Vitamin D status of Arab mothers and infants by muq18838


									                                                                                                J Arab Neonatol Forum 2004; 1:15-22

                               Vitamin D status of Arab mothers and infants

                                                        Adekunle Dawodu

      International Health Program Center for Epidemiology and Biostatistics, Cincinnati Children’s Medical Center, Cincinnati, US

Introduction                                                            in early morning, late evening, in the winter and at high
Owing to increasing reports of vitamin D deficiency rickets             altitudes greater than 350 because these factors increase the
among minority groups1,2,3 and the high prevalence of                   ozone layer which absorbs more of the UV radiation required
hypovitaminosis D in adults, especially in the United States            for vitamin D synthesis.6 In addition, inadequate exposure of
and Canada,4,5 reports of studies on vitamin D in the last              the skin to sunshine by avoiding sunlight, wearing excessive
decade had focused on these Western countries. In addition              clothing (especially wearing black clothing while outdoors),
to metabolic bone disease, recent studies suggest that vitamin          and use of sunscreens may reduce endogenous production of
D deficiency could increase the risk of certain cancers, heart          vitamin D.6,16 Compared with light -skinned persons, dark-
disease and autoimmune diseases including rheumatoid                    skinned persons are less efficient in producing vitamin D
arthritis and multiple sclerosis in adults and type 1 diabetes          owing to their increased skin pigmentation.20
mellitus in children.6 Many recent reviews and editorials have,
therefore, focused mainly on the vitamin D status of European           In adults, the major dietary sources of ergocalciferol include
and North American adults 6, 7, 8, 9 pregnant mothers and their         fortified diary products, orange juice and cereals as well as
infants 10,11 as well as the strategies to improve vitamin D            fish and fish oils.6 The dietary sources of vitamin D in infants
stores and reduce the prevalence of hypovitaminosis D.                  are human milk and fortified formula in formula-fed infants.
However, many studies suggest that rickets is more common               However, transplacental transfer of vitamin D is the major
in Arab countries than is reported from the western countries.          source of vitamin D for the fetus and during early infancy.21
12, 13, 14,15
              Further, the prevalence of vitamin D deficiency is
significantly higher in Arab women and children than in the             Both cholecalciferol and ergocalciferol are bound to vitamin
white population. 16,17,18,19 This review will focus on the             D protein in the plasma and transported to the liver where they
physiology of vitamin D, the vitamin D status of Arab                   are converted to 25-hydroxyvitamin D (25-OHD). The serum
mothers and infants, as well as the causes, possible                    circulating    25-OHD       concentration     derived     from
implications and prevention of maternal and infant vitamin D            cholecalciferol and ergocalciferol is used in assessing the
deficiency.                                                             vitamin D status of the body, which will be discussed later in
Physiology                                                              this review.
The main sources of vitamin D are vitamin D produced in the
skin (cholecalciferol or vitamin D3) and from dietary intake            The circulating 25-OHD is bound to vitamin D binding
(ergocalciferol or vitamin D2). However, cholecalciferol is the         protein and transported to the kidneys where it is hydroxylated
most important source of vitamin D stores in the body.                  to produce 1-25-dihydroxyvitamin D- the most biologically
                                                                        active vitamin D metabolite. Other factors regulate the
When the skin is exposed to ultraviolet B radiation at                  production of 1-25-dihydroxyvitamin D from the kidney;
wavelengths 290-320nM, 7-dehydrocholesterol is converted                these include parathyroid hormone (PTH) and serum
to precholecalciferol. Precholecalciferol is then converted to          phosphorus and calcium. Decreases in serum concentrations
cholecalciferol through a process of thermal isomerization.6            of calcium and phosphorus and increases in serum
The factors that influence endogenous production of                     concentrations of PTH stimulate synthesis of 1-25-
cholecalciferol include time of day, season, latitude, length of        dihydroxyvitamin D. 1-25-dihydroxyvitamin D increases
sunshine exposure, percentage of body surface exposed to                intestinal absorption of calcium and phosphorus and decreases
sunlight, and skin pigmentation.6,16 The amount of ultraviolet          phosphorus excretion from the kidney; this maintains serum
(UV) B radiation available for vitamin D synthesis is reduced           calcium and phosphorus homeostasis and is important for
_________________________________________                               bone mineralization. In addition, an increase in serum PTH
Correspondence to: Adekunle Dawodu, Professor, Director                 concentrations in response to low serum calcium
International Patient care and Education, International Health          concentration stimulates calcium and phosphorus mobilization
Program Center for Epidemiology and Biostatistics, Cincinnati           from bone to maintain normal serum calcium and phosphorus
Children’s Medical Center MLC 5041                                      concentrations. Thus, through its active metabolites, vitamin
 3333 Burnet Avenue, Cincinnati, OH 45229-3039, Phone 513-636-          D plays a major role in calcium and phosphorus homeostasis
1966, Email                                   and in bone mineralization.6

Vitamin D status of Arab mothers and infants

Vitamin D Status of Arab Mothers                                     It is also interesting that Arab women living in Europe and
The normal range of serum 25-OHD concentrations is                   other women of Middle Eastern origin who limit sunshine
controversial. In general, the lower limit of normal range           exposure have been shown to have low serum concentrations
(hypovitaminosis D) is defined as serum 25-OHD                       of 25-OHD and a high prevalence of hypovitaminosis D and
concentration of less than 25-37nmol/L 5,22,23,. However, a          vitamin D deficiency. Serum concentrations of 25-OHD and
higher cutoff level of serum 25-OHD concentration (<                 dietary vitamin D intake of 60 veiled Arab women living in
50nmol/L) has been suggested, based on a recent physiologic          Denmark, randomly selected from patients attending Primary
study of the threshold serum 25-OHD concentrations required          Health Centers for reasons not related to vitamin D
to maintain normal serum concentrations of PTH in adults.24          deficiency, were compared with those of 44 age-matched
Other authors25 have proposed a cutoff point of 78nmol/L in          Danish women.31 The mean serum 25-OHD concentration in
adults. In this review, therefore, the serum 25-OHD                  veiled Arab women was 7.1±1.1 nmol/L compared with
concentration used in defining hypovitaminosis D and severe          47.1±4.6 nmol/L in Danish women. Ninety-six percent and 85
hypovitaminosis D (vitamin D deficiency) will be included if         % of the veiled Arab women had serum 25-OHD
that information was reported in the study .                         concentrations <20nml/L and <10nmol/L respectively. None
                                                                     of the Danish women in that study had serum 25-OHD values
Most studies had found that Arab women, lactating mothers            < 10nmol/L and only 9% of the Danish women had values <
and mothers who delivered at term have very low serum 25-            20nmol/L. Studies from Turkey,32 Iran,33 Pakistan, 34 have
OHD      concentrations    and   higher   prevalences    of          also demonstrated a high prevalence of hypovitaminosis D
hypovitaminosis D compared with white women. Two studies             and vitamin deficiency in Middle Eastern women.
from Saudi Arabia about 2 decades ago found that the mean
serum 25-OHD concentrations among Saudi women were                   All these studies suggest that Arab women have lower serum
28.8±10.0 nmol/L26 and 40.8±19.3 nmol/L.27 In a more recent          25-OHD concentrations than the generally accepted lower
study of the relationship between bone mineral density and           limit of normal range (25.0-37.5 nmol/L). In some of the
vitamin D status of Saudi women,28 the results still showed          studies 29,30 nearly all of the subjects had serum 25-OHD
low vitamin D status among Saudi women. In that study, the           concentrations lower than 50nmol/L, which has been
mean serum 25-OHD concentration was 24.5±17.3 nmol/L                 suggested as a lower conservative cutoff point in recent
and 52% of the subjects had hypovitaminosis D (circulating           studies.24,25 Therefore, hypovitaminosis D and in particular,
25-OHD levels <20 nmol/L).                                           vitamin D deficiency, seem to be public health problems in
                                                                     Arab women and other women of Middle Eastern origin.
One study of 33 United Arab Emirates (UAE) and 25 non-               However, lack of standardized definition of hypovitaminosis
Gulf Arab volunteer women and 17 female Europeans                    D and vitamin D deficiency and community-based data
residents in the UAE showed that the mean serum 25-OHD               prevent meaningful international comparison of the magnitude
concentrations were lower in the UAE women ( 21.5 nmol/L)            of the problem. Community-based studies using a generally
than in non-Gulf Arab women (31.5 nmol/L). The mean                  accepted definition are urgently needed to provide baseline
serum 25-OHD concentration of Europeans residing in the              data with which to evaluate the impact of future interventions
UAE (160 nmol/L) was 5- to 7- fold higher than were the              on the prevalence of vitamin D deficiency in Arab countries.
values in the Arabs.16 The prevalence of vitamin D deficiency
(serum 25-OHD concentrations<12.5nmol/L) was 24% among               Vitamin D studies of mother-infant pairs
the UAE nationals and 12% in non-Gulf Arabs. None of the             Some studies have examined the mother-infant vitamin D
Europeans in that study had serum 25-OHD concentrations              status, since it is generally accepted that the vitamin D status
less than 50 nmol/L. In a more recent study of 158 healthy           of the fetus and infant is dependent on the vitamin D status of
UAE women volunteers, the mean serum 25-OHD                          the mother.21 Typically, the vitamin D status of Arab mothers
concentrations was 24.5±10.5 nmol/L, and nearly all the              and their infants at delivery was found to be low and the
subjects in the study had serum 25-OHD concentrations lower          prevalence of hypovitaminosis D was high, but the rate
than 50nmol/L.29                                                     depended on the definitions of hypovitaminosis D and vitamin
                                                                     D deficiency used in the study.
Similarly, low serum 25-OHD concentrations have been
reported in Lebanese volunteer women aged 30-50 years.30 In          In a study of 119 Saudi mothers and their newly born infants,
the study, the serum 25-OHD concentrations were low:                 the mean serum concentrations of 25-OHD were 12, 13.8, and
12.8±9.0 nmol/L in veiled women and 24.5±16.3 nmol/L in              17.5nmol/L in the lower, middle and upper-class women
non-veiled women. Eighty-four percent of all studied subjects        respectively.17 The mean Umbilical cord serum 25-OHD
had serum 25-OHD concentrations lower than 30 nmol/L and             concentration of 7.5nmol/L was very low and was similar in
42% had vitamin D deficiency (serum 25-OHD concentrations            all the 3 classes. Twenty-five percent of the mothers and 68%
<12.5 nmol/L).                                                       of the newly born infants in the study had vitamin D

                                                                                              J Arab Neonatol Forum 2004; 1:15-22

Table 1: Comparison of serum 25-OHD, calcium, phosphate, and alkaline phosphate concentrations of UAE, Libyan and
Norwegian mothers and infants.

                                                  CORD                                               MOTHER
                              UAE                 Libyan       Norwegian          UAE                Libyan         Norwegian
Tests+                        N=40                N=14         N=22               N=40               N=19           N=22
25-OHD (nmol/L)               20.0                20.0         76.0               32.5               34.0           111.0
                              5.0 -72.5           10.0-45.0    31.0-136.3         10.0-87.5          13.3-75.0      55.0-205.3
Calcium (mmol/L)              2.68                2.75         2.83               2.3                2.43           2.48
                              2.25-3.0            2.63-3.03    2.35-3.23          2.25-3.0           2.18-2.63      2.38-2.83

Phosphate (mmol/L)            1.58                1.61         1.68               1.03               1.16           2.00
                              0.98-1.94           1.03-2.19    1.26-2.35          0.65-1.61          0.94-1.61      0.84-1.74
Alkaline Phosphatase(iU/L) 130                    323          206                157                446            350
                              57 - 389            200 - 582    140 – 752          77 - 500           204 – 820      216 - 528
 + values given are median and range

Table 2: Comparison of Serum 25-OHD Concentrations and Sunshine Exposure Characteristics among UAE Nationals, Non-
Gulf Arabs and Europeans (adapted from ref 16)

                                  UAE Nationals               Non-Gulf Arabs             Europeans
                                     N=33                         N=25                     N=17
         Features                 Mean (± ISD)                 Mean (± ISD)             Mean (± ISD)                P Value

Percentage (%) that cover
forearm                                   100.0                       80.0                    11.0                  <0.0001

Percentage (%) that cover
legs                                      97.0                        88.0                    29.4                  <0.0001

Percentage (%) that cover
head                                      97.0                        64.0                    17.6                  <0.0001

                                        2.65                        5.08                     10.91                  <0.0001
Clothing score*                     (0.99-4.31)                 (2.34-7.83)              (8.86-12.96)

Total sunlight exposure                 1.94                        1.61                     3.98
(hours/week)                        (0.61-6.21)                 (0.53-5.36)              (1.23-12.90)

                                        4.35                        7.56                      47.7                  <0.0001
UV skin exposure score**            (1.26-15.03)                (2.25-25.4)              (17.05-133.5)

                                          21.5                     31.5                    160.8                 <0.0001
25-OHD(nmol/L)**                      (11.3-43.5)                (15-66)               (122.5-210.8)
**calculated using the natural log of the values and back-transformed for presentation. * based on the magnitude of clothing.

deficiency (serum 25-OHD, < 12.5 nmol/L). In a comparative             concentrations of the mothers and their term infants were
study of vitamin D status of Libyan and Norwegian mothers              low, and 25% of the mothers had serum 25-OHD
and their newly born infants 15, the mean serum 25-OHD                 concentrations <25 nmol/L.35 The median maternal and
concentrations in Libyan mothers (34 nmol/L) and their                 umbilical cord serum 25-OHD concentrations were 32.5
infants (20nmol/L) were significantly lower than in                    nmol/L and 20 nmol/L respectively. These figures were
Norwegian mothers (111.0 nmol/L) and their infants (76                 similar to the mean serum 25-OHD concentrations of Libyan
nmol/L).                                                               mothers and their infants but very low when compared with
                                                                       the levels in Norwegian mothers and their infants.15 A
In a recent study of 40 UAE mothers aged 16-45 years who               comparison of the results of serum concentrations of 25-OHD,
agreed to be studied at delivery, the mean serum 25-OHD                calcium, phosphorus and alkaline phosphatase among these 3

Vitamin D status of Arab mothers and infants

                                                                       unsupplemented breastfeeding infants of Middle Eastern
                                                                       origin indicate that the circulating 25-OHD concentrations of
                                                                       mothers and infants were low, and majority of the mothers
                                                                       and infants had hypovitaminosis D.19, 34

                                                                       Mean serum concentrations of 25-OHD in 10 white infants
                                                                       studied in summer in Cincinnati was 92.5 nmol/L,40 while the
                                                                       value was 60.0 nmol/L in another study in which the white
                                                                       infants were studied year round.41 The serum 25-OHD
                                                                       concentrations in breastfed infants in summer were 52.5
                                                                       nmol/L (China) 42, 46.3 nmol/L (New Zealand) 38, and 25
                                                                       nmol/L (The Netherlands). 39 In a study 19 from the UAE of
                                                                       90 exclusively breastfeeding infants and their mothers, the
                                                                       median serum 25-OHD concentration in the infants was only
                                                                       11.5nmol/L in summer. In another study of 38 Pakistani
                                                                       breastfeeding infants 34 the mean serum 25-OHD
                                                                       concentration was reported as 24.8nmol/L. The results of this
                                                                       global comparison of serum 25-OHD concentrations of
                                                                       exclusively breast feeding infants are summarized in Fig 1.

                                                                       Prevalences of hypovitaminosis D (serum 25-OHD
                                                                       <25nmol/L) were 82%, 52% and 20% in exclusively breastfed
                                                                       infants studied in the UAE,19 Pakistan 34 and China42
                                                                       respectively. None of 22 exclusively breastfed infants in a
                                                                       study from the United States 36 had hypovitaminosis D. In all
Figure 1: Comparison of mean serum 25-OHD concentrations               the studies from Europe, 39 the United States 36,37 and China,42
(nmol/L) of exclusively breast fed infants                             the maternal serum 25-OHD concentrations were normal
                                                                       ranging from 57-93 nmol/L. In contrast, the mean maternal
ethnic groups is summarized in the table 1. These results              25-OHD concentrations were 21.8nmol/L and 32.0nmol/L in
indicate that despite the low serum 25-OHD concentrations at           the UAE 19 and Pakistani 34 mothers respectively. These
birth, the Arab mothers and their infants were able to maintain        results support the close relationship between maternal and
normal calcium and phosphorus homeostasis possibly from                infant vitamin D status and suggest that majority of Arab
secondary hyperparathyroidism.                                         mothers and their infants have hypovitaminosis D and vitamin
                                                                       D deficiency unless they are supplemented with vitamin D.
A preliminary study of the prevalence of vitamin D
deficiency among 50 Iranian mothers aged 16-40 years and               Causes of vitamin D deficiency
their term neonates showed that the mean serum 25-OHD                  Several authors had suggested that a decrease in the
concentrations of 12.8nmol/L and 4.5 nmol/L in maternal and            endogenous production of vitamin D is responsible for the
umbilical cord blood respectively were very low.33 Eighty              high prevalence of hypovitaminosis D and vitamin D
percent of the mothers had serum 25-OHD concentrations                 deficiency in Arab women. Low dietary intake of vitamin D
lower than 25nmol/L. Almost all the infants born to the                has been implicated as a contributing factor in only few
mothers with serum 25-OHD concentrations lower than                    studies.
25nmol/L had undetectable circulating 25-OHD levels. It is
clear, therefore, that without vitamin D supplementation,              In a study of 271 Lebanese women aged 30-50 years, wearing
infants born to these mothers would be expected to develop             of veil was associated with low 25-OHD levels. Serum 25-
vitamin D deficiency later in infancy.                                 OHD concentrations were negatively correlated with wearing
                                                                       a veil. Vitamin D deficiency (serum 25-OHD level < 12.5
There is a paucity of studies of vitamin D status of                   nmol/L) was present in 62% of veiled women compared with
unsupplemented, exclusive breast feeding Arab infants,                 24% of nonveiled women.30 Another study from the UAE
despite the increase in the rate of breast feeding and the             compared the magnitude of clothing and duration of sunshine
association of prolonged breast feeding with vitamin D                 exposure among Arab women and Europeans residing in the
deficiency rickets. Several European and American studies              UAE, because the extent of UV skin exposure depends on the
have shown that exclusively breastfeeding white infants                degree of clothing and duration of sunshine exposure.16 In
whose mothers had normal vitamin D status were able to                 that study, 95%-100% of Arab women were likely to cover
maintain normal circulating 25-OHD without vitamin D                   their forearms, legs and head while outdoors compared with
supplementation.36-39 In contrast, the few studies of                  10%-30% of Europeans. Further, the average time spent in

                                                                                                J Arab Neonatol Forum 2004; 1:15-22

sunshine outdoors was 1.8 hours/week for Arab women                     rickets.10,47 Neonatal hypocalcemic seizure is a serious
compared with 4 hours/week by the European women. Mean                  complication of vitamin D deficiency in early infancy 10, 21, 46.
serum 25-OHD concentrations were 5- to 7- fold higher in the            Prolonged hypovitaminosis D eventually lead to rickets and
Europeans than in Arabs. Both the magnitude of clothing and             poor linear growth 10,48 in late infancy unless there is adequate
a UV skin exposure score (calculated by combining the                   vitamin D supplementation. Most cases of vitamin D
duration of sunshine exposure and the magnitude of clothing)            deficiency rickets in Arab children result from low vitamin D
correlated with the serum 25-OHD concentrations Table 2.                stores at birth and prolonged breastfeeding without vitamin D
These studies indicate that a combination of heavy clothing             supplementation. 12,14, 49,50 The relationship between maternal
that limits skin exposure to sunshine and a limited time of             vitamin D deficiency and deranged calcium homeostasis and
sunshine exposure while outdoors significantly increases the            rickets in infants demonstrates that rickets in Arab children
risk of hypovitaminosis D and should be addressed in efforts            and other populations where maternal vitamin D deficiency is
to improve endogenous production of vitamin D in Arab                   common should be viewed as disorder of maternal and child
women.                                                                  vitamin D homeostasis. In contrast, rickets in sunny African
                                                                        countries where maternal vitamin D deficiency is rare is
The few studies of dietary vitamin D intake show that Arab              mostly due to inadequate calcium intake.23 This knowledge of
women lack adequate intake of vitamin D. In the study of                the mechanism of disease process is essential in order to
Lebanese women referred to earlier,30 the average dietary               formulate appropriate therapy and prevention strategies.
intake of vitamin D was 100 IU. A similar intake of 100 IU of
vitamin D was reported in another study from Saudi Arabia.26            Prevention of vitamin D deficiency in mothers and Infants
In a study of exclusively breast feeding mothers in the UAE,            It is remarkable that despite the reported high prevalence of
the average maternal daily dietary intake of vitamin D was 88           vitamin D deficiency in Arab women and infants and the
IU.19 These amounts of dietary vitamin D intake were very               proven efficacy of wide spread vitamin D supplementation in
low compared to the generally recommended daily vitamin D               the prevention of vitamin D deficiency, there have been no
dietary intake of 400 IU, and this level is considered                  public health campaigns undertaken to improve the vitamin D
inadequate to normalize vitamin D stores in adults who limit            status in the community. When vitamin D deficiency and
sunshine exposure. 2, 6, 7, 8 The factors that contribute to low        rickets were recognized two decades ago as major public
dietary vitamin D intake were avoidance of milk, and                    health problems in Asians living in the United Kingdom,
consumption of nonfortified dairy products. 19,30                       measures such as wide spread vitamin D supplementation and
                                                                        public campaigns for changes in lifestyle were introduced
High parity was found to be associated with hypovitaminosis             with dramatic reduction in the incidence of rickets.51 Vitamin
D in some studies 30 and not in others.43                               D supplementation (1000 IU/day) was also shown to improve
                                                                        fetal growth and reduce the incidence of neonatal
All the reported studies indicate that the major risk factor for        hypocalcemia in infants born to supplemented pregnant
high prevalences of vitamin D deficiency in Arab women and              mothers.45
other mothers of Middle Eastern origin is a decrease in
endogenous vitamin D synthesis. Inadequate dietary vitamin              Many factors have contributed to the continuing high
D intake and possibly less efficient synthesis of vitamin D             prevalence of hypovitaminosis D in Arab women and infants.
among some dark-skinned Arab women are contributory                     First, there is a lack of awareness of the magnitude of
factors. The high prevalence of vitamin D deficiency in                 hypovitaminosis D and its effects on health owing to delay in
infants is a combined effect of maternal vitamin D deficiency           the clinical manifestation of vitamin D deficiency. Second,
and prolonged breast feeding without vitamin D                          many physicians fail to follow the general recommendation
supplementation because the mother is the major source of               of prescribing vitamin D supplementation to breastfeeding
circulating 25-OHD D concentrations in early infancy.21                 infants whose mothers are at risk of hypovitaminosis D.14
                                                                        Finally, there is a continuing challenge regarding how to
Consequences of Vitamin D deficiency in Mothers and                     effect changes in women’s lifestyles to increase sunshine
Infants                                                                 exposure and endogenous vitamin D production.
It is well known that maternal vitamin D deficiency affects the
mother, fetus and infant. Women with vitamin D deficiency               As indicated in many recent reviews and editorials, it is time
are at risk of osteomalacia, bone fractures, osteoporosis6 and          to take action to eliminate hypovitaminosis D and vitamin D
myopathy associated with vitamin D deficiency.44 Other non-             deficiency.2,6,8 Public health education activities are urgently
metabolic complications of vitamin D deficiency have been               needed to encourage modest sunshine exposure. It should be
discussed in detail in a recent review.6                                emphasized that modest sunshine exposure of the face and
                                                                        hands for 30 minutes three times a week in adults 6 or 2
The multiple effects of maternal vitamin D deficiency during            hours/week in infants 41 during late morning or late afternoon
pregnancy include decreased fetal growth,45 tooth enamel                may be sufficient to produce adequate vitamin D stores. It
hypoplasia,46 poor fetal bone mineralization and congenital             was shown in a study of male Saudi adults with vitamin D

Vitamin D status of Arab mothers and infants

deficiency that exposure to modest increases in sunshine                In conclusion, all of the studies to date suggest that
exposure resulted in significant increases in circulating 25-           hypovitaminosis D and vitamin D deficiency may be an
OHD concentrations.26                                                   unrecognized public health problem among Arab women and
                                                                        their infants. Community-based studies using generally
Vitamin D supplementation, however, remains the best option             accepted definitions are needed to establish the magnitude of
for improving vitamin D status and eliminating                          the problem. In view of the morbidity associated with vitamin
hypovitaminosis D in Arab women and children until                      D deficiency in mothers and growing infants, there is a
modifications in lifestyle can be achieved to improve                   compelling need to take public health measures to improve the
endogenous vitamin D synthesis. Vitamin D supplementation               vitamin D status of Arab women and infants. This should
program should be instituted and made accessible. The                   include wide spread vitamin D supplementation, modest skin
currently recommended daily dietary intake of vitamin D for             sunshine, increase in food fortification with vitamin D, and
all adults is 400 IU. However, because recent studies 6, 31 had         an awareness among the public and physicians on the urgent
shown that a dose of up to 1000 IU of vitamin D daily may be            need to improve vitamin D intake. Future research should
required to maintain normal vitamin D status in adults at risk          focus on the appropriate daily dietary vitamin D intake that
of hypovitaminosis D, it seems prudent to monitor serum 25-             will prevent hypovitaminosis D if sunshine exposure is
OHD concentrations to assess the efficacy of daily 400 IU               limited.
regimen. The dose should be adjusted to ensure that
appropriate vitamin D supplementation is given to achieve               References
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