美国女性在强化后时代叶酸摄入与结直肠癌风险的关联。
Association of folate intake and colorectal cancer risk in the postfortification era in US women.
机构信息
Department of Nutrition, Harvard TH Chan School of Public Health, Boston, MA, USA.
Channing Division of Network Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA.
出版信息
Am J Clin Nutr. 2021 Jul 1;114(1):49-58. doi: 10.1093/ajcn/nqab035.
BACKGROUND
Folate may play a preventive role in the early stages of colorectal carcinogenesis, but long latencies may be needed to observe a reduction in colorectal cancer (CRC) incidence. In addition, concerns have been raised about the potential for cancer promotion with excessive folate intake, especially after the mandatory folic acid fortification in the United States in 1998.
OBJECTIVE
We aimed to examine the association between folate intake in different chemical forms and CRC risk, especially in the postfortification era in the United States.
DESIGN
We prospectively followed 86,320 women from the Nurses' Health Study (1980-2016). Folate intake was collected by validated food frequency questionnaires. CRC was self reported and confirmed by review of medical records. The association between the folate intake and CRC risk was assessed using Cox proportional hazards regression.
RESULTS
We documented 1988 incident CRC cases during follow-up. Analyzing folate intake as a continuous variable, greater total folate intake 12-24 y before diagnosis was associated with lower risk of CRC (per increment of 400 dietary folate equivalents (DFE)/d, HR: 0.93, 95% CI: 0.85, 1.01 for 12-16 y; HR: 0.83, 95% CI: 0.75, 0.92 for 16-20 y; and HR: 0.87, 95% CI: 0.77, 0.99 for 20-24 y); and greater synthetic folic acid intake 16-24 y before diagnosis was also associated with a lower CRC risk (per increment of 400 DFE/d, HR: 0.91, 95% CI: 0.84, 0.99 for 16-20 y and HR: 0.91, 95% CI: 0.83-1.01 for 20-24 y). In the postfortification period (1998-2016), intake of total or specific forms of folate was not associated with CRC risk, even among multivitamin users.
CONCLUSIONS
Folate intake, both total and from synthetic forms, was associated with a lower risk of overall CRC after long latency periods. There was no evidence that high folate intake in the postfortification period was related to increased CRC risk in this US female population.
背景
叶酸可能在结直肠癌（CRC）发生的早期发挥预防作用，但可能需要较长的潜伏期才能观察到 CRC 发病率的降低。此外，人们对过量摄入叶酸可能促进癌症的风险表示担忧，尤其是在美国 1998 年强制叶酸强化之后。
目的
我们旨在研究不同化学形式的叶酸摄入与 CRC 风险之间的关联，特别是在美国强化后时期。
设计
我们前瞻性地随访了 86320 名来自护士健康研究（1980-2016 年）的女性。叶酸摄入量通过经过验证的食物频率问卷收集。CRC 通过病历回顾自行报告和确认。使用 Cox 比例风险回归评估叶酸摄入量与 CRC 风险之间的关系。
结果
在随访期间，我们记录了 1988 例 CRC 病例。分析叶酸摄入量作为连续变量，在诊断前 12-24 年，总叶酸摄入量越高，CRC 风险越低（每增加 400 膳食叶酸当量（DFE）/d，12-16 年 HR：0.93，95%CI：0.85，1.01；16-20 年 HR：0.83，95%CI：0.75，0.92；20-24 年 HR：0.87，95%CI：0.77，0.99）；在诊断前 16-24 年，合成叶酸摄入量较高也与 CRC 风险较低相关（每增加 400 DFE/d，16-20 年 HR：0.91，95%CI：0.84，0.99；20-24 年 HR：0.91，95%CI：0.83，1.01）。在强化后时期（1998-2016 年），即使在使用多种维生素的人群中，总叶酸或特定形式的叶酸摄入与 CRC 风险无关。
结论
在较长的潜伏期后，总叶酸和合成叶酸的摄入均与总体 CRC 风险降低相关。在这个美国女性人群中，没有证据表明强化后时期高叶酸摄入与 CRC 风险增加有关。
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