Water in ... "and for" ... the human body - Total Body Water (TBW)
Water is the fundamental element for the life of the human being and in general of all living organisms. In our body the water content varies according to different parameters: constitution, age and sex; in the newborn, body water (Total Body Water - TBW) reaches 75% of the total mass while in the adult it is around 60%.
Water performs many functions essential to metabolism, such as: solution and transport of nutrients, corpuscolates (blood cells), hormones, catabolites, etc., allows biochemical reactions, contributes to thermoregulation, etc.
The body's lack of water is defined as dehydration, while the excess (pathological) is framed with the term hyperhydration. The amount of water needed for metabolism can be differentiated into:
- Exogenous water: introduced with drinks and food
- Endogenous water: that produced by the oxidation of energy macronutrients inside the cells.
Drinking water
The exogenous water introduced with food and beverages MUST be DRINKING water, and to be defined as such, it is necessary that it possesses some chemical-physical, organoleptic and microbiological requirements:
- It must be clear, colorless, odorless and tasteless, and have a pleasant taste
- Chemical analysis must not show significant traces of contamination (ammonia, nitrates, nitrites, surfactants, heavy metals, etc.)
- Bacteriological analysis should not present colonies of microorganisms
Hardness
Water hardness indicates the content of salts (especially alkaline), such as calcium and magnesium (Ca and Mg - responsible for the formation of "limestone") in the form of: calcium chloride (CaCl 2 ), calcium sulphate (CaSO 4 ), magnesium chloride (MgCl 2 ) and magnesium sulfate (MgSO 4 ).
The water hardness can be TOTAL, PERMANENT and TEMPORARY (depending on the structure of the salts themselves):
- Total water hardness: it is the total of the calcium and magnesium salts dissolved in water
- Permanent water hardness: it is a parameter that measures the quantity of calcium and magnesium salts that remain in solution after boiling
- Temporary hardness of water: it is the difference between total and permanent hardness, therefore it constitutes the quantity of calcium and magnesium bicarbonates that precipitate by boiling water.
Degree of water hardness
The degree of water hardness is expressed in three sizes:
- French grades (also in Italy) (F °): 1 French degree = 10mg of CaCO 3 per liter of water
- German degrees (D ° or DH °): 1 German degree = 10mg CaO per liter of water = 1.79 French degrees
- English grades (° GB): 1 English grade = 10mg of CaCO 3 per 700 grams of water = CaCO 3 1.43 French grades
Types of Water | HARDNESS IN FRENCH DEGREES (F °) |
Very sweet waters | 0-4 |
Fresh water | 4-8 |
Water with medium hardness | 8-12 |
Waters of discrete hardness | 12-18 |
Hard waters | 18-30 |
Very hard water | > 30 |
The water destined for distribution on the water network for the population undergoes various and systematic controls (ASL) aimed at verifying the effective potability of the water supplied; Among the various processes that aim to make drinking water there are also:
- Sedimentation and filtration: to eliminate solid particles, including limestone (calcium and magnesium salts)
- Hardness correction (if necessary): if too hard, drinking water must be softened by using ion exchange water softeners or demineralisers.
Excessive water hardness
Excessively hard water, if drunk, in the long term may not be healthy; especially for subjects suffering from nephrolithiasis (kidney stones) or gravel, calcium salts contribute to the formation of "sharp and easily aggregated crystals" within the urinary tract: the so-called calcium oxalates (main constituents of kidney stones). Despite many scientific insights, they mainly attribute the blame for the formation of kidney stones to SODIUM (Na) and urinary concentration, including the association of an excessive amount of calcium salts and oxalic acid (an anti-nutritional factor present in plant foods: rhubarb, spinach), beets etc) can accelerate the formation and sediment of calcium oxalates. It should be noted, however, that the association within the same meal of foods rich in oxalates with other calcium-rich foods presumably has a protective effect against kidney stones; unsatisfactory, the consequent enteric formation of calcium oxalate aggregates - non-absorbable and then eliminated with faeces - reduces the amount of oxalic acid absorbed by the intestinal mucosa.
Ultimately, the reduction in the intake of food calcium (as a sufficiently absorbable and essential nutritional constituent in rations of about 1g / day) is highly recommended, and given the "doubtful" bioavailability of calcium bound in salts, for subjects suffering from lithiasis it would be a good rule to follow a diet:
- Poor of hard waters
- Poor of oxalic acid
- Rich in very sweet drinking water or (even better) minerals with low fixed residue (minimally mineralized).