Iodine’s role in child growth, metabolism, and fertility

Iodine is involved in the body’s production of thyroid hormones, and we humans need plenty of iodine throughout life, especially during periods such as fetal development and child development. Iodine is also important for brain development and cognitive skills. Severe iodine deficiency during pregnancy and during a child’s first years of life may result in stunted growth and/or mental retardation, but there has been uncertainty about how a minor iodine deficiency affects the child before and after birth. In a review article that is published in Nutrients, the authors look closer at iodine’s role in fertility and child growth. Apparently, iodine deficiencies are quite common, and we even need selenium and other nutrients to secure a well-functioning thyroid gland.

A child’s growth and development during its first years of life is a complicated process that requires plenty of macronutrients (fat, protein, and carbohydrate) and micronutrients (vitamins and minerals). If certain nutrients are lacking it may result in lower adult height. Also, it increases the risk of impaired brain development that can result in poor well-being and lower education.
During the pregnancy, the fetus grows rapidly. Iodine has vital importance for the thyroid hormones that control a host of different processes, including the cell division of the fertilized egg,
fetal development, and cellular energy turnover. Iodine is also important for normal development of the brain and bones.
The ovaries contain comparatively large quantities of iodine, which is important for the estrogen balance and fertility. A Norwegian population study has demonstrated that an iodine intake higher than 100 micrograms per day is linked to improved fertility. Pregnant women, however, should get around 150 micrograms of iodine daily, which is about the same as the recommended intake level.

Iodine deficiency and its serious consequences for the mother and child

During pregnancy, the daily iodine intake should be able to meet the requirement of both the mother and the child. If the mother is iodine-deficient before becoming pregnant, and her body’s iodine reserves are limited, she risks that her thyroid gland’s synthesis of thyroid hormones is too low during the early part of the pregnancy. Also, many women are pregnant for two to three months before they discover that they are expecting.
Insufficient synthesis of thyroid hormones results in hypothyroidism. In connection with pregnancy, hypothyroidism can increase the risk of a miscarriage, preeclampsia, preterm delivery, low birth weight, and stillbirth. There is also a risk that the baby’s brain and nervous system will fail to develop normally.
A child can also be born with hypothyroidism, and the problem can even occur later in life. Iodine deficiencies are widespread in many parts of the world. In placebo-controlled studies from Peru, Algeria, and Bangladesh, iodine supplements have been given to pregnant women. This resulted in increased (and more normal) birth weight and height, compared to the placebo group.

Other important micronutrients for metabolism and pregnancy

In their review article, the authors also mention other nutrients that are important for the thyroid function and for child growth. The thyroid hormones include T4, which is the passive thyroid hormone with four iodine atoms and T3, which is the active thyroid hormone with three iodine atoms. In order to activate T4, the body needs a selenium-containing enzyme called deiodinase. This enzyme works by removing an iodine atom from the passive T4 hormone, which is then converted into active T3.
In our part of the world, however, selenium deficiency is quite common because of the low selenium content in the agricultural soil. That is why farmers for decades have supplemented their livestock with selenium to improve fertility and prevent various deficiency diseases. Vitamin A, iron, and zinc are also important for an optimal thyroid function.
Vitamin D plays a key role in child growth by regulating bone development. Vitamin D is also important for the immune defense and for preventing autoimmune diseases, such as Hashimoto’s disease that causes hypothyroidism and Graves’ disease that causes hyperthyroidism. Pregnant women are advised to take vitamin D all year round, and the same goes for children up to the age of four years.

Facts about iodine sources and iodine-enriched table salt

• There is a lot of iodine in fish, shellfish, seaweed, algae, fish sauce, eggs, and dairy products
• The iodine content in vegetables is limited and depends on the soil they have grown in
• People who do not eat fish or shellfish or are vegetarian/vegan risk an iodine deficiency
• The iodine content in sea salt and Himalayan salt is low and not able to cover the need for the nutrient
• Certain types of table salt are iodine-enriched

Avoid iodine-enriched table salt that contains aluminum as an anticaking agent. Too much aluminum in the body can harm the central nervous system

References:

Jessica Rigutto-Farebrother. Optimizing Growth: The Case for Iodine. Nutrients 2024

University of South Australia. Poor iodine levels in women pose risks to fetal intellectual development in pregnancy. Science Daily 2021

Jane S. et al. Iodine Excretion and Intake in Women of Reproductive Age in South Australia Eating Plant-Based and Omnivores Diets. International Journal of Environmental Research and Public Health 2021

Masahiro Kawahara et al. Neurotoxicity of aluminum and its link to neurodegenerative diseases. Metallomics Research 2021