研究发现，平均每天3个小时暴露在阳光下能够使患上乳腺癌的风险大幅度降低高达50%之多。这项研究表明经常接受阳光的照射能够促进皮肤中合成维生素D，实验室测试表明维生素D对癌细胞有着极强的预防作用。
据国外媒体报道，加拿大科学家在一项研究中比较了3101名乳腺癌受害女性和3471名健康女性志愿者的相关数据信息。每一名受访者都被询问了她们分别在自己十几岁、二十至三十岁，四十至五十岁和六十至七十余岁这四个阶段时期，身处户外活动的时间情况。该项研究结果已经发表在了《美国流行病学杂志》(American Journal of Epidemiology)中。
充足的维生素D帮助男性远离心脏病或中风
研究显示，那些十几岁时，每周至少有21小时暴露与太阳紫外线中的女性，相较那些一天照射太阳不足一小时的受访者，患上乳腺癌的风险要降低29%。四十至五十岁照射太阳时间充足的女性这种风险下降了26%，而超过60岁人的风险竟然下降了50%。
与此同时另一份研究发现，充足的维生素D还能帮助男性远离心脏病或中风。来自美国的这项研究，针对约119,000名成年人进行了长达20年的跟踪调查发现，长期保持600国际单位维生素D摄入的男性要比那些摄入不足100国际单位的男性患上心脏病或中风的风险降低约16%，不过这种模式似乎并不适用于女性。
不过有关专家也同时警告，这两种研究都应该均衡考虑到长时间暴露在阳光下会提高患上皮肤癌风险的因素。（生物谷Bioon.com）
生物谷推荐原文出处：
American Journal of Epidemiology doi: 10.1093/aje/kwn198
Vitamin D From Dietary Intake and Sunlight Exposure and the Risk of Hormone-Receptor-Defined Breast Cancer
Kristina M. Blackmore, Maia Lesosky, Heidi Barnett, Janet M. Raboud, Reinhold Vieth and Julia A. Knight
Evidence has emerged for a role of vitamin D in the development of breast cancer, and there is some suggestion that its antiproliferative effect is greater in hormone-receptor-positive cells. Few epidemiologic studies have considered the association between vitamin D and hormone-receptor-defined breast cancer, and the results are conflicting. Considering 759 cases and 1,135 controls from a case-control study (Ontario, Canada, 2003–2005), the authors examined the association between vitamin D intake at specific ages and combined estrogen-receptor- (ER) and progesterone-receptor- (PR) defined breast cancer. While increased intake of vitamin D (from the sun and diet) was most consistently associated with a significantly reduced risk of ER+/PR+ tumors (e.g., odds ratio = 0.76, 95% confidence interval: 0.59, 0.97 for use of cod liver oil during adolescence), comparable nonsignificant associations were found for receptor-negative (ER?/PR?) (odds ratio = 0.74, 95% confidence interval: 0.53, 1.04) and mixed (ER+/PR?) (odds ratio = 0.79, 95% confidence interval: 0.51, 1.22) tumors. This study suggests that vitamin D is associated with a reduced risk of breast cancer regardless of ER/PR status of the tumor. Future studies with a larger number of receptor-negative and mixed tumors are required.
