Dictionary of Nutrition
It goes without saying that nutrition is an integral part of a healthy lifestyle. Improper nutrition may be the cause of many (not only digestive) problems, provided that “improper” nutrition may mean different things for different people. We will apply more detail to this term, however, in the beginning, we would like to offer a short definition of terms everyone should know:
- Nutrition: in wider sense of the word, it is a science about intake of nutrients and impact of food on human health
- Metabolism: a combination of biochemical processes that your body uses to convert food into energy
- Anabolism: construction process (from simpler substances, more complex ones are created) that consumes energy
- Catabolism: dissociation of substances that releases energy
- Basal metabolic rate: energy required to keep your vital organs functioning while the body is at rest (on a diet, or during long-term fasting BMR decreases)
- Energy balance: state when intake equals output
= nutrients the body needs in extensive amounts to acquire energy
In human body, proteins serve as “building material” contributing, among other things, to the creation of hormones and antibodies. Proteins are chains of amino acids (organic compounds) of various length. Proteins commonly consist of 20 basic amino acids (although there are around 500 to be found in nature), nine of them classified as “essential amino acids”. The body is unable to create essential amino acids on its own, therefore, it is vital to get them, in sufficient amount, from our nutrition.
Rich sources of essential amino acids include milk, eggs and meat. Proteins of vegetable origin may lack certain essential amino acids, so with strict vegan diet, proteins must be received from a different source. Also, the use of received proteins depends on the contents of the essential amino acid with the lowest contents. This means that in case of lack of one essential amino acid, the body is unable to efficiently use the other amino acids that were received in sufficient amount.
The organism does not store amino acids – it uses the required ones, discharging the rest. Intake of essential amino acids should therefore be stable, if possible. In case of insufficient intake of proteins, health issues such as compromised immunity, hair loss, body mass loss, etc., occur.
Carbohydrates represent a significant (under common circumstances even primary) source of energy. We divide carbohydrates into complex and simple ones (monosaccharides – e.g. glucose, and disaccharides – e.g. lactose). Complex carbohydrates (polysaccharides – e.g. starch, fibre) consist, simply put, of longer chains requiring longer time for the body to process them compared to monosaccharides.
Significant saccharides include fibres – soluble and insoluble. Soluble fibre can absorb water (increasing its volume, leading to the feeling of saturation). Also, it regulates digestion of fats and other saccharides. Insoluble fibre is a key component for the function of the large intestine, where fibre works as a “brush” that cleans it.
We mainly get glucose, one of the monosaccharides, by dissociation of disaccharides and polysaccharides. Glucose is subsequently absorbed in the small intestine.
Glucose concentration in blood (glycaemia) is regulated by number of mechanisms (effects of opposing hormones – insulin, anabolic hormone, decreases the blood sugar and catabolic hormones – e.g. glucagon increase it) and is strictly kept within a constant range. Certain glycaemia fluctuation commonly occurs – e.g. after eating, glycaemia is higher than on an empty stomach; glycaemia generally decreases during fasting, increased physical activity or lack of saccharides in food.
Various types of food have different impact on glycaemia after eating. This is the basis of the glycemic index expressing the speed of use of glucose from certain type of food (i.e. speed of transformation to bodily glucose), informing us about the creation and speed of release of glucose to the blood stream. People with diabetes, obesity (or increased risk of obesity), athletes, and people who work physically should pay close attention to the glycemic index values.
- Food with low GI (< 55): most fruits and vegetables, legumes, brown bread
After consumption of these, glycaemia slowly increases and therefore blood sugar does not oscillate. That is why food with low GI is particularly convenient for people with diabetes or on a reduction diet.
- Food with medium GI (56-69): sweet fruit, wholegrain bakery products, white rice, corn, pineapple, bananas, potatoes
- Food with high GI (>70): glucose, cornflakes, potato chips, puffed rice cakes, honey, puffed rice, white flour, beer
These increase the level of glycaemia very fast. Under certain circumstances, speedy increase of blood sugar is good, for instance in case of hypoglycaemia or after demanding physical activity.
Fats represent a significant source of energy. Fats in food are called triglycerides (they are composed of one molecule of glycerol and three molecules of fatty acids). Triglycerides are the main component of vegetable oils and animal fats. They play a role in hormone functioning (some hormones are soluble in fats – e.g. glucocorticoids, sex hormones, some hormones are derived from cholesterol – e.g. steroids), and allow, among other things, for absorption of vitamins. They are also important for the functioning of brain, heart and the immune system.
We divide fats into vegetable and animal fats according to their origin. A widely adopted notion that all animal fats are bad and all vegetable fats are good is just not true. However, most vegetable fats include composition of fatty acids convenient for human body.
Fatty acids can be saturated or unsaturated (according to the chemical bond structure). Unsaturated fatty acids also include essential fatty acids. Body is unable to produce these acids and requires their intake in food. These include omega-3 and omega-5 fatty acids, that can be found in fish, sea animals, linseeds, pumpkin seeds, sunflower seeds, soya oil, rape oil, leafy vegetables or walnuts.
Fats should constitute 30-35% of total daily energy intake. The recommended ratio is 1:3 to the benefit of unsaturated fatty acids.
= summary designation for minerals, vitamins and trace elements, “micro” meaning the body requires them in much smaller amounts than macronutrients.
Vitamins are important for metabolism and we need them in the most extensive amounts, compared to other micronutrients. There are vitamins soluble in water (B, C), and vitamins soluble in fats (A, D, E, K). Fat-soluble vitamins are introduced to the blood stream through intestines, and, in case of need, they are stored in the liver. On the other hand, the body does not store too much of water-soluble vitamins that are being discharged in urine, thus requiring regular replenishment.
Sources of water-soluble vitamins: black currant, lemon, orange, strawberries, cabbage (vitamin C); seeds, nuts, yeast, wheat germs, legumes, green leafy vegetables (B complex).
Sources of fat-soluble vitamins: butterfat, egg yolk, meat, colourful vegetables – e.g. carrot, orange, broccoli, spinach (vitamin A); fish liver oil, yeast, eggs, milk (vitamin D); vegetable oils, animal fats, cereal germs, beef (vitamin E); leafy vegetables, yeast (vitamin K).
Minerals and trace elements
We receive minerals (substances required to be taken in in daily amounts exceeding 100 mg) and trace elements (lower daily consumption) in food and water. Minerals are part of body tissue construction process, they regulate metabolic processes and are required for management of the function of nerves, heart, muscles and brain. The most important minerals include calcium (bones and teeth), sodium (water retention, prevents excessive loss of fluids), phosphorus, potassium, chlorine and magnesium. Essential trace elements include iron (production of red blood cells), iodine (thyroid hormones), zinc (organism growth), manganese, etc.