Giovannucci E, Stampfer M J, Colditz G A, Hunter D J, Fuchs C, Rosner B A, Speizer F E, Willett W C
Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA.
Ann Intern Med. 1998 Oct 1;129(7):517-24. doi: 10.7326/0003-4819-129-7-199810010-00002.
High intake of folate may reduce risk for colon cancer, but the dosage and duration relations and the impact of dietary compared with supplementary sources are not well understood.
To evaluate the relation between folate intake and incidence of colon cancer.
Prospective cohort study.
88,756 women from the Nurses' Health Study who were free of cancer in 1980 and provided updated assessments of diet, including multivitamin supplement use, from 1980 to 1994.
442 women with new cases of colon cancer.
Multivariate relative risk (RR) and 95% CIs for colon cancer in relation to energy-adjusted folate intake.
Higher energy-adjusted folate intake in 1980 was related to a lower risk for colon cancer (RR, 0.69 [95% CI, 0.52 to 0.93] for intake > 400 microg/d compared with intake < or = 200 microg/d) after controlling for age; family history of colorectal cancer; aspirin use; smoking; body mass; physical activity; and intakes of red meat, alcohol, methionine, and fiber. When intake of vitamins A, C, D, and E and intake of calcium were also controlled for, results were similar. Women who used multivitamins containing folic acid had no benefit with respect to colon cancer after 4 years of use (RR, 1.02) and had only nonsignificant risk reductions after 5 to 9 (RR, 0.83) or 10 to 14 years of use (RR, 0.80). After 15 years of use, however, risk was markedly lower (RR, 0.25 [CI, 0.13 to 0.51]), representing 15 instead of 68 new cases of colon cancer per 10,000 women 55 to 69 years of age. Folate from dietary sources alone was related to a modest reduction in risk for colon cancer, and the benefit of long-term multivitamin use was present across all levels of dietary intakes.
Long-term use of multivitamins may substantially reduce risk for colon cancer. This effect may be related to the folic acid contained in multivitamins.
高叶酸摄入量可能降低患结肠癌的风险，但叶酸剂量、摄入时长的关系以及饮食来源与补充剂来源叶酸的影响尚不清楚。
评估叶酸摄入量与结肠癌发病率之间的关系。
前瞻性队列研究。
来自护士健康研究的88756名女性，她们在1980年无癌症，并在1980年至1994年期间提供了饮食的最新评估，包括多种维生素补充剂的使用情况。
442例结肠癌新发病例的女性。
能量调整叶酸摄入量与结肠癌的多变量相对风险（RR）及95%可信区间（CI）。
在控制年龄、结直肠癌家族史、阿司匹林使用情况、吸烟、体重、体力活动以及红肉、酒精、蛋氨酸和纤维摄入量后，1980年能量调整叶酸摄入量较高与较低的结肠癌风险相关（摄入量>400μg/d与摄入量≤200μg/d相比，RR为0.69[95%CI，0.52至0.93]）。当同时控制维生素A、C、D和E的摄入量以及钙的摄入量时，结果相似。服用含叶酸多种维生素的女性在使用4年后对结肠癌无益处（RR为1.02），在使用5至9年（RR为0.83）或10至14年（RR为0.80）后仅有不显著的风险降低。然而，使用15年后，风险显著降低（RR为0.25[CI，0.13至0.51]），这意味着每10000名55至69岁女性中结肠癌新发病例为15例而非68例。仅饮食来源的叶酸与结肠癌风险适度降低相关，长期服用多种维生素的益处存在于所有饮食摄入水平。
长期服用多种维生素可能大幅降低患结肠癌的风险。这种效应可能与多种维生素中所含的叶酸有关。
