteins for Indians is 1g per kg weight of body. Thus a 60kg person would need about 60g of protein per day. As children are rapidly growing, they need more than 1g per day per kg. Also pregnant and lactating women need more. There are also higher requirements for sports persons, and convalescing patients.

You can get proteins from any common food you consume. Milk, meat, egg, fish, grains, pulses, and seeds are good sources of proteins. Although commonly vegetables and fruits are not considered good sources, some of them have significant amounts of proteins.

Although many foods and ingredients have good amounts of proteins, it must be realised that some of them may be complete proteins containing all the essential amino acids in required amounts. Some proteins from grains and pulses may be deficient in some essential amino acids so their quality is not as high as the complete proteins. However, mixing different proteins to cover the deficiency may help improve the quality of proteins.

There is also another indicator of quality of proteins based on digestibility, namely PDCAAS (Protein Digestibility Corrected Amino Acid Score). Some of the vegetarian sources do have digestibility as a hurdle that lowers the PDCAAS value. Here also preparing concentrate or isolate would improve these values too.

Proteins need to taken in diet every day. Unlike fats and to some extent carbohydrates, proteins cannot be stored in body for future use. If there is excess of protein intake above the requirement per day, it is converted to carbohydrate and used for energy purpose. If not required for energy purpose the excess is then converted to fat. Thus previous day’s excess protein cannot be used the next day but one needs fresh protein intake.

If there is deficiency of protein in diet, then the protein needs are fulfilled by breakdown of body proteins from muscles and other tissues. Hence there must be adequate protein amount in our diet to satisfy our daily requirements.

Animal sources are quite rich in protein and also contain proteins of high quality. Milk protein as well as whey protein and casein and egg are among the highest quality proteins. Among plant proteins soy protein is considered a high quality protein. Grains have lysine as limiting amino acid whereas pulses contain good amount of lysine and has methionine limitation which is more in grains. So mixing the grains and pulses provides higher quality of mixed proteins which is traditionally practiced with rice and dal or roti and dal. Some of the good sources of proteins are given here with their protein contents.

Food Type Protein Content (%)
Chicken 25.9
Fish (Mackerel) 18.9
Prawns 19.5
Hen’s Eggs 13.3
Cow’s Milk 3.3
Cheese 24.1
Curd 3.1
Masur (Red Lentils) 25.1
Chickpeas (Bengalgram) 17.1
Rajmah (kidney bean) 22.9
Groundnut 25.3
Wheat Flour 12.1
White Bread 7.8
Rice (uncooked) 6.8
Wheat vermicelli 8.7
Almonds 20.8

Source: Nutritive Value of Indian Foods by Gopalan et al., NIN/ICMR

As mentioned earlier, animal foods are high in protein. However, the diet based on animal foods will be lacking in dietary fibre and some of the other healthy substances. Animal foods also contain high amount of saturated fats. The exception being fish which has omega 3 fats very beneficial for health. However some benefits of animal foods is presence of some minerals and vitamins especially in meat which contains heme iron which has much better bioavailability. Animal foods commonly are rich in B-complex vitamins.

The plant food diet besides being richer in dietary fibre, also contains fats which are essential polyunsaturated fatty acids. Dietary fibre not only helps in controlling the blood sugar and cholesterol but also helps in maintaining good microbiota in gut. It also helps in controlling weight as it provides satiety feeling. Plant foods with dietary fibre also prevent certain cancers. Polyunsaturated fatty acids are beneficial for heart health. Plant food diets are also provide some vitamins like A, E and C and some minerals.

When increasing the protein intake in the diets, it may be useful to know that meat, fish and eggs are high in protein. Some milk products like cheese also provide good amounts of protein. Plant sources like pulses, oil seeds such as groundnut (peanut) and soya bean are rich in protein. Nuts like almonds and pistachio are quite useful although they are more expensive.

Cereal grains and millets along with pulses also can become very useful inputs of proteins especially for vegetarians. Although their protein quality may be lower which can be elevated by combining them and also by addition of milk or soya protein to the diet. These are adequate for common people but sports persons especially athletes and gymnasts require much higher inputs of proteins as their extremely vigorous training and practice causes a lot of wear and tear of muscles which needs to be repaired needing much higher levels of proteins.

Another higher requirement is for children that are rapidly growing as well as for lactating and pregnant women. They must be given very carefully planned diet that are rich in high quality proteins. If that is difficult then there are many protein rich products that are available that could be consumed. Many of these protein mixes are available for specific category such as for children or for women and have micronutrients also added to them so a otherwise poor diet can be adequately compensated by these products.

In conclusion, the health of all very much depends on healthy diet. Proteins are a very important part of the healthy diet and can come from many protein rich foods. A proper selection of foods will provide not only adequate amounts of high quality protein intake but also other components essential for health.

Dr Jagadish Pai

Editor, PFNDAI

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