Water hardness

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 organism the water content varies according to different parameters: constitution, age and sex; in the newborn, water body (Total Body Water - TBW) reaches 75% of the total mass while in the adult it is around 60%.

Body water is distributed 2/3 inside the cells (intracellular water) and 1/3 in circulating fluids (extracellular water = plasma + interstices). NB. Excessive variations in the water balance and / or in the distribution of body water can compromise the state of health until death (even in a few days).
Water performs many essential functions for metabolism, such as: solution and transport of nutrients, corpuscles (blood cells), hormones, catabolites, etc., allows biochemical reactions, contributes to thermoregulation, etc.
Body water deficiency is defined as dehydration, while excess (pathological) is framed with the term hyperhydration. The amount of water necessary for metabolism can be differentiated into:

Exogenous water: introduced with drinks and food
Endogenous water: that produced by the oxidation of energetic macronutrients inside the cells.

Drinking water

The exogenous water introduced with food and drinks MUST be DRINKING water, and to be defined as such, it must possess certain chemical-physical, organoleptic and microbiological requirements:

It must be clear, colorless, odorless and tasteless, and have a pleasant taste
The chemical analysis must not show significant traces of contamination (ammonia, nitrates, nitrites, surfactants, heavy metals, etc.)
The bacteriological analysis must not show colonies of microorganisms

Hardness

The hardness of the water 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 (CaCl2), calcium sulphate (CaSO4), magnesium chloride (MgCl2) and magnesium sulfate (MgSO4).
The hardness of the water can be TOTAL, PERMANENT and TEMPORARY (based on the structure of the salts themselves):

Total hardness of water: it is the total of calcium and magnesium salts dissolved in water
Permanent hardness of water: it is a parameter that measures the amount of calcium and magnesium salts that remain in solution after boiling
Temporary hardness of water: it is the difference between the total hardness and the permanent one, therefore it constitutes the quantity of calcium and magnesium bicarbonates that precipitate by boiling the water.

Degree of hardness of the water

The degree of water hardness is expressed in three quantities:

French degrees (also in Italy) (F °): 1 French degree = 10mg of CaCO3 per liter of water
German degrees (D ° or DH °): 1 German degree = 10mg of CaO per liter of water = 1.79 French degrees
English degrees (° GB): 1 English degree = 10mg of CaCO3 every 700 grams of water = CaCO3 1.43 French degrees

Types of Waters

HARDNESS IN FRENCH DEGREES (F °)

Very sweet waters

0-4

Sweet waters

4-8

Medium hard water

8-12

Water with moderate hardness

12-18

Hard waters

18-30

Very hard waters

> 30

The water intended for distribution on the water network for the population undergoes various and systematic checks (A.S.L.) aimed at verifying the effective potability of the water supplied; among the various processes that aim to make water drinkable there are also:

Sedimentation and filtration: to eliminate solid particles, including limestone (calcium and magnesium salts)
Correction of hardness (if necessary): if too hard, drinking water must be softened by using softeners or ion exchange demineralizers.

Excessive hardness of the water

Excessively hard water, if drunk, may not be healthy in the long term; especially for those suffering from nephrolithiasis (kidney stones) or renella, the calcium salts contribute to the formation of "sharp and easily aggregable crystals" inside the urinary tract: the so-called calcium oxalates (main constituents of kidney stones). Although many scientific studies mainly attribute to SODIUM (Na) and urinary concentration the blame for the formation of kidney stones, also 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 others rich in calcium presumably has a protective effect against kidney stones;" in fact, the consequent enteric formation of calcium oxalate aggregates - non-absorbable and therefore eliminated with the faeces - reduces the amount of oxalic acid absorbed by the intestinal mucosa.
Ultimately, the reduction of dietary calcium intake (as a sufficiently absorbable and essential nutritional constituent in rations of about 1g / day) is strongly NOT RECOMMENDED, and given the "dubious" bioavailability of calcium bound in salts, for subjects suffering from lithiasis renal it would be a good rule to follow a "diet: