Proteins are essential elements to life as they help with growth and repair, and are needed for good functioning and the structure of all living cells. Keep reading this article to learn more about them.
What are proteins made of?
They are made up of amino acids linked together. As mentioned in our other article Proteins – What They are and Why We Need Them, there are about 20 different amino acids commonly found in animals and plants. A typical protein may contain 300 or more, with their own specific number and sequence. The amino acids can be arranged in millions of different ways, and that determines which specific function the resulting protein will have in the body. Moreover – each species has its own characteristic proteins, meaning the proteins of the human muscle are different than those of beef muscle.
We classify amino acids into essential (those the body cannot produce and must be acquired through food) and non-essential (those the body can produce on its own). When a protein contains essential amino acids in the right portions required by humans, we say it has high biological value, and vice versa – when a protein has insufficient portions of one or more amino acids, it has low biological value.
Proteins in our body are constantly being built and disposed of in a cycle. When we ingest food, the proteins are broken down and digested into amino acids, which are then absorbed and used to make other proteins in the body.
Where can I find proteins?
We can find them in both animal and plant foods, but we need to be careful about their biological value. In general, animal sources, such as meat, poultry, fish, eggs, milk, cheese and yogurt, have higher biological value proteins, while plants, such as legumes, grains, nuts, seeds and vegetables, provide low biological value proteins. This means that people who avoid all foods of animal origin may have problems with meeting their protein requirements, especially in periods of growth, when the protein requirements are higher (such as in children and pregnant women). However, combining different sources of plant proteins in the same meal can result in a mix of higher biological value. Omnivorous diets on the other hand (which contain foods derived both from animals and plants) provide adequate amounts of protein.
Does lack of protein affect our health?
Yes, protein deficiency does affect our health and causes protein energy malnutrition (PEM), which describes various disorders occurring mainly in developing countries, and mainly affect young children as a result of too little energy and too little protein in the diet.
Marasmus and Kwashiorkor are the two most common forms of PEM. The first is a chronic condition that affects young children who have been weaned off breast milk and are given a diet which does not contain enough energy and protein. It is characterized by muscle wasting and an absence of subcutaneous fat. Kwashiorkor on the other hand, affects slightly older children who, after an extended period of breastfeeding, have been weaned onto a diet mainly comprising of starchy foods, which is low in protein and energy. Both can be overcome with medical treatment and an adequate diet.
Protein intake is also often connected to chronic diseases, as scientific studies suggest that mortality rates from cancer and cardiovascular diseases are lower in those who avoid eating meat. However, even though vegetarian and vegan diets tend to be higher in fiber, fruits and vegetables than an omnivorous diet, there is no scientific justification for eliminating lean meat from the diet, as the studies are often confounded by factors such as smoking, social class and body mass index.
About 10-15% of our total energy intake should come from proteins, meaning about 0,75g of protein per kilogram of body weight per day. The needed protein can be easily provided by two to three servings of animal foods, or four servings of vegetable protein sources (such as whole grain cereals, vegetables, legumes, nuts and seeds). And whichever diet you choose, you should still make sure that it is balanced, provides a variety of different foods, includes plenty of fruits and vegetables, and is accompanied by a healthy lifestyle – meaning getting more exercise, maintaining a healthy body weight and no smoking.
Also, do not forget to pay attention to the food labels, and keep in mind you rarely eat straight protein, as some of it comes packed with saturated fat. When choosing meat, lean towards the leanest cuts. The same goes for dairy products – skim or low-fat versions are healthier choices for you. Moreover, beans, soy, nuts and whole grains offer protein without much saturated fat, but with plenty of dietary fiber and micronutrients to help keep your body happy and healthy.
Adapted from www.eufic.org