Essential nutrients in the human diet: what are proteins, sugars, fats?

A person's quality of life is largely influenced by the food he or she eats. This must contain essential nutrients, also called macronutrients. Another important component of the diet is the supporting nutrients or micronutrients.

Human nutrition

We should eat in such a way as to prevent diseases that are caused by poor nutrition, such as obesity, diabetes and atherosclerosis.

The diet must contain essential nutrients:

• Protein.
• fats (lipids)
• sugars (carbohydrates)

These substances are a source of energy for the body. They are involved in the construction of cells and tissues and in proper metabolism.

Equally important for the human body are the supporting substances:

• vitamins
• minerals
• trace elements
• water

The human diet should cover the energy requirements of the body. It should provide all the substances important for its proper function, depending on the age, sex, physical stature and energy expenditure of the person concerned.

There are certain principles to be followed in the diet. It is all about feeling good. Therefore, it is important that the diet is:

• moderate - energy intake must match energy expenditure
• balanced - essential nutrients, sugars, fats, proteins must be in the right proportion
• regular - the daily energy intake should be spread over five meals in reasonable quantities
• varied - the diet must have a sufficient representation of supporting substances
• sufficient fluid intake - at least 2 to 3 litres of water per day

The recommended distribution of essential components in the diet should be 10% protein, 26% fat and 64% sugars.

Protein and its importance to the body

Proteins are of vital importance to the body. They are its basic substances. They are involved in tissue construction, various functions and are part of a large number of hormones.

The energy value of protein is 17.1 kJ/1 g.

Depending on a person's sex, age and physical activity, their daily intake should not exceed 10-12% of the total diet.

The minimum protein intake for low physical activity is approximately 0.5 g/1 kg of body weight. However, the optimal intake per day should be in the range of 0.8 to 1.2 g/1 kg of body weight.

In one day, a person degrades 20 to 30 g of protein. To replace it sufficiently, about 50 to 70 g should be taken in.

Plant or animal protein?

In terms of a healthy diet, many people would prefer vegetable protein. However, the representation in adulthood should be at least 50:50. However, the optimum is 40% animal versus 60% vegetable.

This is also because most pure plant proteins are incomplete. Some of them lack sufficient amounts of amino acids needed for healthy human development.

Therefore, their replacement by proteins of animal origin is possible only if their intake is varied and in sufficient quantities.

Proteins of animal origin are more complete. They contain a greater quantity of essential amino acids, which the body cannot produce itself. It is therefore dependent on external intake.

However, it is important to remember certain facts.

Excessive protein consumption puts a strain on the digestive tract, the liver, the kidneys and the body in general.

The quality and quantity of the proteins consumed must be taken into account. Plant and especially animal proteins have a lower energy potential for the organism because of their difficulty in processing in the digestive tract. Thus, more energy is spent on digesting them than is left for other activities.

Fats and their importance for the body

Fats are the largest reservoir of energy. They are part of cell membranes and organelles. They are involved in their construction. They are also needed for the absorption of fat-soluble vitamins (A, D, E, K).

The brain tissue and the peripheral nervous system have a high proportion of fats. Therefore, they are needed for their proper function.

Fats, lipids, are characterised by their high energy yield. From 1 g, up to 38.9 kJ of energy can be released. In this respect, they are the largest source of energy. This is especially true when the demands on the body are increased, for example during physical exertion.

They protect the body against temperature losses. They also have a protective function for certain internal organs against mechanical damage.

Fat is also present in foods of animal or vegetable origin. An essential element of lipids, which determines their quality, are fatty acids.

Fats should occupy about 26% of the daily energy intake.

From the point of view of a healthy diet, the ratio and proportion of saturated and unsaturated fatty acids in the human diet is essential. Unsaturated fatty acids are of great importance to the body. They are found in vegetable oils and marine fish.

In childhood, the consumption of fats is higher. It is 4 to 5 g/1 kg of body weight. Gradually, this requirement decreases. In adulthood, it is recommended to consume 1 g of fats/kg of body weight per day.

In principle, the proportion of fat in energy intake must be less than 30 %. For an adult, the ideal daily fat intake is 50 to 80 g. Cholesterol intake must not exceed 300 mg per day.

There is a tendency to reduce saturated fats in the diet. They cause obesity, atherosclerosis and their complications. Large amounts of these fats are found in meat and meat products and in milk and its products.

You might also be interested in this article on obesity and overweight.

Sugars and their importance for the body

Sugars or carbohydrates are an immediate source of energy for the human body. They are known in the form of starch (potatoes, rice, pasta) as polysaccharides and sugar as mono-oligosaccharides.

Carbohydrates should cover 50 to 65% of a person's energy needs.

They are divided into usable and unusable. Being unusable means that they are not a source of energy.

The following table shows the breakdown of sugars

Plant starches are the most abundant in human nutrition. Fibre is also of great importance.

Glucose

Otherwise known as grape sugar, it is the most important carbohydrate in the human body. It is needed for the proper functioning of certain organs. Energy is mainly drawn from it by the brain or muscles.

Normal levels of glucose in the body range from 3.3 to 6.6 mmol/l. Its level is maintained by various hormones. The most important of these are insulin and glucagon.

The amount in the blood depends on food intake, physical exercise or stress factors. In case of a deficiency, the body can also create it from fats or proteins.

Fructose

Fruit sugar is a component of sucrose. It is found in honey or some fruits. It has a faster metabolic activity than glucose.

Sucrose

Found in cane or beet sugar. In concentrated amounts in sweets including chocolate. Excessive consumption of sucrose leads to obesity, atherosclerosis or diabetes.

The energy content should be around 10%.

Lactose

Otherwise known as milk sugar. Its main source is milk or milk products. It is supposed to supply about 10% of an adult's energy. It is found in breast milk at about 7%. In cow's milk it is slightly less, about 5%.

Galactose

Lactose is the main source of lactose. It is important for the mental development of children. It should certainly not be absent from their diet.

Maltose

Found mainly in malt.

Starches

Starches are the largest source of carbohydrates. Of all carbohydrates, starches contribute the most to the production of energy. This makes them a useful polysaccharide.

In terms of good nutrition, it is important to have a higher proportion of plant starches in the diet. We get them from rice, potatoes, corn, wheat and other cereals and their products.

Of the usable polysaccharides, starches should make up 50 to 75 % of the diet.

The use of sugars and fats in the body depends on the intensity and duration of physical activity.

Fibre

It is not a source of energy and therefore belongs to the group of unusable carbohydrates. However, this does not diminish its value in a healthy diet. It is well resistant to digestion and therefore increases stool volume. It has a good effect on motility, i.e. the motility of the digestive tract.

It speeds up the passage of food through the intestines. This means that the fats are not absorbed sufficiently. So their content in the blood is reduced.

Fibre is used to prevent atherosclerosis, diabetes and colon cancer.

Read our article on the effects of fibre on the body.

Carbohydrates should not be avoided. Their deficiency causes various metabolic disorders. The energy content should not fall below 10%. This represents approximately 50 g of usable carbohydrates.

The daily intake depends mainly on physical activity.

Children, because they are more physically active, have a recommended daily intake of 10 to 15 g of carbohydrate per kg of body weight. For adults, this is 5 to 8 g. This represents 300 to 500 g per day, depending on age, gender and, above all, physical activity. However, of this amount, no more than 10 % should be refined sugar.

Fibre should not be forgotten either, with a recommended daily intake of 20 to 30 g.

If carbohydrate intake is low and prolonged, there is a risk of impaired health. In the beginning, this is manifested by impaired concentration, reduced physical and mental performance. In extreme cases, sweating, pallor, trembling, disorientation and even hypoglycaemic shocks may occur. Endurance athletes may also be at risk if they do not replenish carbohydrates during exercise.

In contrast, prolonged high carbohydrate intake can cause diabetes.

As well as essential nutrients, supporting substances are also important for humans. This group includes vitamins, minerals, trace elements and water.

Vitamins

These are essential nutrients, i.e. the body cannot make them on its own. Except for vitamin K.

The reserves of vitamins in the human body are minimal. Of the fat-soluble vitamins, A and D are stored in the liver. Therefore, if they are insufficiently supplied by food, they can cover the body's needs for a few months.

However, the water-soluble ones have almost no reserves. For this reason, the organism is dependent on their constant intake through food.

Vitamins are important in regenerative processes and immunity. They help in blood formation, strengthen the nervous system, mental performance and suppress stress.

Some vitamins, especially group A, E, C and β-carotenes, are antioxidants. They protect the cells of our body from free radicals that are produced during metabolic processes. They are useful in the prevention of cardiovascular and cancer diseases, diabetes and slow down aging.

The table below shows the distribution of vitamins according to their solubility

Water-soluble vitamins are easily absorbed. They are also easily eliminated from the body. For this reason, overdosing can be very difficult.

Vitamins A and D from the fat-soluble group can be toxic in high doses.

Minerals

Like vitamins, they are protective for humans. About 20 of them are needed for our body.

They are active, for example, in metabolic processes. They also help to maintain the acid-base balance. They are part of various enzymes and are involved in the construction of tissues.

Minerals account for approximately 4% of a person's body weight.

In larger amounts, some can be toxic to our bodies.

The most important are sodium, chlorine, potassium, calcium, magnesium, phosphorus and sulphur.

Sodium and chlorine are found in table salt. If a person eats a normal diet, it is almost impossible to have a deficiency of these in the body. They are excreted in sweat, urine and faeces. Therefore, care should be taken to replenish them, especially during physical exercise or in warm environments.

When they are excessively and prolongedly added, they contribute to the development of hypertension, i.e. high blood pressure. Therefore, it is desirable to regulate the salt intake in the body. The ideal is 3 g per day. In a tolerable level, it can still be 5 to 8 g of salt per day.

Potassium is found mainly in meat, soya, beans and potatoes. The daily consumption is approximately 2.5 to 4 g. Its deficiency results in heart rhythm disorders or muscle weakness.

Calcium is involved, among other things, in the construction of bone tissue. For this reason it is particularly important in childhood. It is needed for good muscle contraction or for blood clotting.

99% of calcium is found in bones and teeth. It makes up 2% of total body mass.

Its deficiency results in rickets in childhood, osteomalacia in adulthood and osteoporosis in later life.

The main sources of calcium are milk and dairy products, which provide up to 50% of the daily requirement. Plant sources include soya beans, beans, poppy seeds, nuts and almonds, but these contain smaller amounts. Calcium is blocked by fibre.

The recommended daily allowance of calcium is 1 g. For breastfeeding women, this allowance is higher, at approximately 1.5 g.

Magnesium is mainly important in the metabolism of sugars. It is found in bones in the muscles or in the liver. The best sources of magnesium are plant chlorophyll, cocoa, nuts, soy and cereals.

Elevated levels suppress central nervous system activity and reduce muscle contractions. Conversely, reduced levels result in greater central nervous system activity, dilation of blood vessels in the periphery or even cardiac arrhythmias.

Its optimal daily dose is 0.4 g.

Phosphorus is the second most abundant element in the human body. It is found in food in sufficient quantities. Therefore, there is no problem with its deficiency.

Like calcium, phosphorus is also involved in bone structure. Its main source is animal foods. In plant foods, like calcium, it is found only in small amounts.

The daily intake should be 1 to 1.2 g.

Sulphur is mainly found in cartilage or connective tissue. It is involved in the breakdown of foreign substances from the body. It is found in protein, dairy products and eggs.

The daily dose of sulphur is 0.5 to 1 g.

Trace elements

Their concentration in the body is small. As a rule, it is not more than 50 mg/kg body weight.

The most important for the organism are iron, iodine, selenium, copper, zinc, fluorine, manganese and cobalt.

For example, iron is used in the body to carry oxygen. In its case, it is the use to the body that is important. Not its content in food. Most of the iron that can be used is found in blood, in the intestines, in meat and in egg yolk.

The daily dose in adulthood should be 10 to 16 mg.

The table below lists the most important trace elements in the body, their uses and sources

Water

It is an essential and basic part of the internal environment of the human body. It helps maintain its stability and the normal function of all cells.

There are about 40 litres of water in the human body. In an adult male this is about 60%. In women it is about 50% and in children up to 70%.

Most of the water (about 25 litres) is found in the cells. Blood plasma contains about 3 litres of water. The interstitial space (intercellular space) contains the rest of the water. The cells draw nutrients and all the substances needed for their activity from it. In turn, they excrete all the products of metabolism, i.e. unnecessary substances and carbon dioxide, into it.

Water acts as a solvent in the body and a large number of metabolic processes take place in it. It is helpful in the digestion of food, excretion of harmful and unnecessary substances from the body. It plays a major role in thermoregulation.

The loss of approximately 20% of water is life threatening to the body.

However, the body can also obtain water from food. By oxidising 1 g of fat, it obtains 1.07 g. For sugars, it is 0.6 g and for proteins, 0.41 g.

A large number of foods contain more than 70% water. Most of it - up to 95% - is found in fresh vegetables and fruit. In milk it is about 87% and in potatoes and eggs about 75%.

Ordinarily, a person maintains the balance between water intake and output quite precisely. However, its loss depends on body temperature, ambient temperature and physical exertion. When it increases, and therefore excessive sweating, it is necessary to think about mineral replenishment.

An adult has an average loss of 2.5 litres of fluid per day. This amount needs to be replenished regularly.