Urinary Iodine Concentrations and Mortality Among U.S. Adults

[helvella]

Iodine is, was, and will continue to be a controversial subject. There are people who have what I consider massive intakes of iodine (from supplements such as Lugol's or nascent iodine) and who suggest that we should all follow their example. There are others who are very cautious and positively avoid foods known to have significant iodine content.

[My own approach is to be cautious of known high iodine foods such as some seaweeds and (quoting from another paper I recently posted) pollock from Sweden! At the same time, I am happy to consume dairy, fish, and some seaweed. Of course, that also implies that I do not take Lugol's, nascent iodine, etc.]

This paper suggests that high intake (more than 400 micrograms a day) have a higher all-cause mortality. Of course, as usual, the paper indicates the need for further research.

Thyroid. 2018 Jun 8. doi: 10.1089/thy.2018.0034. [Epub ahead of print]

Urinary Iodine Concentrations and Mortality Among U.S. Adults.

Inoue K1, Leung AM2, Sugiyama T3, Tsujimoto T4, Makita N5, Nangaku M6, Ritz BR7.

Author information

1 UCLA Fielding School of Public Health,, Department of Epidemiology, Los Angeles, California, United States ; [e-mail].

2 VA Greater Los Angeles Healthcare System, Division of Endocrinology, 11D , 11301 Wilshire Blvd , Los Angeles, California, United States , 90073 ; [e-mail].

3 National Center for Global Health and Medicine,, Diabetes and Metabolism Information Center, Research Institute, Tokyo, Japan ; [e-mail].

4 National Center for Global Health and Medicine, Department of Diabetes, Endocrinology, and Metabolism, Center Hospital, Tokyo, Japan ; [e-mail].

5 The University of Tokyo, Endocrinology and Nephrology , 7-3-1,Hongo,Bunkyo-ku , Tokyo, Japan , 1138655 ; [e-mail].

6 The University of Tokyo School of Medicine, Department of Nephrology and Endocrinology, Tokyo, Japan ; [e-mail].

7 UCLA Fielding School of Public Health, Department of Epidemiology, Los Angeles, Colorado, United States ; [e-mail].

Abstract

BACKGROUND:

Iodine deficiency has long been recognized as an important public health problem. Global approaches such as salt iodization that aim to overcome iodine deficiency have been successful. Meanwhile, they have led to excessive iodine consumption in some populations, thereby increasing the risks of iodine-induced thyroid dysfunction, as well as the comorbidities and mortality associated with hypothyroidism and hyperthyroidism. We aimed to elucidate whether iodine intake is associated with mortality among U.S. adults.

METHODS:

This is an observational study to estimate mortality risks according to urinary iodine concentrations (UIC) utilizing a nationally representative sample of 12,264 adults ages 20 to 80 years enrolled in the National Health and Nutrition Examination Survey (NHANES) III. Crude and multivariable Cox proportional hazards regression models were employed to investigate the association between UIC (<50, 50-99, 100-299, 300-399, and >400 μg/L) and mortalities (all-cause, cardiovascular, and cancer). In sensitivity analyses, we adjusted for total sodium intake and fat/calorie ratio in addition to other potential confounders. We also conducted stratum-specific analyses to estimate the effects of UIC on mortality according to age, sex, race/ethnicity, and eGFR category.

RESULTS:

Over a median follow-up of 19.2 years, there were 3,159 deaths from all causes. Participants with excess iodine exposure (UIC >400 μg/L) were at higher risk for all-cause mortality compared to those with adequate iodine nutrition (HR, 1.19; 95% confidence interval [CI], 1.04-1.37). We also found elevated HRs of cardiovascular and cancer mortality, but the 95% CI of our effect estimates included the null value for both outcomes. Low UIC was not associated with increased mortality. Restricted cubic spline models showed similar results for all outcomes. The results did not change substantially after adjusting for total sodium intake and fat/calorie ratio. None of the potential interactions were statistically significant on a multiplicative scale.

CONCLUSION:

Higher all-cause mortality among those with excess iodine intake, compared with individuals with adequate iodine intake, highlights the importance of monitoring population iodine status. Further studies with longitudinal measures of iodine status are needed to validate our results and assess the potential risks excess iodine intake may have on long-term health outcomes.

PMID: 29882490

DOI: 10.1089/thy.2018.0034

ncbi.nlm.nih.gov/pubmed/298...

[Justiina]

One question could be if it's just high intake of iodine or does a malfunction cause you to lose or rapidly excrete iodine without using it. Ofc some people take ridiculous amounts of iodine which is a problem as iodine in the end is toxic but those that are around 400-500 could normal diet in are high on iodine.

It's weird if low iodine isn't problem as it would indeed indicate you were more prone to fall ill based on what we know about necessity of iodine.

[helvella Administrator Thyroid UK in reply to Justiina]

My reading was that >400 would include people on megadoses. Quite possibly, if the analysis was reworked with more ranges (e.g. 400 to 499, 500 to 599, etc.) we might see a picture in which the 400 to 499 was not particularly different to lower ranges, but higher ranges were more obviously a problem?

[Justiina in reply to helvella]

Should look into UI for those who are on mega doses like 50 mg, can't be just 400 or so as iodine is not stored that way you'd only pass fraction of it. Despite some say it would mean you were deficient and that's why absorb majority of what you took. But if indeed mega doses show up only UI around 500 then problem solved. That 50mg does do something either shady or all high dosages are in harmful form or just humbug.

If UI is ~400 then iodine consumption should be around 500-1000 mcg?

But yeah have no idea what is UI for those on truly mega doses or does the range just end yo certain number. Getting true number would show what happens when you flood your system with iodine!

[Justiina in reply to helvella]

Seems that urine iodine test can detect values high as 30 000 and that indeed is high compared to 400.

So id consider that 400 still quite decent, tho you pass some by sweat and through bowel so in that light 400 could be high if you pass a lot through bowel. That could explain it.

[Chippysue]

Dr David Brownstein iodine book is excellent.

[helvella Administrator Thyroid UK in reply to Chippysue]

I have not read his book but does he not generally recommend doses of iodine that would likely take people into the higher all-cause mortality range?

[helvella Administrator Thyroid UK in reply to helvella]

And one thing I do agree with Brownstein about:

Rebecca,

The patch test is not an accurate test. The best test is the iodine loading test. You can find this test on-line. It is best to work with an iodine-knowledgeable doctor.

DrB

drbrownstein.com/iodine-def...

[Chippysue in reply to helvella]

He is one of the best doctors, I watched a recording of him telling his story and showing his clinic. Like all of the best doctors he stepped out of mainstream medication because he couldn’t live a lie, he is an expert who I would listen to.