Protein as a nutrient
The role of proteins in the body is usually described as structural-regulating. Well, the author of the above characteristic would probably write that, for example, the egg plays a chicken-forming role for the chicken. Perhaps – from a certain point of view – he is right, but for me it is just an unnecessary multiplication of beings.
Protein is nitrogen-rich, specialized molecule that bring matter to life. It can be said that – for matter – the protein plays organism-creating role: it enables broadly understood variability, i.e. actions and reactions within matter itself. In a word: life.
Proteins as biomolecules are complex particles, consisting of smaller “bricks” – amino acids. There are only 20 types of protein building bricks (20 different amino acids). Well, there are about 500 amino acids in nature, but only 20 of them are found in proteins – the same 20 (!) in plant proteins and in animal proteins. The quality of each protein depends on the number and order of its bricks.
In every second of our life, proteins not only watch over the transformation of matter that takes place in us (metabolism), but also undergo transformation themselves. This means that two opposite processes run in us permanently and in parallel – the synthesis of proteins from amino acids and the breakdown of proteins into amino acids (proteolysis).
This is called the metabolic turnover of proteins, and its characteristic feature is that 65-80% of amino acids released from “old” proteins immediately resynthesis to “new” proteins. The remaining 20-35% is oxidized (converted into energy), so this is part of the protein that we lose every day.
The daily performance of this exchange is very important, especially when considering how much protein we should eat.
How much protein we should eat
Most often we need:
0.8 -1 g / kg / day
(grams of protein per kilogram of body weight per day).
*) Generally, the demand for protein is estimated at 10% of energy from food (ie ~ 50g / day), but this standard is deliberately overstated (to “please everyone”) because it was determined without taking into account the harmfulness of excess protein in the diet. Read more about the dangers of excess animal protein in the diet HERE.
Let’s look at the 4 cases we can encounter while being on various stupid diets:
(Let’s assume you were a healthy man weighing 165 lbs [75 kg])
- No protein in diet:
(see case “A” in the picture below):
If there is no protein in your diet at all (but you supply energy by eating carbohydrates and fats), you lose 31 grams of protein a day – even though your body saves protein (These 31 grams are a metabolic turnover).
- You eat proteins:
If you still supply energy by eating carbohydrates and fats – your body stops saving protein only when you eat more than 75 grams of protein a day. Any excess protein – as unnecessary – is converted into glucose or fat. (Of course, a metabolic turnover equal to 31 grams of protein per day occurs continuously).
- Only proteins in diet:
If your diet contains only proteins (in excess) – any surplus over 31 grams (metabolic turnover)- is converted into energy (i.e. oxidized or converted into glucose).
- You starve:
If you do not supply energy (you do not eat anything), you lose 62 grams of protein a day – 31 grams is metabolic turnover, and the remaining 31 grams are converted into glucose. This protein comes from your muscles, that is: you eat yourself. (That’s why when we’re starving – we’re losing not only fat reserves, but also muscle mass.)
The experiment presented in the picture above was carried out based on the measurement of nitrogen content in urine.
An important feature of catabolism of amino acids is that the human body (as well as other mammals) can not oxidize amino groups. We separate them from amino acids, build them in urea and excrete them in the form of urine. This means that by examining urine content – we get ideas about the intensity of the protein degradation process: the higher the degradation, the more nitrogen we excrete.
The quality of protein
(not fully valuable value)
I do not know how it is in other countries, but when talking about protein Polish dietetics uses two terms that irritate me a lot: “fully valuable” and “not fully valuable” proteins. If they could stop at talking about essential or indispensable amino acids – I would not be so furious, but..
The protein quality issue always seemed to me… suspicious. First of all because I am allergic to propaganda, and secondly – because I have the soul of an iconoclast. The so-called “common knowledge”, which nobody dares to undermine – sometimes it turns out to be mere marketing manipulation.
Where does the idea of distinguishing protein quality come from?
It is “well known” that among 20 bricks (amino acids) building our proteins – up to eight (and even nine in children) we can not synthesize ourselves. These amino acids are called exogenous, i.e. those that must be supplied from outside. It is also “well known” that we synthesize two further bricks only on the basis of these exogenous ones, and with the production of other two – we have problems, for example during diseases. It remains only 7 with which theoretically we never have a problem (so-called endogenous).
Having such a well-established basis, common knowledge – without blinking an eye – divides proteins into full valuable and defective ones. Full valuable are, of course, those that contain all the exogenous amino acids – animal proteins. An incomplete value is attributed to all vegetable proteins, as many of them do not contain all exogenous amino acids at once.
Well, I think this division is illogical, unnecessary and even harmful.
A) Such a distinction of protein sources would make sense only if there was a necessity of feeding only one type of food product for a month, a year, a decade or until the end of our lives.
However, this necessity means:
– Firstly: that we would rather not have an influence on the menu selection.
– Secondly: if we could even choose only animal products as a source of protein – we would have died because of deficiencies of some B vitamins, some minerals and unsaturated fatty acids (unless the fish were our choice). The “full value” attributed to animal products is therefore very incomplete, because it omits our needs not related to amino acids.
B) We need to eat ALL amino acids – not just exogenous ones – because of our nitrogen balance! For the reconstruction of proteins, we need NITROGEN, which is excreted by us every day in an amount corresponding to the degradation of 31 grams of protein.
A) No sensible person ever estimates the amount and quality of amino acids in each meal.
B) Our biggest problem – which is also the cause of many civilization diseases, including obesity – is not a shortage of protein in the diet, but something exactly opposite: its excess! What is the meaning of exploring which amino acid we can eat and which we must – if our daily portion of them is two- and sometimes five times greater than the maximum recommended dose?
A) Differentiation of proteins into those of full value and not full value – has been used (for decades) by producers of animal food for unfair marketing propaganda, which from year to year deepens the pandemic of the metabolic syndrome and related diseases.
B) This propaganda led to the following:
– Part of humanity (not so small!) identifies protein only with animal products – meat, cheese, eggs, milk, fish. (It is they who always ask this epic-legendary question: “You’re vegan.. Where do you get the protein from?”)
– The others – so those who know anything about the existence of vegetable protein – consider them to be defective = bad, unlike good animal protein – which is NOT TRUE!
C) “Full value” animal protein practically always occurs in the company of saturated fat and cholesterol, which – in fact – we should not eat at all.
Just take a look at the table of % protein content, comparing animal and vegetable products:
We, the people – we are herbivores!
We just do not like meat (!!!): To eat it at all, we must first: season it and cook it, fry it, smoke it, roast it or grill it. (Have you ever seen a lion grilling?)
So how could it be possible for vegetable protein to be … defective for us?
If that were the case – VEGANS could not exist. Meanwhile, they are much better than omnivores. Why? Because plants are a better source of protein for us than animals.
How can I be sure of this?
We live in the 21st century – the century of a thriving “metabolic syndrome”. *
* Metabolic syndrome is the simultaneous occurrence of many disease entities, one of which involves the next; the first of the domino blocks is almost always improper nutrition. The syndrome includes, among others: obesity, insulin resistance, type II diabetes, hypercholesterolemia, hypertriglyceridemia, atherosclerosis, ischemic heart disease, hypertension, myocardial infarction, cerebral stroke and some cancers).
Now you will understand why I am annoyed by the division into good-animal proteins and bad-vegetable ones: Not only because – following his trail – we would have to admit that pork knuckle is healthier than rice.
The decisive role in the formation of the metabolic syndrome has animal products, namely exactly those that are called full-value – just because they contain a full set of 20 amino acids. Meanwhile, each (!) cholesterol molecule and 99.9% saturated fat molecules we’ve ever eaten – they came from animals.
While animal protein practically always occurs in the company of cholesterol and saturated fat – vegetable proteins learn about their existence only on our pan or plate. However, it is these proteins that we are told to define as … defective. Why?
Because (for example):
Corn – is poor in tryptophan and lysine.
Wheat – is poor in lysine.
Some types of beans – they are poor in methionine,
We have nothing more against them!
When I hear that the protein is bad, because it contains 19 amino acids – and could have 20 – I am always reminded of a Polish comedian (Laskowik) and his sketch about the tractor:
“The tractor broke down”
“And more specifically?”
“Its wheel broke down”
“OK.. How many wheels does the tractor have?”
“So – how many wheels are good?”
“Then why don’t you say that way? Three good ones!!”
So the tractor was almost unbroken.
We said that wheat is poor in lysine.
OK! But this means that wheat IS NOT POOR in the 19 remaining amino acids:
- aspartic acid,
- glutamic acid,
- tyrosine and
If someone ever tells me that he has spent a week in his life eating only wheat, or only beans, then I still will not accept the argument of the incomplete value of vegetable proteins. I will think, however, that something was wrong with him – and that will only confirm my belief that I was right.
Let’s just remember one thing:
Natural vegetable products
are not worse, but a BETTER supplier of protein
than animal products.
They do not affect the formation of the metabolic syndrome, but even the opposite – they prevent it.
The basic principle of proper nutrition has always been, is and will be DIVERSITY. It is diversity that forces the mutual complementation of the nutrients we eat. This also applies to proteins: the deficiency of an amino acid in one type of protein is compensated by the occurrence of this amino acid in a protein from another source.
And the omnipotent guard of the full value of protein in our meals – is the so-called APPETITE (today for that, tomorrow for something else).
- With the limited availability of carbohydrates and fats, the amino acids are oxidized with the release of energy.
- If you consume excess protein that your body is unable to use for the purpose of remodeling protein molecules, amino acids are converted into glucose, and when there is no need for additional energy – into fat (deposited in adipose tissue).
The reason for the success of protein diets lies in the fact that proteins are very bad fuel! Their oxidation is a very energy-wasting process, which is why the value of energy obtained from proteins is much lower than energy from glucose and fats.
To make it more funny – let us recall the knowledge used by traditional dieticians to prepare menus. I mean the so-called “Atwater’s equivalents”, assigning 1 g fat, protein and carbohydrates to the amount of kcal that we allegedly get from their oxidation.
And now – for a small variety – let’s look at the quotes, which are summaries of three articles on the catabolism of carbohydrates, fats and proteins:
“Calculated per unit of mass, it can be assumed that the oxidation of 1 g oleic acid provides 0.475 mole of ATP (…) This value is therefore almost three times (2.91 times) greater than the analogous value calculated for glucose.”
“The oxidation of 1 g of glucose per mass unit results in the synthesis of 0.163 moles of ATP (…)”
“Calculated per unit of mass, the oxidation process of 1 g of the amino acid mixture provides about 0.052 moles of ATP (…). This value is 3 times lower than that obtained from the oxidation of 1 g glucose, and more than 9 times less than from the oxidation of 1 g oleic acid.”
Source: Prof. Janusz Keller, “Nutrition of Man”, volume 1
edited by Jan Gawęcki, chapter 8, year 2012
Let’s evaluate these proportions “by eye”:
Let us admit that the standard dietary knowledge is slightly different from the actual state; the right ratio is not 9:4:4, but 9:3:1.
The effectiveness of protein diets comes precisely from this proportion.
But let’s not get into the euphoria: we MUST NOT use high-protein diets! Because much faster, more durable and healthier – it would be chopping off your leg. To this day, however, nobody came up with the idea of “chop-off diet”. And let it stay like that.
What’s so funny about that?
It just seems that all the energy tables of all diets in the world written by all traditional nutritionists – are wrong 🙂
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