最近肠道杂志（Gut）有文献认为“生活在阳光充足的地域如美国南方的人，较生活在阳光较少的美国北方地区的人们患炎症性肠病（如克罗恩病、溃疡性结肠炎，Inflammatory bowel disease (IBD) includes Crohn's disease and ulcerative colitis）者少”。据此，有专家推测可能与阳光照射促进皮下组织合成维生素Ｄ有关，即人体内的维生素Ｄ有利于调整或增强机体的免疫力而有助于炎症性肠病的预防。事实果真如此？我个人认为很难说，毕竟炎症性肠病之发病机理复杂，参与因素众多，如其发生与环境、遗传、感染和免疫等诸多因素有关。因此，目前认定阳光照射的时间（实为维生素Ｄ之水平）与炎症性肠病发病有关为时尚早！

Inflammatory Bowel Disease Less Common in Sunny States

Researchers say sunshine may boost vitamin D levels, affecting immune function

THURSDAY, Jan. 12 (HealthDay News) -- People who live in sunnier regions of the United States are less likely to develop inflammatory bowel disease, a new study says.

The findings support previous European research and could lead to new types of treatment and preventive measures, the study authors said.

Inflammatory bowel disease (IBD) includes Crohn's disease and ulcerative colitis, which can be extremely painful and require surgery. The causes of IBD remain largely unknown.

In this study, researchers analyzed long-term data collected from 238,000 participants in the Nurses' Health Study I and the Nurses' Health Study II, which were launched in 1976 and 1989, respectively. None of the participants had inflammatory bowel disease at the start of the studies.

Compared to participants who lived in northern areas of the United States, those living in southern areas were 52 percent less likely to develop Crohn's disease by the age of 30 and 38 percent less likely to develop ulcerative colitis.

The study appears online in the journal Gut.

"A leading explanation for this north-south gradient in the risk of ulcerative colitis and Crohn's disease may be differences in exposure to sunlight, or UVB radiation, which is generally greater in southern latitudes," wrote Dr. Hamed Khalili, of Massachusetts General Hospital in Boston, and colleagues.

"UV radiation is the greatest environmental determinant of plasma vitamin D, and there is substantial experimental data supporting a role for vitamin D in the innate immunity and regulation of inflammatory response," they noted.

SOURCE: Gut, news release, Jan. 11, 2012