Revista de Medicina Desportiva (English) January 2019 | Page 17

Other food sources of calcium
include green leaf vegetables, dry
fruits, seeds and fortified indus-
trialized juices. The bioavailability
of calcium from vegetables is in
general high but it is reduced by
the link with oxalates in the case
of spinach, kale and beans. On the
other hand, although vegetables
are a good source of bioavailable
calcium, the necessary amount to
attend the daily needs is substan-
tial, and this creates difficulties to
obtain the dietetic needs of calcium
only with ingestion of vegetables.
Some cereals, like plain cereals, have
phytates, that also reduce the bioa-
vailability of calcium.
The vegetable beverages seem to
have low bioavailability for calcium,
even when they are fortified with
this mineral. Therefore, these are
not alternative routes to the dairy
products during pediatric age.
Table 3. Foods rich on vitamin D and
comparison with sun exposure
Food
Vitamin
furnished
(UI)
Salmon (aquaculture) 100g 100-250
Sardine 100g 300
Mackerel 100g 250
Tuna fish 100g 236
Eggs 100g 20
Milk (fortified) 240mL 100
Yogurt (fortified) 240mL 100
  About 3
000
Cheese (fortified) 4 slices
Sun exposure for 5-15
minutes (arms and legs)
100
Source: Dietary Guidelines for Americans, 2010
The daily recommendations of
vitamin D during pediatric age are
indicated on Table 4.
Table 4. Vitamin D recommendations
Age
Vitamin D
Vitamin D is a fat-soluble hormone
needed for reabsorption of calcium.
Many studies came out trying to
study the extra-skeletal effects of
vitamin D. Since the receptors for
vitamin D are located on the major-
ity of body cells, it is not a surprise
that the levels of this hormone can
influence the risk of development
of cancers (prostate, breast, colon,
pancreas), auto-immune diseases,
infectious diseases and cardiovascu-
lar risk.
The cutaneous synthesis of sun
exposure is the main source of vita-
min D (about 90%). The capacity of
synthesis is variable, and it depends
of several factors: skin pigmentation,
duration of sun exposure, hour of
sun exposure, exposed body area,
use of sunscreens, seasons and geo-
graphic latitude.
There are few foods rich on vita-
min D (Table 3) and they include
fat fish (salmon, sardine, tuna fish,
mackerel) and fortified industria-
lized foods (milk, yogurts, cheese,
butter and cereals).
Portion
Daily
recommendations of
vitamin D (UI/day)
0 – 6 months 400*
6 – 12 months 400*
1 – 3 years 600
4 – 8 years 600
9 – 13 years 600
14 – 18 years 600
14 – 18 years,
pregnant/lactating 600
* Adequate ingestion. Institute of Medicine, 2010

The obese children and adoles-
cents have a high risk of vitamin D
deficiency due to the sequestration
of this hormone in the fat tissue, and
these subjects need higher doses to
have adequate levels of this vitamin.
Oral supplementation of 400 IU/
day must be universal for all infants
(0-12 months old). There aren’t uni-
versal recommendations of supple-
mentation after 12 months old, but
the Society for Pediatric Gastroen-
terology Hepatology and Nutrition
(ESPGHAN) advises the adoption of
national measures concerning diet
recommendations, food fortification
and supplementation with vitamin
D according local context. In Portu-
gal, although the scarcity of studies
about the prevalence of its deficit, it
is presumed that it is high.
Physical exercise and style life
deposition, in particular during
puberty. The site of the greatest bone
mineral deposition is exercise spe-
cific, since it depends on the pattern
of the load of the physical activity.
Mineral bone density in gymnastics
is greater on the hip and low back, in
runners is on the neck of the femur
and on rowers is on low back.
Between the ages of 5 and 17 years
it is recommended moderate to
vigorous physical exercise for 60
minutes daily. On pediatric age it is
fundamental that this activity has a
ludic component, takes into consi-
deration the individual interests and
develops future motor skills.
Other modifiable factors
The changes on style life can also
give additional risk for reduction of
the bone mineral density. On adults,
smoking, caffeine and alcohol
ingestion are associated with the
decrease on bone mineralization,
so therefore these behaviors should
be avoided during adolescence.
The maintenance of a correct body
weight and body composition dur-
ing infancy and adolescence are of
extreme importance, since a great
decrease of weight is a risk factor to
the reduction on BM.
In conclusion, since infancy and
adolescence are a critical period
for optimization for bone health of
the adult, it is of paramount impor-
tance to intervene on the modifiable
determinants, namely the adequacy
of calcium ingestion and vitamin D,
physical exercise and adoption of
healthy lifestyles on this age group.
Bibliography
1. Golden NH, Abrams SA. Committee
on Nutrition. Optimizing bone health in
children and adolescents. Pediatrics. 2014;
134(4):e1229-43.
2. Braegger C et al. Vitamin D in the healthy
European paediatric population. J Pediatr Gas-
troenterol Nutr. 2013; 56(6):692-701.
3. Pludowski P et al. Vitamin D supplementation
guidelines. J Steroid Biochem Mol Biol. 2018;
175:125-135.
4. Abams, Seven A. Calcium requirements in
adolescents. UpToDate. 2018. Disponível em:
http://www.uptodate.com/online>. Acesso
em: 23/10/2018.
Physical exercise involving ground
impact promotes the bone mineral
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