Re: "Iodine Content in Milk Alternatives" by Ma et al. (Thyroid 2016;26:1308-1310)

Thyroid function and iodine intake: global recommendations and relevant dietary trends

Iodine is a micronutrient that is essential for thyroid hormone production. Adequate iodine intake is especially important during pregnancy and early life, when brain development is dependent on thyroid hormones. Iodine intake recommendations vary around the world, but most recommendations generally reflect the increased requirements during pregnancy and lactation, although adequate iodine intake before pregnancy is also important. Tremendous progress has been made in improving iodine intake across the world over the past 30 years, mainly through salt-iodization programmes. However, in countries without strong iodine fortification programmes, and with shifts in dietary patterns, a need has arisen for health organizations, governments and clinicians to ensure that adequate iodine is consumed by everyone in the population. For example, in countries in which adequate iodine intake depends on individual food choice, particularly of iodine-rich milk and dairy products, intake can be highly variable and is also vulnerable to changing dietary patterns. In this Review, iodine is considered in the wider context of the increasing prevalence of overweight and obesity, the dietary trends for salt restriction for cardiovascular health and the increasing uptake of plant-based diets.

Assessment of Dietary Intake of Iodine and Risk of Iodine Deficiency in Children with Classical Galactosaemia on Dietary Treatment

Iodine is an essential mineral required for the synthesis of thyroid hormones. Iodine plays a critical role in growth and neurocognitive development. Classical galactosaemia is a disorder resulting from an inborn error in galactose metabolism. Its current management consists of life-long lactose and galactose dietary restriction. This study estimated dietary intakes of iodine in infants and children with classical galactosaemia in the Republic of Ireland. The diets of 43 participants (aged 7 months-18 years) with classical galactosaemia were assessed for iodine intake using an iodine-specific food frequency questionnaire. Intakes were compared to the European Food Safety Authority (EFSA) dietary recommendations for iodine intake. The potential role of iodine fortification of dairy alternative products was also examined. There were no significant differences observed between sex, ethnicity and parental education and meeting dietary iodine recommendations. Differences, however, were seen between age groups, causing the p value to approach statistical significance (p = 0.06). Infants consuming infant formula were likely to meet iodine recommendations. However, over half (53%) of children aged 1-18 years had average intakes below the recommendations for age. For these children, consumption of iodine-fortified dairy alternative milk was the leading source of iodine in the diets, followed by fish/shellfish and eggs. An assessment of iodine intake should be undertaken during dietetic reviews for those with classical galactosaemia. Mandatory iodine fortification of all dairy alternative products would result in 92% of the total population cohort meeting iodine recommendations based on their current consumption.

Iodine and Iodine Deficiency: A Comprehensive Review of a Re-Emerging Issue

Iodine is a mineral nutrient essential for the regulation of a variety of key physiological functions including metabolism and brain development and function in children and adults. As such, iodine intake and status within populations is an area of concern and research focus. This paper will review recently published studies that focus on the re-emerging issue of iodine deficiency as a global concern and declining intake among populations in developed countries. Historically, the implementation of salt-iodization programs worldwide has reduced the incidence of iodine deficiency, but 30% of the world’s population is still at risk. Iodine nutrition is a growing issue within industrialized countries including the U.S. as a result of declining iodine intake, in part due to changing dietary patterns and food manufacturing practices. Few countries mandate universal salt iodization policies, and differing agriculture and industry practices and regulations among countries have resulted in inconsistencies in supplementation practices. In the U.S., in spite of salt-iodization policies, mild-to-moderate iodine deficiency is common and appears to be increasing. European countries with the highest incidence of deficiency lack iodization programs. Monitoring the iodine status of at-risk populations and, when appropriate, public health initiatives, appear to be warranted.

Low Iodine Intake from Dairy Foods Despite High Milk Iodine Content in Israel

BACKGROUND

Milk is a major source of iodine in human nutrition. Because both iodine content and the consumption of milk and dairy vary widely over time and populations, their contribution to iodine intake must be evaluated regularly. A recent national iodine survey found Israel's population to be mildly iodine deficient, possibly due to unmonitored changes in the food content of dietary iodine. Accounting for dairy iodine content can help guide efforts to prevent iodine deficiency.

OBJECTIVES

This study aimed to determine the iodine concentration of dairy products typically consumed in the Israeli diet, and to estimate iodine intake from dairy products among Israeli adults.

METHODS

Iodine was analyzed in 33 selected dairy products that account for 89% of the total population's dairy intake according to the "MABAT" Israeli National Health and Nutrition survey. Based on these data, the distribution of iodine intake from milk, dairy, and dairy-based foods in the adult population was calculated.

RESULTS

Israeli milk is rich in iodine, with a mean concentration of 22 μg/100 g. However, due to low dairy consumption, the mean iodine intake from milk and dairy was only 34 μg/day (median 23 μg/day; range: 0-337 μg/day) or 22% of the recommended daily allowance. Self-reported intake among poor, male, and Arab subgroups was even lower.

CONCLUSIONS

Because Israeli milk and dairy products are iodine rich, their contribution to the population's iodine intake would increase if they were consumed in greater amounts, particularly by high-risk groups. Dairy's potential contribution to iodine nutrition should be considered in recommendations for dairy consumption and iodine prophylaxis.