Page 371 - Color Atlas of Biochemistry

362 Nutrition
Minerals and trace elements
A. Minerals
Water is the most important essential inor-
ganic nutrient in the diet. In adults, the body also on the composition of the diet. One ex-
has a daily requirement of 2–3 L of water,
which is supplied from drinks, water con-
tained in solid foods, and from the oxidation
water produced in the respiratory chain (see
p. 140). The special role of water for living
processes is discussed in more detail else-
where(seep. 26).
The elements essential for life can be div-
ided into macroelements (daily requirement
>100 mg) and microelements (daily require-
ment < 100 mg). The macroelements include
the electrolytes sodium (Na), potassium (K),
calcium (Ca), and magnesium (Mg), and the
nonmetals chlorine (Cl), phosphorus (P), sul-
fur (S), and iodine (I).
The essential microelements are only re-
quired in trace amounts (see also p. 2). This
group includes iron (Fe), zinc (Zn), manganese
(Mn),copper(Cu), cobalt (Co),chromium (Cr),
selenium (Se), and molybdenum (Mo). Fluo-
rine (F) is not essential for life, but does pro- anemia.
mote healthy bones and teeth. It is still a
matter of controversy whether vanadium,
nickel,tin,boron,and silicon also belongto
the essential trace elements.
The second column in the table lists the
average amounts of mineral substances in
the body of an adult weighing 65 kg. The daily
requirements listed in the fourth column also
apply to an adult, and are average values.
Children, pregnant and breast-feeding wo-
men, and those who are ill generally have
higher mineral requirements relative to
body weight than men.
As thehuman body is able to storemany
minerals, deviations from the daily ration are
balanced out over a given period of time.
Minerals stored in the body include water,
which is distributed throughout the whole
body; calcium, stored in the form of apatite
in the bones (see p. 340); iodine, stored as
thyroglobulin in the thyroid; and iron, stored
in the form of ferritin and hemosiderin in the
bone marrow, spleen, and liver (see p. 286).
The storage site for many trace elements is
the liver. In many cases, the metabolism of
minerals is regulated by hormones—for exam-
+
ple, the uptake and excretion of H 2 O, Na ,
Koolman, Color Atlas of Biochemistry, 2nd edition © 2005 Thieme
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2+
Ca , and phosphate (see p. 328), and storage
–
of Fe 2+ and I .
Resorption of the required mineral sub-
stances from food usually depends on the
body’s requirements, and in several cases
ample of dietary influence is calcium (see
p. 342). Its resorption as Ca 2+ is promoted by
lactate and citrate, but phosphate, oxalic acid,
and phytol inhibit calcium uptake from food
dueto complex formation and theproduction
of insoluble salts.
Mineral deficiencies are not uncommon
and can have quite a variety of causes—e. g.,
an unbalanced diet, resorption disturbances,
and diseases. Calcium deficiency can lead to
rickets, osteoporosis, and other disturbances.
Chloride deficiency is observed as a result of
–
severe Cl losses due to vomiting. Due to the
low content of iodine in food in many regions
of central Europe, iodine deficiency is wides-
preadthere andcan lead to goiter. Magnesium
deficiency can be caused by digestive disor-
ders or an unbalanced diet—e. g., in alco-
holism. Trace element deficiencies often re-
sult in a disturbed blood picture—i. e., forms of
The last columninthe table lists some of
the functions of minerals. It should be noted
that almost all of the macroelements in the
body function either as nutrients or electro-
lytes. Iodine (as a result of its incorporation
into iodothyronines) and calcium act as sig-
naling substances. Most trace elements are
cofactors for proteins, especially for enzymes.
Particularly important in quantitative terms
are the iron proteins hemoglobin, myoglobin,
andthe cytochromes(see p. 286),aswell as
more than 300 different zinc proteins.