Protein is the basic component of the body. It can be found in all the body parts, even in hair. That is why, it is one of the basic components that should be included into a diet. Which products can be defined as valuable sources of protein? How should I eat them so that the body uses it optimally? What is the easily-absorbed protein? Let us give you a clue.
Proteins are the basic and crucial components of the diet. They are built of amino acids bound by peptide bonds. However, proteins of various origins are not similar to each other. To the contrary, they differ in structure, and the key issue is the number of amino acids they contain. We distinguish between simple proteins that are built mainly of amino acids and complex proteins (proteids) that include some other particles, too. The proteins that are built of several dozen amino acids are called polypeptides. When proteins are built of four to ten amino acids, we call them oligopeptides and the ones composed of two peptides are called dipeptides.
Protein – function in the body
Protein is the basic component and functional element of the body. If we could look inside the body, we would discover that there is practically no process that would not involve protein or a structure that is built of it.
First of all, protein take part in the growth and development of the body. They also participate in the gene expression process. They help to regulate metabolic processes, as well as to transport key substances, as oxygen or iron, outside the body. They are also the reserves of nitrogen that is lost when we breathe or menstruate.
Without proteins, our muscles would not contract – as they are their contractile elements. We would not see, as there would be no element that helps to transport light stimuli to the neurons. Without them our tissues would not regenerate and the body – defend from infections (antibodies are composed of proteins, too).
Proteins are crucial not only for antibodies. Without them there would be no important elements the body is composed of, like enzymes, neurotransmitters or hormones.
How much protein should I eat daily?
Demand for protein, like in the case of many other nutrients, depends on the age. It may also change, depending on many other factors.
Younger people need more protein, as it is used to build the tissues in the body. Also the elderly should deliver slightly more protein than adults. Increased demand for this macronutrient is also observed in pregnant and breastfeeding women. In case of the former, protein is necessary to build the tissues of the foetus and to meet the needs of the mother’s body, that is working at full capacity. Breastfeeding mothers need protein to maintain lactation.
It should not be a surprise that also sportsmen show an increase need for protein. In order to meet the increased needs of the body, they often use specialist protein supplements. Maximum amounts of this nutrients is consumed by bodybuilders, that is individuals whose goal is to build muscle mass.
Also the state of health influences the need for protein – after an illness a weak body needs to regenerate, therefore it needs necessary building material that will enable the process. We also need more protein when our body weight is higher.
According to the “Nutrition standards for the population of Poland” designed by the Food and Nutrition Institute (link: https://ncez.pl/upload/normy-net-1.pdf) the recommended daily protein allowance for all adults (including the elderly) should be about 0.9 g per each kilogram of body weight a day (RDA). In order to make the calculations easier, we should round up the amount to 1 g/kg. In case of the elderly and children aged 1 to 3 years of age, the diet should provide about 1.2 g of protein per a kilogram of body weight a day (in the case of some elderly people, it may be increased up to 1.5 g/kg body weight a day). Teenagers should eat slightly less protein, about 1.10 g of protein per kg body weight. The standard for pregnant women is 1.2 kg/g, and for breastfeeding women – 1.45 g/kg a day. As far as sportsmen are concerned, the amount should be from 1.2 – 1.4 g to even 2.2 g per kilogram of body weight a day, depending on the severity of workouts and on the effect they desire to obtain. If you want to define your need for protein precisely, you should visit an expert, e.g. a dietician.
| Sex/age (in years) | Body weight (kg) | Recommended Daily Allowance RDA (g/kg b.w./24h) |
| CHILDREN | ||
| 1-3 | up to 12 | 1.17 |
| 4-9 | 13-27 | 1.10 |
| BOYS | ||
| 10-15 | 38-54 | 1.10 |
| 16-18 | 67 | 0.95 |
| GIRLS | ||
| 10-15 | 38-51 | 1.10 |
| 16-18 | 56 | 0.95 |
| MEN | ||
| ≥ 19 | 55-85 | 0.90 |
| WOMEN | ||
| ≥ 19 | 45-75 | 0.90 |
| Pregnancy | 1.20 | |
| Lactation | 1.45 | |
| THE ELDERLY | ||
| ≥ 65 | no available data | 1.20-1.50 |
The table based on the data from the materials that can be found on the webpage of the National Centre for Nutrition Education titled “What is the daily protein allowance?”, by Zofia Chwojnowska, Eng. (Data obtained on: 08.06.2020).
Easily absorbed protein – what is it and where can I find it?
You should remember that not only quantity of proteins we eat is important, but also their nutritional value. It means, that the proteins we consume should contain a proper amount of exogenous amino acids, i.e. amino acids that the body cannot synthesise independently. There are also endogenous amino acids, that can be synthesised by the body. They include eight (in the case of children – nine) substances: phenylalanine, isoleucine, leucine, lysine, methionine, threonine, tryptophan, valine and histidine, which is important in the diet of children. Sometimes also arginine is classified as an exogenous amino acid.
As explained in the mentioned “Nutrition standards for the population of Poland”, proteins that contain all the necessary amino acids are defined as complete proteins (also called whole proteins or proteins of higher nutritional value). They include proteins of animal origin, but not only meat (e.g. turkey, chicken or fish meat), but also eggs, milk and its products (butter or cheese). In contrast, plant-derived proteins are called incomplete proteins or deficient proteins (and also proteins of lower nutritional value), as they do not contain or contain negligible amounts of exogenous amino acids.
This division does not mean, however, that we should eat only proteins that are thought to be essential. The mores so because plants provide a number of valuable substances, like fibre, vitamins, minerals and many other. Therefore, we should combine in a diet both, animal-derived and plant-derived proteins, as the former improve the use of the latter. This is the case of, for example, milk (that contains a lot of lysine), that can be combined with cereal products (so porridge for breakfast is a great idea, as long as you can eat it, of course).
Valuable sources of protein – what products should I choose?
What products are classified as rich sources of protein? Respectively, they are: meat, eggs but also milk and its products. How much protein do they provide?
Meat, depending on its type, provides on average 14 to 24 % of protein per 100 g. We will find less protein in meats with higher fat content. According to the recommendations by the Food and Nutrition Institute (link: https://ncez.pl/abc-zywienia-/zasady-zdrowego-zywienia/podstawowe-zasady-zdrowego-zywienia) we should eat the maximum of 0.5 kg of red meat per week (and the recommended amount should not be eaten during one meal. At best it should be divided into two portions, eaten on various days). It is a good idea to select white meat (turkey, chicken meat) or lean red meats (beef, some parts of pork, like loin). Turkey meat is a good source of protein (it is about 19-20 g of protein per each 100 g of meat), but also of B vitamins and other nutrients, such as zinc, potassium and phosphorus. Turkey meat is nutritious (due to the high level of polyenoic acids), but has lower calorific value. It also contains small amounts of fat and cholesterol.
Specialists advise not to fry, but to stew and roast the meat, and before cooking – remove the skin which is often high in fat.
Also fish are a good source of protein – they provide about 15-23 % per 100 g. However, in the case of fish, unlike in the case of meat, it is better to choose fatter species, as the fat they contain include unsaturated fats that are beneficial to the cardiovascular system. According to the recommendations, we should eat fish two times a week, at least.
Also eggs are a rich source of protein. The contain about 12 percent of absorbable protein. Although fat content in an egg is about 10%, its yolk provides as much as 30% of this nutrient. If there are no contraindications, we may eat as many eggs as we want. However, in some diets (used in cardiovascular diseases, for example), too many eggs are not recommended, as they contain a lot of cholesterol. It should be noted, however, that they provide lecithin that helps to get rid the excess cholesterol from the body. You should remember that the issue of too high levels of cholesterol in the body is often genetically conditioned. The scientists prove that, contrary to the common opinion, eating eggs does not influence cholesterol levels (link: https://ncez.pl/abc-zywienia-/zasady-zdrowego-zywienia/bialko-w-zoltku–czyli-wartosc-odzywcza-jaj-).
We may provide the complete protein with milk and its products (kefir, yogurt, cheese). According to the recommendations by FNI, we should drink two glasses of milk a day. Apart from protein (about 3.4 g per 100 g of milk), it also contains calcium and B vitamins. Milk may be replaced with any milk products, like kefir (about 3.6 g of protein per 100 g), plain yogurt (about 4.3 g of protein per 100 g) and also quark (about 15 g for fat quark and about 25 g for skimmed quark) and cheese (about 27 g per 100 g). The former, however, although it has a lot of calcium, should be restricted in a diet, as it also contains a lot of saturated fatty acids. As far as yogurts are concerned, we should select plain ones, as additives usually mean more carbohydrates (often in the form of white sugar, that should be avoided) and less protein.
Remember that although protein is important for normal functioning of our body, we should not exceed the recommended daily intake for too long. It may help to reduce body weight quickly, but it may also lead to numerous harmful consequences, like inflammation of the kidney or liver insufficiency.
