Gann P H, Hennekens C H, Sacks F M, Grodstein F, Giovannucci E L, Stampfer M J
Department of Preventive Medicine, Northwestern University School of Medicine, Chicago, IL 60611.
J Natl Cancer Inst. 1994 Feb 16;86(4):281-6. doi: 10.1093/jnci/86.4.281.
Although some evidence suggests that dietary fat intake is related to prostate cancer, epidemiologic studies have been inconsistent.
Our purpose was to assess the association between plasma lipid levels, particularly linoleic and alpha-linolenic acids, and the development of prostate cancer.
In 1982, at the start of the Physicians' Health Study, 14916 U.S. male physicians provided plasma samples, which were frozen at -82 degrees C. Data accumulated from a series of questionnaires were used to assess the intake of various foods. We used a nested case-control design to compare the fatty acid compositions in plasma from 120 men who later developed prostate cancer with 120 matched controls who did not. Individual fatty acids were measured in plasma as a percentage of total fatty acids, using capillary gas chromatography. Conditional logistic regression models were used to obtain odds ratio estimates while adjusting simultaneously for the effects of one or more potential confounders.
The relative risks (RRs) of prostate cancer for men in successively higher quartiles of plasma alpha-linolenic acid level were 3.0 (95% confidence interval [CI] = 1.2-7.3), 3.4 (95% CI = 1.6-7.5), and 2.1 (95% CI = 0.9-4.9), compared with those with levels below the detection threshold (P trend = .03). For linoleic acid, RRs in successively higher quartiles were 0.7 (95% CI = 0.4-1.5), 0.8 (95% CI = 0.4-1.6), and 0.6 (95% CI = 0.3-1.3), with the lowest quartile as referent (P trend = .24). The effect estimates were not notably altered by adjustment for exercise, body mass, meat and dairy consumption, or other fatty acid levels in the plasma. The RR for eating red meat at least five times per week compared with less than once a week was 2.5 (95% CI = 0.9-6.7) and was little changed by adjustment for alpha-linolenic acid, although alpha-linolenic acid levels were correlated with intake of red meat and butter. The association of alpha-linolenic acid levels with prostate cancer was greater among men with low linoleic acid and reduced meat intake.
These results suggest that low plasma levels of alpha-linolenic acid might be associated with reduced risk of prostate cancer, independently of high meat intake. High linoleic acid and low marine fatty oils were not associated with increased risk, as previously hypothesized.
The effects of dietary alpha-linolenic acid, particularly from vegetable sources, warrant further study. The effects of dietary linoleic acid and marine fatty acids seen in animal bioassays might not apply to human prostate cancer.
尽管一些证据表明饮食脂肪摄入与前列腺癌有关，但流行病学研究结果并不一致。
我们的目的是评估血浆脂质水平，特别是亚油酸和α-亚麻酸与前列腺癌发生之间的关联。
1982年，在医生健康研究开始时，14916名美国男性医生提供了血浆样本，并在-82℃下冷冻保存。通过一系列问卷调查积累的数据用于评估各种食物的摄入量。我们采用巢式病例对照设计，比较了120名后来患前列腺癌的男性与120名匹配的未患前列腺癌的对照者血浆中的脂肪酸组成。使用毛细管气相色谱法测量血浆中各脂肪酸占总脂肪酸的百分比。使用条件逻辑回归模型在同时调整一个或多个潜在混杂因素影响的情况下获得比值比估计值。
与血浆α-亚麻酸水平低于检测阈值的男性相比，血浆α-亚麻酸水平处于四分位数依次升高组的男性患前列腺癌的相对风险（RR）分别为3.0（95%置信区间[CI]=1.2-7.3）、3.4（95%CI=1.6-7.5）和2.1（95%CI=（0.9-4.9），P趋势=0.03）。对于亚油酸，四分位数依次升高组的RR分别为0.7（95%CI=0.4-1.5）、0.8（95%CI=0.4-1.6）和0.6（95%CI=0.3-1.3），以最低四分位数为参照（P趋势=0.24）。对运动、体重、肉类和奶制品消费或血浆中其他脂肪酸水平进行调整后，效应估计值没有明显改变。与每周食用红肉少于一次相比，每周至少食用红肉五次的RR为2.5（95%CI=0.9-6.7），对α-亚麻酸进行调整后变化不大，尽管α-亚麻酸水平与红肉和黄油的摄入量相关。在亚油酸水平低且肉类摄入量减少的男性中，α-亚麻酸水平与前列腺癌的关联更强。
这些结果表明，血浆α-亚麻酸水平低可能与前列腺癌风险降低有关，与高肉类摄入量无关。如先前假设的那样，高亚油酸和低海洋脂肪油与风险增加无关。
饮食中α-亚麻酸，特别是来自植物来源的α-亚麻酸的作用值得进一步研究。在动物生物测定中观察到的饮食中亚油酸和海洋脂肪酸的作用可能不适用于人类前列腺癌。
