Iodine Intake During Pregnancy

Iodine is an essential micronutrient. We ingest iodine from the foods we eat. The iodine content in the foods we eat is linked to the iodine that is in the soil that the food is grown in. Animal sources of iodine are also affected by their diet, whether iodine is present or not in what they are eating. Iodine is irregularly distributed over the earth. Mountain regions and flood plains are often deficient in iodine.

Iodine is essential in fetal development. During pregnancy a woman will need about 50% more iodine in her diet than normal. Most prenatal vitamins have iodine added into them. If you still show low levels of iodine during pregnancy your doctor may want to add an iodine supplement as well. Iodine levels during pregnancy have been linked to brain development of the fetus.

A mild deficiency may have long term effects on the child that aren’t reversed during childhood years even if they receive enough iodine. Iodine intake while breastfeeding is also important. If you aren’t breastfeeding, fortified infant formulas usually have iodine added into them. An infant needs 110 mcg of iodine per day until they are 6 months.

The food that contains iodine is changed into iodide, which is taken in by the digestive system. In the thyroid gland, iodide is employed in the production of thyroid hormones. The kidney excretes excess iodine in urine.

The nutritional requirement for iodine is currently considered to be in the range of 0.10 to 0.14 mg per person per day for adults.

Iodine Function

Iodine is necessary in the human diet since it is mandatory for the production of thyroid hormones like tri-iodo- and tetra-iodothyronine (also named T3 and T4 or thyroxine). The hormones created by the thyroid have a large impact on multiple areas of the body, like the general metabolism, the cerebral growth of a baby in the womb, and the development of bones, particularly for a young one in the uterus who is given iodine from the placenta. Therefore, if a mom does not have the required amount of iodine there could be severe implications for both the mom and her baby. Iodine deficiency or an overabundance of iodine both can cause a condition known as goiter, which occurs when the thyroid gland enlarges, in both adults and children. The signs and symptoms of acute iodine poisoning are nausea and loose stools, convulsions, confusion and fainting. Adverse reactions, like iodide mumps, may arise following treatments that contain iodine (EVM, 2003).

Since 2013, the National Diet and Nutrition Survey has taken urine samples to determine iodine levels. The results demonstrate that the urine iodine levels of children and grown-ups in the NDNS groups agree with the World Health Organisation (WHO) criteria. This criteria state that a populace with no iodine inadequacy should have a middle urinary iodine focus of between 100 µg/L and 199 µg/L, and the extent should be lower than 20% of the populace with an iodine focus underneath 50 µg/L. The concentration of iodine in the urine of women aged 16 to 49 was 98 micrograms per liter, and 21 percent of that population had concentrations below 50 micrograms per liter. They don’t abide by the more stringent requirements that apply to pregnant and nursing women, which is determined by the average iodine level in their urine at 150 to 249 µg/L (WHO, 2007; SACN, 2014). An analysis of urinary iodine levels during the Rolling Programme Years 9-11 report demonstrated that there were no statistically meaningful alterations over time in any age/sex categories (Public Health England, 2020; British Nutrition Foundation, 2020).

Good Sources Of Iodine

Sea water is a good iodine source. Seaweed and fish that eat seaweed are also good sources of iodine. Iodine is mostly found in animal proteins and sea vegetables.

Foods that contain iodine are nori, kelp, kombu, wakame, seaweed, cod, canned tuna, oysters, shrimp, iodized table salt, milk, cheese, yogurt, eggs, beef liver, chicken, and fortified infant formula.

Universal salt iodization is now a widely accepted strategy for preventing and correcting iodine deficiency disorders. This has been a common practice to use common salt as a vehicle for iodine fortification for the past 75 years.

Status in Pregnancy

Pregnant women, nursing women, and children younger than 3 years old are at high risk for iodine deficiency. However, an iodine deficiency can happen at any stage of life.

Irreversible damage to the brain and nervous system and the growth and development of a fetus can happen if there is a iodine deficiency.

Iodine requirements increase during pregnancy because of the needs of the fetus for iodine and the frequent urination by the mother.

After it is ingested, iodine is quickly taken in by the body and reaches the circulatory system. The thyroid converts the circulating iodine by oxidizing it, thus allowing it to be used to form the thyroid hormones triiodothyronine (T3) and thyroxine (T4). The thyroid hormones are responsible for maintaining normal metabolism and guaranteeing that the heart, brain and other organs are performing optimally. Most of the iodine present in the body is located in the thyroid glands; however, other areas such as the mammary glands, eyes, stomach lining, cervix, and salivary glands have some non-hormone-based iodine as well (Ahad et al, 2010).

Thyroid function and iodine levels are altered during pregnancy. During the first stages of pregnancy, Thyroid Stimulating Hormone (TSH) triggers an elevation in the production of thyroid hormone by the mother (Glinoer, 2001). It is speculated that the rise of GFR during pregnancy results in a reduction of iodine found in the bloodstream (Glinoer, 2007; Gaberscek and Zaletel, 2011); however, it remains uncertain as to whether this might be counterbalanced by an improved capacity of the kidneys to keep iodine. Any decrease in plasma iodine levels would, at least partially, be due to an increase in the plasma volume. A percentage of thyroid hormone from the mother is passed on to the infant in the womb, as is iodine via the placenta’s NIS (sodium/iodide symporter) (Glinoer, 2001; Zimmermann, 2009). The production of thyroxine, which is a necessity for mental development, is reliant upon iodine (Ahad et al, 2010). Iodine in what someone eats is very important for the brain to develop in certain time periods, influencing how neurons, glial cells, and the process of myelination connect. This also affects neuron migration and the formation of synapses (Choudhry et al, 2018).

The UIC found in the urine is a good sign of how much iodine has been ingested recently, since around 90 percent of ingested iodine will end up in urine (Rohner, 2014). A UIC of at least 100 μg/L shows adequate iodine intake for mothers breastfeeding their babies and for children under two years old, while pregnant women need a median level of between 150-249 μg/L for sufficient consumption (Harding, 2017). Lower than 100 μg/L in pregnant women indicates not enough iodine is being taken. Pregnant women are viewed as having an excessive amount of UIC levels if the count is greater than 500 µg/kg, as determined by the World Health Organization, United Nations Children’s Fund, and International Council for the Control of Iodine Deficiency Disorders (WHO, UNICEF and ICCIDD, 2007).

Katko et al (2018) determined iodine status in 164 Hungarian pregnant women during their 16th week of pregnancy, the time period in which major brain development occurs, by measuring plasma thyroglobulin (Tg) in lieu of UIC. It was discovered that the daily consumption of iodine was reflected in the UIC, whereas Tg related to the overall amount of iodine stored over time.

16 healthy nursing American women without a history of thyroid illness had to swallow 600 micrograms of potassium iodide (456 micrograms of iodine) after not eating anything throughout the night. At the start of the experiment and at each hour for eight hours after, samples of breast milk and urine were examined to observe the level of iodide ingested. The amount of iodine that was consumed throughout the testing period was also monitored. At the start, the breastmilk and urine iodine values were 45.5 micrograms per liter and 67.5 micrograms per liter, respectively. After giving KI, the average increase in the amount of iodine in breastmilk moved up to 280.5 μg/L, with the highest concentration registering at 354 μg/L. The amount of iodine in the breastmilk reached its highest point 6 hours after the intake of KI, with the times ranging from five to seven hours. Consumption of dietary iodine sources contributed an additional 36–685 micrograms of iodine intake in the span of 8 hours. Based on the work of Leung et al (2012), it was determined that any measurements of iodine in breastmilk should be taken into account alongside a person’s iodine intake.

It has been established that inadequate iodine levels are a problem in maternal health, however, too much iodine can also be taken in and may potentially have an effect on maternal health. Ingesting too much iodine can be attributed to drinking water that contains naturally-occurring iodine, consuming seaweed, taking iodine supplements or pills, drinking milk that has had iodine added as a feed supplement, or consuming produce cleaned with an iodophor sanitizing agent. In general, an excessive amount of iodine has no effect on healthy people. Those with autoimmune thyroid conditions such as Hashimoto’s or Graves’ Disease, as well as newborns, are likely to have a negative reaction.

The Study

Verifying the accuracy and being able to reproduce the results of a new food frequency questionnaire assessing iodine intake among Norwegian expectant mothers.

Background

In Norway, adding iodine to salt is not a requirement, and the permissible amount of iodine in table salt is set at a small amount (5 μg/g). Therefore, milk and dairy items, fish, and eggs are the primary food sources of iodine in Norway. It has been demonstrated that in a few European nations, inclusive of Norway, expectant mothers suffer from a mild to moderate insufficiency of iodine. Not many proven techniques exist to efficiently measure iodine consumption. The objective of this research was to measure the accuracy and consistency of a novel iodine-specific food frequency questionnaire implemented with Norwegian pregnant women.

Methods

A questionnaire (I-FFQ) containing 60 food products and supplement inquiries was made to estimate iodine consumption among 137 pregnant women in the 18th to 19th weeks of pregnancy. An order of operations consisting of six days of monitoring the iodine levels in particular foods, the pooled estimation of urine tests done over six days to measure iodine concentration, and tests of thyroid function were employed as reference methods. An assessment of the validity was conducted with correlation analyses, Cohen’s weighted kappa, Bland-Altman plots, and linear regression analyses. A subgroup of 47 people was surveyed in order to measure the accuracy of the I-FFQ during the 35th to 36th week of pregnancy.

Study design and subjects

This study’s findings were drawn from the Mommy’s Food study, which was a randomized controlled trial that was conducted in Norwegian pregnant women. The objective of this research was to see if increasing the consumption of codfish during pregnancy has any effect on 1) the iodine levels in the mother and 2) the development of the baby. Markhus et al. provide a comprehensive description of the study design, from the enrollment of participants to the randomization to the process and ethics. This paper used data from before the intervention, in the 18th/19th week of gestation, to assess the accuracy of the I-FFQ. One hundred and thirty-seven expectant mothers from Bergen, Norway participated in this research. Individuals were enlisted between January 2016 and February 2017. A total of 124 people provided I-FFQ data, 134 individuals supplied food diary information, and 134 participants presented UIC documentation. The sample size was judged to be sufficient in order to validate an FFQ in a population group, which requires at least 50 to 100 participants. To evaluate the accuracy of the I-FFQ, data from the control group after the intervention (from gestational week 35 to week 36) was employed. The Randomized Controlled Trial set-up allowed us to examine the reproducibility of the results using just the control group (n = 47) since the aim of the intervention was to raise the iodine intake of the subjects. Including the intervention group would not be appropriate for gauging reliability.

Data Collection Methods

I-FFQ

An I-FFQ that provides approximations of the amounts of food and supplements consumed was set up in the online questionnaire in order to obtain details about the participants’ typical diets that emphasize foods which are abundant with iodine. Participants were asked to provide an approximate assessment of the diet they have had since becoming pregnant as a part of the I-FFQ filled out between weeks 18-19 of gestation. In the I-FFQ filled out in the 35th-36th week of pregnancy, the participants were asked to provide an account of their dietary habits over the previous 16 weeks since their last survey.

The I-FFQ questioned participants on the how often they consumed seafood at dinner, warm lunch, and as a spread with a total of 21 questions for dinner and warm lunch and 14 questions for the spread. What type of seafood or products were consumed? The spacing between given options went from “never” to “three times a week or more”, covering a span of five possibilities. In addition, there were 24 kinds of food that involved drinking milk and dairy product consumption (including mixed food with milk like pancakes, waffles and porridge) with frequency categories ranging from “never” to “three or four times daily” (with a total of seven frequency categories). Questions were asked about the amount of seafood, milk and dairy products that were consumed during a meal, with options ranging from less than half a portion to three portions (a total of five possible amounts). Regarding eggs, the weekly intake could range from less than one per week to eight or more per week, with six possible levels of intake in between. Altogether, 60 food items known for their iodine content (fish and seafood, milk and dairy products, and eggs) were considered in the calculation of dietary iodine intake using the I-FFQ. Moreover, the I-FFQ asked about types, brands, and how often dietary supplements were consumed.

The numerical continuous data which came from the I-FFQ were worked out through the calculation of indexes adhering to the strategy specified by Markhus et al. For determining seafood intake, as soon as the frequency of consumption was said as an interval (i.e. 1-2 times a week), the minimum frequency in that span was taken into account (in this case, 1 time a week). This was the result of remembering being likely to overestimate small amounts when asked specifically about various food items. For milk, dairy products, eggs and dietary supplements, the mean frequency consumption was 1.5 times per day when the frequency consumption was given in the form of a range (ex. 1 to 2 times per day). These food groups contained only a few questions in detail. The frequency at which each question was answered was multiplied by the amount of the portion people reported that they consumed per week in order to calculate an estimate of their total weekly intake.

Results

The estimated iodine intake derived from the I-FFQ and food diary showed a strong association (r = 0.62, P < 0.001), while the I-FFQ and UIC had an adequate correlation (r = 0.21, P = 0.018). No notable link was identified between the I-FFQ and thyroid function tests. The I-FFQ showed an intake of higher iodine than what the food diary recorded, with an average difference of 33 μg/day. The results from the Bland-Altman plots had a wide range of agreement, but only a small amount of participants fell outside of it (5.2–6.5%). There was no variation in the predicted iodine consumption from the I-FFQ evaluated at weeks 18 to 19 and weeks 35 to 36 of pregnancy (P = 0.866), and the two timepoints showed a high correlation (r = 0.63, P < 0.001).

Conclusion

This study concludes that the I-FFQ has utility for estimating and comparing iodine intake among Norwegian pregnant women, confirming its reliability through the reasonably high correlation and agreement compared with estimated iodine intake from a 6-day detailed food consumer report and UIC. The I-FFQ further showed strong reproducibility. Hence, this I-FFQ can be applied to gauge and keep track of iodine intake in this group of people. The resurgence of iodine deficiency in Norway and Europe requires validated, non-intrusive, cheap and fast techniques to examine iodine intake and to locate women in danger of not taking enough iodine.