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<<   作成日時 : 2008/12/26 20:31   >>

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 水銀を含んだ魚の摂取についてFDA食品医薬品局は警告を緩めることを計画していることが先週明らかになり、環境保護活動家や公衆衛生当局は懸念を表明している。
 ワシントン・ポストが公表した素案には、妊娠した女性や子供にとって魚の摂取による利点が水銀による問題よりも勝っていることを示唆している。
 EPA環境保護局は迅速に反応して、「重大な懸念」を表明し、厳格な長期的科学的検討が必要であり、水銀汚染を軽く見ることはできない立場であると繰り返した。
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 妊娠中、哺乳中、妊娠可能性のある女性、子どもは、水銀の最も高いレベルを持つ4つの魚種−サメ、メカジキ、サワラ、アマダイ−を避けるように推奨し、食事の魚介類は週に6オンスを2人前を上限とするよう勧めている。
 ほとんどの成人にとっては、魚づくしの食事でも水銀レベルを気にする必要はほとんどないとされているが、胎児や乳幼児にとっては神経系に有毒な作用を引きおこす可能性がある。
 魚の食事は健康に良く、蛋白質とオメガ3脂肪酸は神経系の発育に重要であるため、胎児・乳幼児には必要とされる。
 問題はどのようにプラスとマイナスが加算されるかである。ハーバード・メディカルスクールのDr. Emily Oken は「FDA/EPAガイドラインは水銀汚染のリスクを第一と考えていたけれども、魚の栄養分の利点を考慮していなかった(それは水銀のリスクを相殺するかもしれない)」「その時点では、妊娠中に魚の全体の効果を見たどのような研究もなかった」と言う。
 魚食の明らかな利点があり、さらに水銀という欠点があるので、利点を最大化するには最も良い種類の魚を摂取するように勧めることである。
 1999年から2004年までの国民健康保険と栄養の調査調査データに基づくと、米国女性における水銀濃度レベルは確実に低下しており、オメガ3レベルと魚消費は堅調に推移している。水銀の高い魚を避けていることを示している。McCarthy は魚がオメガ3脂肪酸の唯一のソースではないと指摘している。
 栄養分を含む重要な植物にはアマニ、クルミ、ペカン、カリフラワー、ブロッコリ、芽キャベツ、豆腐、ケール、カラードグリーンズがある。
 政府機関が科学的事実を確定するまで、魚食のための現在のガイドラインは有効である。
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妊婦はもっと魚を食べるべきか?
http://kurie.at.webry.info/200710/article_24.html
妊娠中の魚の食べ方が子どもに影響
http://kurie.at.webry.info/200812/article_40.html
水銀による健康障害
http://kurie.at.webry.info/200801/article_45.html
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Will FDA relax its warnings on seafood?
Environmentalists fear that guidelines about seafood will be eased. Agency says it just wants input.
By Jill U. Adams
December 22, 2008
http://www.latimes.com/features/health/la-he-closer22-2008dec22,0,3013558.story

News reports last week about a Food and Drug Administration report have environmentalists and public health officials worried that the agency wants to relax warnings about eating mercury-contaminated fish. A leaked draft report, obtained by the Washington Post, suggests that the benefits of eating fish may outweigh the risks of ingesting mercury even for pregnant women and children.

A quick reaction from the Environmental Protection Agency expressed "serious concerns" about the "scientifically flawed" report and, invoking the holy grail of scientific rigor, reiterated the agency's stance that mercury contamination cannot be taken lightly.

FDA officials say they're not preparing to change the guidelines but simply soliciting comments from other government scientists, according to an e-mail from FDA spokeswoman Stephanie Kwisnek.

The EPA and environmental activists appear skeptical. "It's important to note these comments -- from EPA -- have been very negative," says Sonya Lunder, a senior analyst at the nonprofit Environmental Working Group. The advocacy organization, which has seen both the draft report and the EPA response, is adamantly opposed to any attempt to ease the warnings about mercury in fish.

The apparent clash between the two agencies is a turnaround from four years ago when they issued a joint advisory with specific fish-consumption recommendations for groups at the highest risk for mercury-related health problems: women who are pregnant or nursing, women who might become pregnant and children. That advice included avoiding shark, swordfish, king mackerel and tilefish -- four fish species with the highest levels of mercury. The advisory also set an upper limit for eating seafood of any kind at two 6-ounce servings per week for those groups.

The science behind the policy is tricky. It's hard enough for epidemiologists to correlate one dietary factor to a health outcome. In this case, policymakers must assess what's known about two components of fish -- mercury and omega-3 fatty acids -- which have opposing effects on normal child development. Studies often look at either the risk of mercury intake or the benefit of fish eating, but rarely both.

It's true that people accumulate mercury in their bodies from eating contaminated fish. For most adults, there is little concern about the levels of mercury found even in a fish-filled diet. For fetuses and babies, however, mercury can easily have toxic effects on the nervous system, says Kathryn Mahaffey, a lecturer at the George Washington School of Public Health in Washington, D.C. Formerly a senior scientist at the EPA, Mahaffey led the agency effort to define a benchmark mercury level for the 2004 advisory.

It also is true that eating fish is good for you. It's a good source of protein and omega-3 fatty acids, which are "critical in the development of the nervous system," says William McCarthy, professor of public health at UCLA. "So our babies, if we want them to have well-functioning brains, absolutely need the omega-3s."

What's hard to say is how the pluses and minuses add up. "The FDA/EPA guidelines were considering the risks of mercury primarily as a contaminant but did not consider the benefits of the nutrients of fish, which may offset the risks of mercury," says Dr. Emily Oken, a physician and assistant professor at Harvard Medical School in Boston. "Because at that time, there had not been any studies that looked at the overall effect of fish during pregnancy."

Says Lunder: "There are some benefits to eating fish and there are obviously drawbacks like mercury, and the way to maximize that is to steer people to the best species," which the current guidelines do.

(For more information on mercury levels~frf/sea-mehg.html in different fish, go to the FDA website. For advisories on local fish consumption, go to the California Office of Environmental Health Hazard Assessment's site. )

Lunder cites a recent study of Mahaffey's, based on National Health and Nutrition Examination Survey data from 1999 to 2004 and published online in Environmental Health Perspectives in August, that showed mercury levels in American women are dropping steadily, but omega-3 levels and fish consumption are holding steady.

"It shows that [the current] guidance is working and people are getting the message and avoiding the highest mercury fish," Lunder says. A reversal of that advice would raise mercury exposure, she says, putting kids at risk.

McCarthy points out that fish are not the only good source of omega-3 fatty acids. Significant plant sources of the nutrient include flax seed, walnuts, pecans, cauliflower, broccoli, Brussels sprouts, tofu, kale and collard greens.

Until the government agencies sort out the science, the current guidelines for eating fish stand.

advisories~frf/sea-mehg.htmladvisories

health@latimes.com

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