綜合維他命可以降低吸菸者罹患肺癌的可能性

一份美國新的研究指出，綜合維他命，葉酸還有綠色葉菜類可以降低曾經吸菸和正在吸菸者肺癌的發展。

一份在癌症研究期刊(Cancer Research)線上發表的一篇文章指出，攝取較高的特定微量元素可以降低影響基因信號生成的甲基化(methylation )。許多基因在細胞作用(例:細胞分裂)上扮演著重要的角色，進而在肺腫瘤裡甲基化，顯示出微量元素降低罹癌機率的潛力。微量營養素對吸煙者的角色研究是具爭議性的； 最值得注意的是 Alpha-生育酚(Alpha-Tocopherol)對Beta胡蘿蔔素癌症預防 (ATBC) 試驗，結果顯示beta胡蘿蔔素營養補充品有可能會增加罹患肺癌的機率。

一項由美國國家癌症研究所(National Cancer Institute-NCI)所贊助的研究指出，減少基因甲基化並攝取富含植物化學物質的綜合維他命營養補給品，包括維他命C，胡蘿蔔素，葉黃素，葉酸，維他命A還有K。這類的微量元素可以在綠色葉菜類裡可以找到。

每月至少攝取12份綠葉蔬菜的人降低了17%甲基化的危險性 ; 每日攝取至少750毫克的葉酸則有16%。研究者並指出，綜合維他命使用者降低了43%基因甲基化的機率，即使使用綜合維他命的時間並沒有與甲基話之間有關聯性。

Multivitamins may cut lung cancer risk in smokers

Multivitamins, folate, and green leafy vegetables may reduce the risk of developing lung cancer in current and former smokers, says a new study from the US.

Higher intakes of certain micronutrients may reduce a process called methylation which affects gene signaling. Many genes involved in critical cell functions, including cell division, are methylated in lung tumours, showing the potential of the micronutrients to reduce the risk of lung cancer, according to findings published online ahead of print in Cancer Research.

The role of micronutrients in smokers is controversial with some studies; most notably the Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Trial, reporting that beta-carotene supplements may increase the risk of lung cancer.

The new study, supported by the US National Cancer Institute (NCI), part of the National Institutes of Health, showed that reduced gene methylation with the intake of multivitamin supplements that are rich in phytochemicals, such as vitamin C, carotenoids, lutein, folic acid, and vitamins A and K. Such micronutrients are also present green leafy vegetables.

“This is the first cohort-based study to identify dietary factors associated with reduced promoter methylation in cells exfoliated from the airway epithelium of smokers,” wrote the researchers, led by Steven Belinsky, PhD, from the Lovelace Respiratory Research Institute in Albuquerque.

“Novel interventions to prevent lung cancer should be developed based on the ability of diet and dietary supplements to affect reprogramming of the epigenome,” they added.

‘Impressive’ study

Commenting independently on the study, a spokesperson for ingredient supplier DSM told NutraIngredients that the study illustrates how complex micronutrient research is.

“It impressively shows, for example, that supplements containing beta-carotene, conceivably increasing the risk of lung cancer in heavy smokers when taken in extremely high doses over years, have the potential to reduce cancer risk even in smokers,” said the spokesperson.

“Additionally, the study is further evidence that nature-identical, synthetic micronutrients in multivitamins can be effective in disease risk reduction as micronutrients from vegetables and fruits.”

Study details

Just over 1,100 current and former smokers participating in the Lovelace Smokers Cohort submitted sputum samples and completed questionnaires regarding their dietary intake. The sputum samples were used to examine the degree of methylation of eight genes commonly silenced in lung cancer and associated with risk for this disease.

People who ate at least 12 servings of green leafy vegetables per month had a 17 per cent lower risk of methylation, while a daily folate intake of at least 750 micrograms was associated with a 16 per cent lower risk.

Current multivitamin users had a 43 per cent lower risk of gene methylation, added the researchers, although there was no association between the duration of use and methylation..

More research needed

Sudhir Srivastava, PhD, chief of the Biomarkers Research Group at the NCI called for additional research to independently validate the study’s observations, and also to help resolve contradictions between varying studies.

“This particular study used a well-planned design and can serve as a basis for future identification of the mechanistic targets of these dietary factors,” said Srivastava, who was not involved in the study.

“Such studies are important steps for the future success of chemopreventive strategies.”

資料來源: Cancer Research
Published online ahead of print, doi: 10.1158/0008-5472.CAN-09-3410
“Multi-Vitamins, Folate, and Green Vegetables Protect Against Gene Promoter Methylation in the Aerodigestive Tract of Smokers”
Authors: C.A. Stidley, M.A. Picchi, S. Leng, R. Willink, R. Crowell, F.G. Flores, H. Kang, T. Byers, F.D. Gilliland, S.A. Belinsky