Diets-Metabolism   [back to the Category]

Proteins   [read the french version]

Author :   Dr Paule Nathan

PROTEINS

Proteins or protides are the basic constituents of living organisms. Our organism is, in fact, essentially made up of proteins. Proteins themselves are formed by amino acids, the basic elements released during the digestion process. Proteins are the "bricks" which make up the structures of the edifice we call our body. We refer to them as builder elements because they form the framework of our muscles, bones and skin. Proteins need replacing regularly. The amino acids that make up proteins are contained in animal proteins (red meat, poultry, eggs, fish and milk products) and vegetable proteins (pulses, bread, etc.). Both types of protein provide the essential amino acids which cannot be synthesized by the human body.
Protein plays a minor energy-giving role. 1g protein provides 4 Cal and an average nutrition provides between 60 to 80g protein; therefore its energy intake level is equal to just 240 to 320 Cal.

The need for protein is continuous
Protein replacement is continuous. The speed of this replacement varies according to the tissues. Blood, liver and brain proteins are replaced much faster than those of the bone. Thus, hepatic cells are the first to be destroyed during fasting. We estimate that 300g protein is destroyed in our body every day. This disintegration releases amino acids which, for the most part, are recycled; however, 50 to 80g are destroyed. These amino acids must, therefore, be replaced by an external intake as our bodies do not store protein.

The role of proteins
They have numerous roles:
- they have a structuring role in that they form the raw material which builds, maintains and replaces tissues. They are the basic constituents for cells and noble tissues: muscle, liver, bone, digestive tract, brain and skin.
They play a part in growth and tissue replacement. They are, therefore, essential throughout our lives, especially during growth, pregnancy and demanding physical activities such as ballet dancing.
- they have a fundamental role in the movement of water within the body; a result of their strong affinity with water molecules. For example, a protein called albumin keeps water inside blood vessels. If the amount of this protein in the vessels is too low, water has a tendency "to leak" out of the vessels towards the cellular environment which can cause oedemata. This situation can be seen in certain illnesses or, when nutritional intake levels have insufficient proteins. Some female ballet dancers who restrict their nutritional intake level in order to lose weight or, to maintain a weight said to be "superthin", can develop these oedemata if their protein intake levels are too low. Unfortunately, when this happens, their tendency is to cut down even more, an action which further undermines corporal harmony.
- they have a functional role inasmuch as they form the skeleton of the antibodies that help to protect the organism against microbes. They take part, as does haemoglobin, in the transportation of oxygen. They also form the basic structure for enzymes and hormones.

Protein composition
Twenty or so different amino acids exist in nature. Associations of these amino acids create variable combinations of the long tangled chains we call proteins. Digestion, cooking and industrial preparations cause proteins to split up into their basic element; amino acids.
Every protein has a very specific amino acid composition that follows a well established sequence. We believe that the human body is capable of synthetizing some 60,000 of the different proteins that it requires; the smallest being made up of just a few amino acids whilst the biggest proteins number several hundreds of amino acids. The assembly order of amino acids is characteristic to each protein and is well established. Protein synthesis and assembly can only take place, if all the constituent elements, amino acids, are all available. For example, if we feed young animals exclusively with one type of protein, they will stop growing, decline and die. If we add the missing amino acids to their food intake level they will grow normally.

Amino acids
Amongst the 20 amino acids provided by nutrition and used by the organism;
- eight are called essential amino acids because man's organism cannot synthesize them. Therefore, they must, imperatively, be supplied by food. They are lysin, methionin, leucine, isoleucine, phenylalanine, tryptophan, threonine, valine. Lysin, methionin and tryptophan are the three rarest amino acids in our nutrition.
It is possible to replace two of them;
- methionin with cystine
- phenylalanine with tyrosine
Two are essential for growth;
- arginine
- histidine (we believe that histidine is also essential for adults, making a total, therefore, of 9 essential amino acids)
- Other amino acids can be produced by man: alanine, arginine, aspartic acid, cysteine, nor-leucine, serine, glutamic acid, glycine, histidine, proline, tyrosine

Simultaneous intake of amino acids is essential
It is essential to provide all the amino acids necessary for protein synthesis through nutrition because the organism is in a state of perpetual replacement. There must be simultaneity in intake levels. All the necessary amino acids must, in fact, be available at the moment the protein is created. If an amino acid is missing, synthesis will not take place or will not take place properly and the amino acids that are available will be wasted. Furthermore, an amino acid that is available but low in quantity, will restrict the use of the other amino acids; it, then, constitutes a restricting factor.
Trémolière's comparison, using a three-coloured flag, speaks for itself: "If we have one hundred blue bands and one hundred white bands but only ten red bands, we will only ever make ten three-coloured flags, however many extra blue and white bands we may have because the corresponding number of red bands is missing". The missing amino acid is called the "restricting amino acid", the fact that it is proportionally insufficient, restricts the use of the other amino acids.
The egg is our reference protein because it contains all the amino acids in the correct proportions. It is a high biological value protein which provides amino acids in correct proportions. Eggs aside, food proteins whether their source is animal or vegetable are deficient in certain amino acids. A meal must, therefore, contain varying protein intake levels. A nutrition that provides half animal and half vegetable proteins is sufficient to provide the organism with the required good biological value proteins.

The main restricting factors are:
- methionin from animal and leguminous proteins (soya, lentils, chickpeas, bean lentils, broad beans). The amino acid composition of animal proteins is extremely close to human proteins and they have a very good digestive use coefficient, they are said to have high biological values. Leguminous proteins need to be supplemented with proteins from cereals and cereal products (wheat, rye, maize, oats, rice).
- lysin from cereal and cereal product proteins. This is why we recommend that they be supplemented with the relevant animal or vegetable proteins.

Protein supplementation rules must be applied to special diets.
As a general rule, if we act in accordance with today's customary eating patterns, we consume a stock of proteins which will be used all in all, to synthesize the required proteins.
But if, for example, we want to exclude animal food products from our nutrition, we must supplement our nutrition with the various vegetable proteins so that deficiencies are avoided. For example, the association of a leguminous food product with a cereal food product at the same meal, using the proportion of 2/3 cereals and 1/3 pulses, gives a satisfactory balance. The leguminous food products provide lysine, contained in insufficient quantity in cereals and the cereals provide a supplement of methionin, contained in insufficient quantity in the leguminous food products. Vegetarians who eat eggs and milk, do not have any deficiencies because egg proteins contain the essential amino acids, providing that they are consumed in sufficient quantities but watch out for an excess of cholesterol. Vegans should eat milk products and eggs in order to balance their food intake levels or else watch out for deficiencies.
Supplementation can only work, if it is carried out at the same meal because all the proteins required for efficient synthesis must be available at the same time. Consequently, it is advisable to be wary of dissociated diets which by dissociating the intake levels of the various food categories prevent the necessary supplementation. The result being unbalanced nutrition with poor protein balance.

Numerous countries have, unknowingly, been great dieticians ahead of time.
Their traditional dishes associate proteins which when eaten together optimize food intake levels:
-in India: rice + lentils
-in North Africa: couscous + chickpeas
-in Mexico: maize + haricot beans
-in North America: maize + dried peas
-in Europe: cereals + milk for breakfast

This chart allows you to associate foods for a vegetarian diet

cereals - seeds (sesame, sunflower)
l - l
l - l
l - l
l - l
l - l
milk products pulses
lentils

However be careful of certain circumstances which can lead to essential amino acid deficiencies.
In the event of a vegan or poorly balanced vegetarian diet:
@ Vegetarian diets.
Male and female ballet dancers who wish to follow a vegetarian diet can, by using the supplementation method obtain a good source of proteins.
Egg-eating vegetarians can correctly balance their food intake levels as the egg provides optimal amino acid balance. Furthermore, the egg yolk, rich in iron, makes up any iron deficiency caused by the absence of red meat or liver in the nutrition.
@ For vegans, it is advisable to get them to eat eggs and milk products, especially young dancers, in order to avoid serious deficiencies that can cause wasting muscle and caries as well as avoiding major deficiencies in essential elements. A diet that does not contain any animal protein is dangerous. Fortunately, dancers rarely become vegans.
@ We actually recommend that a dancer follows a semi-vegetarian nutrition in order to induce a more longilineal figure. We restrict meat and favour vegetable proteins whilst maintaining recommended protein intake levels and avoiding deficiencies.

Where do we find proteins in our foods?
They come from two sources, the animal kingdom and the vegetable kingdom. They are animal proteins and vegetable proteins.
- Foods rich in animal proteins are:
@ on the one hand, milk and milk products which are rich in calcium:
- yoghurt 3 to 5%,
- powdered milks provide 25% in whole milk and 35% in skimmed milk
- milk
- fromage frais 11 to 14%, fermented cheese and cheese spread 20 to 35%
- milk desserts, ice-creams
@on the other hand, protein filled meat products:
- red meat contains 16 to 20%,
- seafood: fish 18 to 20%, shellfish 11 to 23%
- poultry: white meat, game 18 to 28%
- eggs 12% in the whole egg, 11% in the egg white and 16% in the egg yolk
- offal 20 to 30%
- cooked meats 10 to 43%
These two types of animal proteins would be interchangeable, if milk products did not have such high fat (unless they are partially or completely skimmed) and low iron contents; and meat, eggs and fish did not have such a low calcium content. The high fat content of full-fat cheese or fatty meats make their calorie and saturated fats contents too high. Both of which are harmful to the organism when taken in too large a quantity.

Foods rich in vegetable proteins are also mainly starch-based foods:
@ cereals, wheat, rice contain about 12% protein, potatoes 2%
@ bread 7%
@ leguminous products (lentils-chickpeas-dried beans-bean sprouts), and seaweed provide on average 20% protein.

Protein production and the world economy
If we think in terms of the world economy, animal proteins are expensive; it takes 10kg of vegetable protein produced by developing countries to produce 1kg of animal protein that is consumed by "rich" countries. 2/3 of the world's cereals are given over to stock raising for the provision of meat products for rich countries! So, the cultivation of vegetable proteins provides the protein intake levels for us humans!!!

Recommended intake levels
Recommended intake levels stand between 10 to 12% of the average daily calorie intake levels for industrialized countries, 14 to 15% for town-dwelling populations of poor countries. They are, in fact, determined in accordance with the protein value contained in food.
Individual protein requirements are related to a person's weight, age and sex. Requirements increase during growth, pregnancy and breast-feeding.
The protein requirement for an infant is 2g per kilo of weight per day, that of an adult 1 to 1.5g per kilo of weight per day. The WHO recommends a minimum intake level of 0.75g protein per kilo per day, which constitutes the minimum security threshold before serious deficiencies start to occur. In France, we count on 1g protein per kilo of weight per day, which gives on average for adults: an intake level superior to 55g protein for female dancers and 70g for male dancers. We recommend that the protein intake level be balanced by equating the intake level between animal and vegetable proteins; that is an intake level made up of 50% animal proteins and 50% vegetable proteins.
Add it up for yourself: for an adult male weighing 75kg, we recommend an average intake level of 75g protein per day. Use the protein content in everyday foods chart, given further on, as a guide.
Neither too much.
A high intake level of animal proteins does not increase vitality nor life-expectancy. It can even be responsible for attacks of gout, an excess of cholesterol, weight gain, or kidney problems. The animal protein intake level for our industrialized countries is, essentially, made up of fatty red meats, cooked meats, full-fat cheeses which, high in saturated fats, are responsible for the evolution of illnesses caused by obesity. It is therefore recommended that their consumption be reduced in favour of pulses and wholemeal cereals, thus providing essential elements such as magnesium, vitamins and fibre. Elements which are, all too often, lacking from our intake levels and which greatly favour the harmonization of our bodily functions. For those who consume very little animal proteins (poor countries or practising vegetarians), we recommend an intake of proteins that is higher than for a population which generally eats a good proportion of animal proteins, but this will probably mean an increased calorie intake level.
This intake level can be deliberately increased when the total protein intake level must be increased because of poor supplementation or, during weight-loss diets, when the total calorie intake level is below 1,800 Calories.
Nor too little.
Be careful of diets that become more and more restrictive, undertaken with the aim of losing weight but which only reduce protein and calorie intake levels; such diets can provoke stubborn weight-loss and cause oedemata. Furthermore, the drop in metabolic requirements induced by this type of diet means that, in the end, weight gain is inevitable because, although the muscle is a big energy consumer, fatty tissue consumes but little. If, during a weight-loss diet, the protein intake level is low, weight loss will be carried out at the expense of the muscular-mass and the female dancer will definitely put on weight when she stops dieting because her requirements will be lower. Hence, the ascending yo-yo effect, the more we go on poorly balanced diets, the more supplementary weight we put on. It is one of the most common reasons for regaining weight after a diet, especially amongst teenagers and young adults, as the female dancer must be "superthin" in order to succeed. Weight-loss, poorly conducted, is always the source of weight gain with additional, increased adiposity which reflects immediately on the figure. This is why, for weight-loss diets, protein intake levels are always maintained and can even go up to 20% of the energy intake level; only, of course, for the duration of the diet. Afterwards, a stabilization period will allow intake levels to be rebalanced so that weight stability is obtained.
These mistakes are made, at present, by certain teenagers specializing in ballet dancing and by young female dancers who, by dieting very restrictively, reduce their noble mass. Thus, creating a future osteoporosis and a disharmonious figure because fatty tissue has a tendency to evolve jointly with muscle wasting. We would find, in such a case, the clinical indications for protein deficiency: oedemata, asthenia, hypoproteinaemia, dry skin, hair loss. It resembles the serious clinical picture of protein deficiency known as "Kwashiorkor syndrome" that is found in third world countries. These are emaciated children, with large ascitic bellies, thin, emaciated limbs with oedemata; they are easily spotted on the television.

Protein content in foods
Eating 70g meat or fish per day does not mean to say that we are eating 70g protein because in 70g meat there is only 14g protein. Use the chart and calculate your intake level.
We find 20g protein in:
- 250cc milk
- 50g powdered, unsweetened, skimmed milk
- 100g ham
- 250g bread
- 200g fromage frais
- 4 yoghurts
- 100g red meat or poultry
- 100g fish
- 2 eggs
- 60g Gruyere cheese
- 75g (90) Camembert cheese
- 250g pulses
- 1 kilo potatoes
- 6 small cream cheese desserts

Sources of protein amongst low-fat foods (useful for fat-free or weight-loss diets)
Provides, amongst other elements, 20g protein
- 80g bean sprouts, kidney
- 100g shrimps, crab, lobster, scallops
- 120g non-oily fish: bass, fresh cod, hake, sea bream, whiting, dab, sole, trout, haddock, pike, skate, dried cod, perch
- 100g chicken, turkey, or rabbit, duck-with the fat removed, pigeon
- 100g tripe, sweetbread
- 100g liver, lamb, beef, veal, pork
- 120g salmon, sardine, turbot
- 100g horsemeat
Provides 15g protein
- 100g lean ham
- a dozen oysters
- 100g cooked mussels, cooked snails, frogs legs
- 120g fromage frais with 0% fat content
- 2 eggs
- 100g red meat: beef, veal, lamb (lean part of the lamb with the fat removed)
- _ litre skimmed or semi-skimmed milk
Provides 5g protein
- 1 yoghurt
- 1_ small cream cheese desserts
- 60g wholemeal bread
- 70g corn flakes
- 140g milk

@Add it up for yourself
100g processed bread = 7g wholemeal bread = 8g
100g cooked pasta = 3.4g uncooked pasta = 12.5g
100g cooked lentils = 5g raw lentils = 12.5g
1 x 55g egg = 6.5g
Egg yolk = 3.5g
Egg white = 3g
1 yoghurt = 5.2g
100g milk = 3.5g

@You must take the cooked food content into account, both values are rarely expressed in food composition charts so be careful of making a mistake. We could, for example, say that mushrooms were a protein-rich food; this is actually true if, we take the dried mushroom value. But once reconstituted with the addition of water, mushrooms only contain 4g protein per 100g.

@my advice:
Rotate animal proteins for different meals. Vary their intake level, for example, by eating fish, poultry, ham, eggs, fresh red and white meat in turn. We eat too much fresh meat, some people even eat it for their lunch and their evening meal; this is not good for our bodies. The actual recommendation is, that meat be eaten, three or four times a week which is what happens when you rotate their intake level in this way. This system also allows you to eat fish 2 to 3 times a week which gives very good cardio-vascular protection. Bear this in mind when doing your shopping. Furthermore, from time to time, say 2 to 3 times per month, you can replace meat with a lentil dish.