Arsenic in Kelp Supplements
Just updated the Iodine page of VeganHealth.org regarding arsenic in kelp supplements:
“Most iodine supplements are simply tablets made from kelp. Being a seaweed, kelp likely contains at least small amounts of arsenic. There are some very rare cases in which people taking kelp supplements have developed symptoms of arsenic toxicity (8). A survey of kelp supplements in the U.S. found that eight out of nine batches contained some level of arsenic (8). Another survey in the UK of imported seaweed found very little arsenic in kelp, and no detectible amounts of inorganic arsenic, which is the harmful type (9).
“It is very unlikely that, taken at recommended amounts of 150 µg every other day, arsenic toxicity is likely to occur from kelp supplements. However, if you are concerned, at least one company makes iodine tablets that appear not to come from kelp: Nature’s Plus Potassium Iodide.”
Some additional notes:
The highest level of arsenic found in U.S. supplements was 34.8 mg/kg (8). My iodine supplement contains 225 µg of iodine in 45 mg of kelp. The Joint FAO/WHO Expert Committee on Food Additives (JECFA) has set a tolerable intake of 15 mg/kg of body weight per week (9). For a 140 pound person, that would be 953 mg per week. Supplementing three times per week with the tablets I have, at the highest toxicity level found, arsenic exposure would still be less than 5 mg per week, well below the 925 mg level.
Wakame, kombu, and arame are all types of kelp.
References
8. Amster E, Tiwary A, Schenker MB. Case report: potential arsenic toxicosis
secondary to herbal kelp supplement. Environ Health Perspect. 2007 Apr;115(4):606-8. Epub 2007 Jan 18. | Link | Follow-up letters to the editor.
9. Rose M, Lewis J, Langford N, Baxter M, Origgi S, Barber M, MacBain H, Thomas K. Arsenic in seaweed–forms, concentration and dietary exposure. Food Chem Toxicol. 2007 Jul;45(7):1263-7. | Link
October 30th, 2012 at 9:07 am
Do you know if the organic certification process for sea vegetables as foods rules out arsenic, or is it caveat emptor?
October 30th, 2012 at 9:23 am
AmyLu,
I’ve never heard that it does.
October 30th, 2012 at 4:16 pm
Okay, thanks! How often do you find it safe to eat sea vegetables, given that that is the case?
October 31st, 2012 at 9:06 am
AmyLu,
The second study linked to above examined arsenic in kelp (arame, wakame, and kombu), hijiki, and nori. The researchers concluded that only hijiki had enough arsenic to be worried about. I personally would not eat more than 3 servings of seaweed a week unless I knew where it was coming from, but that’s just an arbitrary guess.
March 7th, 2013 at 6:50 am
Toxity of organic and inorganic arsenic is very different. The cases reported above did not differentiate and may be causing undo alarm. The symptoms exhibited by the patient were not classic arsenic toxicity symptoms. When discussing these cases the following analysis should also be cited. One can also research organic and inorganic arsenic to become more educated.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2137117/
March 7th, 2013 at 3:18 pm
Joe,
Do you work with the supplement industry? I included a link to that letter in the citation for reference 8 in my post.
April 8th, 2013 at 5:06 pm
Very interesting. I have started taking an iodine supplement based on the recommendations on your site. It contains 50 to 150 micrograms per kelp tablet. However, I also note that I eat alot of yogurt (twice per day), and wonder if that would contain an adequate dietary supply due to the use of iodine in the dairy process (cleaning of teats and so forth). I don’t eat any seaweed – I tried cooking this one day, and found the smell and taste to be foul.
Other supplements I ingest – vitamin D 1000 IU od, vitamin B12 100 mcg OD, omega-3 containing 600 mg of EPA+300 mg of DHA. I am a “lacto-vegan”, but my only source of dairy is yogurt. I eat soy twice daily.
April 8th, 2013 at 5:24 pm
Dan,
I have not done an analysis on how much iodine is in yogurt, though you could check it out at PeaCounter.com (those numbers should only be considered to apply to the US, though – and I don’t even know if they list iodine). The amount you’re taking sounds like a safe amount to me, even if there is iodine in your yogurt.
April 9th, 2013 at 7:34 am
Jack,
Thank you for the info. I greatly enjoyed all the information on your site and read the original articles in JCEM on iodine deficiency in vegans.