The Straight Dope

Go Back   Straight Dope Message Board > Main > Cafe Society

Reply
 
Thread Tools Display Modes
  #1  
Old 08-23-2010, 08:16 AM
Gary T Gary T is offline
Member
 
Join Date: Mar 2002
Location: KCMO
Posts: 9,508
Iodine in sea salt

I'm confused about the iodine content of sea salt. Growing up I heard that seafood was a good source of iodine, but I see conflicting statements about iodine in sea salt. Some say it's a good source of iodine (which makes sense given the iodine in seafood), others say sea salt does not contain a significant amount of iodine. Is this a complex subject, where either statement could be true depending on exactly which variety of sea salt? Anyone know the straight dope?
Reply With Quote
Advertisements  
  #2  
Old 08-23-2010, 05:03 PM
FallenAngel FallenAngel is offline
Guest
 
Join Date: Jul 2000
I don't know much about the iodine content, but as a serious amateur cook I live by Michael Symon's mantra on the three kinds of generally available salt: Top with finishing salt, cook with kosher salt, put iodized on your driveway.
Reply With Quote
  #3  
Old 08-23-2010, 07:01 PM
moejoe moejoe is offline
Guest
 
Join Date: Apr 2010
Only if it's been iodized, iodine has to be purposely added to salt. Check the label.
Reply With Quote
  #4  
Old 08-23-2010, 07:21 PM
pulykamell pulykamell is online now
Charter Member
 
Join Date: May 2000
Location: SW Side, Chicago
Posts: 30,446
Here's some information

Quote:
It is a myth (often also false advertising) that “natural” sea salt contains significant amounts of iodine. The iodide content of seawater is only 64 µg/kg or 2.1 mg I/kg NaCl. In evaporatively prepared salt, the iodide/chloride ratio is even lower because of iodine loss; crystallization processes leave iodide selectively in the mother liquor. Aquaron (60) examined 81 “natural” salt samples from 21 countries: all contained <0.7 mg I/kg with the exception of Nigerian samples (1.4–6.5 mg I/kg) made from underground brine. He also examined iodized salts from many countries. Although a limited number of samples were analyzed, it cannot be reassuring to the U.S. population that the United States and Spain were the only two countries where the salt samples consistently fell below the respective recommended iodization levels.
Compare those numbers with:

Quote:
The U.S. Food and Drug Administration (USFDA) recommends 60–100 mg KI/kg salt, equivalent to 46–76 mg I/kg salt.
Reply With Quote
  #5  
Old 08-23-2010, 07:39 PM
Peremensoe Peremensoe is offline
Guest
 
Join Date: Apr 2010
Quote:
Originally Posted by moejoe View Post
Only if it's been iodized, iodine has to be purposely added to salt. Check the label.
No. Iodine occurs naturally in seawater. (In fact, most of the iodine on earth is in the ocean.) It is inevitable that sea salt contains trace iodine along with many other minerals. Saltwater fishes tend to concentrate the relatively low levels of iodine in seawater by taking it up in their thyroids. So fish heads are the most iodized part of the fish. (Seaweed like kelp also seems to concentrate seawater iodine, but I don't know what the mechanism is.)

Different samples of sea salt have differing levels of iodine, but apparently all or almost all sea salts have less than what is added to (most) rock salt intended for table use. Where the information is available, sea salts seem to run around 9 ppm iodine, compared with 44-77 ppm for commercially iodized rock salt in the United States and 10-22 ppm in Europe. Iodized salt in other parts of the world is even less standardized, with (ostensibly iodized) samples in South Africa found ranging from 0-97 ppm.

Iodine deficiency is a very serious health risk, but excessive iodine can also be a problem, leading to hypothyroidism and autoimmune thyroiditis.
Reply With Quote
  #6  
Old 08-23-2010, 08:09 PM
DrDeth DrDeth is offline
Charter Member
 
Join Date: Mar 2001
Location: San Jose
Posts: 22,473
Quote:
Originally Posted by FallenAngel View Post
I don't know much about the iodine content, but as a serious amateur cook I live by Michael Symon's mantra on the three kinds of generally available salt: Top with finishing salt, cook with kosher salt, put iodized on your driveway.
One can certainly differentiate the moth feel of Kosher salt when sprinkled over something, but once dissolved it's just plain old NaCl. Now, in a very light broth someone MIGHT be able to taste the iodine in iodized salt. But most can't. So, he's an elitist who knows nothing about basic chemistry. In fact the salt one puts on the driveway is not iodized.

moejoe is correct. Table salt is purified/refined to the extent that any remaining iodine is negligible. In order to make a nutritional difference, it has to be added back. When they purify table salt, they take more than iodine from it. Most rock salt was laid down from ancient seabeds anyway, so it'd have the same tiny, tiny trace of iodine left after being refined. Table salt- including Kosher, rock and sea salt is almost pure NaCla, the additions being anti-caking agents. For soups, baking, etc, there is nothing wrong at all with iodized salt, and goiter is not a happy thing.

Kosher salt has a very different grain, instead of cubic crystals, kosher salt has a flat platelet shape. Most Kosher salt is not iodized, but it could be. It often contains sodium ferrocyanate. It is not recommended for baking. It's great for meat.

Now, Grey Salt/ Fleur de sel, is specially harvested Sea Salt without being refined. It does have a trace amount of iodine- and other minerals- in it*. It's also super expensive. it is one of several salts know as a "finishing salt". In some cases, it can add a desired flavor to certain foods. There are at least 8 types I know of so saying "the three kinds of generally available salt" is also wrong in that regard.

However, Iodine is not even on the list of the 11 common minerals/elements in seawater. Thus seawater has less Iodine than Florine (0.000068).
http://en.wikipedia.org/wiki/Sea_water
Reply With Quote
  #7  
Old 08-23-2010, 08:47 PM
Peremensoe Peremensoe is offline
Guest
 
Join Date: Apr 2010
Quote:
Originally Posted by DrDeth View Post
moejoe is correct. Table salt is purified/refined to the extent that any remaining iodine is negligible. In order to make a nutritional difference, it has to be added back. When they purify table salt, they take more than iodine from it. Most rock salt was laid down from ancient seabeds anyway, so it'd have the same tiny, tiny trace of iodine left after being refined.
Who refines sea salt? The whole point is the flavor, texture and trace minerals.

moejoe is correct that refined salt has iodine added to it.
Reply With Quote
  #8  
Old 08-23-2010, 09:02 PM
Peremensoe Peremensoe is offline
Guest
 
Join Date: Apr 2010
Quote:
Originally Posted by DrDeth View Post
However, Iodine is not even on the list of the 11 common minerals/elements in seawater. Thus seawater has less Iodine than Florine (0.000068).
http://en.wikipedia.org/wiki/Sea_water
Right. That's seawater. Only about 3.5% of that is salts and trace elements. If the 9 ppm iodine figure for the salt is typical, that would put the iodine content around 0.000000315, if all the components of the seawater, besides water, were left in the salt crust. But I expect that's not the case; iodine content itself (again, always speaking of unrefined sea salt) is subject to differences in handling, so I imagine that's equally or even more true of other components. If so, the iodine content of the seawater could be lower still, and yield the product I referred to.

Last edited by Peremensoe; 08-23-2010 at 09:05 PM..
Reply With Quote
  #9  
Old 08-24-2010, 12:43 AM
DrDeth DrDeth is offline
Charter Member
 
Join Date: Mar 2001
Location: San Jose
Posts: 22,473
Quote:
Originally Posted by spark240 View Post
Who refines sea salt? The whole point is the flavor, texture and trace minerals.

moejoe is correct that refined salt has iodine added to it.
Nearly everyone. The stuff that's white and is sold as "Sea Salt" is refined. Grey Salt is oddly enough- grey.

wiki "Refined salt, which is most widely used presently, is mainly sodium chloride. Food grade salt accounts for only a small part of salt production in industrialised countries (3% in Europe[16]) although worldwide, food uses account for 17.5% of salt production.[17] ...
The manufacture and use of salt is one of the oldest chemical industries.[18] Salt can be obtained by evaporation of sea water, usually in shallow basins warmed by sunlight;[19] salt so obtained was formerly called bay salt, and is now often called sea salt or solar salt. Rock salt deposits are formed by the evaporation of ancient salt lakes,[20] and may be mined conventionally or through the injection of water. Injected water dissolves the salt, and the brine solution can be pumped to the surface where the salt is collected.
After the raw salt is obtained, it is refined to purify it and improve its storage and handling characteristics. Purification usually involves recrystallization. In recrystallization, a brine solution is treated with chemicals that precipitate most impurities (largely magnesium and calcium salts).[21] Multiple stages of evaporation are then used to collect pure sodium chloride crystals, which are kiln-dried."

Italics mine.

Here's an article on Fleur de Sel aka Grey Salt, which is salt from the sea, of course. It's grey, with irregular crystals.

http://www.davidlebovitz.com/2006/09/fleur-de-sel-de-1/

Note that it has to be hand harvested, otherwise you have just plain old dehydrated sea water, which is (wiki) "Completely raw sea salt is bitter because of magnesium and calcium compounds, and thus is rarely eaten. "

Even Grey salt has little Iodine:
http://www.saltinstitute.org/Article...-health-issues
"Although often promoted as a more healthful alternative to refined table salt, natural sea salt has little iodine and is a poor choice for those concerned about ensuring their iodine sufficiency. Two studies have examined this question carefully:

Fisher and L'Abbe (1980) tested non-iodized sea salt and iodized table salt and sea salt. The authors found 52.9 - 84.6 micrograms iodine/gram of salt in iodized salt and 1.2 - 1.4 micrograms iodine/gram in non-iodized sea salt. [see Fisher, Peter W. F. and Mary L'Abbe. 1980. Iodine in Iodized Table Salt and in Sea Salt . Can. Inst. Food Sci. Technolo. J. Vol. 13. No. 2:103-104. April]
Aquaron (2000) determined iodine content of natural sea salt and rock salt, and iodized salt. The author found iodine levels of less than 0.71 milligrams iodine/kilogram of salt (micrograms/gram) in non-iodized salt and 7.65 - 100 mg iodine/kg of salt in iodized salt (depending on the country's iodine laws). [see Aquaron, R. 2000. Iodine content of non iodized salts and iodized salts obtained from the retail markets worldwide. 8th World Salt Symposium . Vol. 2:935-940]"


Now, yes, Fleur de Sel aka Grey Salt is indeed salt from the sea. But it's not sold just as "sea salt" which is more or less pure NaCl, refined and purified. For example "La Baleine Sea Salt" is pure white salt. It runs about $2 a pound. Grey Salt runs about $15 a pound up to $60 a pound.
http://www.amazon.com/Fleur-Sel-Cama...2628395&sr=8-8
Reply With Quote
  #10  
Old 08-26-2010, 03:41 PM
Jet Jaguar Jet Jaguar is offline
Guest
 
Join Date: Jan 2001
I've heard all about the dangers of iodine deficiency and people living in places with no natural iodine in the soil, but do I, as someone that doesn't live off the land and gets all their food from typical American supermarkets with products shipped in from all over the world, really need iodized salt? Or am I going to sprout a goiter if I cook exclusively with sea salt instead of iodized table salt?
Reply With Quote
  #11  
Old 08-26-2010, 04:38 PM
StGermain StGermain is online now
Charter Member
 
Join Date: Nov 1999
Location: Toon Town
Posts: 9,345
I've eaten iodized salt my whole life and still got a goiter. I'm now thyroid-less.

StG
Reply With Quote
Reply



Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 01:35 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.

Send questions for Cecil Adams to: cecil@chicagoreader.com

Send comments about this website to: webmaster@straightdope.com

Terms of Use / Privacy Policy

Advertise on the Straight Dope!
(Your direct line to thousands of the smartest, hippest people on the planet, plus a few total dipsticks.)

Publishers - interested in subscribing to the Straight Dope?
Write to: sdsubscriptions@chicagoreader.com.

Copyright © 2013 Sun-Times Media, LLC.