To complement any alternative or conventional treatment for autoimmune or subclinical hypothyroidism women in the preconception stage can begin to fortify and prepare their bodies for a healthy pregnancy by eating a diet that encourages optimal thyroid function. Research has shown iodine, selenium, zinc, and iron to be essential nutrients for the proper function of all thyroid hormone cycle processes. As such, they should be given special attention when developing dietary guidelines for a hypothyroid woman wishing to conceive.
Iodine is an essential trace mineral needed for the synthesis of thyroid hormone. When iodine is deficient, thyroid hormone production decreases. In order for the mother to be capable of producing enough thyroid hormone for both herself and the baby iodine intake must increase from 150mcg to 220mcg per day. (Leung, 2012) Pregnant women should be sure to consume an adequate amount of iodine-rich foods such as sea vegetables, cod, haddock, ocean perch, and iodine-fortified foods.
Iodine deficiency can manifest as muscle cramps, cold hands and feet, weight gain, poor memory, constipation, depression, and headache. Inadequate use of iodized salt, exposure to goitrogenic chemicals, soil erosion, mineral depletion, the addition of bromine to processed foods, and the nutrient-poor, standard American diet all contribute to iodine deficiency in the United States. (Fallon, 1999)
Selenium requirements increase during pregnancy from 55mcg to 60 mcg per day. Selenium is an essential nutrient that is used in the process of making thyroid hormone. It is thought that even a mild to moderate nutritional selenium deficiency might be responsible for the development of autoimmune thyroid disorders in patients with genetic predisposition. Selenium substitution may improve immune function as well as decrease the inflammatory activity in patients with autoimmune thyroiditis, thus lessening the risk of miscarriage. In addition, research shows that selenium supplementation may decrease inflammatory activity in thyroid autoimmunity. Good food sources include brazil nuts, cremini and shiitake mushrooms, eggs, and seafood, particularly cod, shrimp, tuna (limit to 6 ounces a week), sardines and wild caught salmon.
Zinc is a crucial mineral for the body, particularly to the thyroid. It plays a critical role is the conversion of inactive hormone (T4) to active hormone (T3) as well as allowing T3 to work effectively within each of our cells. Though true zinc status is difficult to measure, low serum levels are commonly linked to hypothyroidism and supplementation has been shown to improve thyroid function. Independent of the thyroid, zinc participates in hundreds of other reactions in the body; its role in cell division and differentiation, gene expression, fetal growth and lactation all reinforce the importance of zinc status during pregnancy. The consequences of zinc deficiency in pregnancy can be severe, resulting in miscarriage, preeclampsia, pre-term delivery, or low birth weight.
Pregnancy increases a woman’s recommended daily allowance from 8mg to 12mg per day. Prenatal supplements rarely include zinc due to potential absorption interference with iron and folate and it is estimated that 82 percent of pregnant women have inadequate dietary intake. Adequate dietary zinc must be a priority for any woman considering pregnancy, particularly so for women with hypothyroidism. Good food sources include beef, legumes, nuts, dairy and seafood. Vegetarian and vegan women may be at greater risk for inadequate intake, particularly as zinc competes for absorption with vegetarian-sourced iron.
Iron status has great implication for the thyroid. The thyroid is dependent on iron in order to make thyroid hormone. A woman’s iron needs will increase during pregnancy due to the dramatic increases in red blood cell production and plasma volume. Iron deficiency during pregnancy increases the risk of premature birth and increases risk of low infant iron stores, impaired cognitive function, and behavioral development.
Iron deficiency is the world’s most common nutritional deficiency, and major risk groups for iron deﬁciency include women of childbearing age, pregnant women, and lactating postpartum women. One study found that 18 percent of pregnant women in the United States had iron deficiency. Rates of deficiency were 6.9 percent among women in the first trimester, 14.3 percent in the second trimester, and 29.7 percent in the third trimester. Pregnancy increases the female recommended dietary allowance from 18mg to 27mg per day.
There are two forms of dietary iron: heme (animal sources) and nonheme (plant sources and iron-fortified foods). In general, heme iron is more available to the body than nonheme iron. Sources of heme iron include beef, pork and lamb, as well as seafood like oysters, clams, salmon, and shrimp. Sources of nonheme iron include nuts, beans, fortified grain products, leafy greens, and dried fruits like raisins, prunes, and apricots. Vitamin C enhances the bioavailability of nonheme iron. Calcium may reduce the bioavailability of both heme and nonheme iron.
Optimal thyroid health through nutrition involves a synergistic relationship between these four nutrients, which are independently and collectively vital. Women should be encouraged to prepare for pregnancy by consuming a diet rich in these vital minerals. Ideally, every pregnancy would start with a nutrient-rich, preconception diet. Because iodine, selenium, zinc and iron are of heightened importance to pregnancy and thyroid function, women with subclinical or auto-immune hypothyroidism should take extra care to address their nutrition needs for optimal maternal and fetal health.
By Haylee Nye, NCNM Naturopathic Medicine Program Edited by Dr Elise Schroeder