最新证据!高水平维生素D或能降低患癌风险
2018/03/09
最新发表在BMJ上的一篇论文证实,一项针对日本成年人的大型研究发现,高水平的维生素D可能与患癌(包括肝癌)风险降低有关。


图片来源:BMJ( DOI:https://doi.org/10.1136/bmj.k671)

维生素D可由皮肤被阳光照射产生,有助于维持体内的钙水平,从而使骨骼、牙齿和肌肉保持健康。近年来,越来越多的证据表明,维生素D可能对其他慢性疾病(包括某些癌症)有好处;但迄今为止,大多数研究都是在欧洲或美国人群中进行的,来自亚洲人群的证据非常有限。

由于维生素D的浓度和代谢会因种族而异,因此,弄清楚在非白种人人群(non-Caucasian populations)中是否会出现类似的效果非常重要。正是基于这样的背景,一个设在日本的国际研究小组开始评估,是否维生素D与“总癌症风险以及特定部位癌症的风险”有关。

在这项题为“Plasma 25-hydroxyvitamin D concentration and subsequent risk of total and site specific cancers in Japanese population: large case-cohort study within Japan Public Health Center-based Prospective Study cohort”的研究中,科学家们分析了来自Japan Public Health Center-based Prospective (JPHC) Study这一项目的数据。该调查共涉及了33,736名年龄在40岁到69岁之间的男性和女性参与者。

在研究开始时,参与者们提供了关于病史、饮食和生活方式的详细信息,并被采集了血液样本用以测量维生素D水平。随后,他们平均被监测了16年,期间,新发了3,301例癌症。


Credit: CC0 Public Domain

在调整了几个已知的癌症风险因素后,如年龄、体重(BMI)、身体活动水平、吸烟、酒精摄入量和饮食因素,研究人员发现,在男性和女性中,较高水平的维生素D都与总体癌症相对风险(relative risk of overall cancer)降低(约20%)有关。此外,较高的维生素D水平还与肝癌相对风险降低30-50%有关,且这种相关性在男性中更加明显。

同时,研究人员注意到,没有一种被调查的癌症表现出,与“较高维生素D水平有关” 的患癌风险增加。

不过,研究人员也指出了这一研究的一些局限性,如被调查的特定器官癌症的数量相对较少。此外,虽然他们调整了几个已知的风险因素,但不能排除“其他因素也可能会对结果产生影响”这种可能性。

总结来说,作者们认为,他们的发现支持了维生素D可能有助于预防某些癌症这一理论,但或许存在一个上限效应,因此,需要进一步的研究来阐明维生素D用于癌症预防的最佳浓度。

参考资料:

Higher Vitamin D levels may be linked to lower risk of cancer

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  • Plasma 25-hydroxyvitamin D concentration and subsequent risk of total and site specific cancers in Japanese population: large case-cohort study within Japan Public Health Center-based Prospective Study cohort

    Objective To evaluate the association between pre-diagnostic circulating vitamin D concentration and the subsequent risk of overall and site specific cancer in a large cohort study. Design Nested case-cohort study within the Japan Public Health Center-based Prospective Study cohort. Setting Nine public health centre areas across Japan. Participants 3301 incident cases of cancer and 4044 randomly selected subcohort participants. Exposure Plasma concentration of 25-hydroxyvitamin D measured by enzyme immunoassay. Participants were divided into quarters based on the sex and season specific distribution of 25-hydroxyvitamin D among subcohorts. Weighted Cox proportional hazard models were used to calculate the multivariable adjusted hazard ratios for overall and site specific cancer across categories of 25-hydroxyvitamin D concentration, with the lowest quarter as the reference. Main outcome measure Incidence of overall or site specific cancer. Results Plasma 25-hydroxyvitamin D concentration was inversely associated with the risk of total cancer, with multivariable adjusted hazard ratios for the second to fourth quarters compared with the lowest quarter of 0.81 (95% confidence interval 0.70 to 0.94), 0.75 (0.65 to 0.87), and 0.78 (0.67 to 0.91), respectively (P for trend=0.001). Among the findings for cancers at specific sites, an inverse association was found for liver cancer, with corresponding hazard ratios of 0.70 (0.44 to 1.13), 0.65 (0.40 to 1.06), and 0.45 (0.26 to 0.79) (P for trend=0.006). A sensitivity analysis showed that alternately removing cases of cancer at one specific site from total cancer cases did not substantially change the overall hazard ratios. Conclusions In this large prospective study, higher vitamin D concentration was associated with lower risk of total cancer. These findings support the hypothesis that vitamin D has protective effects against cancers at many sites.

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