Many women have trouble getting pregnant initially because their thyroid hormones are too low and are often put on synthroid (synthetic T4) to help boost fertility. However, these women may be missing a very important mineral called iodine! It takes 4 iodine molecules to make T4 and three iodine molecules to make T3, your active forms of thyroid hormone. Iodine is essential at all stages of life, but particularly for fetal brain development during the first 4-6 weeks of pregnancy (1). Iodine deficiency is the most common preventable cause of mental retardation worldwide (called cretinism).
Now the Lancet has just released a study linking low iodine status in UK pregnant women to lowered cognition in their children years later (2). Specifically, mothers with low iodine levels had children in the lowest quartile for verbal IQ, reading accuracy, and reading comprehension (2). Earlier studies found that nearly 1/5th of UK women (child-bearing age) did not intake enough iodine daily (3).
There are an increasing proportion of women who are avoiding common sources of iodine for safety reasons, such as reducing salt intake to lower blood pressure, avoiding fish due to high mercury content, or avoiding dairy because of the hormone and toxin overload. The NHANES data from the USA found the average adult iodine levels decreased by over 50% from the 1970s to the 1990s and 35.3% of pregnant women in 2008 had low iodine levels (1). The recommended daily allowance (RDA) for iodine is 250 mcg during pregnancy and 290 mcg for breastfeeding for women with adequate levels of iodine, but women deficient in iodine may need higher amounts for adequate supplementation.
You can get iodine naturally from the following sources:
Seaweed (kelp, nori, dulce) Saltwater Fish (Alaskan salmon, codfish, haddock, sardines, trout) and Shellfish (shrimp, clams, lobster, oysters) Organic Iodine fortified dairy products (milk/cheese/yogurt) Organic Eggs Iodized Salt Plants Grown in Iodine-Rich Soil (potatoes, spinach, beet leaves, asparagus).
It is important to get tested for iodine deficiency before taking iodine supplementation because excessive amounts can cause over-stimulation of the thyroid. If you have signs of fatigue, neck swelling/congestion, difficulty concentrating, difficulty losing weight, hair loss, brittle nails, infertility, miscarriages, hypothyroidism, and/or intolerance to cold environments, please call our office to get tested for iodine deficiency!
1. Leung AM, Pearce EN, Braverman LE. Sufficient iodine intake during pregnancy: just do it. Thyroid. 23:1;7-8. doi:10.1089/thy.2012.0491.
2. Bath S, et al. Effect of inadequate iodine status in UK pregnant women on cognitive outcomes in their children: results from the Avon Longitudinal Study of Parents and Children (ALSPAC). The Lancet, Early Online Publication 22 May 2013. doi:10.1016/S0140-6736(08)61345-8.
3. Bath S, et al. Iodine status of UK women of childbearing age. J of Human Nutrition and Dietetics. Aug 2008. 21:4;379-80. doi: 10.1111/j.1365-277X.2008.00881_9.x.