Seafood and mercury

[anthrax]

After tuna & mercury, here is seafood & mercury

Eating too much seafood, which can contain high levels of the toxic substance mercury, could be linked to an increased risk of infertility in men and women, researchers said this week.

Scientists at The Chinese University of Hong Kong found that infertile couples who consumed large amounts of seafood had higher blood mercury concentrations than fertile couples.

"Seafood contaminated with mercury is a possible source of excessive mercury exposure in our infertile population," said Dr Christine Choy, whose research is published in the British Journal of Obstetrics and Gynaecology.

 

[Naxis]

On that note...

I dont know why this is limited to Canadians, but...

"Certain fish species sold in Canada, namely, shark, swordfish, and fresh and frozen tuna, contain mercury at levels which are known to exceed the 0.5 ppm guideline. Based on current data available, average mercury levels in these species are at or near 1.0 ppm (the current guideline for methyl mercury in the United States) with a typical range of 0.5 - 1.5 ppm. Application of the 0.5 ppm mercury guideline to these species would virtually eliminate these types of fish from the Canadian diet."

"Specifically, pregnant women, women of childbearing age and young children are advised to limit the consumption of shark, swordfish and fresh and frozen tuna to no more than 1 meal per month. For others in the population, a consumption level of no more than 1 meal per week is recommended for these species. It is important to note that such advice does not apply to canned tuna. Mercury levels in canned tuna are typically well below the 0.5 ppm guideline."

Evidently the tuna used in canned tuna is too young to have accumulated any kind of dangerous mercury levels.

 

[anthrax]

In north Europe (I think it is Norway or Sweden) the heath authorities also advise not to eat those species more than once a week

But, as you said canned tuna should be OK

 

[chillin408]

I read on some post on usenet where someone was saying something ot the effect that fishes that contain selenium are less problematic as far a mercury poisoning because selenium binds to mercury...something like that

 

[Puttn]

i never realized the bad effects of mercury til now... canned tunas pretty safe tho right

 

[chillin408]

The following is not to say that ingesting mercury is safe,(!) but only that it's interesting to note the antagonism between it and selenium. I don't know how much the selenium in fish helps, though.
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[Selenium and mercury. (Un)healthy antagonism?]

[Article in Dutch]

Schuurs AH, Groten J, van Dokkum W, van den Heuvel J.

Vakgroep Cariologie en Endodontologie, Academisch Centrum Tandheeelkunde Amsterdam (ACTA).

The trace element selenium is involved in the protection against damage caused by free radicals. Selenium prevents carcinogenesis and growth of neoplasms. However, the mechanism is insufficiently known. Furthermore, selenium interacts with mercury, thereby preventing toxic reactions to high doses of mercury. The intake of selenium and the desired minimum and maximum concentrations are described.

Publication Types:
Review
Review, Tutorial

PMID: 11921953 [PubMed - indexed for MEDLINE]


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[Supplementary selenium , an antidote against mercury?]

[Article in Dutch]

Schuurs AH, Groten J, van Dokkum W, van den Heuvel J.

Vakgroep Cariologie en Endodontologie, Academisch Centrum Tandheelkunde Amsterdam (ACTA).

The consequences of both a high and a low intake of selenium are described in this article. Mercury released by dental silver amalgam might affect the protective functions of selenium. However, the literature does not sustain the existence of such an effect. In view of the small margin between safe and toxic doses of selenium and the absence of a scientific consensus as to the possible toxic effects of mercury from amalgam (additional to dietary mercury), it does not seem to be warranted to advise suppletion of selenium.

PMID: 11921941 [PubMed - indexed for MEDLINE]

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Dental amalgam and selenium in blood.

Hol PJ, Vamnes JS, Gjerdet NR, Eide R, Isrenn R.

Department of Odontology-Dental Biomaterials, University of Bergen, Aarstadveien 17, Bergen, N-5009, Norway.

It has been suggested that selenium (Se) exhibits protective effects against mercury (Hg) toxicity in humans due to formation of a Hg-Se complex bound to selenoprotein P in blood. The aim of the present study was to investigate Se concentrations in persons who had been examined with respect to general health problems associated with dental amalgam fillings. The Se concentrations were determined in whole-blood samples of 80 individuals by hydride generation atomic absorption spectrometry. The subjects comprised two main groups: 21 healthy controls with amalgam fillings and 20 patients who claimed symptoms from existing amalgam fillings. The median concentration of Se in blood (119.2 microg/L) was statistically significantly lower in subjects who claimed symptoms of mercury amalgam illness than in healthy subjects with amalgam (130.3 microg/L). The difference was more evident in individuals with more than 35 amalgam surfaces (P=0.003). Additional control groups without amalgam fillings comprised 19 healthy controls without amalgam experience and 20 subjects who have had amalgam fillings removed due to suspected symptoms associated with amalgam. The Se concentrations in these groups were not different from those with amalgam. It is indicated that persons with ill health self-related to dental amalgam might have a Se metabolism different from that of healthy people.

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just a heading:
Efficacy of selenium in tuna and selenite in modifying methylmercury intoxication.

Ohi G, Nishigaki S, Seki H, Tamura Y, Maki T.

PMID: 954708 [PubMed - indexed for MEDLINE]
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Here is an opposing article:
[Health effect of long-term diet mercury contaminated tuna. Part II. Accumulation and retention of mercury and selenium in organs and clinical symptoms (author's transl)]

[Article in Japanese]

Shiramizu M, Yamaguchi S, Kaku S.

Health effects of long-term tuna diet in cats were examined. The cats were fed daily with three kinds of tuna, containing different concentrations of mercury and selenium. The following results were obtained. 1) A high correlation was noted between the amount of fish intake and the mercury level in hair and blood samples of cats. 2) Mercury levels in organs were elevated corresponding with the amount of tuna consumption, but the distribution of mercury in organs of cats exposed to mercury in tuna flake differed from that in tuna fresh meat. In the liver, the ratio of methyl mercury to the total mercury was very low with an average of 11.5% of the ratio. 3) With regard to selenium, there was no correlation between intake of selenium and selenium levels in the cerebrum, celebellum, and kidneys, exept in the liver (r=0.766). 4) None of the cats had definite methyl mercury poisoning, but some slight disturbances were noted in several cats.

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There's more; if you wish to do a pubmed search, you'll find them. Keywords "selenium mercury" or "selenium mercury tuna" . Again this isn't to say eating tuna is safe, just that it's interesting to note that the selenium might make it harder to be mercury poisioned.