Protein is a basic need for a healthy body. It is needed altough we choose to become vegetarians. In this case, it's more important to build a well-thought-of diet which contains legumes even if we don't like it.
What are proteins and why do we need them?
Proteins are essential nutrients for the human body to build cells, skin, bones, blood, muscle, and organs; and keep them all in a healthy condition. Proteins are built up of chains of amino acids. As the body digests proteins, the amino acids that are left help towards breaking down the food. Similar to carbohydrates and healthy fats, it’s a macronutrient, which means that we need a relatively large amount to stay healthy. (Not like vitamins that are micronutrients, and we need small amounts to keep the levels filled up.)
There are three kinds of amino acids: essential, nonessential and conditional. Human body itself cannot make the essential amino acids, so we have to get it from food. As the body doesn’t store protein, it’s important to balance the intake for the whole day. It’s not like a fat soluble vitamin that you can get from one meal and you're fine for that day. The nonessential amino acids are the result of the digestion process, our body makes them as they break down essential amino acids. The last type, the conditional amino acids, are usually needed by the body in times of illness or stress.
Food sources can provide us complete proteins (including all type of amino acids) or incomplete proteins (including a limited variety of amino acids). Getting enough protein from incomplete sources needs to be planned well, and requires combining and pairing large quantities of food sources. Animal sources are complete proteins. Vegetables are incomplete sources.
Proteins are needed for building new cells, maintaining cells, keeping your children's growth, and producing enzymes and hormones.
What food sources contain protein?
Although you don’t need to eat meat to get protein, the easiest way to have it is to consume many kinds of meat in a balanced diet. Vegetables and nuts provide lesser quality of protein compared to animal sources, but they have an advantage: they don’t contain cholesterol. Strict vegetarians who don’t eat milk and eggs have to plan their with great consideration, because these two sources help much with their protein content. Without eggs and milk, the only sources are vegetables, but compared to the amount of protein from animal sources, only a large amount of legumes can provide the same amount of protein as that with a meal that contains meat. Among all beans, soy beans contain the highest amount of protein. A cup of cooked soy beans contains about 20 grams of protein which is one third higher than the daily need.
Good sources of protein are: turkey, chicken, bison (also called buffalo meat), lean cuts of beef or pork (round, top sirloin, or tenderloin without any visible fat), fish or shellfish, pinto beans, black beans, kidney beans, lentils, split peas or garbanzo beans, nuts and seeds such as almonds, hazelnuts, mixed nuts, peanuts, peanut butter, sunflower seeds, walnuts, tofu, tempeh and other soy protein products, low-fat dairy products, and eggs.
What is the recommended amount of protein in a well-balanced diet?
Even though the easiest way to get proteins is to eat meat, we cannot consume meat without limit, because it can cause high cholesterol or other diseases. Vegetarians can have protein from vegetable sources with a well-planned diet, which involves eating a wide variety of legumes.
The recommended intake of protein changes as the person ages. Modify it if there’s a medical condition that requires more protein or less. The usual suggested amount is two or three servings of food rich in protein. A meal with 2 or three ounces of lean meat, poultry, or fish can be replaced with half a cup of cooked dried beans. There are many options for snack or dinner such as eggs, peanut butter or cheese. Note that eggs are high in cholesterol too, so try to eat a moderate amount and do not include it daily, the same way eating peanuts and oily nuts needs to be limited, because of their fat content.
The usual recommended amount by grams is 0.75 g/kg for adult women and 0.84 g/kg for adult men. For pregnant and breastfeeding women and for men and women over 70 years of age, the daily need is around 1 g/kg.
This can modified up to 1.8 g/kg/day if the person is an athlete or performs hard work day by day.
Not consuming enough protein may lead to serious medical conditions such as decreased immunity, stunted growth, and heart problems.
About high-protein diets
Protein is an essential nutrient, but we need an exact amount of it. The excess protein wastes energy from the body, and requires an increased need of calcium, vitamins B and other nutrients, and breaks the body’s acid/base balance. A high-protein diet is usually linked with calcium desorption in the bones, therefore there’s the increased in the calcium need. This is why it’s not recommended for a person with risk of osteoporosis.
There’s a misunderstanding regarding body building, that excess intake of protein builds up muscles. In fact, excess protein is stored in the body as fat, and only performs its role of muscle repair and restoration after the exercises.
About protein supplements
Protein supplements are usually known as a body builder's supplements. This kind of supplements are for gaining weight in a short period of time and for gaining stronger muscles.
There are many misunderstandings about consuming protein for growing muscles. The first thing was already mentioned before, that there’s a limit about how much muscle growth it can provide. Increasing the limit won’t increase the effect no matter how much surplus protein you consume.
The other fact is that protein alone doesn’t grow muscles, it's used to increase their weight.
The average daily protein need is easily achieved through a balanced diet. A higher protein intake requires more physical training than what the normal lifestyle includes. Consuming more protein than what the body uses has many side effects such as weight gain (in form of fat), bone loss (occurred by the surplus ammonia as a by-product, and because of kidneys uses calcium for restoring the body’s acid balance), kidney damage, dehydration (as the body tries to eliminate the surplus protein by increasing water metabolism), and intestinal irritation.
The key is to consume a carefully calculated amount of protein right after exercising.