咖啡：健康之选还是心脏杀手?
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3月4日讯 /生物谷BIOON/--你是否曾因为豆腐脑甜咸党之争失去一段宝贵的友谊？你是否因为一条裙子究竟是蓝黑色还是白金色而导致家庭不和？看了下面的研究，你会发现你的身边有多了一样新的"绝交利器"。
咖啡作为人类消费最多的饮品之一，其作用一直饱受争议。人们争论的焦点在于这种含有咖啡因的饮料对饮用者的心血管有何作用？这一激烈争论自从咖啡的理化性质被解析以来就一直存在。最近来自韩国的科学家公布了一项研究，他们发现饮用咖啡能够降低血管阻塞的风险，而这也是心脏病发作的主要诱因之一。韩国科学家们在调查了超过25000人之后得出了这一结论。研究发现，每天饮用适量咖啡（3-5杯）的受访者患有心血管疾病的风险更低。
不过，这一研究显然也只是为这一问题更添了一把柴。长期以来，医学工作者通过使用血管造影术等方法来试图为这一问题盖棺定论，但却得出了截然不同的结论。有些实验表明咖啡会导致血液中胆固醇水平升高以及血压上升，进而增大患上心脏病的风险；而另一些研究人员却宣称咖啡具有保护心脏的作用。而此次韩国科学家的这一研究则采用了不同的研究指标。前期研究发现，人体血管中会出现不同程度的钙沉积，这种沉积的程度与心脏病的发病有着密切联系。研究人员在调查中发现，许多没有心脏病病史的受访者血管内部也存在这种沉积。因此，研究人员着重调查了这种钙沉积与咖啡饮用量之间的关系，并最终得到了这一结论。
不过，研究人员同时表示他们还需要进一步的验证这一结论。
咖啡中的咖啡因被认为是能够刺激大脑兴奋，但是这种物质同时也引发了许多人对于咖啡是否健康的争论。不同国家的健康专家对这一问题的看法也不尽相同。美国的营养学专家就曾建议每人每天摄入的咖啡因含量不应大于400mg。而英国则认为除了孕妇之外，不必限定人们摄入咖啡因的含量。而孕妇摄入咖啡因的含量则应控制在200mg以下，既每天饮用不超过两杯速溶咖啡。
小贴士：一些饮料的咖啡因含量
速溶咖啡：100mg/杯
淋式咖啡：140mg/杯
茶：75mg/杯
可乐：40mg/听（生物谷）
详细英文报道：
Drinking a few cups of coffee a day may help people avoid clogged arteries - a known risk factor for heart disease - Korean researchers believe.
They studied more than 25,000 male and female employees who underwent routine health checks at their workplace.
Employees who drank a moderate amount of coffee - three to five cups a day - were less likely to have early signs of heart disease on their medical scans.
The findings reopen the debate about whether coffee is good for the heart.
Heart effects
There is a lot of confusion when it comes to the effect of coffee on heart health.
angiogram showing an obstructed coronary artery
In heart disease, the arteries supplying the heart muscle can become blocked
Some studies have linked consumption to heart risk factors, such as raised cholesterol or blood pressure, while others suggest the beverage may offer some heart protection.
But there is no conclusive evidence either way, and the latest research from South Korea, which is published in the journal Heart, only adds to the discussion.
Unexplained link
In the study, the researchers used medical scans to assess heart health.
Specifically, they were looking for any disease of the arteries supplying the heart - the coronary arteries.
In coronary heart disease, the coronary arteries become clogged by the gradual build-up of fatty material within their walls.
The scan the researchers used looks for tiny deposits of calcium in the walls of the coronary arteries to provide an early clue that this disease process may be occurring.
None of the employees included in the Korean study had outward signs of heart disease, but more than one in 10 of them were found to have visible calcium deposits on their scans.
The researchers then compared the scan results with the employees self-reported daily coffee consumption, while taking into account other potential heart risk factors such as smoking, exercise and family history of heart problems.
People who drank a few cups of coffee a day were less likely to have calcium deposits in their coronary arteries than people who drank more than this or no coffee at all.
The study authors say more research is needed to confirm and explain the link.
Coffee contains the stimulant caffeine, as well as numerous other compounds, but its not clear if these might cause good or harm to the body.
Victoria Taylor of the British Heart Foundation said: "While this study does highlight a potential link between coffee consumption and lower risk of developing clogged arteries, more research is needed to confirm these findings and understand what the reason is for the association.
"We need to take care when generalising these results because it is based on the South Korean population, who have different diet and lifestyle habits to people in the UK."
line
How much caffeine?
coffee beans
o In the US, experts say up to 400mg a day appears to be safe for most healthy adults
o There is no recommended daily upper limit for caffeine consumption in the UK, except for pregnant women
o If you e pregnant, you should limit the amount of caffeine you have to 200mg a day - equivalent to two mugs of instant coffee
o one mug of instant coffee: 100mg
o one mug of filter coffee: 140mg
o one mug of tea: 75mg
o one can of cola: 40mg
Source: NHS Choices
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