一杯のコーヒーが微小血管機能を改善した（Abstract: 12428）

一杯のコーヒーに含まれるカフェインが微小血管内皮機能を改善する

Caffeine in a cup of coffee ameliorates microvascular endothelial function

一杯のコーヒーに含まれるカフェインが微小血管機能改善に役立つ可能性があるとの研究結果が2013年American Heart Association学会で発表された。27人の健常成人を対象とした二重盲検プラセボコントロールクロスオーバースタディの結果、カフェイン入りのコーヒーを1杯飲むことにより微小血管内皮機能が有意に改善することが示された。具体的には、カフェイン入りのコーヒーを1杯飲んだ者はカフェイン抜きのコーヒーを飲んだ者と比較し、75分間の指先血流量が30%増加した。スタディの参加者は通常コーヒーを飲まない人々で、22～30歳であった。1日目にそれぞれの参加者は、5オンスのカップ1杯のレギュラーまたはカフェイン抜きコーヒーを飲んだ。その後研究者らはレーザードップラーフローメトリーを用いて指先血流の反応性充血を計測した。2日後に1回目と違う方のコーヒーを飲んだ後に同様の実験が行われた。カフェイン入りのコーヒーは、カフェイン抜きのコーヒーよりも微小血管内皮機能の指標である指先血流の閉塞後反応性充血を有意に増強させた（P <0.05）。心拍数は2群間で同等であった。これらの結果は、少なくとも一部はコーヒー摂取による心血管死亡率減少との関連の説明となる可能性がある。

The caffeine in a cup of coffee might help your small blood vessels work better, according to research presented at the American Heart Association's Scientific Sessions 2013.

A double blind, placebo-controlled, crossover study of 27 healthy adults showed – for the first time – that drinking a cup of caffeinated coffee significantly improved microvascular endothelial function. Specifically, participants who drank a cup of caffeinated coffee had a 30 percent increase in blood flow in their finger over a 75-minute period compared to those who drank decaffeinated coffee.

"This gives us a clue about how coffee may help improve cardiovascular health," said Masato Tsutsui, M.D., Ph.D., lead researcher and a cardiologist and professor in the pharmacology department at the University of the Ryukyus in Okinawa, Japan.

The study adds to a growing body of research about coffee, the most widely consumed beverage worldwide. Previous studies showed that drinking coffee is linked to lower risks of dying from heart disease and stroke, and that high doses of caffeine may improve the function of larger arteries. These findings may explain, at least in part, the association of coffee consumption with reduced mortality of cardiovascular disease.

Study participants were people who did not regularly drink coffee, ranging in age from 22 to 30. On one day, each participant drank one five-ounce cup of either regular or decaffeinated coffee. Then researchers measured finger blood flow with laser Doppler flowmetry, a non-invasive technique for gauging blood circulation on a microscopic level. Two days later, the experiment was repeated with the other type of coffee. Neither the researchers nor the participants knew when they were drinking caffeinated coffee.

The researchers noted blood pressure, heart rate, and vascular resistance levels. They also took blood samples to analyze levels of caffeine and to rule out the role of hormones on blood vessel function.

Compared to decaf, caffeinated coffee slightly raised participants' blood pressure and improved vessel inner lining function. Heart rate levels were the same between the two groups.

It's still unclear how caffeine actually works to improve small blood vessel function, although Tsutsui suggests that caffeine may help open blood vessels and reduce inflammation.

"If we know how the positive effects of coffee work, it could lead to a new treatment strategy for cardiovascular disease in the future," said Tsutsui.

Co-authors are Katsuhiko Noguchi, Ph.D.; Toshihiro Matsuzaki, M.D., Ph.D.; Mayuko Sakanashi, Ph.D.; Naobumi Hamadate, Ph.D.; Taro Uchida; B.Sc.; Mika Kina-Tanada, D.D.S.; Haruaki Kubota, M.D.; Junko Nakasone, Ph.D.; Matao Sakanashi, M.D., Ph.D.; Fumihiko Kamezaki, M.D., Ph.D.; Akihide Tanimoto, M.D., Ph.D.; Nobuyuki Yanagihara, Ph.D.; Yusuke Ohya, M.D., Ph.D.; Hiroaki Masuzaki, M.D., Ph.D.; and Shogo Ishiuchi, M.D., Ph.D.

The study was funded in part by the All Japan Coffee Association.