Iodine deficiency epidemic
Although most of us believe we are not deficient in iodine since the fortification of salt with iodine, the fact is most people are deficient and don’t know it. Due to changes in food intake, eating patterns and food production methods, iodine intake has been decreasing in the U.S. since the early 70’s. Even worse, we are exposed to increasing levels of environmental toxins that either block the absorption of iodine or block its actions in the body.
Author: Joseph Pizzorno, ND Source: Vitamin Retailer Magazine, November 2009
According to the National Health and Nutrition Survey (NHANES), 24-hour urine levels of iodine have decreased from average levels of 320 mcg/L during 1971-1974 to 165 mcg/L in 2001-2002 – a drop of almost 50%.1,2 NHANES (2003-2004) found a urinary iodine level of <50 mcg/L in 12% of the U.S. population, indicating severe deficiency (<100 mcg/L is indicative of deficiency).3 Iodine levels in the breast milk of nursing mothers in Boston showed that only 47% contained sufficient amounts of iodine to meet infant requirements.4 This dramatic drop in iodine intake is made worse by an increasing level of iodine uptake inhibitors – perchlorate, nitrate, and thiocyanate – in the food supply and environment.
Why has this happened?
Iodised salt is very effective in normalising iodine intake. The problem is we eat less iodised salt. This has occurred for 2 reasons: first, we’ve all been told to decrease salt intake because excess consumption can elevate blood pressure. However, the more important cause is that almost everyone now eats more processed foods and meals at restaurants—most of these do not use iodised salt! This is made worse by the fact that the iodised salt sold for home use often contains less iodine than stated on the label and two other good sources of iodine, bread and milk products, now contain very little due to changes in how they are produced.
Dairy products used to contain a significant amount of iodine since it was used to disinfect cow udders and dairy processing equipment. Now, however, antibiotics and other methods are used instead. In addition, less iodine is used in feed supplements. With these changes, the average iodine content of U.S. whole cow’s milk had decreased from 602 mcg/L in 1978 to 155 mcg/L in 1990. A 2002 study found as little as 88 mcg/L, less than 15% of those measured in 1978.5 This is worsened by the substitution of soft drinks for milk by children, adolescents and adults so we drink less milk which has less iodine.6,7,8
Another significant source of iodine in the past was bread since iodate-based bread conditioners were used to prolong shelf life. Today, most commercial bakeries are using bromate-based conditioners instead.
Iodised salt may have less than we think because it evaporates over time from salt containers and shakers.9 The rate of evaporation is increased by humidity and heat. In the summer in humid areas of the country, the half life of iodine in salt can be as little as one week! Many in the natural products field use sea salt as a supposed better alternative to regular salt. Unfortunately, it is not iodised.
What happens when iodine levels are too low?
Everyone is aware that iodine is required to produce thyroid hormones, so if levels are too low people suffer hypothyroidism. This is one reason the incidence of clinical and subclinical hypothyroidism affects 10-15% of the population, especially women. Probably more prevalent are the other problems found in people with low to marginal levels of iodine. It is well known that low iodine levels in fetuses and children leads to impaired mental development and research has now shown an increased incidence of fibrocystic breast disease and breast cancer.10,11 Some research has also shown that iodine deficiency may contribute to obesity, attention deficit hyperactivity disorder (ADHD), psychiatric disorders, and fibromyalgia.
Are sea vegetables a good source of iodine?
Although sea vegetables, i.e., seaweed, are common in many traditional diets – especially the Japanese, they are not commonly consumed in the U.S. Most people think of sea vegetables as a food source for iodine. Some are, but many aren’t, and you have to eat more than just a few sprinkles. Also, some may be contaminated with toxic metals.
As the table below shows, the amount of iodine in seaweed varies greatly.12
Just as sea vegetables have a high affinity for iodine, they also have a high affinity for toxic metals such as arsenic, lead, cadmium and mercury.13 So be sure to only use those which are certified organic and preferably with an analysis of iodine and toxic metal content.
Iodine deficiency is a common and growing problem in North America. Fortunately, eating enough of the right kind of seaweed will replenish iodine supplies.
- Hollowell JG, Staehling NW, Hannon WH, et al. 1998 Iodine nutrition in the United States: trends and public health implications: iodine excretion data from the National Health and Nutrition Surveys I and III (1971–1974 and 1988–1994). J Clin Endocrinol Metab. Oct1998;83(10):3401-8 View Abstract
- Caldwell KL, Jones R, Hollowell JG. Urinary iodine concentration: United States National Health And Nutrition Examination Survey 2001-2002. Thyroid. Jul2005;15(7):692-9 View Abstract
- Caldwell KL, Miller GA, Wang RY, et al,. Iodine status of the U.S. population, National Health and Nutrition Examination Survey 2003-2004. Thyroid. Nov2008;18(11):1207-14
- Pearce EN, Leung AM, Blount BC, et al. Breast milk iodine and perchlorate concentrations in lactating Boston-area women. J Clin Endocrinol Metab 2007;92:1673-1677 View Abstract
- Pearce EN, Pino S, He X, et al. Sources of dietary iodine: bread, cows’ milk, and infant formula in the Boston area. J Clin Endocrinol Metab. Jul2004;89(7):3421-4 View Abstract
- Keller KL, Kirzner J, Pietrobelli A, et al. Increased sweetened beverage intake is associated with reduced milk and calcium intake in 3- to 7-year-old children at multi-item laboratory lunches. J Am Diet Assoc. Mar2009; 109(3):497-501 View Abstract
- Rampersaud GC, Bailey LB, Kauwell GP. National survey beverage consumption data for children and adolescents indicate the need to encourage a shift toward more nutritive beverages. J Am Diet Assoc. Jan2003;103(1):97-100 View Abstract
- Bleich SN, Wang YC, Wang Y, et al. Increasing consumption of sugar-sweetened beverages among US adults: 1988-1994 to 1999-2004. Am J Clin Nutr. Jan2009;89(1):372-81 View Abstract
- Dasgupta PK, Liu Y, Dyke JV. Iodine nutrition: iodine content of iodized salt in the United States. Environ Sci Technol. Feb2008;42(4):1315-23 View Abstract
- Patrick L. Iodine: deficiency and therapeutic considerations. Altern Med Rev. Jun2008;13(2):116-27
- Aceves C, Anguiano B, Delgado G. Is iodine a gatekeeper of the integrity of the mammary gland? J Mammary Gland Biol Neoplasia. Apr2005;10(2):189-96 View Abstract
- Teas J, Pino S Critchley A and Braverman LE. Variability of Iodine Content in Common Commercially Available Edible Seaweeds. THYROID 2004;14:836-41 View Abstract
- van Netten C, Hoption Cann SA, Morley DR, van Netten JP. Elemental and radioactive analysis of commercially available seaweed. Sci Total Environ. Jun2000;255(1-3):169-75 View Abstract