原帖在此: Fuhrman on egg, diabetes risk and cardiovascular risk?
昨晚讀了蓍草網友貼出來的薈萃文獻,加上益生菌貼的文章,把話題隻集中在“雞蛋是否與胰島素抗拒或者糖尿病相關”這個起始問題方麵, 簡單說一下看法。
薈萃文獻主要結論分為兩個部分,一部分是針對健康人,一部分是針對糖尿病人。糖尿病人飲食上需要注意忌口是常識,所以下麵對糖尿病人這部分結果就不作評論。
那麽對於健康人來說,多吃雞蛋會不會增加糖尿病的風險呢?
薈萃文獻說是會增加42%的風險:
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.
數據來源於下麵這4個研究:
the Cardiovascular Health Study (顯示雞蛋與糖尿病風險無關)
the Adventists’ Health Studies, (顯示肉,加工肉與糖尿病風險有關,沒看到雞蛋的影響)
the Physicians’ Health Study + the Women’s Health Study, 顯示雞蛋與糖尿病正相關增加風險 (薈萃文獻和這兩個研究有全文,所以我主要看了這兩個研究的細節)
然後益生菌提供了兩個新的研究, 結論相反
一為芬蘭研究,其結果是雞蛋和糖尿病負相關,多吃雞蛋反而降低了38%的風險(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.)
第二個是日本的大樣本調查,也是說多吃雞蛋和糖尿病無關或者負相關 (無全文)
那麽我們老百姓信誰好呢?
先看看周福滿是怎麽質疑芬蘭研究的:
“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. ”
他的意思是這個研究裏麵有“混雜因素”(confounders),多吃雞蛋的那組人占年輕,少吸煙,少高血壓,少吃碳水等優勢,即存在一種“健康偏差”。但是此研究是做了數據矯正處理的, 排除了“混雜因素”,我覺得Fuhrman單單用它來否定這個研究結果, 沒有說服力。
混雜因素是營養流行病學調查共有的一個特點/弱點,有太多的幹擾因素,因此存在大量的莫衷一是、眾說紛紜、互相矛盾的各種研究。
我們對比一下the Physicians’ Health Study , the Women’s Health Study 這兩個研究,看看它們有沒有“混雜因素”?
下麵這個圖表非常清晰地顯示,吃最多雞蛋的那一組,存在著“不健康偏差”:吸煙喝酒高血壓多、鍛煉少、熱量攝入多,等等。其數據也做了矯正處理,對“混雜因素”做了處理。
薈萃文獻的作者自己指出這個局限性:“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.” 所以如果要質疑芬蘭的偏差,同樣可以質疑Fuhrman自己引用的研究結果偏差。它們還有另外一個不足: 沒有任何血檢指標(這也是作者自己指出的),缺乏受試者的血糖值,胰島素值等數據。而芬蘭與日本的研究包括這些生物指標數據, 所顯示的結果多了一層機理上的支持。
下麵說一說薈萃分析的另一個看點。
它的主要結論之一其實是雞蛋與心血管疾病和腦卒中無關。
周福滿寫的這本新書名字是“The End of Heart Disease”,主題是預防心血管疾病。雞蛋黃可說是膳食膽固醇的代名詞。可他引用的這篇文獻說:多吃雞蛋與各種心血管疾病和腦卒中均無相關。不知Dr. Fuhrman書裏有無提到過這部分內容, 有何說法? 還是說,多吃雞蛋會增加心血管疾病風險?
另外有個有趣的細節,就是圖片裏那四個綠圈裏的數據對比。雞蛋吃多了,真的會使人血液裏的膽固醇上升嗎?