Iodine Status in the Elderly: Association with Milk
Intake and Other Dietary Habits
Sara Watutantrige-Fernando1*, Susi Barollo1, Loris Bertazza1, Francesca Sensi1,
Elisabetta Cavedon1,Simona Censi1, Nicola Veronese2, Filippo Ceccato1, Federica Vianello3, Marco Boscaro1, DavideNacamulli4, Valentina Camozzi1, Caterina Mian1
1Endocrinology Unit, Department of Medicine, University of Padua, Via Ospedale Civile n. 105, 35128 Padua, Italy
2Geriatrics Division, Department of Medicine, University of Padua, Via Ospedale Civile n. 105, 35128 Padua, Italy
3Radiotherapy Unit, Istituto Oncologico Veneto, IOV-IRCCS, Via Giustiniani n. 2, 35128 Padua, Italy
4Endocrinology Unit, Department of Medicine, Padua General Hospital, Via Ospedale Civile n. 105, 35128 Padua, Italy
Sara Watutantrige-Fernando, MD, Endocrinology Unit, Department of Medicine, University of Padua, Via Ospedal Civile n. 105, 35128 Padua, Italy; Tel: +39-04982134266; Fax: +39-049657391. E-mail:
Received:December 23, 2016; Accepted: January 23, 2017; Published: February 27, 2017
Citation: Watutantrige-Fernando S, Barollo S, Bertazza L, Sensi F, Cavedon E, et al. (2017) Iodine Status in the Elderly:Association with Milk Intake and Other Dietary Habits. J Nutrition Health Food Sci 5(1): 1-5.
Background: Iodine deficiency is still an issue with important
consequences, not only in younger people, but also in the elderly. We
proposed to assess iodine status in elderly females, to analyze their
eating habits and to compare results with our previous findings on
female from childhood to fertile age.
Materials and Methods: This observational study that
involved 189 menopausal women (51-86 years old) undergoing
endocrinological evaluation at our center in the Veneto region, a
northeast Italian area. We measured Urinary Iodine Concentration
(UIC) from spot urine samples and participants were asked to fill
in a food frequency questionnaire; we also collected data on bone
metabolism from the hospital laboratory database network system.
Results: The median UIC of the sample as a whole was 30 μg/l,
corresponding to a moderate iodine deficiency. Among these subjects
47.7% were daily milk consumers: such women had a higher UIC
than the occasional milk consumers (43 vs 30 μg/l, P= 0.0041).
Regarding other dietary habits, a great proportion of women resulted
undernourished; moreover the declining trend in milk consumption
with increasing age is similar to the age-related decline in UIC and
24h-Urinary Calcium (U-Ca).
Conclusions: women of menopausal age in our series were
lacking in iodine because of reduced milk intake, in the contest of a
major condition of global undernourishment. We confirm that milk
is per se an important source of iodine if consumed in appropriate
Keywords: Iodine; UIC; Milk; Urinary calcium; Elderly
Iodine deficiency is a problem seen worldwide, and it has been
well documented that it is the “single most important preventable
cause of brain damage” . Even today, 30% of school-aged
children are thought to be iodine-deficient . Iodine deficiency
can have a spectrum of consequences of various severity and
types, according to the entity of the deficiency, at all ages . The
most known and relevant consequence is represented by cognitive
impairment responsible, particularly in high-income countries,
for poor intellectual performances (e.g. a lower verbal and total
Intelligence Quotient, poor reading accuracy and comprehension)
. At all ages, iodine deficiency can cause goiter, which is only
reversible with iodine supplementation in younger people .
Iodine deficiency is also related to a greater susceptibility to
nuclear radiation, and ensuring an optimal iodine intake can
downgrade thyroid cancer to the less aggressive histotypes [6, 7].
In adults, the main disorders related to iodine deficiency include
impaired mental function, reduced work productivity, and toxic
nodular goiter. Studies in the literature have often concentrated
on iodine deficiency in younger people, while limited data are
available on the elderly. In 1998 Laurberg et al  focused on
elderly subjects and found that the population iodine intake is
an essential determinant of which types of thyroid disorders are
common: indeed a deficient iodine intake, even mild or moderate,
that is common in European countries, is related to goiter and
thyroid hyperfunction, while a relative high iodine intake is
related to impaired thyroid function. In the elderly, thyroid
dysfunctions can have a more relevant clinical impact than in
younger subjects, being the main dangers of hyperthyroidism
atrial fibrillation (with the risk of reduced cardiac function and
embolism) and osteoporosis, while lipid abnormalities with
atherosclerosis in case of reduced thyroid function [9-11]. On
the basis of these evidences, we concentrated our study on the
elderly, particularly in a subset of menopausal women, because
the elderly represent a considerable proportion of the general
population thanks to an increasing life expectancy . The aims
of this study were: i) to assess iodine status in older women; ii)
to analyze their eating habits; and iii) to compare the results with
our previous findings on females, where we found a descendant
trend in milk consumption, corresponding to descendant UIC
values, starting from childhood to fertile age .
Materials and Methods
From October 2015 to January 2016 we consecutively
recruited 189 women of menopausal age undergoing
endocrinological evaluation at our center in the Veneto region
of north-eastern Italy (an area of mild iodine deficiency) .
All participants were invited to complete a food frequency
questionnaire consisting of two parts: 1) the first recorded
date and place of birth, personal history of kidney insufficiency
or intestinal malabsorption, recent exposure to iodine contrast
media, thyroid diseases, use of iodine-containing products (food
supplements, medicines); 2) the second consisted of a food
frequency questionnaire concerning whether they used iodized
salt and, if so, for how many years they had done so, and asking
a quantification of a wide series of food, typically included in our
diet, such as their daily dietary intake of cow’s milk, yoghurt,
cheese, meat, eggs, fish, and soy milk. Milk intake was scored as: 0
for no milk; 1 for occasional consumption; 2 for one cup a day; and
3 for more than 1 cup a day. The intake of yoghurt, cheese, meat,
eggs, fish, and own production aliments was scored as: never
(0), at least once a week (1), more than once a week (2). The use
of iodized salt, cassava, cabbage, turnips, mustard, horseradish,
seaweed, estro-progestinic drugs, and smoking were scored as
YES or NO. Although beyond the purposes of this study, assuming
a global malnutrition in this subset of women in the light of the
preliminary data regarding iodine status and dietary habits, we
collected data on bone metabolism from the hospital laboratory
database network system: vitamin D values were expressed as
nmol/l (normal: 75-250) and 24h-urinary calcium (U-Ca) values
as ng/24 h (normal: 100-300). Participants collected 20 ml spot
urine samples in the morning, which were divided into aliquots
and kept refrigerated below 20°C until the time of assay. The
Urinary Iodine Concentration (UIC) was expressed as μg/l and was
measured in duplicate using the colorimetric ceric ion arsenious
acid method in a second-generation Technicon Auto-Analyzer
(Brain Luebbe GmbH, Germany) . The intra- and inter-assay
coefficients of variation were 5.7% and 5.5%, respectively. The
study was conducted according to the guidelines laid down in the
Declaration of Helsinki; verbal informed consent was obtained
from all participants, and was witnessed and formally recorded;
the present study was notified to our Local Ethical Committee
(Azienda Ospedaliera di Padova, code number: 0029374).
The Kolmogorov-Smirnov test was used to test the normal
distribution of the UIC: the values were not normally distributed,
so they are given as medians and 95% Confidence Intervals (CI);
the vitamin D and U-Ca values were normally distributed. The
Mann-Whitney test was used to study the differences in UIC visà-
vis the use of iodized salt, milk intake, and U-Ca and vitamin D
levels. The chi-square test was used to explore the relationship
between adequate iodine status (adopting the WHO’s UIC cutoff of
≥100 μg/l) and dietary habits and bone metabolism parameters.
A P value < 0.05 was considered statistically significant.
The women were a mean 66 years of age (min 51, max 86),
and their median UIC was 30 μg/l (min 22, max 542; 95% CI 30-35
μg/l); according to the WHO classification, 34/189 (18%) women
were mildly deficient and 113/189 (60%) were moderately
iodine deficient, moreover we found no severely iodine deficient
women. Their clinical data and dietary habits are shown in Table
1. Concerning available eating habits, 53/174 women (30.5%)
did not drink milk, 38/174 (21.8%) did so occasionally, 72/174
(41.4%) drank 1 cup a day, and 11/174 (6.3%) drank more than
1 cup a day. On the whole, 139/174 women (80%) had a UIC
< 100 μg/l. The daily cow’s milk consumers had a median UIC of
44 μg/l, while for the occasional milk drinkers it was 30 μg/l (P=
0.0041); among the women with a UIC ≥100 μg/l, 69% were daily
milk consumers whereas among those with a UIC < 100 μg/l, 42%
uses it regularly (P=0.01).
Data on iodized salt use was available for 187 women of
Table 1:Clinical data and dietary habits
(UIC ≥100 μg/l)
Vitamin D (nmol/l)
UIC: urinary iodine concentration, U-Ca: 24h urinary calcium
whom 112 (59.9%) used it regularly: 149/187 (79.7%) had a UIC
< 100 μg/l. The UIC of iodized salt users did not differ significantly
from that of non-users (30 μg/l in both groups, P= 0.587). No
significant association emerged between UIC and time since
starting to use iodized salt.
No significant associations were found between UIC and
consumption of dairy products, fish, beef or chicken meat, or
other individual characteristics (kidney insufficiency, intestinal
malabsorption, recent use of iodine contrast media, thyroid
disorders, iodine drugs or supplements, smoking habits).
Regarding eating habits, the women declared to consume
once a week or less or not at all the entire range of food evaluated
(score 0-1): 116/172 (67%) reported a score 0-1 for yogurt,
105/178 (59%) for chicken, 127/179 (71%) for beef, 174/178
(98%) for eggs and 152/180 (84%) for fish; despite other
products cheese was consumed more than once a week by
119/180 women (66%).
Regarding bone metabolism, we were able to collect data on
40 subjects. Their mean vitamin D level was 88.16 nmol/l (min
38, max 171; 95% CI 76.23-95.22) and their mean U-Ca level was
152 ng/24h (min 7.6, max 328; 95% CI 126.03-178.42). There
were 15/40 women (37.5%) with U-Ca levels below the normal
limit, 23/40 (57.5%) had normal U-Ca levels, and 2/40 (5%) had
excessive U-Ca levels.
The UIC of the subjects with normal U-Ca levels did not
significantly differ from that of the hypocalciuric subjects (with
36.6 μg/l and 30 μg/l, respectively; P= 0.213). As a whole, the
proportions of hypocalciuric subjects differed significantly by
UIC, however: 9/10 women (90%) with an adequate UIC had
normal U-Ca levels, whereas this proportion was lower (14/30,
46.7%) among the iodine-deficient subjects (P< 0.05, Figure 1). As
for the association between milk consumption and U-Ca, 16/22
daily milk consumers (72.72%) had normal U-Ca levels, while
9/18 occasional or non-consumers (50%) were normocalciuric
(P=0.15). No significant association emerged between UIC and
vitamin D levels.
Figure 1: Relationship between urinary iodine concentration (UIC) and
24h urinary calcium (U-Ca).
In the last few decades many social and economic steps
have been taken to promote iodine prophylaxis because iodine
deficiency can have severe consequences for people of any age.
Some population groups are particularly vulnerable to iodine
deficiency, primarily fetuses/neonates and pregnant/lactating
women. Iodine is important because it is a constituent of thyroid
hormones that are essential to the development of the central
nervous system. In 2013, Raymann et al  studied 1,040 motherchild
pairs, matching mothers’ iodine status in the first trimester
of gestation with data on the cognitive outcomes of their 8- to
9-year-old children. They demonstrated that children born of
iodine-deficient mothers had a worse cognitive status. Apart from
these particularly susceptible groups, iodine deficiency can also
negatively affect adults in a number of ways, the most important
of which is a greater probability of developing goiter. There is
a paucity of information in the literature on iodine status in the
elderly, probably because some structural glandular changes
are so established and irreversible in adult age that correcting
iodine status could well be irrelevant. The Pescopagano study 
clearly demonstrated that improving iodine status only reduced
the frequency of nodular goiter in younger people because of the
irreversible fibrotic changes occurring in longstanding goiter.
In some published reports, iodine status in the elderly was
considered as part of broader population-based studies: judging
from these surveys, individuals from 60 years old onwards seem
to have a lower UIC than other age groups. Zou et al  published
a cross-sectional study on iodine status comparing rural and
urban residents in a Chinese Province: they concluded that the
rural population had a higher UIC than the city dwellers (170.1
μg/l versus 153.5 μg/l). Concentrating on iodine status by age, the
UIC was 154 μg/l for the elderly rural residents, and 129.5 μg/l
for the elderly urban population. Much the same results emerged
from a cross-sectional study conducted in Spain : this survey
confirmed that people >65 years old had a significantly lower UIC
than the younger age groups (109.33 μg/l versus 161.52 μg/l). A
study conducted by Tang  in Taiwan 5 years after mandatory
salt iodization was stopped also showed that older individuals
had a lower UIC level than younger people (88 μg/l versus 100
μg/l), and this was particularly evident in older females (79 μg/l).
In the light of these studies, we analyzed iodine status in women of
menopausal age, collecting 188 urine samples and questionnaires
on individual dietary habits. All the women were residents of the
Veneto region, an area of mild iodine deficiency (median UIC
81 μg/l), with some differences between the mountainous, hilly
and lowland areas (where the median UIC is 94, 54, and 77 μg/l,
respectively) . The median UIC for our sample as a whole
was 30 μg/l, indicative of a moderate iodine deficiency according
to the WHO classification . When we investigated cow’s milk
consumption, we found that more than 50% of the women drank
milk only occasionally. Comparing these data with our previous
findings in younger females in various age brackets , we
identified a global declining trend in the consumption of cow’s
milk with age: while the majority of 4-year-olds and 12-year-olds
drank milk daily (73.42% and 62.30%, respectively), women of
fertile and menopausal age were less likely to drink milk every
day (55.08% and 47.7%, respectively, P< 0.0001) (Figure 2).
There may be several explanations for these different dietary
habits: 1) younger people, and infants in particular, are used
to drinking milk as a natural continuation of lactation; 2) milk
is rich in nutrients and parents consider it important to ensure
that their children (even in adolescence) have an adequate intake
of minerals, proteins and vitamins; 3) as they grow up, children
and adolescents gradually change their dietary habits, acquiring
personal tastes and different lifestyles; 4) being rich in nutrients,
milk is also rich in cholesterol and, in adulthood, many people
tend to exclude it from their diet to avoid hypercholesterolemia
and reduce the related cardiovascular risks. Moreover, some
Authors associate its consumption to many other diseases,
the most significant of which is cancer [19, 20]. The low milk
consumption identified in the elderly is in line with the declining
trend in people’s UIC with age (Figure 3), since milk consumption
was confirmed as the only factor influencing the UIC in this subset
of subjects too.
Daily cow’s milk consumption was associated with a
significantly higher median UIC in our series of elderly women
(44 versus 30 μg/l, P=0.004), but the small difference in UIC
between milk consumers and non-consumers in our sample goes
to show that even drinking milk daily cannot assure an optimal
UIC. One in two of our subjects (83/174, 47.7%) were used to
drinking milk daily, but only 28.9% of them had an adequate
UIC. This could relate to the fact that we did not ascertain how
much milk they drank in absolute terms, and it is likely that the
elderly drank smaller volumes of milk than younger people. Daily
milk consumption coincided with an adequate iodine status in all
female subgroups, irrespective of age, in a previous study of ours
, but not in the present case. Hypothesizing an inadequate
nutrient intake, we analyzed our sample’s other dietary habits:
we found that a considerable proportion of the women consumed
the other foods investigated only occasionally or not at all (yogurt
67%, chicken 59%, beef 71%, eggs 98%, fish 84%). Taking a wider
Figure 2: Milk consumption among female groups (Children; SAC:
School age children; Fertile women, Menopausal women).
Figure 3: Urinary iodine concentration (UIC) distribution among female
groups (Children; SAC: School age children; Fertile women, Menopausal
point of view, to confirm a comprehensive malnutrition state, we
analyzed, where available, data on bone metabolism (U-Ca and
vitamin D) from the hospital laboratory database network system
and we assessed U-Ca levels as a marker of milk intake and an
indirect indicator of iodine intake, given that milk is an important
source of iodine and calcium . Although a single UIC value
from spot urine samples does not allow to extrapolate the real
iodine status of a done single subject, we observed that among
our subjects with low U-Ca levels, the vast majority (93.33%)
were also iodine-deficient, whereas 90% of the women with an
adequate iodine status also had good U-Ca levels. These findings
suggest that the iodine deficiency identified in the elderly relates
to a limited global consumption of milk (even among those who
drink milk daily). In addition, a limited milk consumption was
also associated with a broader deficiency of several nutrients.
Elderly people tend to gradually eat less for numerous reasons,
including loss of appetite, gustatory dysfunctions, declining basal
metabolism, and economic issues too [22, 23].
Iodized salt was used by 59.9% of the women in our sample,
but we found no significant difference in terms of UIC between
users and non-users. This proportion of users is similar to the
figure identified in our previous study (in 2011), suggesting that
our iodine prophylaxis program has yet to reached the target
90% coverage . Among the women who were using iodized
salt, the proportion of iodine-sufficient individuals was only
21.42%; in other words, even regular iodized salt consumption
is unable to assure an optimal iodine intake. This could be due to
the inappropriate storage of iodized salt and to part of the iodine
in the salt being lost during cooking processes.
Hyperthyroidism is known to be more common in areas
of mild-to-moderate iodine deficiency than in areas of severe
iodine deficiency, where hypothyroidism typically occurs. A
higher incidence of hyperthyroidism is positively associated
with the incidence of toxic multinodular goiter  because
iodine deficiency promotes the growth of clusters of autonomous
thyrocytes, resulting in the overproduction of thyroid hormones.
Correcting iodine deficiency in the elderly could help to reduce
this autonomization process, leading to a normalization of TSH
and thyroid hormones, containing the cardiovascular and skeletal
consequences of hyperthyroidism in a particularly vulnerable
and susceptible population.
We conclude that iodine deficiency is still an issue that
affects a sizable part of the population, including the elderly. We
should continue to educate people to consume products rich in
iodine, such as iodized salt and cow’s milk, emphasizing that the
iodine content of such foodstuffs may be lost with storage and
cooking, and may be insufficient. We should also pay attention
to ensuring that the elderly maintain an adequate iodine status
to avoid preventable cardiovascular consequences related to
We thank Frances Coburn for text editing, and Dina Pozza for
help in storing and analyzing the urine samples.
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