What is the evidence that all pregnant women should follow the American Thyroid Association’s recommendation to take a daily iodine supplement?
Iodine Supplements Before, During, and After Pregnancy
Although severe iodine deficiency was eliminated in the United States nearly a century ago, after the introduction of iodized salt, iodine intake has declined in recent decades. Public health efforts to limit salt intake to decrease cardiovascular risk, in conjunction with increasing use of non-iodized salt, may in part be to blame.
Now, not adding salt to foods is a good thing, as sodium is considered the second leading dietary killer in the world—second only to not eating enough fruit. But if you do add table salt, make sure it’s iodized, as it is a myth, and often also false advertising, that so-called “natural” sea salt contains significant amounts of iodine.
Fruits and vegetables provide iodine, but the amounts can vary depending on where it’s grown; how much iodine is in the soil. Because iodine is particularly important for fetal brain development, there’s a recommendation that all U.S. women who are pregnant, lactating, or even planning a pregnancy should ingest dietary supplements containing 150mcg of potassium iodide per day.
Is there evidence that they’re not getting enough now? Well, we’d like to see urine levels in pregnant women over 150. But in the U.S., pregnant women only average about 125. For example, a recent survey in New York City showed only about half of pregnant women were making the cut. Don’t most women take prenatal vitamins, though?
Only about half of prenatal multivitamins contain any iodine at all. And so, only about one in five pregnant women in the U.S. are following the recommendations of the American Thyroid Association to take a daily iodine supplement—specifically in the form of potassium iodide rather than seaweed, as the levels in seaweed are subject to natural variability. Though the iodine content was as much as 90% off in some of the potassium iodide prenatal supplements, the kelp supplements varied even wider, off by as much as 170%.
Now, the American Thyroid Association admits they don’t have evidence that the current borderline insufficiency levels are leading to undesirable outcomes, and so, their recommendation that all pregnant women take iodine supplements is a bit tenuous. But until such data are available, they figure better safe than sorry.
A randomized, placebo-controlled interventional trial would answer the question once and for all, but the existing evidence for iodine supplementation during pregnancy is so convincing that it would be considered unethical to randomize pregnant women to a placebo. And so, when it comes to sufficient iodine intake during pregnancy, I’d recommend, just do it.
To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Katie Schloer.
Please consider volunteering to help out on the site.
- C A Swanson, E N Pearce. Iodine insufficiency: a global health problem? Adv Nutr. 2013 Sep 1;4(5):533-5.
- Public Health Committee of the American Thyroid Association, D V Becker, L E Braverman, F Delange, J T Dunn, J A Franklyn, J G Hollowell, S H Lamm, M L Mitchell, E Pearce, J Robbins, J F Rovet. Iodine supplementation for pregnancy and lactation-United States and Canada: recommendations of the American Thyroid Association. Thyroid. 2006 Oct;16(10):949-51.
- P K Dasgupta, Y Liu, J V Dyke. Iodine nutrition: iodine content of iodized salt in the United States. Environ Sci Technol. 2008 Feb 15;42(4):1315-23.
- S S Lim, T Vos, A D Flaxman, G Danaei, K Shibuya, H Adair-Rohani, M Amann, H R Anderson, K G Andrews, M Aryee, C Atkinson, L J Bacchus, A N Bahalim, K Balakrishnan, J Balmes, S Barker-Collo, A Baxter, M L Bell, J D Blore, F Blyth, C Bonner, G Borges, R Bourne, M Boussinesq, M Brauer, P Brooks, N G Bruce, B Brunekreef, C Bryan-Hancock, C Bucello, R Buchbinder, F Bull, R T Burnett, T E Byers, B Calabria, J Carapetis, E Carnahan, Z Chafe, F Charlson, H Chen, J S Chen, A T Cheng, J C Child, A Cohen, K E Colson, B C Cowie, S Darby, S Darling, A Davis, L Degenhardt, F Dentener, D C Des Jarlais, K, Devries, M Dherani, E L Ding, E R, Dorsey, T Driscoll, K Edmond, S E Ali, R E Engell, P J Erwin, S Fahimi, G Falder, F Farzadfar, A Ferrari, M M Finucane, S Flaxman, F G Fowkes, G Freedman, M K Freeman, E Gakidou, S Ghosh, E Giovannucci, G Gmel, K Graham, R Grainger, B Grant, D Gunnell, H R Gutierrez, W Hall, H W Hoek, A Hogan, H D Hosgood 3rd, D Hoy, H Hu, B J Hubbell, S J Hutchings, S E Ibeanusi, G L Jacklyn, R Jasrasaria, J B Jonas, H Kan, J A Kanis, N Kassebaum, N Kawakami, Y H Khang, S Khatibzadeh, J P Khoo, C Kok, F Laden, R Lalloo, Q Lan, T Lathlean, J L Leasher, J Leigh, Y Li, J K Lin, S E Lipshultz, S London, R Lozano, Y Lu, J Mak, R Malekzadeh, L Mallinger, W Marcenes, L March, R Marks, R Martin, P McGale, J McGrath, S Mehta, G A Mensah, T R Merriman, R Micha, C Michaudm V Mishra, K Mohd Hanafiah, A A Mokdad, L Morawska, D Mozaffarian, T Murphy, M Naghavi, B Neal, P K Nelson, J M Nolla, R Norman, C Olives, S B Omer, J Orchard, R Osborne, B Ostro, A Page, K D Pandey, C D Parry, E Passmore, J Patra, N Pearce, P M Pelizzari, M Petzold, M R Phillips, D Pope, C A Pope 3rd, J Powles, M Rao, H Razavi, E A Rehfuess, J T Rehm, B Ritz, F P Rivara, T Roberts, C Robinson, J A Rodriguez-Portales, I Romieu, R Room, L C Rosenfeld, A Roy, L Rushton, J A Salomon, U Sampson, R Sanchez-Riera L, Sanman E, Sapkota A, Seedat S, Shi P, Shield K, Shivakoti R, Singh GM, Sleet DA, Smith E, Smith KR, Stapelberg NJ, Steenland K, Stöckl H, Stovner LJ, Straif K, Straney L, Thurston GD, Tran JH, Van Dingenen, A van Donkelaar, J L Veerman, L Vijayakumar, R Weintraub, M M Weissman, R A White, H Whiteford, S T Wiersma, J D Wilkinson, H C Williams, W Williams, N Wilson, A D Woolf, P Yip, J M Zielinski, A D Lopez, C J Murray, M Ezzati, M A AlMazroa, ZA Memish. A comparative risk assessment of burden of disease and injury attributable to 67 risk factors and risk factor clusters in 21 regions, 1990-2010: a systematic analysis for the Global Burden of Disease Study 2010. Lancet. 2012 Dec 15;380(9859):2224-60.
- S Y Lee, A M Leung, X He, L E Braverman, E N Pearce. Iodine content in fast foods: comparison between two fast-food chains in the United States. Endocr Pract. 2010 Nov-Dec;16(6):1071-2.
- J J Gahche, R L Bailey, L B Mirel, J T Dwyer. The prevalence of using iodine-containing supplements is low among reproductive-age women, NHANES 1999-2006. J Nutr. 2013 Jun;143(6):872-7.
- A Stagnaro-Green, S Sullivan, E N Pearce. Iodine supplementation during pregnancy and lactation. JAMA. 2012 Dec 19;308(23):2463-4.
- R Pessah-Pollack, D C Eschler, Z Pozharny, T Davies. Apparent insufficiency of iodine supplementation in pregnancy. J Womens Health (Larchmt). 2014 Jan;23(1):51-6.
- A M Leung, E N Pearce, L E Braverman. Sufficient iodine intake during pregnancy: just do it. Thyroid. 2013 Jan;23(1):7-8.
- A Stagnaro-Green, M Abalovich, E Alexander, F Azizi, J Mestman, R Negro, A Nixon, E N Pearce, O P Soldin, S Sullivan, W Wiersinga; American Thyroid Association Taskforce on Thyroid Disease During Pregnancy and Postpartum. Guidelines of the American Thyroid Association for the diagnosis and management of thyroid disease during pregnancy and postpartum. Thyroid. 2011 Oct;21(10):1081-125.
- E N Pearce. U.S. iodine nutrition: where do we stand? Thyroid. 2008 Nov;18(11):1143-5.
- A M Leung, E N Pearce, L E Braverman. Iodine content of prenatal multivitamins in the United States. N Engl J Med. 2009 Feb 26;360(9):939-40.
Image thanks to il-young ko via flickr
Although severe iodine deficiency was eliminated in the United States nearly a century ago, after the introduction of iodized salt, iodine intake has declined in recent decades. Public health efforts to limit salt intake to decrease cardiovascular risk, in conjunction with increasing use of non-iodized salt, may in part be to blame.
Now, not adding salt to foods is a good thing, as sodium is considered the second leading dietary killer in the world—second only to not eating enough fruit. But if you do add table salt, make sure it’s iodized, as it is a myth, and often also false advertising, that so-called “natural” sea salt contains significant amounts of iodine.
Fruits and vegetables provide iodine, but the amounts can vary depending on where it’s grown; how much iodine is in the soil. Because iodine is particularly important for fetal brain development, there’s a recommendation that all U.S. women who are pregnant, lactating, or even planning a pregnancy should ingest dietary supplements containing 150mcg of potassium iodide per day.
Is there evidence that they’re not getting enough now? Well, we’d like to see urine levels in pregnant women over 150. But in the U.S., pregnant women only average about 125. For example, a recent survey in New York City showed only about half of pregnant women were making the cut. Don’t most women take prenatal vitamins, though?
Only about half of prenatal multivitamins contain any iodine at all. And so, only about one in five pregnant women in the U.S. are following the recommendations of the American Thyroid Association to take a daily iodine supplement—specifically in the form of potassium iodide rather than seaweed, as the levels in seaweed are subject to natural variability. Though the iodine content was as much as 90% off in some of the potassium iodide prenatal supplements, the kelp supplements varied even wider, off by as much as 170%.
Now, the American Thyroid Association admits they don’t have evidence that the current borderline insufficiency levels are leading to undesirable outcomes, and so, their recommendation that all pregnant women take iodine supplements is a bit tenuous. But until such data are available, they figure better safe than sorry.
A randomized, placebo-controlled interventional trial would answer the question once and for all, but the existing evidence for iodine supplementation during pregnancy is so convincing that it would be considered unethical to randomize pregnant women to a placebo. And so, when it comes to sufficient iodine intake during pregnancy, I’d recommend, just do it.
To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Katie Schloer.
Please consider volunteering to help out on the site.
- C A Swanson, E N Pearce. Iodine insufficiency: a global health problem? Adv Nutr. 2013 Sep 1;4(5):533-5.
- Public Health Committee of the American Thyroid Association, D V Becker, L E Braverman, F Delange, J T Dunn, J A Franklyn, J G Hollowell, S H Lamm, M L Mitchell, E Pearce, J Robbins, J F Rovet. Iodine supplementation for pregnancy and lactation-United States and Canada: recommendations of the American Thyroid Association. Thyroid. 2006 Oct;16(10):949-51.
- P K Dasgupta, Y Liu, J V Dyke. Iodine nutrition: iodine content of iodized salt in the United States. Environ Sci Technol. 2008 Feb 15;42(4):1315-23.
- S S Lim, T Vos, A D Flaxman, G Danaei, K Shibuya, H Adair-Rohani, M Amann, H R Anderson, K G Andrews, M Aryee, C Atkinson, L J Bacchus, A N Bahalim, K Balakrishnan, J Balmes, S Barker-Collo, A Baxter, M L Bell, J D Blore, F Blyth, C Bonner, G Borges, R Bourne, M Boussinesq, M Brauer, P Brooks, N G Bruce, B Brunekreef, C Bryan-Hancock, C Bucello, R Buchbinder, F Bull, R T Burnett, T E Byers, B Calabria, J Carapetis, E Carnahan, Z Chafe, F Charlson, H Chen, J S Chen, A T Cheng, J C Child, A Cohen, K E Colson, B C Cowie, S Darby, S Darling, A Davis, L Degenhardt, F Dentener, D C Des Jarlais, K, Devries, M Dherani, E L Ding, E R, Dorsey, T Driscoll, K Edmond, S E Ali, R E Engell, P J Erwin, S Fahimi, G Falder, F Farzadfar, A Ferrari, M M Finucane, S Flaxman, F G Fowkes, G Freedman, M K Freeman, E Gakidou, S Ghosh, E Giovannucci, G Gmel, K Graham, R Grainger, B Grant, D Gunnell, H R Gutierrez, W Hall, H W Hoek, A Hogan, H D Hosgood 3rd, D Hoy, H Hu, B J Hubbell, S J Hutchings, S E Ibeanusi, G L Jacklyn, R Jasrasaria, J B Jonas, H Kan, J A Kanis, N Kassebaum, N Kawakami, Y H Khang, S Khatibzadeh, J P Khoo, C Kok, F Laden, R Lalloo, Q Lan, T Lathlean, J L Leasher, J Leigh, Y Li, J K Lin, S E Lipshultz, S London, R Lozano, Y Lu, J Mak, R Malekzadeh, L Mallinger, W Marcenes, L March, R Marks, R Martin, P McGale, J McGrath, S Mehta, G A Mensah, T R Merriman, R Micha, C Michaudm V Mishra, K Mohd Hanafiah, A A Mokdad, L Morawska, D Mozaffarian, T Murphy, M Naghavi, B Neal, P K Nelson, J M Nolla, R Norman, C Olives, S B Omer, J Orchard, R Osborne, B Ostro, A Page, K D Pandey, C D Parry, E Passmore, J Patra, N Pearce, P M Pelizzari, M Petzold, M R Phillips, D Pope, C A Pope 3rd, J Powles, M Rao, H Razavi, E A Rehfuess, J T Rehm, B Ritz, F P Rivara, T Roberts, C Robinson, J A Rodriguez-Portales, I Romieu, R Room, L C Rosenfeld, A Roy, L Rushton, J A Salomon, U Sampson, R Sanchez-Riera L, Sanman E, Sapkota A, Seedat S, Shi P, Shield K, Shivakoti R, Singh GM, Sleet DA, Smith E, Smith KR, Stapelberg NJ, Steenland K, Stöckl H, Stovner LJ, Straif K, Straney L, Thurston GD, Tran JH, Van Dingenen, A van Donkelaar, J L Veerman, L Vijayakumar, R Weintraub, M M Weissman, R A White, H Whiteford, S T Wiersma, J D Wilkinson, H C Williams, W Williams, N Wilson, A D Woolf, P Yip, J M Zielinski, A D Lopez, C J Murray, M Ezzati, M A AlMazroa, ZA Memish. A comparative risk assessment of burden of disease and injury attributable to 67 risk factors and risk factor clusters in 21 regions, 1990-2010: a systematic analysis for the Global Burden of Disease Study 2010. Lancet. 2012 Dec 15;380(9859):2224-60.
- S Y Lee, A M Leung, X He, L E Braverman, E N Pearce. Iodine content in fast foods: comparison between two fast-food chains in the United States. Endocr Pract. 2010 Nov-Dec;16(6):1071-2.
- J J Gahche, R L Bailey, L B Mirel, J T Dwyer. The prevalence of using iodine-containing supplements is low among reproductive-age women, NHANES 1999-2006. J Nutr. 2013 Jun;143(6):872-7.
- A Stagnaro-Green, S Sullivan, E N Pearce. Iodine supplementation during pregnancy and lactation. JAMA. 2012 Dec 19;308(23):2463-4.
- R Pessah-Pollack, D C Eschler, Z Pozharny, T Davies. Apparent insufficiency of iodine supplementation in pregnancy. J Womens Health (Larchmt). 2014 Jan;23(1):51-6.
- A M Leung, E N Pearce, L E Braverman. Sufficient iodine intake during pregnancy: just do it. Thyroid. 2013 Jan;23(1):7-8.
- A Stagnaro-Green, M Abalovich, E Alexander, F Azizi, J Mestman, R Negro, A Nixon, E N Pearce, O P Soldin, S Sullivan, W Wiersinga; American Thyroid Association Taskforce on Thyroid Disease During Pregnancy and Postpartum. Guidelines of the American Thyroid Association for the diagnosis and management of thyroid disease during pregnancy and postpartum. Thyroid. 2011 Oct;21(10):1081-125.
- E N Pearce. U.S. iodine nutrition: where do we stand? Thyroid. 2008 Nov;18(11):1143-5.
- A M Leung, E N Pearce, L E Braverman. Iodine content of prenatal multivitamins in the United States. N Engl J Med. 2009 Feb 26;360(9):939-40.
Image thanks to il-young ko via flickr
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Iodine Supplements Before, During, and After Pregnancy
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Content URLDoctor's Note
Women eating plant-based diets may find this video of special importance: Pregnant Vegans at Risk for Iodine Deficiency.
This isn’t to say sea vegetables aren’t good for you in their own right. See Which Seaweed Is Most Protective Against Breast Cancer?.
For more videos on having a healthy pregnancy, see:
- Heart Disease May Start in the Womb
- Lead Contamination of Tea
- Caution: Anti-Inflammatory Foods in the Third Trimester
- Flame Retardant Pollutants and Child Development
- Why Do Vegan Women Have 5x Fewer Twins?
- Pollutants in Salmon and Our Own Fat
- Bacon, Eggs, and Gestational Diabetes During Pregnancy
- How Long to Detox from Fish Before Pregnancy?
- Meat Fumes: Dietary Secondhand Smoke
- Natural Treatments for Morning Sickness
- Morning Sickness May Protect Mother and Child
- The Effect of Animal Protein on Stress Hormones, Testosterone, and Pregnancy
- Maternal Diet May Affect Stress Responses in Children
- Should Pregnant and Breastfeeding Women Take DHA?
- Should Vegan Women Supplement with DHA During Pregnancy?
And for more on iodine, see my newer 2021 videos Are Vegans at Risk for Iodine Deficiency? and The Healthiest Natural Source of Iodine.
If you haven’t yet, you can subscribe to my videos for free by clicking here. Read our important information about translations here.