While largely recognized for the role it plays in thyroid health, iodine plays a bigger role than that when it comes to women’s health. It plays an important role in oestrogen metabolism, breast tissue development, ovulation, foetal development and more. Many people are unaware that female breast tissue has a greater concentration of iodine, and thus, requires more of this nutrient. The full extend of iodine’s role in women’s health is yet to be uncovered, but there’s a growing body of research exploring just how essential this nutrient is. Iodine is heavily concentrated in the thyroid, breasts, ovaries and cervix, which highlights the areas in which it plays a role in women’s health.

Iodine and thyroid function

The concentration of iodine in the thyroid is very high, more than 1000 times that in the muscles. Approximately one-fourth of thyroid iodine is in the two main thyroid hormones, T4 (thyroxine) and T3 (triiodothyronine). Thyroxine itself is nearly two-thirds iodine. The thyroid hormones, particularly thyroxine, are responsible for our basal metabolic rate (BMR) – that is how our body uses energy. Thyroid hormones are required for cell respiration, and the production of energy. They are also needed for normal growth and development, protein synthesis, and energy metabolism.

Iodine is essential for the production of the body’s thyroid hormones and is required for normal thyroid function. Goiter, an enlargement of the thyroid gland, develops when this important metabolic gland does not have enough iodine to manufacture hormones. The thyroid increases its cell size to trap more iodine, which leads to the whole gland increasing in size, creating swelling in the neck. If inadequate iodine intake continues, the production of thyroid hormone will start to decline, which can lead to symptoms such as fatigue, weight gain, constipation, coldness of the body, menstrual irregularities and hair loss. This condition is known as hypothyroidism and it is more common in women than man.

Iodine and breast health

Research shows that iodine has beneficial effects with regards to breast cancer risk, fibrocystic breast disease, premenstrual breast tenderness and mammary dysplasia. Iodine seems to have antioxidant properties in the breasts, and protect them from cellular damage. (1)

Iodine also helps promote the normal development of breast tissue and protects against the formation of abnormal cells. All this might partially explain why diets containing sufficient amounts of iodine are associated with reduced risk of breast cancer. (2)

In addition, iodine is associated with protective properties against fibrocystic breasts – a condition characterized by lumpiness in one or both breasts. Iodine supplementation has been shown to be beneficial in treating this condition. (3)

Iodine in fertility, pregnancy and lactation

It seems iodine also plays a role in fertility and conception. Research from 2018 suggests that women with lower iodine status have a longer time to conception compared to those with adequate iodine levels. (4)

Iodine is required for ovulation, progesterone production and oestrogen metabolism. Iodine may play a helpful role for reducing PMS as well.

Severe iodine deficiency in utero is also associated with increased risk of miscarriage, stillbirth, congenital abnormalities, and low birth weight. (5)

In pregnancy, iodine is essential for the baby’s growth, brain and thyroid development. Even mild iodine deficiency during pregnancy is associated with neurological and cognitive impairments in children. Children of iodine-deficient mothers are more likely to have a lower verbal IQ, reading accuracy and comprehension than those born to mothers with sufficient iodine levels during pregnancy. (6)

Note, that the iodine requirements for pregnant and lactating women increase considerably from 150mcg / day to 220 and 270 mcg / day.

Iodine and the immune system

Iodine may be important in the body as a way of helping to deactivate unwanted bacteria – similar to the way we use iodine-containing preparations as skin disinfectants or water purifiers. In this way, and perhaps others, iodine may play an important role in supporting our immune system.

Correcting iodine deficiency

Deficiencies of iodine can be very common, especially in areas where the soil is depleted. As the soil contains various amounts of iodine, it will affect the iodine content of crops. Several months of iodine deficiency can lead to goiter and/or hypothyroidism. Iodine itself usually will not cure goiter and hypothyroidism but it will often slow down their progression. The mineral selenium is also required for the conversion of thyroid hormones.

Iodine is well absorbed from the stomach into the blood. About 30% goes to the thyroid gland, depending on the need. Iodine is eliminated rapidly. The remaining iodine is filtered by the kidneys into the urine. Our bodies do not conserve iodine as well as iron for example, and we must obtain it regularly from the diet. However, it is important to take care when supplementing iodine.

High iodine intake may actually reduce thyroxine production and thyroid function. People with thyroid disease need to be particularly careful when supplementing iodine, as both too much and too little can make the situation worse.

It is recommended to consult your health care provider if you think there is an iodine imbalance. Your doctor can run blood tests for you and give you advice on the amounts you need to supplement, while monitoring you closely.

Recommended Dietary Allowances (RDA) for iodine

Age	Male	Female	Pregnancy	Lactation
Birth to 6 months	110 mcg	110 mcg
7-12 months	130 mcg	130 mcg
1-3 years	90 mcg	90 mcg
4-8 years	90 mcg	90 mcg
9-13 years	120 mcg	120 mcg
14-18 years	150 mcg	150 mcg
19+ years	150 mcg	150 mcg	220 – 250 mcg	290 mcg

Sources of iodine

Seaweed (such as kelp, kombu, and wakame) is one of the best sources of iodine, but it is highly variable in content. Other good sources include seafood, dairy foods (partly due to the use of iodine feed supplements and iodophor sanitizing agents in the dairy industry), grain products, and eggs. Iodine is also present in in human breast milk.

Fruits and vegetables contain iodine, but the amount varies depending on the iodine content of the soil, fertilizer use, and irrigation process. Iodine content in plant foods can range from as little as 10mcg/kg to 1 mg/kg dry weight (7).

Selected Food Sources of iodine

Food	Approximate mcg per serving	Percent DV %
Seaweed, whole or sheet, 1 g	16 to 2,984	11% to 1989%
Cod, cooked, 85g	99	66%
Yogurt, plain, low fat, 240g	75	50%
Iodized salt 1.5g (app. ¼ tsp)	71	47%
Milk, reduced fat, 245ml	56	37%
Fish sticks, 85 g	54	36%
Bread, white, enriched, 2 slices	45	30%
Shrimp, 85g	35	23%
Egg, 1 large	24	16%
Tuna, canned in oil, 85g	17	11%
Prunes, dried, 5 prunes	13	9%
Cheese, cheddar, 28g	12	8%
Lima beans, mature, boiled, 65g	8	5%