OUR NUTRITIONAL NEEDS
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Our bodies need energy to function. Food provides this energy in the form of nutrients. To fuel our bodies with the right nutrients, a varied and balanced diet is essential.
Two main categories of nutrients are essential to the proper functioning of our bodies : macronutrients (proteins, lipids and carbohydrates) provide the fuel, while micronutrients (vitamins and minerals) ensure the perfect assimilation of macronutrients. These nutrients are said to be essential because our bodies cannot produce them in sufficient quantities. A shortage of these nutrients, even light, will trigger health issues; severe shortage will trigger sickness.
Macronutriments represent, with water, 98% of our food intake and are the fuel to our bodies. They divide in 3 groups:
Carbohydrates or sugars, mainly provide energy but also fibres. Sugars can be divided into « complex sugars » when they contain starch (cereals, potatoes, legumes, etc.) and in « simple sugars » when they contain fructose, glucose, lactose or saccharose (fruits, vegetables, milk, honey, etc.).
Proteins are our construction blocks. They are needed to build and repair bones, skin, cell membranes, antibodies, hormones... Proteins can be animal (meat, fish, eggs, dairy products) or vegetable (cereals and legumes).
Lipids,
or fat,
are essential to the proper functioning of circulatory, hormonal, immunity and nervous systems. We will come back to lipids in more details in the coming lines.
Micronutriments are mainly vitamins and minerals. Even if they make their way in trace quantities only (micro or milligrams) and represent hardly 2% of our food intake, they are indispensible to life. Micronutriments do not provide energy, thus no calories, but ensure several functions, amongst others as antioxidants.
CARBOHYDRATES
Carbohydrates are essential to the proper functioning of our muscles and our brain : they are the source of energy that our bodies can use the fastes and are involved in the synthesis of proteins.
There are simple and complex carbohydrates or sugars. Simple sugars include glucose, fructose and galactose that can further produce saccharose (= table sugar), lactose or maltose. Complex sugars include starch, glycogen and fibres.
What is their role ?
The main role of sugars is to provide energy to our body cells (1g of sugars supplies 4 calories). When we eat carbohydrates, they transform more or less rapidly in glucose that is fueling some of our body cells, like brain cells. Glucose if the only fuel for our brain, and we need approximately 140 g of it daily.
Complex sugars, and fibres in particular, play an important role in regulating appetite. They help reach satiety quicker and longer. This is why they must be included in our diet.
How much do we need ?
Carbohydrates should represent between 45 and 55% of total calories intake in a balanced diet.
Main sources of carbs are cereals, fruits, vegetables and legumes.
PROTEINS
Proteins are the main components of all our body cells. They are chains of amino acids that can be part of muscles, skin, nails, hair, blood, etc. They are also the basis of numerous hormones, enzymes and antibodies and are essential to growth, repair and defence of body tissues.
What is their role ?
A structuring role, participating to the renewal of muscular tissues , integuments (hair and nails), bone matrix, skin, etc.
Proteins are involved in several physiological processes, in the shape of digestive enzymes, hemoglobin, hormones, receptors or immunoglobulins (antibodies) for example.
They also represent the only source of nitrogen to our bodies.
How much do we need ?
A health diet should include 25 to 35% of proteins of the total food intake, or 0,8 grams per kg of body weight, ideally both animal and plant proteins as they are complementary. Animal proteins are mainly found in meat, fish, seafood, eggs and milk products. Plant proteins can be found in bread, cereals and starches.
LIPIDS
What is their role ?
They are a big contributor to our energy needs as 1 gram of lipids provides 9 kcal, against 4 kcal per gram for proteins and sugars.
They are the main components of cell membranes. Each cell of our body is surrounded by a membrane mainly made of lipids, which quality will depend on the quality of lipids we eat. Moreover, our brain is composed of lipids for more than 60%.
Lipids are also responsible for our skin plasticity and elasticity as they are important parts of dermal cells.
In our bodies, some vitamins can only be assimilated with the help of food fats. They are called fat-soluble vitamins : A, D, E and K.
Fatty acids enable the systhesis of specific hormones and contribute to regulating essential functions of our bodies.
Lipids are often demonized because of their high energy supply and we may be tempted to exclude them from our diet to lose weight. This would be a mistake because of shortage of lipids can be a fertile ground to inflammation and to fall of form.
This is why it is essential to ensure a sufficient intake of lipids, and more importantly, of quality lipids.
DEFINITION OF LIPIDS
Lipids are molecules made of fatty acids, of which there are about 40 types including saturated and unsaturated fatty acids.
Saturated fatty acids
Often called 'bad fats’ because, when consumed in excess, they favour weight gain and increase the risk of heart and vascular diseases, saturated fats are not said to be essential because our bodies can manufacture them.
These fats are nevertheless not that bad if you chose them wisely and of good quality. They are a major component of our cell membranes, of some hormones and they also provide vitamins A, D, E and K.
In reasonable quantity and of good quality, they are good for our health. Main sources of saturated fats are tropical fats, milk products, cold cuts and fatty meats.
Unsaturated fatty acids
They ensure several functions in our bodies, particularly in the hormonal synthesis and play a protective role against heart and vascular diseases through fighting arterial hypertension. Main sources of unsaturated fatty acids in food are plant oils, meat, fatty fish and eggs.
Essential fatty acids
Essential fatty acids are part of the polyunsaturated fats and are said to be essential as they cannot be synthesized by our bodies. There are 2 types of essential fatty acids : linoleic acid l’acide linoléique, an omega-6 et fatty acid, and a-linolenic, an omega-3 fatty acid. They play an important role : they fight heart and vascular issues as well as hypertension. The only solution is to consume these essential fatty acids through food (plant and fish oil for example) or supplementation.
The ratio between omega-3 and omega-6 is key as an imbalance between the two can generate an important imbalance in our fatty acid status. Indeed omega-6, when taken in excess, prevent omega-3 from producing a beneficial effect on our health.
Which lipids should you chose ?
Going through the definition of lipids gave you a first idea of the type of lipids you should favor on your diet.
Les graisses à éviter
Les acides gras dits « trans » et des huiles partiellement hydrogénées, issus des processus industriels. En trop grande quantité, ils augmentent par contre les risques de maladies cardiovasculaires.
Afin de les éviter, essayez d’éliminer au maximum de votre alimentation les fast foods, plats préparés et autres préparations industrielles, en particulier les viennoiseries, pâtisseries, biscuits et autres friandises industrielles.
Les graisses à consommer impérativement, avec modération
Il s’agit des acides gras saturés. On les a longtemps tenues responsables de pathologies diverses (maladies cardiovasculaires, cholestérol, etc.), mais en réalité, tous les acides gras saturés ne sont pas à mettre dans le même panier.
En premier lieu, notre corps en a besoin d’une certaine quantité par jour : il ne s’agit donc surtout pas de les éliminer, mais de ne pas en abuser. En effet, consommées en excès, elles pourraient avoir des effets néfastes sur l’organisme (résistance à l’insuline, diminution de l’utilisation des graisses pour fournir de l’énergie, etc.).
Vous devez néanmoins en consommer un minimum, de manière modérée, d’autant plus si vous choisissez bien vos sources.
