The Silent Epidemic of Iodine Deficiency


  • Iodized salt is the chief source of iodine in the industrialized world.
  • Rates of iodine deficiency have reached epidemic levels, increasing fourfold over the past 40 years.
  • Recent scientific analysis reveals that many commercial table salt brands now contain inadequate amounts of iodine.
  • Iodine is critical to healthy thyroid function.
  • Inadequate iodine intake causes weight gain, low energy, depression, cardiovascular disease, cognitive decline, and a variety of cancers.
  • Iodine is vital to breast health in older women, with low intake correlated to increased risks for breast cancer and fibrocystic breast disease.

Unknowingly Robbing Our Bodies

In nature, iodine is a relatively rare element. It’s found in abundance in the ocean. Its presence in soil, on the other hand, is very low in many places around the world, including the United States.

Iodine is essential to life and especially crucial for brain development in children, making its deficiency the number one cause of preventable mental retardation worldwide.

It also plays a central role in healthy function of your thyroid gland. This is why the most visible symptom of iodine deficiency is goiter—the unsightly, painful enlargement of the thyroid gland that manifests as an enormous swelling around the neck and larynx.

While goiter was relatively common a few generations ago, most middle age and younger Americans have never seen it. This is largely due to the industry practice of salt iodization in this country, first implemented in the 1920s after the effects of iodine deficiency were recognized and since emulated around the world.2,5,6 (The Morton company was the first to add iodine to salt in 1924, after a successful public health campaign.)7 Unfortunately, as evidenced by recent FDA findings, many table salt makers are now failing to add iodine in quantities sufficient to support optimal health.

Other consequences of iodine deficiency, so-called iodine deficiency disorders (IDD), are subtle and may inflict greater damage.6,8 It is estimated that IDDs affect between 800 million and 2 billion people worldwide; reduction in salt intake is likely to drive those numbers still higher.2,9-11

The health benefits of reducing salt intake have been well established.9,12,13 Millions of Americans are slashing their use of salt to protect themselves against high blood pressure and cardiovascular disease.

But by cutting our salt intake we are also cutting our iodine intake, which is why mean urinary iodine levels (a measure of iodine sufficiency) plummeted by more than half over a 20-year period.4,14 Additional, otherwise healthy behaviors have also contributed to inadequate iodine intake. (See Table 1.)

The danger of low dietary iodine is further compounded by your body’s decreased ability to utilize it, the result of contamination by a ubiquitous environmental toxin called perchlorate.

Originally developed for explosives and rocket fuel,18 perchlorate now pervades ground water and food supplies throughout the US. It’s even used as a flavor-enhancer in certain foods.19-21 Perchlorate blocks the thyroid gland’s ability to absorb and utilize dietary iodine, an effect that is of concern when iodine intake drops off.18,22

The US recommended dietary allowance (RDA) for iodine is 150-290 micrograms (mcg) for adults, while the Food and Nutrition Board of the Institute of Medicine has set the tolerable upper limit at 1,100 mcg.18,23,24

By way of comparison, the average daily Japanese consumption of iodine ranges from 5,280 to 13,800 mcg of iodine, with no harmful effects and a host of benefits.18,25,26 The Japanese experience is shedding new light on the importance of iodine, not only for thyroid health, but on other body functions as well. In particular, compelling evidence is emerging about the role of iodine in maintaining breast health, a major concern for millions of American women.

Since thyroid function is a puzzle to many people, we’ll begin with a brief overview of that important gland and its requirements for iodine. Then we’ll turn to the role of iodine in maintaining breast health, particularly in preventing breast cancer and fibrocystic breast disease.

Your Thyroid Gland and the Role of Iodine

Your thyroid gland is located in the front of your neck, just below your voice box. The thyroid produces two forms of thyroid hormone, both of which are derived from the amino acid tyrosine and several atoms of iodine. Thyroid hormones control your body’s metabolism, regulating everything from body temperature and heart rate to glucose consumption and even blood lipid levels.27-29

Too much thyroid hormone (hyperthyroidism) results in an excessively high metabolic rate. People with this condition have rapid heart rates and often palpitations,29 excessive sweating, and may feel much warmer than other people do, even in a cool room. In extreme cases they may lose weight and experience muscle weakness.

Too little thyroid hormone (hypothyroidism) results in just the opposite set of symptoms: a slower than normal heart rate,29 a chronic feeling of being cold, constipation, unexplained weight gain, dry skin, hair loss or coarse dry hair, weakness, muscle aches, depression, and fatigue.30,31 In extreme cases, people with low thyroid function experience cognitive decline,32 and babies born to mothers with inadequate iodine levels are at high risk for a unique form of mental retardation known as cretinism. Cognitive impairment caused by low thyroid function is reversible with iodine or thyroid hormone supplementation.32,33

Both over- and under-production of thyroid hormone are associated with the thyroid gland swelling known as goiter. In hyperthyroidism, the goiter is the result of inflammation of the gland as it is under attack by an overactive immune system.

In hypothyroidism, the goiter develops as the thyroid attempts to make more thyroid hormone in the absence of sufficient dietary iodine.

Iodine deficiency is the most common cause of goiter, and since it causes hypothyroidism, is also the most common endocrine (glandular) problem in the world.18 Iodine deficiency is most prevalent in people who live far inland, away from the oceans that provide our best source of iodine. Those areas are commonly referred to as “goiter belts,” because of the high rates of impaired thyroid function.5

Iodine deficiency disorders can produce symptoms of low thyroid function (hypothyroidism) even without abnormalities in measured thyroid hormone levels.34 Recent evidence suggests, for example, that iodine deficiency is linked to obesity, cognitive impairment, psychiatric disorders, fibromyalgia, and a variety of cancers.34

Paradoxically, another major consequence of mild-to-moderate iodine deficiency in older adults is hyperthyroidism (excessive thyroid function), especially in women.35 This is the result of rapidly growing thyroid gland nodules that over-produce thyroid hormone; it can trigger cardiac arrhythmias, osteoporosis, and muscle wasting.35

Among those negative consequences is the impact of iodine deficiency on breast health. Compelling data are emerging that link iodine deficiency to breast cancers and high rates of fibrocystic breast disease, two of the greatest concerns of older women in the US. It’s worth exploring those data here; including evidence that iodine supplementation can promote healthy breast tissue.

Fortunately, all iodine deficiency disorders and related health dangers can be prevented by adequate intake of iodine.8

The Role of Iodine in Cardiovascular Health

Iodine and iodine-rich foods enjoy a long history as natural therapies for hypertension and cardiovascular disease.4 Even when no overt symptoms are evident, hypothyroidism can contribute to heart disease and stroke, and it increases the risk of death from these conditions.63-65

Thyroid dysfunction creates unfavorable disturbances in lipid profiles, elevating low-density lipoprotein (LDL) and total cholesterol levels and raising the risk of atherosclerosis.27,28,66 Hypothyroidism also weakens the heart muscle, causing it to “squeeze” less firmly with each contraction; it can cause cardiac arrhythmias as well.29,63,67 These effects may not be evident at rest, but become important during moderate exercise.63 Low thyroid function is also associated with higher waist-to-hip ratios, an obesity-related risk factor for cardiovascular disease.68

Restoring normal thyroid function helps reverse multiple cardiovascular risk factors, most notably adverse lipid profiles.27 Yet mainstream medicine has traditionally used thyroid hormone treatment, which may be dangerous if it over-drives an already weakened heart.69

Iodine therapy shows promise in safely and effectively modulating these health concerns.

Iodine Protects Against Stomach Cancer

The thyroid gland, breast tissue, and portions of the digestive tract share similarities in that all of them contain a rich concentration of iodine.42,70 Stomach lining cells in particular concentrate iodine, capitalizing on its antioxidant effects.71

This has led medical researchers to investigate whether iodine deficiency plays a role in cancers of the digestive tract.

They found that people living in iodine-deficient areas of the world are not only prone to iodine-deficiency goiters, but also have higher rates of stomach cancers.71 Stomach cancer patients in a landlocked area of Iran were 2.5 times as likely to have severe iodine deficiency than control patients.72 Gastric cancer is the most common cancer in parts of northeastern Turkey where iodine deficiency is common, and iodine levels in gastric cancer tissue were markedly lower than those in surrounding healthy tissue.73

Increased iodine intake has been strongly correlated with a reduction in stomach cancer rates in recent years.74

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