原帖在此: Fuhrman on egg, diabetes risk and cardiovascular risk?
昨晚读了蓍草网友贴出来的荟萃文献,加上益生菌贴的文章,把话题只集中在“鸡蛋是否与胰岛素抗拒或者糖尿病相关”这个起始问题方面, 简单说一下看法。
荟萃文献主要结论分为两个部分,一部分是针对健康人,一部分是针对糖尿病人。糖尿病人饮食上需要注意忌口是常识,所以下面对糖尿病人这部分结果就不作评论。
那么对于健康人来说,多吃鸡蛋会不会增加糖尿病的风险呢?
荟萃文献说是会增加42%的风险:
Results: A total of 22 independent cohorts from 16 studies were identified, including participants ranging in number from 1600 to 90,735 and in follow-up time from 5.8 to 20.0 y. Comparison of the highest category (≥1 egg/d) of egg consumption with the lowest (<1 egg/wk or never) resulted in a pooled HR (95% CI) of 0.96 (0.88, 1.05) for overall CVD, 0.97 (0.86, 1.09) for ischemic heart disease, 0.93 (0.81, 1.07) for stroke, 0.98 (0.77, 1.24) for ischemic heart disease mortality, 0.92 (0.56, 1.50) for stroke mortality, and 1.42 (1.09, 1.86) for type 2 diabetes.
数据来源于下面这4个研究:
the Cardiovascular Health Study (显示鸡蛋与糖尿病风险无关)
the Adventists’ Health Studies, (显示肉,加工肉与糖尿病风险有关,没看到鸡蛋的影响)
the Physicians’ Health Study + the Women’s Health Study, 显示鸡蛋与糖尿病正相关增加风险 (荟萃文献和这两个研究有全文,所以我主要看了这两个研究的细节)
然后益生菌提供了两个新的研究, 结论相反
一为芬兰研究,其结果是鸡蛋和糖尿病负相关,多吃鸡蛋反而降低了38%的风险(After adjustment for potential confounders, those in the highest compared with the lowest egg intake quartile had a 38% (95% CI: 18%, 53%; P-trend across quartiles <0.001) lower risk of incident T2D. Analyses with metabolic risk markers also suggested an inverse association with fasting plasma glucose and serum C-reactive protein but not with serum insulin.)
第二个是日本的大样本调查,也是说多吃鸡蛋和糖尿病无关或者负相关 (无全文)
那么我们老百姓信谁好呢?
先看看周福满是怎么质疑芬兰研究的:
“Scientists have questions on the impact of this study because the group with the higher intake was more likely to be younger, with less likelihood of smoking and less heart disease and hypertension; they also had a notably higher fiber and lower carbohydrate intake. With such a healthier cohort, it may not be the four eggs eaten every week that made them healthier. ”
他的意思是这个研究里面有“混杂因素”(confounders),多吃鸡蛋的那组人占年轻,少吸烟,少高血压,少吃碳水等优势,即存在一种“健康偏差”。但是此研究是做了数据矫正处理的, 排除了“混杂因素”,我觉得Fuhrman单单用它来否定这个研究结果, 没有说服力。
混杂因素是营养流行病学调查共有的一个特点/弱点,有太多的干扰因素,因此存在大量的莫衷一是、众说纷纭、互相矛盾的各种研究。
我们对比一下the Physicians’ Health Study , the Women’s Health Study 这两个研究,看看它们有没有“混杂因素”?
下面这个图表非常清晰地显示,吃最多鸡蛋的那一组,存在着“不健康偏差”:吸烟喝酒高血压多、锻炼少、热量摄入多,等等。其数据也做了矫正处理,对“混杂因素”做了处理。
荟萃文献的作者自己指出这个局限性:“Additional limitations of the present study include the observational nature of the study design in which residual confounding or unmeasured confounding could partly or completely explain our results.” 所以如果要质疑芬兰的偏差,同样可以质疑Fuhrman自己引用的研究结果偏差。它们还有另外一个不足: 没有任何血检指标(这也是作者自己指出的),缺乏受试者的血糖值,胰岛素值等数据。而芬兰与日本的研究包括这些生物指标数据, 所显示的结果多了一层机理上的支持。
下面说一说荟萃分析的另一个看点。
它的主要结论之一其实是鸡蛋与心血管疾病和脑卒中无关。
周福满写的这本新书名字是“The End of Heart Disease”,主题是预防心血管疾病。鸡蛋黄可说是膳食胆固醇的代名词。可他引用的这篇文献说:多吃鸡蛋与各种心血管疾病和脑卒中均无相关。不知Dr. Fuhrman书里有无提到过这部分内容, 有何说法? 还是说,多吃鸡蛋会增加心血管疾病风险?
另外有个有趣的细节,就是图片里那四个绿圈里的数据对比。鸡蛋吃多了,真的会使人血液里的胆固醇上升吗?