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Proteins are necessary for the body formation, for the immune system, for the synthesis of enzymes and many other factors of a healthy functioning organism. For this process to happen, are necessary various amino acids (called essential amino acids). The combination of different food groups serves to better supply with all the necessary components, since the amino acid compositions can complement and enhance each other. In addition to the value, the bioavailability respectively digestibility of the proteins is also decisive.
The best sources of proteins can be found in legumes (including soy products), fish, the white of the eggs, low-fat poultry, and low-fat dairy products. Nuts, seeds and whole grains, as well as dried mushrooms, provide an additional good protein contribution (a graphical overview shown in the pyramid below).
Annotation: The combination of different food groups is the best way for many reasons because you should always pay attention to a balanced mix in all components of the diet. It always does not depend on isolated components of the macro and micronutrients but on the interaction of many substances.
In the diet of our cultures, there is a sufficient protein supply; the protein content in the distribution of the recommended macronutrients is often even too high so that it neither lack to a sufficient biological value nor sufficient bioavailability of the proteins. Exceptions exist in malnourished persons (in case of diseases, poverty, eating disorders, etc.) or in persons who have a very unbalanced diet. This consists in one-sided nutrition with food from almost exclusively fast available carbohydrates and/or fat components (e.g. a diet with almost only noodles or pastry from white flour, potatoes [fries], rice, confectionery. Therefore, this could be even with vegans, who combine their food insufficiently (a consumption of too little or no legume products, nuts, and other seeds, as well as whole grains).
Many foods from animal products, provide plenty of proteins, but often at the same time fat, which is disadvantageous in the long run, because of the saturated fatty acids (risk increase for various diseases). Even low-fat meats increase risks for a variety of chronic diseases if you consume it frequently and it comes from red meats (these are all meats except fish and poultry meet).
A good protein supply can also be achieved with a purely vegetable diet (vegan), but this is sometimes more difficult, and you need some knowledge about the combination of foods. A well-balanced vegetarian diet containing no meat, but milk and/or egg products facilitate the adequate supply of protein and is usually no challenge for it.
Protein intake from plant sources has the advantage of avoiding the unfavorable fatty acids and cholesterol*, while providing the very important phytochemicals, fiber as well as more of some vitamins and minerals.
* Cholesterol reduction may be considered in certain contexts (it does not necessarily depend on the diet).
A well-balanced composition between slow carbohydrates and proteins means that the carbohydrate content in the diet still dominates. Choose slow carbohydrates from foods that contain carbohydrates and good protein doses combined. The vegetables provide this ratio very well. When it comes to bread, choose it with whole grains, seeds, and nuts. The addition of vegetable flour to bread dough can turn the bread into so-called "protein bread".
The previously much higher recommended dosages of protein intake are refuted. Study data and more accurate measurements of metabolism and tissue-building capacity show that the need has been significantly overestimated, and the over-consumption of protein in the context of further imbalances can increase some long-term pathological risks (especially the overweight problem in children).
The protein content of the daily diet should make up about 12-15% of the calories needed (1g of protein, provides 4.1 kcal of energy– the same as carbohydrates). With an energy requirement of 2000 kcal a day, this corresponds to about 75g of protein per day. More precisely, the protein intake can be calculated with the simple formula 0.75g to 1.2g protein/kg body weight/day (at 0.8g protein on 75kg bodyweight, that corresponds to 60g protein per day).
The calculation is especially correct if the recommended normal body weight is approximately correct. People who have healthy kidneys can tolerate 20-25% proteins of their energy intake, usually without kidney strain, but all people who already have kidney function restrictions or metabolic restrictions (metabolic syndrome, pre-diabetes)* should generally only consume the 0.8g protein / kg bm, which corresponds to about 10% of the daily energy needs of a person with an average physical activity (American Diabetes Association; Harvard School of Public Health).
* Many people are affected by the metabolic syndrome without noticing it in the first few years.
Annotation: Although diets with a higher protein and lower carbohydrate- and fat-content are sometimes beneficial for weight loss for some period, too much protein is also disadvantageous. Deficiencies in phytochemicals are often caused by the less well-balanced food composition. Overall, excess calories, whether carbohydrates, fat or protein are converted into body fat and stored in depots.
Protein requirements according to age groups and gender
(the topic of pregnancy, lactation and baby feeding; and exercise intensity follows in another newsletter)
Depending on age, gender, growth phase, and physiological stress, it´s recommended to consume 0.75 - 1.2g protein per kilogram of body mass (kg bm ). As a rule, 0.8-0.9-1.0 g protein / kg bm is sufficient for children, adolescents and adults; only infants (1st year) have a higher need (1.3 - 1.8g / kg bm), it´s better defined as the recommendation with 1.8g protein / 100kcal (about 1.2g protein / 100ml); with adequate energy supply.
On average, significantly more than the recommended amount of protein is consumed in the industrialized countries, which is certainly not necessary. However, since excess consumed proteins are metabolized, it usually has no direct negative effects, as long as it is not too much over long period and there is no kidney disease or metabolic disorder.
The slightly higher protein requirement during the growth phases (in pregnant women, infants, children, and adolescents) exist through higher tissue building and adjustments to physical stress (e.g. pregnancy and lactation). For serious infectious diseases and athletes with high-performance levels, additional higher protein intake may be beneficial at some periods. However, the higher demand is no challenge usually, as the well-composed diet can meet the protein requirement easily.
The minimum amount of daily protein intake, that normally excludes deficiencies under normal circumstances, is defined by adult health institutions at 0.6 g protein per kg body mass per day. With a safety margin, it is recommended for adults 0.75g / kg bm / day (calculated on the bioavailability of protein from milk or egg).
As for infants, children and adolescents in the growth phases, as well as pregnant and breastfeeding women, the protein requirement is partly higher (see Table 1). This table doesn’t include the athletes.
Table 1 shows the "safe level" for the protein intake that avoids deficiency (uncorrected for the biological value "amino acid score", transferred to a supply of mixed nutritional proteins, based on the age and bioavailability of high-quality proteins (such as milk and egg).
|Age group||Reference protein intake|
|1-3 years||1.0 - 1.2g/kg|
|3-5 years||0.9 - 1.1g/kg|
|5-14 years||0.9 – 1.0g/kg|
|14-18 years*(M = male, W = female)||*M: 0.9-0.95g/kg / *W: 0.8-0.9g/kg|
|Adults*(M = male; W = female)||*M: 0.75-0.8g/kg / *W: 0.75-0.8g/kg|
|Adults over age 65
extra protein a day
|up to 6th month: 0.9g/kg + 7g
6th-9th month 1g/kg + 21g
|Breastfeeding 0 - 6 months extra protein a day||1.2g/kg + 23g/day|
|Breastfeeding over 6 months extra protein a day||1.2g/kg + 23g/day|
** Instead of protein per kg-body mass, today for infants up to 12 months the amount of protein (in normal drinking behavior) should be calculated on the drinking volume - 1.8g protein to 100 kcal (depending on the mixture it´s about 1.2g protein / 100ml).
The demand values of the individual amino acids as synthesis components for the proteins are well researched. Simply, one can say that a protein biological value is higher, the more amino acids it delivers, which the body cannot produce itself (essential amino acids).
The higher the biological value of the protein is the lower is the necessary amount of proteins per kg of body weight to achieve a good protein balance.
Animal-derived proteins are generally of higher biological value than plant proteins because they usually contain more of the various essential amino acids. You do not need animal foods to provide you with all the necessary amino acids. Egg protein serves as a reference protein and has the biological value of 100, followed by milk and fish as well as meat.
* To be continued
Prof. Dr. Werner Seebauer is Dean of Studies – Association of German Preventologists, Head of Preventive Medicine Department of Institute of Transcultural Health Sciences (European University Viadrina) and Head of Preventive Medicine – NESA (The New European Surgical Academy). Since 2000, prof. dr. Werner Seebauer worked only in preventive medicine, after ten years spent at the Frankfurt University Hospital. He is also involved in the medical professionals training for nutrition and prevention.