Szilagyi Andrew, Nathwani Usha, Vinokuroff Christina, Correa José A, Shrier Ian
Division of Gastroenterology, Department of Medicine, The Sir Mortimer B Davis Jewish General Hospital, McGill University, Canada.
Nutr Cancer. 2006;55(2):141-50. doi: 10.1207/s15327914nc5502_4.
Dairy food consumption has been inconsistently shown to protect against colorectal cancer (CRC) in case-based studies, and no clear benefits against recurrent colonic polyps (CRP) have been reported. Based on population-based studies we have hypothesized that dairy food intake may have anti-CRC effects at both low intake lactase non-persistent (LNP) populations and at high intake lactase persistent (LP) subjects. We separately analyse existing case-based studies and divide origins into high LNP (>or= 80% LNP prevalence), low LNP (prevalence <or= 20%) and mid LNP countries (21-79% prevalence), which coincide with low, high, and mid quantity dairy food intake regions, respectively. Odds ratios and relative risks (RR) of highest versus lowest dairy intake within each group are analyzed together for assessment of protection against CRC and CRP. Eighty studies met stipulated criteria. Thirteen analyzed the effect on recurrent polyps. Forest plots from 2 regions, high LNP (low dairy food intake) RR = 0.84 [95% confidence interval (CI) = 0.73-0.97) and low LNP (high dairy food intake) RR = 0.80 (95% CI = 0.73-0.88) demonstrated significant protection against CRC. In mixed LNP/LP populations (mid dairy food intake) nonsignificant protection was found RR = 0.92 (95% CI = 0.79-1.06). Similar regional analysis for CRP failed to show significant protective effect in any region. This meta-analysis supports that the highest level of dairy food consumption protects subjects in both high and low LNP regions but not in areas with significant mixed LNP/LP populations. In both groups, dairy foods had no effect on polyp formation, suggesting it may only protect against CRC at late stages of promotion. These results raise the possibility that LNP/LP status may be partly responsible for the discrepant results with respect to the relationship between dairy food consumption and CRC.
在基于病例的研究中，乳制品消费对结直肠癌（CRC）的预防作用并不一致，且尚无针对复发性结肠息肉（CRP）的明确益处的报道。基于人群研究，我们推测，在低乳糖酶不持续（LNP）人群低乳制品摄入量时以及高乳糖酶持续（LP）人群高乳制品摄入量时，乳制品摄入可能具有抗结直肠癌作用。我们分别分析现有的基于病例的研究，并将来源地分为高LNP（LNP患病率≥80%）、低LNP（患病率≤20%）和中等LNP国家（患病率21%-79%），它们分别与低、高和中等乳制品摄入量地区相对应。分析每组中最高与最低乳制品摄入量的比值比和相对风险（RR），以评估对结直肠癌和CRP的预防作用。80项研究符合规定标准。13项分析了对复发性息肉的影响。来自高LNP（低乳制品摄入量）地区RR = 0.84 [95%置信区间（CI）= 0.73 - 0.97]和低LNP（高乳制品摄入量）地区RR = 0.80（95%CI = 0.73 - 0.88）两个地区的森林图显示对结直肠癌有显著预防作用。在混合LNP/LP人群（中等乳制品摄入量）中未发现显著预防作用RR = 0.92（95%CI = 0.79 - 1.06）。对CRP的类似区域分析在任何地区均未显示出显著的保护作用。这项荟萃分析支持，最高水平的乳制品消费对高LNP和低LNP地区的人群有保护作用，但对LNP/LP人群显著混合的地区则没有。在两组中，乳制品对息肉形成均无影响，表明其可能仅在促进的后期阶段预防结直肠癌。这些结果增加了一种可能性，即LNP/LP状态可能部分导致了乳制品消费与结直肠癌关系方面的结果差异。
