Proteins are everywhere in our bodies — hair, skin, muscles, bones and tissues. About 10,000 different types of proteins create the blueprint of our bodies and make us who we are.
“These macronutrients perform critical functions in our body,” says Dr Aftab Ahmed, senior medical consultant with continuum-care centre Sukino Healthcare, Bengaluru. “They build our bones, muscles, cartilages and skin, repair tissues, carry oxygen throughout the body, supply nutrients, make enzymes for digesting food and regulate hormones.”
According to a paper published by the US-based government health website National Institutes of Health, each protein molecule has a unique sequence of the 20 different types of amino acids. Hence thousands of different proteins are known, each with its own amino acid sequence – which, in turn, decides its shape and function.
Understanding amino acids
During digestion, the body’s proteins get continuously broken down into amino acids through a process called protein synthesis. Since these amino acids fuel the body to perform various critical functions, there is a need for a constant supply of these acids.
Some amino acids can be recycled from the process of breakdown. These are the non-essential amino acids (NEAAs) — not because they aren’t essential, but because the body can produce them internally. But since this is not enough, the body needs to replenish the amino acids from external dietary sources. These are the essential amino acids (EAAs).
There are two sources of EAAs: animal and plant proteins. The number of amino acids in a protein is the primary differentiating factor between these sources: animal proteins contain all the nine EAAs, whereas plant proteins are said to be lacking in one or two EAAs.
How much protein do we need daily?
“On average, the daily requirement of protein for an adult is 0.8gm per kilo bodyweight, which can be met through vegetarian and non-vegetarian dietary sources,” says Pariksha Rao, a senior clinical nutritionist from Bengaluru. “Pregnant women and adolescents need higher protein intake to support the rapid growth and development of tissues and muscles. Older adults need more protein to preserve muscle mass and reduce age-related muscle loss. This, in turn, improves strength and overall quality of life.”
Rao says athletes and bodybuilders need to consume more protein to build extra muscle and repair and strengthen muscle tissues. “The intake depends on their body mass, [and the] duration and type of exercise they perform. About 1.5-2g/kg body weight is acceptable,” she says. “During recovery from an injury or surgery, the body breaks down muscles and other energy sources since a person is unable to eat. Hence the protein requirement increases to prevent further breakdown and muscle repair.”
Mubaraka Palanpurwala, senior dietitian at Bengaluru-based online training and nutrition platform NWS (Nourish with Sim), says when protein foods are consumed, not only the protein in them but all the other nutrients that come along with them — like carbohydrates, fats and sodium — are also consumed. It’s the entire protein package and not only the amount of protein that influences the health of individuals.
“Red and processed meat is high in cholesterol, sodium and saturated fats, and should be consumed in moderation,” Palanpurwala says. “Diabetics should be mindful of their carbohydrate intake along with protein.”
Health benefits
Protein-rich foods increase the feeling of fullness compared with foods high in carbohydrates and fats. A 2015 study in the American Journal of Clinical Nutrition indicates that high-protein diets (i.e., 1.2 – 1.6 g/kg per day) can help in reducing calorie intake and consequently help in weight loss.
“Protein helps in repairing and strengthening muscle tissue, and is therefore beneficial for athletes and exercising individuals,” says Palanpurwala. “However, the aim should be to get the protein requirement through a balanced diet. Protein supplements can be limited for individuals who have high protein requirements but want to restrict their calorie intake.
“It is also beneficial in increasing muscle mass and strength with the progression of age and reducing the risk of sarcopenia (a condition where there is loss of muscle mass due to old age).”
Too much protein in your diet?
According to the European Food Safety Authority, although consuming twice the amount of protein required daily is considered safe, individuals with kidney disease should consult a dietitian. Just like carbohydrates and fats when consumed during a calorie surplus, excess protein can be converted to body fat, leading to weight gain.
“A higher-than-normal intake for prolonged periods in the absence of special requirements can lead to side effects,” says Rao. “Our body reacts to excess protein intake by causing bloating, abdominal distention and flatulence, and can lead to an imbalance in bone, liver and kidney metabolism.”
Consuming excessive red and processed meat is associated with the risk of cancer.
But since red meat is a good source of protein and other essential nutrients such as iron, vitamin B12 and zinc, it need not be avoided altogether to reduce risk. The World Cancer Research Fund recommends trying to consume no more than three portions (around 350-500g cooked weight) of red meat per week and very little, if any, processed meat.
It is also worth remembering that animal-based proteins use more resources and produce more greenhouse gases compared to plant-based sources.
Protein deficiency
An estimated one billion people worldwide suffer from inadequate protein intake. The most severe form of protein deficiency is known as kwashiorkor.
“While a high-protein diet causes side effects, a low-protein diet [has] adverse health effects too,” says Rao. “The most common symptom is fatigue, weakness, brittle hair and nails, dry and itchy skin, recurring and slowly healing infections, loss of muscle mass, increased hunger and disruption in bone health.”
Dr Ahmed of Sukino Healthcare says loss of muscle mass is one of the first signs of inadequate protein intake. “When the body doesn’t get enough protein, it tends to pull it from the skeletal muscles to preserve the other important tissues, leading to loss of muscle mass,” he says. “Furthermore, the lack of protein in the body also increases the risk of bone fractures. Bigger appetite, increased calorie intake, fatty liver and stunted body growth in children are other symptoms.”
