Human Nutrition

Introduction

The human nutrition is the science devoted to the study of the human eating beginning with the ingestion of food up to absorption and assimilation of nutritious principles.

It is also the study of the processes which allow living organisms to support their life via the use of food to assure the needs of the body in terms of energy and maintaining of its structure.

A food isn't a simple assemblage of biochemical substances: he defines itself by his capacity to be usable or available for a living organism and by his possibility of participating in his functioning and in the satisfaction of his needs of all kinds (energetics. nitrogenous, vitamin, mineral, etc.).

In short, the nutritional value of an agroindustrial material depends first of all on the digestibility of its nutriments, then on their metabolic use ;

This document will be dedicated, above all, to introduce the different classes of nutriments, to know :

• Carbohydrates ;
• Proteins ;
• Lipids ;
• Vitamins and
• Mineral salts.

Then one are going to be approached the aspects of a balanced nutritional regime as well as consequences of a malnutrition or a surnutrition to the health of the individual.

In the third and last part, the link between food industries and human nutrition by the study of the effects of food technologies on the nutritional quality of food as well is going to be established as the contribution of the agro-industry to struggle against disturbances caused by to deficiency in micronutriments.

Classes of nutriments

Carbohydrates

Carbohydrates or carbohydrates, called commonly sugars, are chemical compounds based on 3 molecules : Carbon, Hydrogen and Oxygen, their title role is to give in the organism living an energy source where a gramme of carbohydrates can give 4 kilocalories.

Carbohydrates can be subdivided into 3 groups according to the complexity of their chemical structures, they find :

• Monosaccharides or simple sugars constituted by the single molecule, said dare, as the glucose, the fructose, the ribose ;
• Disaccharides, said diholosides, composed further to the link of two molecules of simple sugars, they name as examples : The lactose (characteristic sugar of the milk), the maltose (characteristic sugar of the malt) and sucrose (sugar of table).
• Polysaccharides composed of a succession of simple sugars inter-linked between them to give rise to complex sugars as the starch, abounding in cereals, or glycogen, form of stocking of sugars at the level of the liver. The starch is the polysaccharide most abounding in the human eating gift in a big variety of vegetables such as leguminous plants, cereals, tubers or fruits.

To use carbohydrates, human organism must first transform them into simple nutriments: the glucose. 2 essential operations are wanted to tell here by transformation :

• Catabolism : It is the operation relating to the metabolism of deterioration ;
• Anabolisme : it is the operation relating to the metabolism of synthesis

Catabolism, alphas-amylases (salivary and intestinal) begin since mastication up to digestion, under the influence of various secretions and notably. The so got glucose is routed to the user organs; while the rest will be stocked as energy reservation in form of glycogen in the liver. The surplus is going to be transformed into lipids and put in reservation in form of adipose cloths.

In adult's normal diet, food glucidiques should bring two thirds (2/3) of the complete energy of ration. In case of necessity, carbohydrates can be synthetized by organism from lipids and proteins: It is the néoglucogenèse or anabolisme.

Carbohydrates exist in the almost totality of food, for some food he is the major constituent ; it is the case of cereals (rice, sorghum, corn, wheat, barley) and starchies (manioc, potato, soft potato):

Proteins

Proteins are chaines composed of successions of amino acids among 20 amino acids that use the human body, every amino acid includes two functions : A carboxylique (-COOH) function and a function amine (-NH3).

Proteins assure 2 roles at the level of organism :

• An energy role : A gramme of proteins can give 4 kilocalories of energy following the example of carbohydrates ;
• A role of structure : maintaining of the muscular mass and of the other protein structures (DNA and others).

Proteins can be of animal or plant origin. Among food rich in proteins, they name as examples :

• Products of animal origin : Meats, fish, liver, milk, yoghurt, cheese...
• Products of plant origin : Lenses, beans...

Lipids

A lipid is a succession of fatty acids, these last are classified in 2 groups :

• Saturated fatty acids : where the link between carbons is assured by covalentes simple links ;
• Unsaturated fatty acids : where the link between carbons is assured by covalentes links double or triple ; if there is the single link unsaturated monoskiing unsaturated is spoken of fatty acids if there is more than a link unsaturated, they speak in that case about polyunsaturated fatty acids.

Vitamins

According to their solubility in aqueous or oily middle, vitamins are classified in 2 classes :

• Hydrosoluble vitamins : these are soluble vitamins in the water as the vitamin C and vitamins of the group B.
• Liposolubles vitamins : these are soluble vitamins in an organic solution as the hexane or the acetone, they are in number of four : Vitamin A, vitamin D, vitamin E and vitamin K.

The most important sources of vitamins of feeding are: Fruits and vegetables, pulses, products of animal origin, and cereals.

Vitamin A (rétinol)

Among products the richest in vitamin A, they find :

• Products of animal origin : full cream milk or enriched, yolk, liver,
• Products of plant origin : oil of red or enriched palm, vegetables with leaves green-dark (leaves of baobab, of manioc, of soft potato), fruits and vegetables with yellow-orange colouring (tomato, carrot, marrow, papaya, mango, banana, lawyer, guava, etc.)

In the course of the recent years, knowledge on functions of the vitamin A strongly increased. Considering the fact that nuclear receivers of rétinoïdes were identified in practically all types of cells, it would be possible to say that the vitamin A plays a role, direct or indirect, in several functions at the level of the body, to be known :

• Vision ;
• cellular differentiation ;
• the embryogénèse ;
• immune answer ;
• reproduction and
• growth

Vitamins of the group B

They are found in the sound of cereals, leguminous plants (beans, niébé, dolique, peanut, sesame, pulses). Some of these vitamins, such as the vitamin B1, are thermosensibles.

Vitamin C (ascorbic acid)

She is found in citrus fruits (orange, lemon, grapefruit, tangerine, clementine, etc.). The vitamin C has several roles: the synthesis of some neuromediators, etc intervenes in the training of the collagen, improves the absorption of the iron.

Mineral salts

Mineral salts play an important role in the maintaining of the water balance of the human body as well as the good behaviour of its metabolism and its vital functions as cardiac function.

Among mineral salts necessary to the metabolism of the human body, they name for example :

• Iron (Fe) : there are 2 types : héminique iron (of animal origin) and iron héminique not (of plant origin). He enters ferriprive anaemia in the composition of the haemoglobin of the red cell where from in case of iron weak nutritional contributions , he also enters the constitution of the myoglobine and several systems enzymatiques as that of cellular breathing. The products of animal origin as meats, fish, eggs and ovoproduits are very rich iron, they find such some rich plant iron products as leguminous plants, however the iron of animal origin is more comparable by the human body than that of plant origin.
• Iodine (I) : very important for the mental and psychomotor development of the individual. In case of deficiency in iodine, the person is attained of the goiter and a remarkable mental delay and loses her capacities to take initiatives or to be active in the society. This problem of deficiency in iodine is often present in the hilly zones where the products of the sea (fish and others) are rare and the soil is very poor in iodine.
• Calcium (This) : The calcium participates in structure and in constitution of bones and of teeth, a weak contribution in calcium can give rise to fragile bones and weakened teeth. Food the richest in calcium is the milk and the cheeses.
• Magnesium (Mg) : He contributes to the production of energy, synthesis of proteins, muscular shrinkage and transmission of nervous impulse. A deficient contribution in Mg can cause muscular cramps. Among products rich in Mg pulses, chocolate, and the dry fruits are named (almonds, nuts, hazelnuts, figs).
• The phosphorus (P) is one of the constituents of the cellular membrane; he gives in the cell of energy in the form of adénoside-triphosphate (ATP). The milk, cheeses, the dry fruits, meats, pulses, the fish and eggs are rich products in P.
• The potassium (K) of the body has an action on heart rate and content of water of organism by participating to balance the pomp potassium-sodium. It is found in bananas, potatoes, fish, apricots, etc.

Balanced nutrition

Needs in energy

• "Reference man": Adult of masculine sex in good health, weighing 65 kg, working 8 hours a day working, exercising a moderate social and professional activity, having 8 hours a day of sleep. His needs are estimated in 46 Kcal / kg of weight / day that is 3.000 Kcal / J. 
• "Reference woman" : A woman who weighs 55 Kg, in good health, occupied in domestic duties 8 hours a day or used in an unit with moderate activity. She passes 8 hours a day to the bed. His needs are estimated in 40 Kcal / kg of weight / day that is 2.200 kcal / J.

Consequences of an unbalanced nutrition

Often when they don't pay attention to our diet, they risk having one of both cases of nutritional rocking :

• Malnutrition : it is the insufficiency of contribution in nutriments, that is to say a non-satisfaction of the nutritional needs of organism.
• Surnutrition : It is the case of an excessive contribution of nutriments that exceeds needs requested by the body.

An unbalanced nutrition can cause several disturbances, they name as examples :

• MPE : Protéino-energy Malnutrition, is an illness caused by a weak contribution in carbohydrates and in proteins. This illness is characterised by the decline of the muscular mass and of the adipose cloth caused by to a very poor nutritional contribution.
• Disturbances of vision : Deficiency in vitamin A which can go up to crepuscular blindness.
• Weaken ferriprive : it is the anaemia caused by an iron deficiency in the daily food ration. This illness apparait mainly at the persons with mainly plant diet and where iron contribution is very weak or not very comparable by the body.
• Goiter : the deficiency in iodine augments the volume of the thyroid gland at the level of the neck; the iodine intervenes in the synthesis of necessary hormones for the development of the brain and of the nervous system and especially the psychomotor development of the child.
• Obesity : It is the state of a body that receives more nutriments than that it needs, the rest is stocked in form of grease contributing so to augment quantitatively the adipose cloth at the obese person. When the food behaviour of the obese persons is analysed on qualitative plan, some disturbances and notably fact are found that the ingestion of food isn't corrélée with the degree of hunger or of satiety. Obesity can be owed in :
• Obésité : C’est l’état d’un corps qui reçoit plus de nutriments que dont il a besoin, le reste est stocké sous forme de graisse contribuant ainsi à augmenter quantitativement le tissu adipeux chez la personne obèse. Lorsqu'on analyse sur le plan qualitatif le comportement alimentaire des personnes obèses, on trouve un certain nombre de troubles et notamment le fait que l’ingestion des aliments n'est pas corrélée avec le degré de faim ou de satiété. L’obésité peut être due au :
  • Nibbling: ingestion of small quantities of food in very reduced intervals ;
  • Crises of bulimia: behaviour consisting in ingesting quantities of food, even if she is bad, without pleasure food.

Obesity can cause several cardiovascular diseases of order, high blood pressure, diabetes, etc.

Food technologies and nutrition

Influence of food technologies on the nutritional quality of food

influence of the technological treatments on the digestibility of the starch

Food is generally used having suffered a technological transformation and/or a treatment of cooking of domestic type. Consequences of treatments to the properties of starches depend on some of their intrinsic physical and chemical characteristics. Moreover, modifications physicochimiques starches led by the applied treatments are likely to orientate their digestive then metabolic future to more or less energy ways.

Influence of the technological treatments on lipids

The thermal treatments suffered by lipids can affect significantly the quality of lipids, it is possible to name the example of the fryings where the temperature attains easily 180°C what draws away :

• Thermo Oxidation of the present vitamins in the food under the influence of heat and as a result, an important loss in nutritional value of the product. As well as the impairment of acids linolénique and linoléique, fatty acids considered as necessary to the human body.
• Appearance of new compounds :
• Apparition de composés nouveaux :
  • Composite fowls responsible for the smell as the cétones and aldehydes formed during the thermal treatment ;
  • Radical free characterised by a greedy and unstable chemical structure in electrons where from their danger on human organism.

Influence of the technological treatments on the nutritional value of the food proteins

Generally food containing proteins suffers several most used but thermal treatments stay :

• The thermal treatments : Sterilisation, appertisation, pasteurisation.
• Reduction of the content of water : Drying, evaporation, salting, concentration.

These treatments can influence the nutritional quality of contribution in proteins by denaturation of these. As for the digestibility of proteins, it is especially changed by changes of conformation, by the training of bridges covalents, by isomérisation or else by modifications of the lateral chains of residues of amino acids admitted by protéases as sites of hydrolysis ; what reduces the rate of absorption of proteins or ingested amino acids.

Influence of the food fibres on the bioavailability of minerals

Among the comments which it is possible to issue concerning the role of the food fibres in the bioavailability of minerals the role of the acid is phytique in the reduction of the absorption of the iron and as a result the provocation of a ferriprive anaemia at people with a diet based principally on cereals and whose contribution in animal proteins is limited.

On the contrary, besides the acid phytique, other linked anti-nutriments are powerful factors of malnutrition to be known :

• the acid oxalique (spinach, sorrel, beetroot, cress, chocolate) reducing the absorption of the calcium, of the magnesium and of the zinc ;
• and the tea which includes tannins the inhibitive action of which on the absorption of the iron was shown well.

Influence of technologies on vitamins

The influence of the thermal treatments on contents of vitamins is very significant for vitamins thermosensibles or thermolabiles :

• Case of the vitamin C in juices of citrus fruits: A lot of this vitamin is oxidised under the influence of the pasteurisation which suffers the product.
• Case of the vitamin B1 (thiamine) in the milk: These vitamins are oxidised under the influence of the temperature and lose so their nutritional value ; for the thiamine more the thermal treatment more is extended they lose in vitamin content.
• Case of the vitamin A in the yellow and orange fruits and enriched food as the vegetable oil or full cream milk strengthened in Vitamin A: The culinary treatments of cooking and heating can damage vitamin A until 40 % initial contents in.

Strategies of struggle against deficiencies in micronutriments

Supplémentation

The World Health Organisation (WHO) recommends currently that the additional, relatively modest needs, in vitamin A during the pregnancy are covered by feeding, or by supplémentation not exceeding 10.000 UI every day during the pregnancy.

Food fortification

In industrial countries, the food fortification constitutes for a long time a strategy admitted of improvement of contribution in micronutriments. Some examples of strengthened products are named :

Fortification in vitamin A : In Denmark, during the first world war, an epidemic xérophtalmie developed in parallel in a substitution of the butter by the margarine, poor in vitamin A. The margarine counts among foodstuff in the world most often strengthened in vitamin A today.

The food fortification gives potentially a medium live broadcasting, efficient and lasting to correct deficiency in vitamin A. In practice, he sometimes proved to be however difficult to unite all requested criteria. The first efforts aiming at strengthening raw materials had to overcome obstacles of technological order. Today, such factors aren't any more considered as limitative.

Many food was strengthened in vitamin A. Among these products the margarine, food oils, cookies, the milk, the glutamate of monosodium and others.

The fortification of the sugar remains in force at present in several countries of Central America, and is under way of introduction in some countries of Latin America and of Africa, notably in Zambia and in Nigeria.

Consequence of the recent and powerful rebound of interest towards the fortification of food in micronutriments in developing countries, several tendencies free and which will raise difficulties probably within the foreseeable future in term of excessive contribution in vitamin A resulting from a fortification anarchic and not controlled by foodstuff if they know that in high doses, the vitamin A becomes toxic and that the access to the strengthened products is given to all population those who have access to products rich in vitamins A of part of their diet or purchasing power. In some countries, more than 20 foodstuff is strengthened at present in vitamin A at a high level, what poses possible problems of excessive contributions.

Iron fortification : A programme of fortification of the iron flour and vitamins B was thrown in collaboration with the direction of the population and the association of the professionals of the sector miller in Morocco. The purpose of this fortification is to struggle against ferriprive anaemia from which endure mainly the women and more particularly those surrounding walls. However some criticisms can be issued if they know that technologically, it is really very difficult to have a homogeneous lot in iron content seen the difficulty of the operation of solid-solid mixture.

Fortification there iodizes : In Morocco, a programme of fortification in iodine was launched. This fortification took vector as food the salt of table to which was figured up the iodate of potassium (KIO₃) to assure the target population a daily contribution in iodine capable of meeting needs in iodine especially for the persons inhabitants in mountain regions and soil of which is poor in iodine.

Improvement of diet

There are four types of strategies tending to reach the targets of dietary modification:

• education or nutritional communication, who often use an approach of social marketing, to improve practices relating to the consumption of the available food sources rich in vitamin A, iron and in iodine.
• the breast-feeding, which constitutes a powerful protection against the xérophtalmie, following partly from regular contribution by the milk of préformée vitamin A. The World Health Organisation recommends that all new-born babies are exclusively breast-fed during at least four-six months, and that they continue being breast-fed from the age of six months with in addendum adequate food complements.
• the horticultural interventions (or of domestic supply), for example the family gardens, which aim at augmenting the availability of food rich in vitamin A.
• the économico-food politics affecting availability, prices and real request of food rich in vitamin A, iron and iodine to give them at prices accessible to populations subjects of deficiency; they allude here to the products of animal origin which aren't often within the reach of the divested social classes.

Nutritional toxicology

Generality on the composition of an agroindustrial product

In its natural state, a food is made up first of all of nutritious elements coming directly from ambient middle or coming from modifications of synthesis performed by living organism, from the contributions of the soil and of the water in the case of vegetables or of consummate ration if it is about animal productions. All the components so worked out form theoretical nutritious potential: it will be efficient only as much as these elements (carbohydrates, lipids, proteins, vitamins, minerals) will turn out to be usable by the man or the animal.

Some components of the food aren't considered to be nutriments ; it is the case of the cellulose of vegetables, tannins in the tea and flavonoïdes of fruits and vegetables, phytates of cereals as well as the oxalique acid of spinaches. Some of them have even an antinutritional activity as acids phytique which chélate the iron and reduces its absorption appreciably.

Agricultural productions contain also very often another category of substances: these are foreign subjects (pollutants and xénobiotiques) coming incidentally from environment and from suffered manipulations.

They name as examples :

• Vegetable oils polluted by polycyclic aromatic hydrocarbons and more precisely benzopyrènes.
• Red meats containing high contents of antibiotics and veterinary medicaments due to the treatment before butchery or polluted chemically by dioxins.
• Vegetables containing contents, in active subjects of pesticides, superiors in the maximum border of wastes. These contents are often due to the not respect for delay before harvest.
• Food (Peanuts, corn, orange juice) polluted by mycotoxines as the aflatoxine, the patuline or the ochratoxine.

As for the transformed foodstuff, these make the object of introduction of food additives, who too, contain a toxicologique power :

They name as examples :

• The amaranth (E123), known by its carcinogenic effect, used in red wines.
• The potentially allergenic tartrazine (E102), used in gaseous drinks and several products object of colouring.
• Polyols (sorbitol, maltitol, xylitol) which is édulcorants used in chewing gum, able to have laxative effects in case of an excessive consumption.
• Intoxications with various heavy metals (cadmium, mercury, chromium) are determined in the nearness of their places of use, especially after pollution of a source of water used as reservation of drinking water.
• As illustration, as the stock fed in the silage containing mycotoxines, these substances are stocked at the level of the liver. After butchery and consumption of the liver there is the passage of this mycotoxines who was stocked throughout the life of the animal towards the final consumer and when they know that mycotoxines constitutes the molecules of biological origin the most carcinogenic while being a thermostable, they have the idea of the danger incurred by the consumption of such food.
• Antibiotics used there zootechnie or in veterinary medicine, their presence in food articles of animal origin is at the origin of development at the man of floras antibiorésistantes which would cancel the action of antibiotics managed to medical aims.

Ineffectual dose and allowable or acceptable dose

Conclusions of toxicologiques studies bring to light the quantity ingested by a product for which neither toxicity, nor effects considered serious and detrimental in organism are recorded. This value is expressed in weight by bodily kg weighty (lively weight). From these data, an acceptable dose for the man is deducted by taking some precautions. In most cases reasoning is the following:

• mankind is likely to be more sensitive than animal kinds used in studies of toxicology. To parry at this risk, the ineffectual dose is divided by a factor of 10 ;
• given the heterogeneity of human kind, some individuals can give a particular sensitivity, where from appeal in a new safety factor of 10.

In practice, the allowable or acceptable dose is therefore often the hundredth of the ineffectual dose at the animals objects of experimentation.

Example : feeding and colorectal cancer

The colorectal cancer deserves a particular interest. He is, in France, in the first rank of cancers. There are every year 25.000 new cases and 15.000 deceases by colorectal cancer. The knowledge of the factors étiologiques is necessary. After some studies which studied question, it was noted that 3 essential factors can be at the origin of the cancer a colorectal, these factors are the following :

• Animal fats : The risk of colorectal cancer augmented with the importance of contribution in calories, in complete grease, in complete proteins, in saturated fatty acids, in oléique acid and in cholesterol. The multidimensional statistical analysis points out that saturated fatty acids were the nutriment most linked at the risk of colorectal cancer.
• Alcohol : In workers' cohort brewers with a high consumption of beer, the risk of cancer of the rectum is multiplied by 2 in Ireland.
• Tobacco : Risk is almost doubled at the smokers' in comparison with the not smokers and most studies show a relation dose / effect with a relating risk in the order of 5 at the big smokers (more than 30 cigarettes a day).

CONCLUSION

In the present state of our knowledge, it is necessary to be very careful in relation to our food habits to have no unbalanced diet of the nutritional point of view, for it, it is recommended of :

• Use fresh products, mainly fruits and vegetables, the olive oil, honey and dates ;
• Use gently meats and grease of animal origin ;
• Use complete cereals ;
• Reduce consumption in transformed products (salted, sweetened) ;
• Avoid products containing carcinogenic or allergenic additives ;
• Avoid products displayed to contaminating or polluting (Products displayed over the road axles, the neighbouring fields of cement works or other polluting industries)
• Refrain from smoking and from taking alcoholic beverages (wines, beer, calvadoses, liqueurs, spirit).