巧克力與較低中風風險及死亡率有關


  【24drs.com】February 12, 2010 — 一項來自加拿大研究團隊的新綜合分析結果顯示,攝取較多的巧克力可能與降低中風風險和中風相關死亡率有關。
  
  來自兩項前瞻性世代研究結果顯示,相較於未吃巧克力的人,每週食用一次巧克力的人,中風風險下降22%,每週使用含有50公克類黃酮的巧克力者,因為中風死亡的風險下降了46%。第三項研究中,攝取巧克力與中風或死亡則沒有關聯性。
  
  資深作者、加拿大多倫多大學與St. Michael醫院的Gustavo Saposnik醫師向Medscape神經學表示,針對其間關聯性的研究數目仍然很少,我們需要更多前瞻性研究,專一地確認巧克力種類與數量,包括在巧克力組成裡面的類黃酮量,以取得更確認的結論。
  
  在4月份美國神經醫學會第62屆年會之前,這些結果會先在2月11日發表。這篇摘要將於2月17日張貼在http://www.ann.com。
  
  【效應差異】
  研究第一作者、加拿大安大略曼徹斯特漢米爾頓大學Sarah Sahib學士寫到,巧克力包含可可奶油、類黃酮、碳水化合物與維他命。過去的研究,大部分的流行病學研究顯示,攝取巧克力對於心血管疾病效應差異大。而有關攝取異黃酮與中風風險之間的關係目前已知並不多。
  
  為了檢驗這之間的關聯性,作者們進行了一項於2001年至2009年之間發表研究的系統性綜論,以包括類黃酮、黃烷醇、異黃酮與花青素等關鍵字搜尋,以及中風與死亡率。
  
  Saposnik醫師表示,我們找到88篇已發表的文獻,其中包括3篇前瞻性研究,以及另外1篇回溯性研究,提供了有關巧克力攝取對中風風險效應的部分資訊。這些研究中有2篇顯示中風風險下降,而另外2篇則顯示沒有任何差異。
  
  舉例來說,在這3篇前瞻性研究中,1項發現,當其中3%兒茶素是來自巧克力時,攝取類黃酮與中風或死亡風險之間沒有關係(相對風險[RR]為0.92;95%信賴區間[CI]為0.51-1.68)。
  
  然而,第2項研究發現,相較於未攝取者,每週攝取一次巧克力與中風率下降有關(RR為0.78;95% CI為0.65-0.94)。
  
  第3項研究針對攝取類黃酮與中風死亡率之間的關係進行研究,發現50公克的巧克力可以保護免於發生中風(HR為0.54;95% CI為0.30-0.96)。
  
  作者們的結論是,需要之後前瞻性研究評估巧克力為主的類黃酮攝取是否真的可以降低中風風險,或是這項的好處是被較健康的使用者效應所誤導。
  
  【研究充滿挑戰】
  雖然有關這個關係的更多資料將會有所幫助,然而,Saposnik醫師指出,要進行這樣的研究仍有許多挑戰。首先,記錄攝取之巧克力中確切的類黃酮或是其他被認為具有活性物質含量是很重要的。
  
  他指出,有一些研究比較不同食物元素的類黃酮與抗氧化能力。黑巧克力有最高的類黃酮與花青素,這被證實與較低的心血管疾病風險有關,除此之外,黑巧克力有最高的抗氧化活性。
  
  此外,巧克力的種類很多,且要到影響中風風險的量可能帶來一定含量的糖與脂肪,這可能抵銷了好處。Saposnik醫師表示,每天50公克的巧克力是很顯著的數量。
  
  他附帶表示,最後,大型的縱向分析是非常昂貴的,但贊助這種研究的經費卻很少,這可能解釋為什麼大部分證據都是來自流行病學研究。另外一個選擇可能是進行較小型的研究,針對攝取固定數量的巧克力對特定中風風險立即生化指標的效應研究。
  
  這項研究未接受商業贊助。作者們表示沒有相關資金上的往來。

Chocolate Linked to Lower Stroke and Stroke Mortality Risk

By Susan Jeffrey
Medscape Medical News

February 12, 2010 — Just in time for Valentine's Day, a new systematic review from Canadian researchers suggests higher chocolate consumption may be associated with a lower risk for incident stroke and stroke-related mortality.

Results of 2 prospective cohort studies showed, respectively, a 22% reduction in stroke risk for those who had 1 serving of chocolate per week and a 46% reduction in stroke mortality from weekly consumption of flavonoids in 50 g of chocolate vs no consumption. A third study showed no association between chocolate intake and stroke or death.

However, the number of studies looking at this relationship was small, senior author Gustavo Saposnik, MD, from St. Michael's Hospital and the University of Toronto, Canada, told Medscape Neurology. "We need more prospective studies that specifically identify the type of chocolate and the amount, including the amount of flavonoids included in the composition of the chocolate, to make more valid conclusions," he said.

The results were released February 11 in advance of their planned presentation at the upcoming American Academy of Neurology 62nd Annual Meeting in April. The abstract will post to http://www.aan.com on February 17.

Varying Effects

Chocolate contains cocoa butter, flavonoids, carbohydrates, and vitamins. Previous studies, most of them epidemiological, have shown varying effects of chocolate consumption on the risk for cardiovascular disease, the researchers, with first author Sarah Sahib, BScCA, from McMaster University in Hamilton, Ontario, Canada, write. "Less is known about the risk of stroke in association with flavonoid intake," they note.

To examine this association, the authors carried out a systematic review of studies published between 2001 and 2009, using search terms including flavonoids, flavanols, isoflavones, and anthocyanidins, as well as stroke and mortality.

"We found 88 publications, among them 3 prospective studies, and another retrospective study providing some information on the effect of chocolate consumption on the incident risk of stroke," Dr. Saposnik said. "Two of these studies show a reduction in the incident risk of stroke, and the other 2 didn't show any substantial difference."

For example, of the 3 prospective studies, 1 found no association between flavonoid intake and the risk for stroke or death when 3% of catechin intake came from chocolate (relative risk [RR], 0.92; 95% confidence interval [CI], 0.51 - 1.68).

However, a second study found a reduction in incident stroke for chocolate consumption once per week vs no consumption (RR, 0.78; 95% CI, 0.65 - 0.94).

The third study looked at the association between flavonoid intake and stroke mortality and found a suggestion of protection against stroke mortality from 50 g of chocolate (hazard ratio, 0.54; 95% CI, 0.30 - 0.96).

The authors conclude that further prospective studies are needed "to assess whether the benefit of chocolate-based flavonoid consumption truly lowers stroke risk, or whether the apparent benefit is biased by a healthy user effect."

Investigation a Challenge

However, although more data on this link would be helpful, Dr. Saposnik pointed to several challenges to doing these kinds of studies. First, it is important to document the actual content of flavonoids or other substances thought to be active in the chocolate being consumed.

"There are some studies that compare the content of flavonoids for different food elements and antioxidant capacity," he said. Dark chocolate is one with the highest flavonoids and procyanidins, which have been associated with lower cardiovascular risk, and in addition, dark chocolate has the highest antioxidant capacity.

Still, there are varying types of chocolate, and the amounts that are required to affect stroke risk may bring a load of sugar and fats that may work counter to the beneficial effects. "50g of chocolate per day is a significant amount," Dr. Saposnik notes.

Finally, large longitudinal studies are also expensive, and funding for them scarce, which may explain why much of the evidence is coming from epidemiologic studies, he added. One alternative may be to conduct smaller studies, looking the effects of consuming controlled amounts of chocolate on some intermediate biomarker of stroke risk.

The study received no commercial support. The authors have disclosed no relevant financial relationships.

American Academy of Neurology 62nd Annual Meeting. April 10-17, 2010. Published online February 11, 2009.

    
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