Protein is the building block of the body. The word protein is derived from the Greek word protos meaning first, because it is the basic material of all living cells. In adults, approximately 16 per cent of body weight comes from protein. The muscles contain 43 per cent of total protein, the skin 15 per cent and blood 16 per cent.

Grow, grow, grow

We eat protein to grow big and strong. It is the major component of body tissues such as muscle and skin. There is a continuous turnover of body tissue for maintenance throughout life.

Apart from structural functions, protein is required for the production of enzymes, hormones and haemoglobin (carries oxygen to different parts of the body) and antibodies (provides immunity). It is vital for sustenance of life.

Quantity

How much do I need?

Protein is in a continuous state of flux in the body as it synthesises and degrades continuously to meet different physiological needs. Hence, it should be supplied in adequate amounts to the body.

As a part of the balanced diet, 10-15 per cent of total dietary energy should be provided by protein.

The required daily allowance of protein: 0.8 to 1.0 g per kg body weight.

Younger children need more protein than teenagers and teenagers need more protein than adults because they are both growing.

• Younger children: 1-1.1 g/kg body weight/day
• Teenager: 0.85-1 g/kg body weight/day
• Adult: 0.75 -0.8 g/kg body weight/day.

Protein deficiency effects:

• Stunted growth in children
• Muscle wasting
• Weakness
• Anaemia
• Oedema (swelling due to water retention)
• Delayed wound healing
• Lowered immunity
• Impaired digestion
• Fatty liver.

Protein surplus can cause:

• Kidney problems
• Osteoporosis
• Hyperacidity.

Surplus protein cannot be stored by the body. Over-consumption of protein offers no benefits and may have some health risks as mentioned above.

Quality

Protein is made up of single units called amino acids. There are about 25 types of amino acids. Some amino acids can be synthesized by the body, but others must be supplied by the diet. These are known as essential amino acids. The amino acid content of a protein determines its biological value. Foods that contain all the essential amino acids in sufficient quantity are complete and have high biological value.

Protein from animal food sources is of superior quality because of its high biological value. Generally, plant proteins are of low biological value.

The limiting amino acid in wheat is lysine and in pulses is methionine (the essential amino acid that is in shortest supply is called the limiting amino acid). The quantity and quality of protein collectively determines the optimal utilisation of protein by the body.

For vegetarians:

ant proteins are incomplete. Soya protein is the only exception. Nevertheless, this limitation can be overcome by combining plant proteins having different limiting amino acids, which compensates for the lack of essential amino acids in individual items. For example, wheat is low in lysine, while pulses are low in methionine but a diet containing wheat-based foods and pulses will provide both the amino acids for protein synthesis.

Food combining is essential for vegans (those who don’t consume food from any animal source, including dairy). Protein combining is not necessary in a vegetarian diet where milk or eggs or both are consumed.

For non-vegetarians:

though, animal protein is of high biological value, excessive consumption can be harmful because foods like mutton, beef and egg are packed with saturated fat and cholesterol along with proteins. It is higher in calories and lacks dietary fibre. High biological animal protein sources are meat, eggs, milk, dairy products and fish. Eat them, but in moderation.

Athletes

Protein is required by the body for building muscle. Those engaged in strenuous physical activity like athletes, body builders and sprinters need extra protein to replace the protein that is broken down during exercise and build muscle mass. However, protein intake should be increased along with the total calories. The relative percentage should remain the same. Protein intake should be 12 per cent to 15 per cent of total calorie needs.

Here is the protein requirement for:

• Endurance athletes (e.g distance runners): 1.2 -1.4 g/kg body weight/day
• Strength and power activities like body-building, weight-lifting and sprinting: 1.4-1.7 g/kg body weight/day.

Protein breakdown is greater when exercising for a long duration or at high intensity. After training, one should have a meal which is rich in both protein and high in carbohydrates. The amount of protein depends on the intensity and duration of the exercise.

The adequacy and quality of a diet can be measured by the adequacy of protein in the diet. Make sure you have enough for good health.

Ipshita Nandi