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Caffeine Limits Blood Flow


Peter B Wolf
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"Although these findings seem not to have a clinical importance in healthy volunteers, they may raise safety questions in patients with reduced coronary flow reserve, as seen in coronary artery disease, particularly before physical exercise and at high-altitude exposure," the researchers wrote.

It doesn't sound like a healthy person should worry, but I'm going to stop drinking caffeine before I run. I'm also wondering what sort of insight the track coach from my friends' high school had when he told all the kids to stop drinking soda during track season.

I'm curious to see what they find in the follow up studies.

-Linda

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Hey Peter, I've never worried about either side of this argument. I drink coffee every morning (three fresh roasted, fresh gound double espressos, thank you!). I generally work out (weights) in the morning. Never noticed any issues. Never really noticed any enhancements either. I have lots of friends who claim a shot of Joe pumps up their workout. I guess it varies by individual. Have you noticed any good or bad effects??

Ken

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"Although these findings seem not to have a clinical importance in healthy volunteers, they may raise safety questions in patients with reduced coronary flow reserve, as seen in coronary artery disease, particularly before physical exercise and at high-altitude exposure," the researchers wrote.

It doesn't sound like a healthy person should worry, but I'm going to stop drinking caffeine before I run. I'm also wondering what sort of insight the track coach from my friends' high school had when he told all the kids to stop drinking soda during track season.

I'm curious to see what they find in the follow up studies.

-Linda

It is possible the caffeine might be the reason, however there are other reasons to avoid carbonated beverages before and during vigorous exercise. There is a delicate balance that has to be maintained in the circulating blood so it can pick up the fatigue acids (lactic acid) produced when muscles work and which, if they build up in muscles, can cause cramping or a charley horse. Carbonated beverages of any kind in particular lower the serum calcium which has to be at a certain level to pick up the lactic acid, as does excessive water. This is the reason for the electrolyte replacement liquids which replace electrolytes, potassium, sodium and calcium, lost during exercise.

There have been many detailed studies going back 30 years or more that document these effects. Because it is believed carbonated beverages can also influence bone formation in infants, many nutritionists advise giving infants and small children only limited amounts of carbonated beverages. I have worked for an orthopedic surgeon for 38 years and we used to see a lot of fractures in young children and invariably, they drank large amounts of carbonated beverages and very little milk. My boss always advised them to cut way back on the Coke, Pepsi and etc and encourage them to drink milk and eat the right kind of veggies.

Since ideas about the effects of caffeine have yo-yoed back and forth over many years, I wait for the other shoe to drop - or another study to appear.

One of the women in my office has terrible migraine headaches, relieved only by caffeine (tablets) and the change is immediate and profound.

As far as espresso is concerned, I believe that there is much less caffeine in the dark roast coffees than in the lightly roasted beans.

Someone explained to me how caffeine is reduced by heating for long periods but I don't recall the specifics.

"There are, it has been said, two types of people in the world. There are those who say: this glass is half full. And then there are those who say: this glass is half empty. The world belongs, however, to those who can look at the glass and say: What's up with this glass? Excuse me? Excuse me? This is my glass? I don't think so. My glass was full! And it was a bigger glass!" Terry Pratchett

 

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I am a regular coffee drinker, and a regular exerciser. From what I gather from this report of the study, is that there is much more to be found out. These 18 healthy, young coffee drinkers were studied in a 36-hour caffeine fast, and then just after a 200 milligram caffeine consumption under exercise stress.

I think in order to provide better data to decide whether one ought to exercise post-caffeine consumption, this study should be re-done using people who do exercise regularly. A control group who do not normally consume caffeine, and the study group who does regularly consume caffeine. Also, there should be randomized levels of caffeine given (as well as placebos to the control group) to better understand what is going on.

I am not surprised that this lowers the level of blood supply to the heart. Caffeine is a beta-agonist, which means that it raises arterial muscular tension-- it narrows the pipes that supply blood to the heart. Also, it increases the irritability of the muscular system-- so the same neural signal recruits a greater muscular response when caffeine is present.

I wish I knew more about the myocardial reserve to give a good explanation of why that number may or may not be important. I also wish they reported the level of the exercise--even just as far as having the volunteers rate their output on a scale of 1-10.

I only see this as an interesting result, prompting study.

As for andiesenji's question, caffeine is lower in darker roasted beans for 2 reasons, more caffeine goes up the flue of the roaster, as caffeine is prone to sublimation, and at the heats and chemistries of roasting, caffeine gets scavenged and cracked by the environment.

I always attempt to have the ratio of my intelligence to weight ratio be greater than one. But, I am from the midwest. I am sure you can now understand my life's conundrum.

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Another good reason to avoid exercise, and fizzy drinks

Does that mean I need to avoid beer while I'm marathoning? A good espresso stout at mile 18 always boosts the spirits.

I always attempt to have the ratio of my intelligence to weight ratio be greater than one. But, I am from the midwest. I am sure you can now understand my life's conundrum.

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I think this is definitely worth further study. I'm also curious about the delivery method of the caffeine. I've read that tea releases the caffeine more slowly and evenly into your bloodstream. I imagine a pill would act differently. Of course, I am a bit biased as a tea drinker...

In the meantime, if there's a chance that my tea or afternoon diet pepsi will add minutes to my best running time, I'll drink something else. It certainly won't hurt me to skip the fizzy drink.

Does that mean I need to avoid beer while I'm marathoning?  A good espresso stout at mile 18 always boosts the spirits.

I've noticed I run better after a glass of wine, but I assumed it was the "relaxation" factor. Maybe we should lobby the researchers to let us participate in an alcohol and exercise study :cool: .

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Well, I'm not going to lose any sleep over this. As a cyclist who rides regularly, often at high intensity and sometimes over extreme duration, I have personally found caffeine to be beneficial. In fact, it's long been accepted amongst the cycling fraternity that caffeine can actually aid performance - in The Cyclists Training Bible by Joe Friel, he quotes the author of a recent study who says 'caffeine causes a complex chemical change in the muscles that stimulates more forceful contractions during a longer period of time than without it...most have found that caffeine spares muscle glycogen during endurance exercise.'

You can, these days, find studies that are wholly contradictory, of course. But in my personal experience a double shot of espresso (made by myself) before a hard, hilly ride does give me a boost up the hills. And once, before a very long ride (Paris-Brest-Paris) I weaned myself off of caffeine for the week before the event, and thus when I came to drink coffee, I found it had a more powerful effect, not necessarily in aiding performance, but simply in helping to keep me awake while riding through the night.

Now as for alcohol, sadly that most definitely has an immediate detrimental effect for me - my legs simply turn to jelly.

However, a friend of mine ran the Marathon du Médoc this year which takes place through the wine and châteaux country of Bordeaux's Médoc. Apparently there are more than 20 stops along the way offering, no, not l'eau minerale, but vin de Bordeaux, in some cases grands crus classés served in elegant crystal goblets. He managed to make some 11 stops over the course of the 26 miles and his time was no worse than in other marathons. His only regret was not stopping more!

Marc

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