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<<   作成日時 : 2009/12/05 00:25   >>

なるほど(納得、参考になった、ヘー) ブログ気持玉 2 / トラックバック 0 / コメント 0

 1998年以来米国では、先天性神経管障害の発生を減らすために穀物やシリアルに葉酸を強化している。しかし、新たな研究でビタミン大量投与によるガン発症率の増加、特に肺がんと関連するという研究が発表された。
 ノルウェーで1998-2005年に6,261人の虚血性心疾患の患者に葉酸とビタミンB12を投与してホモシステインを低下させる治療を評価する試験が行われた。最新の研究は、同じ患者を2007年までモニターしたところ、治療患者の10%にガンが発症したが、治療しなかった群では8.4%であり、リスクが21%増加した。リスクの増加は、ビタミンB12よりも葉酸の高い血中濃度と関連していた。過剰な葉酸が腫瘍を成長させた可能性がある。
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光沢を失う葉酸/二分脊椎 大腸がん
http://kurie.at.webry.info/200905/article_18.html
葉酸は先天性心疾患を予防する/カナダ
http://kurie.at.webry.info/200905/article_21.html
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Regimens: Cancer Concerns in Big Doses of Folic Acid
http://www.nytimes.com/2009/12/01/health/research/01regi.html
By RONI CARYN RABIN
Published: November 30, 2009

Grains and cereals have been fortified with folic acid in the United States since 1998, as part of an effort to reduce the incidence of neural tube birth defects in babies. But a new study has raised safety concerns, linking megadoses of the vitamin to increased cancer rates, particularly lung cancer.

The study was done in Norway, where foods are not fortified with folic acid, making it possible to compare outcomes among patients treated with supplements and a group given placebos.

Researchers followed 6,261 patients with ischemic heart disease who had participated in two randomized clinical trials set up to assess whether homocysteine-lowering treatment with folic acid and vitamin B12 reduced heart disease. The trials started in 1998 and ended in 2004 and 2005.

The latest study, published in the Nov. 18 issue of The Journal of the American Medical Association, monitored the same patients through 2007. It found that 10 percent of patients who had been treated with folic acid and vitamin B 12 had developed cancer, compared with 8.4 percent of those who had not received the treatment, an increased risk of 21 percent. The analysis indicated that the added risk was associated with high blood levels of folate, rather than vitamin B12.

While experimental evidence has indicated that folate deficiency may promote cancer growth, the study’s authors suggested it was also possible that excess folic acid accelerated the growth of tumors.

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Cancer Incidence and Mortality After Treatment With Folic Acid and Vitamin B12

Marta Ebbing, MD; Kaare Harald B?naa, MD, PhD; Ottar Nyga*rd, MD, PhD; Egil Arnesen, MD; Per Magne Ueland, MD, PhD; Jan Erik Nordrehaug, MD, PhD; Knut Rasmussen, MD, PhD; Inger Nj?lstad, MD, PhD; Helga Refsum, MD, PhD; Dennis W. Nilsen, MD, PhD; Aage Tverdal, PhD; Klaus Meyer, PhD; Stein Emil Vollset, MD, DrPH

画像JAMA. 2009;302(19):2119-2126.

Context Recently, concern has been raised about the safety of folic acid, particularly in relation to cancer risk.

Objective To evaluate effects of treatment with B vitamins on cancer outcomes and all-cause mortality in 2 randomized controlled trials.

Design, Setting, and Participants Combined analysis and extended follow-up of participants from 2 randomized, double-blind, placebo-controlled clinical trials (Norwegian Vitamin Trial and Western Norway B Vitamin Intervention Trial). A total of 6837 patients with ischemic heart disease were treated with B vitamins or placebo between 1998 and 2005, and were followed up through December 31, 2007.

Interventions Oral treatment with folic acid (0.8 mg/d) plus vitamin B12 (0.4 mg/d) and vitamin B6 (40 mg/d) (n = 1708); folic acid (0.8 mg/d) plus vitamin B12 (0.4 mg/d) (n = 1703); vitamin B6 alone (40 mg/d) (n = 1705); or placebo (n = 1721).

Main Outcome Measures Cancer incidence, cancer mortality, and all-cause mortality.

Results During study treatment, median serum folate concentration increased more than 6-fold among participants given folic acid. After a median 39 months of treatment and an additional 38 months of posttrial observational follow-up, 341 participants (10.0%) who received folic acid plus vitamin B12 vs 288 participants (8.4%) who did not receive such treatment were diagnosed with cancer (hazard ratio [HR], 1.21; 95% confidence interval [CI], 1.03-1.41; P = .02). A total of 136 (4.0%) who received folic acid plus vitamin B12 vs 100 (2.9%) who did not receive such treatment died from cancer (HR, 1.38; 95% CI, 1.07-1.79; P = .01). A total of 548 patients (16.1%) who received folic acid plus vitamin B12 vs 473 (13.8%) who did not receive such treatment died from any cause (HR, 1.18; 95% CI, 1.04-1.33; P = .01). Results were mainly driven by increased lung cancer incidence in participants who received folic acid plus vitamin B12. Vitamin B6 treatment was not associated with any significant effects.

Conclusion Treatment with folic acid plus vitamin B12 was associated with increased cancer outcomes and all-cause mortality in patients with ischemic heart disease in Norway, where there is no folic acid fortification of foods.

Trial Registration clinicaltrials.gov Identifier: NCT00671346

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