Protein is one of the important macronutrients of the human body. 16 percent of our total body weight is protein. Muscle, hair, skin, and connective tissues are mainly made up of protein. However, protein plays a major role in all of the cells and most of the fluids in our bodies. In addition, many of our body’s important chemicals -- enzymes, hormones, neurotransmitters, and even our DNA -- are at least partially made up of protein. Although our bodies are good at “recycling” protein, we use up protein constantly, so it is important to continually replace it.
Proteins are made up of smaller units called amino acids. Our bodies can manufacture most of the needed amino acids, but nine of them come from natural food sources. Animal proteins such as meat, eggs, and dairy products have all the amino acids, and many plants have some of them.

Our protein needs depend on our age, size, and activity level. The standard method used by nutritionists to estimate our minimum daily protein requirement is to multiply the body weight in kilograms by 0.8. This is the number of grams of protein that should be the daily minimum. According to this method, a male weighing 67kgs, should eat 54 grams of protein per day.

Athlete: - People who are engaged in endurance exercise (such as long distance running) or heavy resistive exercise (such as body building) can benefit from additional protein in their diets. The current recommendation is for these athletes to consume 1.2 to 1.7 grams of protein per day for each kilogram of body weight.

Pregnant woman: - The minimum protein consumption for pregnant women is about 15 grams per day more than the usual recommended amount, though this is not as crucial in the first half of the pregnancy.

In case of a medical condition, the intake of protein varies. For example, in case of kidney disease, the intake of protein is 0.5 grams per kilogram.

Unlike fat and glucose, our body has little capacity to store protein. If we were to stop eating protein, our body would start to break down muscle for its needs within a day or so.

This is an important question for people on diets that are higher in protein than usual, as low-carb diets tend to be. In a review of the research, the National Academy of Sciences reported that the only known danger from high-protein diets is for individuals with kidney disease. After careful study, they recommend that 10 percent to 35 percent of daily calories come from protein. They point out that increased protein could be helpful in treating obesity. There is also accumulating evidence that extra protein may help prevent osteoporosis.

Extra protein can be broken down into glucose in a process called gluconeogenesis. In low-carb diets, this happens continually. One benefit of obtaining glucose from protein is that it is absorbed into the bloodstream very slowly, so it doesn’t cause a rapid blood sugar increase.