2015年8月29日 星期六

咖啡與健康那些事兒 Questions About Coffee and Health: We Have Some Answers

Questions About Coffee and Health: We Have Some Answers

Q. and A.August 28, 2015
In an article on Monday, I reviewed the evidence behind coffee consumption and health in an effort to put to rest the idea that coffee is a “vice” or something we all need to cut back on.
We received many comments and questions from readers. In fact, we received so many that we thought it might be useful to respond to some of the most frequently discussed ones.
Are the same beneficial relationships seen with decaffeinated coffee?
Most studies did not include data on decaffeinated coffee, either because too few people drank it or because data were not available. The few studies that did, though, had differing results. With respect to cardiovascular disease, decaffeinated coffee did not seem to have the same protective effects as regular coffee. With respect to the one stroke meta-analysis, it seemed to be just as protective as regular coffee. In two breast canceranalyses, decaffeinated had the same nonrelationship as regular coffee. Decaffeinated coffee was also protective against lung cancer, not as protective against Parkinson’s disease, and protective against diabetes and overall mortality, but perhaps to a lesser extent than regular coffee.
But for most studies, there just aren’t data available. The conclusion to take away: There’s less evidence overall for a potential benefit, but still, there’s no evidence of harmful associations.
What constitutes a cup of coffee?
Pretty much all studies defined a cup of coffee as an 8-ounce serving. That’s smaller than what I imagine most people drink. A grande-size coffee at Starbucks (what is called simply “large” at most other coffee houses) is 16 ounces.
Are the same benefits seen with tea?
The literature on tea is about the same size as that for coffee, and reviewing it thoroughly would take more time than is appropriate for this column. However, a number of studies I reviewed did include tea in analyses, and those I can present here. People who drank more tea had a lower risk of Parkinson’s disease and of cognitive decline. Black tea had a potential protective effect against diabetes, but it was not statistically significant. Green tea had no relationship to the development of diabetes.
If we think there’s enough interest in tea, though, we could devote a future column to the evidence on that beverage.
Is the benefit from caffeine or from some other element in coffee?
It’s not known. I also don’t think it’s necessarily the same protective effect in each disease. I think that for many of the neurological issues, it could be caffeine acting as a stimulant in the brain. This hypothesis is supported by the fact that decaffeinated coffee doesn’t seem to be as protective, yet tea is. In some of the other diseases, though, the same benefits aren’t seen from other caffeine-containing beverages. No one is arguing that diet soda consumption is associated with less of a chance of getting cancer. Additionally, some protective effects are seen with decaffeinated coffee as well. It’s likely, therefore, that something else could be at work. We don’t know what, though.
What about high blood pressure or cholesterol?
2005 meta-analysis found that in randomized controlled trials caffeine was associated with an increase in blood pressure. When that caffeine was from coffee, however, the blood pressure effect was small. A 2011 study found that caffeine intake could raise blood pressure for at least three hours. Again, though, there wasn’t a significant relationship between long-term coffee consumption and higher blood pressure. A 2012 meta-analysis of 10 randomized controlled trials and five cohort studies could find no significant effect of coffee consumption on blood pressure or hypertension.
And, as has been reported in The New York Timestwo studies have shown that drinking unfiltered coffee, like Turkish coffee, can lead to increases in serum cholesterol and triglycerides. But coffee that’s been through a paper filter seems to have had the cholesterol-raising agent, known as cafestol, removed.
High blood pressure and high cholesterol would be of concern because they can lead to heart disease or death. Drinking coffee is associated with better outcomes in those areas, and that’s what really matters.
Some readers were upset that I neglected to mention some of the deleterious effects of caffeine. What about jitteriness and mood changes?
I want to reiterate that the point of the piece was not to tell people to drink coffee. As I said in my recent article on food recommendations, I don’t think there is much value in preaching or judging what others eat or drink. Moreover, this evidence is epidemiologic, that is, based on observations of patterns. I don’t want to fall prey to the mistake of recommending we change our eating behavior without evidence from randomized controlled trials.
The point of the article was to show that there’s no evidence that coffee is bad for the average person. Data do not support the idea that we are drinking “too much.” Coffee does not appear to be associated with poor health outcomes — the opposite is true. In light of this, we should stop telling everyone to avoid it, or judging others for drinking it. We should also stop feeling guilty or feel we need to consume less.
That is, unless it’s not making you feel well. As I also said before, individual trial and error is likely necessary when it comes to nutrition. Some people need to avoid caffeine for medical reasons, and they should. If coffee makes you feel bad, or makes it hard for you to sleep, or renders you a less likable person — then by all means feel free to cut back or stop.
But if you like it, then by all means enjoy it.


使用Chemex沖煮法(Chemex pour-over method)製作咖啡。
Heather Walsh for The New York Times
使用Chemex沖煮法(Chemex pour-over method)製作咖啡。
但是,正如《紐約時報》雜誌(The New York Times)曾經報道的,有兩項研究表明,飲用未過濾咖啡(如土耳其咖啡)可導致血清膽固醇和甘油三酯增加。但是,用濾紙過濾咖啡似乎可以去除掉升膽固醇的物質——咖啡醇。