增加摄入维生素Ｄ

可降低乳腺癌、结直肠癌的发生

对抗肿瘤是医学界永不降温的话题。

几乎等同于抗衰老。

相关链接：

Vitamin D&CancerRisk

OTC药物维生素D

维生素D 的食物来源？（原文）

维生素D主要存在于海鱼、动物肝脏、蛋黄和瘦肉中。另外像脱脂牛奶、鱼肝油、乳酪、坚果和海产品、添加维他命D的营养强化食品。也含有丰富的维生素D。植物性食物几乎不含有维生素D，维生素D主要来源于动物性食物。维生素D的来源与其他营养素略有不同，除了食物来源之外，还可来源于自身的合成制造，但这需要多晒太阳，接受更多的紫外线照射。

经常晒太阳，以保证足够的紫外线照射，预防维生素D的缺乏。经常晒太阳，以保证足够的紫外线照射，预防维生素D的缺乏。

但是要记住晒阳光可不是中午去晒,要在早上10点之前下午3点之后才可以晒啊,因为中午的有害光线太多了。

但值得注意的是，维生素D不可过量补充，如果过量服用维生素D，会使体内维生素D蓄积过多，出现中毒的症状，如食欲下降、恶心和消瘦等。

Clinical Context

Higher levels of metabolites of vitamin D have been associated with lower risks for cancer in some observational research, although data regarding the effectiveness of vitamin D supplementation and cancer prevention has not all been positive. In a study of the Women's Health Initiative cohort by Wactawski-Wende and colleagues, which appeared in the February 16, 2006, issue of the The New England Journal of Medicine, supplementation with vitamin D at a dose of 200 IU twice daily failed to reduce rates of colon cancer compared with placebo.

高代谢水平的维生素D与低风险的癌肿相关，这在另外一些研究中也有发现，尽管维生素的用量和防癌效果的联系还没有被明确。

另外一项研究（Wactawski-Wende）认为，每天200国际单位的量是没有效果的。

The dose of vitamin D in the Women's Health Initiative was modest, and subjects were followed up for a mean of only 7 years. It is not clear if there is a threshold for serum 25-hydroxyvitamin D levels, the best serum marker of vitamin D levels, in reducing the risk for cancer. Two current analyses address this issue.

目前，抗癌的门槛剂量并不清楚。 

Vitamin D Appears to Cut Breast and Colorectal Cancer Risk  CME

维生素D可以降低腺癌和结直肠的风险

J Steroid Biochem Mol Biol. Published online January 30, 2007.

Am J Prev Med. 2007;32:210-216.

Release Date: February 12, 2007; Valid for credit through February 12, 2008  

February 12, 2007   

       Researchers say that raising vitamin D levels may prevent up to half of all breast and two thirds of colorectal cancer cases in the United States. Based on the results of 2 separate studies, the investigators recommend a daily intake of 2000 IU of vitamin D3 and, when possible, moderate sun exposure.

美国的研究者说，提高维生素D的水平可以防止一半的乳腺癌和2/3的结直肠癌的病例发生。

这个结论是基于2项独立的研究结果得出的。研究者推荐每天服用2000国际单位的维生素D3和（如果可行就另加）中等程度的日光浴。

"The results are pretty straightforward," Karen Glanz, PhD, director of Emory University's Prevention Research Center at the Rollins School of Public Health in Atlanta, Georgia, said in a news release. However, changing behavior on the basis of these studies may be premature, she noted. The analyses found an association between vitamin D levels and lowered risk, not a definite link, Dr. Glanz said, but adding vitamin D to the diet or taking a supplement would probably not do much harm and there could be a benefit.

During an interview with Medscape, lead author Cedric Garland, DrPH, of the University of California at San Diego, agreed that future consensus is needed, but he recommended no delay in raising vitamin D levels. "We shouldn't hold up implementation," he said. "Inadequate photosynthesis or oral intake of vitamin D is associated with high incidence and mortality rates of breast cancer."

Published in the January 30 Article in Press issue of the Journal of Steroid Biochemistry and Molecular Biology, the researchers pooled dose-response data from 2 previous studies — the Harvard Nurses Health Study and the St. George's Hospital Study. They found that patients with the highest blood levels of 25-hydroxyvitamin D had the lowest risk for breast cancer.

Dr. Garland and his team divided the more than 1700 records in the studies into 5 groups from the lowest blood levels of 25-hydroxyvitamin D (< 13 ng/mL) to the highest (approximately 52 ng/mL). These data also included whether the patient had developed cancer.

The investigators found that patients with serum 25-hydroxyvitamin D of approximately 52 ng/mL had a 50% lower risk for breast cancer than those with serum measuring less than 13 ng/mL. This level corresponds to a vitamin D intake of 4000 IU per day, which exceeds the National Academy of Sciences upper limit of 2000 IU per day. "Leading researchers are building a case to have this level increased," Dr. Garland told Medscape, "but in the meantime, we are recommending a daily intake of 2000 IU."

The group is also calling for an additional 10 to 15 minutes of daily sun exposure when appropriate — an amount estimated to be equivalent to an oral intake of 3000 IU of vitamin D3.

But What About the Risk for Skin Cancer?

As previously reported by Medscape, the American Academy of Dermatology has voiced concern about the vitamin D literature prescribing the health benefits of sunlight. "While many health issues are complex and involve multiple factors, we know that ultraviolet light is the primary cause of skin cancer, and avoiding excessive exposure to the sun and other forms of ultraviolet radiation is the solution," Clay Cockerell, MD, president of the academy said in a news release.

During an interview with Medscape, Dr. Garland emphasized that his group is advocating prudence and moderation, including the use of a broad-brimmed hat. "I think most physicians will see this as a well-controlled and reasonable approach," he added.

The article points out that sun exposure is inadvisable for patients with primary photosensitivity disorders, people taking photosensitizing medications, and anyone with a personal or close family history of skin cancer or actinic keratosis.

Evidence Stacking in Favor of Vitamin D

Dr. Garland was also a coauthor of a second study examining the effect of vitamin D levels on colon cancer risk. Published in the February issue of the American Journal of Preventive Medicine, the researchers conducted a meta-analysis of 5 studies examining serum 25-hydroxyvitamin in colorectal cancer.

The investigators combined the findings of the 5 studies using standard methods for pooled analysis. There were 535 cases and 913 controls or 1448 participants in total. The researchers divided the results into quintiles with median 25-hydroxyvitamin values of 6, 16, 22, 27, and 37 ng/mL.

Previous studies had shown that lower blood levels of vitamin D did not protect against colorectal cancer, but in the current study, the researchers came to a different conclusion. "Through this meta-analysis we found that raising the serum level of 25-hydroxyvitamin D to 34 ng/mL would reduce the incidence rates of colorectal cancer by half," lead author Edward Gorham, MPH, PhD, a research epidemiologist with the Naval Health Research Center in San Diego told reporters. "We project a two-thirds reduction in incidence with serum levels of 46 ng/mL."

The amount of dietary vitamin D needed to reach the serum levels that appear to be protective against colorectal cancer — 1000 to 2000 IU per day — would not pose any risk, Dr. Gorham said. "The Institute of Medicine has set a 'No Adverse Effect Level' of 2000 IU per day for vitamin D intake, so this recommendation would be safe for most people."

(来源)

以下文字出自：

http://blog.sina.com.cn/u/40da7e4f010007ce

美国研究人员最新发布的研究报告说，补充维生素D可以对预防乳腺癌和结肠癌起到一定效果。
   
　　美国加利福尼亚大学圣迭戈分校癌症预防专家领导的研究小组在最新一期《类固醇生物化学和分子生物学杂志》上报告说，他们收集了之前两项大规模的维生素D研究数据，并将1760人的实验数据按照血清中25－羟基维生素D的水平高低分为5组。结果发现，人体血清中25－羟基维生素D的水平越高，罹患乳腺癌的风险就越低。报告作者之一塞德里克·加兰博士认为，如果每天额外摄入2000国际单位的维生素D3，就可以使患乳腺癌的风险降低50%。
   
　研究人员还在12日出版的《美国预防医学杂志》上报告说，如果将人体血清中的25－羟基维生素D水平保持在每毫升34毫微克，结肠癌发生率可降低一半。如果进一步提高到每毫升46毫微克，可将结肠癌发生率减少三分之二，而这需要每天额外补充2000国际单位的维生素D3。
   
　　研究人员表示，补充维生素15的方式包括调整饮食、服用片剂和晒太阳等。如果天气允许，人们每天最好花上10分钟到15分钟晒太阳。

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维生D与抗癌