Caffeine Blues_ Wake Up to the Hidden Dangers of America's #1 Drug ( PDFDrive )

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  Source: Neal L. Benowitz, M.D., “Clinical Pharmacology of Caffeine,” Annual Review of Medicine, 1990;4l:277–88.

  CHECK YOUR PRESSURE

  First of all, increases in blood pressure due to caffeine are often quite significant.

  Even in moderate doses, caffeine can raise blood pressure in healthy young men and women to the level of borderline hypertension.2, 3 In those with existing hypertension, caffeine can be even more dangerous. The key factor, once again, is stress.

  The first hint of this intriguing phenomenon came in 1969, when researchers tested caffeine’s effect on blood pressure in rats. They found that caffeine produced only modest increases in blood pressure and were about to write it off; but they decided to repeat the experiment on stressed rats. Sure enough, when the rats were given caffeine and then placed in a crowded situation (i.e., under stress), their blood pressure increased dramatically.4

  Since then, the same pattern has been identified in humans. When subjects are relaxed, caffeine does not appear to raise blood pressure significantly. These are the studies most often cited by the caffeine industry. But is this an accurate representation of most people’s lives? Real life is stressful, and caffeine multiplies the increase in blood pressure and the subsequent damage.5

  Throughout this book, I have emphasized the point that any evaluation of caffeine must look carefully at those who are most vulnerable. In this regard, recent research on men with borderline hypertension is quite revealing. It was found that in this group, the increase in blood pressure after ingestion of caffeine was greater than that found with healthy controls. What’s more, this group also had an exaggerated response to caffeine combined with a stressful task.6 In other words, caffeine intake is most dangerous for those who are most vulnerable (read: most stressed), a pattern that we will see numerous times in subsequent chapters.

  HABITUAL COFFEE DRinkers: ALSO

  AT RISK

  It was long believed that habitual coffee drinkers did not suffer the increased blood pressure seen when caffeine is administered to non–coffee drinkers.

  Recent research, however, has revealed that caffeine can affect blood pressure in just about anyone.7 One study with sixty “heavy” coffee drinkers found that caffeine continued to cause increases in blood pressure, and the authors emphasized in their conclusion that these effects “do not appear to habituate with regular use.”8

  As it turns out, the hypertensive effects of caffeine appear to be related to changes in blood caffeine levels. While habitual drinkers tend to maintain levels of caffeine through repeated doses throughout the day, these levels drop during sleep. In other words, the lower a person’s caffeine level first thing in the morning, the greater the hypertensive effect of those first few cups of coffee.

  Experts estimate that at least 25 percent of the general population has earlymorning blood levels of caffeine low enough for normal caffeine consumption to raise their blood pressure.9

  Now, this brings up a very intriguing point. According to national health statistics, an individual is more than 50 percent more likely to have a heart attack on a Monday than on a Saturday. At first, everyone took this as simple evidence that Mondays are high-stress days and Saturdays are relaxed days. But researchers were surprised to find that the pattern held even among those with

  researchers were surprised to find that the pattern held even among those with low-stress jobs. It turns out that caffeine is the critical factor. Since most people consume less coffee on the weekends, a coffee drinker’s blood caffeine level will tend to be lowest on Monday morning, just when he or she is likely to slam down the most coffee. The resulting increase in blood pressure, while temporary and unlikely to show up in a scientific study, may well prove fatal.

  “The cardiovascular effects of caffeine may persist throughout the day with repeated administration of moderate amounts of caffeine.

  Habitual caffeine use does not necessarily lead to complete tolerance, which suggests that caffeine’s cardiovascular effects could contribute to an increased risk of cardiovascular disease.”

  Source: J. D. Lane and D. C. Manus, “Persistent Cardiovascular Effects with Repeated Caffeine Administration,” Psychosomatic Medicine, July–August 1989;51(4):373–80

  RESEARCH CAPSULE

  Diet Pills and Caffeine: A Deadly Duo

  Prior to the Controlled Substances Act of 1970, most diet pills contained amphetamine drugs, which effectively suppress appetite but cause addiction and dangerous side effects. When the FDA banned amphetamines, manufacturers created similar effects (and side effects) with the combination of two central nervous system stimulants, caffeine and phenylpropanolamine (PPA). In the mid1980s, the FDA moved against this dangerous mix because of a number of deaths associated with its use. Too late for some users, research found that while both drugs alone increase blood pressure, the combination of caffeine and PPA could result in massive increases, triggering stroke and heart attack.10–11, 12, 13

  That’s why today the active ingredient in most diet pills available without a prescription is phenylpropanolamine alone.

  However, while caffeine-PPA combinations may be banned, people using PPA diet pills still drink coffee, sometimes lots of coffee. What’s more, PPA is frequently overused. The reasons for this become clear once you understand how PPA works. Again, it’s related to stress hormones, this time norepinephrine.

  As described in Chapter 2, norepinephrine (NE) is a powerful biochemical produced in the adrenals and nervous system that affects mind, mood, and behavior. PPA (like amphetamines) causes a rapid release of NE, which creates stress but feels like “energy.” NE also suppresses appetite. The problem is that amphetamines and PPA do not increase the brain’s synthesis of NE. If you’re releasing more NE but you’re not replacing NE stores in the brain, you will ultimately experience a rebound “letdown.” As brain levels of NE fall, users must take more and more PPA to experience the same amount of appetite suppression. Such overuse may not only raise blood pressure, but also cause insomnia, irritability, headache, anxiety, and panic. When caffeine is added to the equation, the likelihood (and severity) of adverse effects is multiplied, due most likely to the fact that PPA can produce dramatic increases in blood caffeine levels.14 Cases have been reported where individuals suffered manic psychosis after ingesting caffeine and PPA.15

  “The effects of the widely consumed drugs caffeine and

  phenylpropanolamine are mediated through activation of the central and sympathetic nervous systems. Severe, life-threatening, and occasionally fatal hypertensive reactions have been reported after their combined use.”

  Source: C. R. Lake, D. B. Rosenberg, S. Gallant et al., “Phenylpropanolamine Increases Plasma Caffeine Levels,” Clinical Pharmacology and Therapeutics, June 1990; 47(6):675–85.

  THE WHOLE STORY

  Most people assume that caffeine raises blood pressure because it makes your heart beat faster or harder. If this were the case, you would expect your blood pressure to return to normal fairly soon after a cup of coffee—and that doesn’t happen. The fact is that caffeine causes vascular resistance, a condition in which the blood vessels (especially in the extremities) constrict and reduce blood flow.16 This stress response was very useful a few thousand years ago in the face of imminent physical harm. Vascular resistance reduced blood loss from injuries.

  But today all it does is raise your blood pressure and make your fingers cold.

  Actually, vascular resistance affects many areas of the body and mind. As

  Actually, vascular resistance affects many areas of the body and mind. As discussed in the previous chapter, caffeine reduces circulation in certain areas of the brain. Once again, the fightor-flight/survival part of the brain remains unaffected, but areas associated with long-term memory and learning can be impaired.

  Put on your physiology hat. Can you think of another condition in which vascular resistance could cause a major problem? How about the increased circulation associated with exercise? He
re the muscles are working hard and starved for oxygen and fuel. Under conditions of vascular resistance, the entire system can go into hyperdrive, elevating blood pressure much higher than it would be at rest. A study with healthy young men (none of whom had high blood pressure) published in the American Journal of Cardiology showed that a modest amount of caffeine taken before exercise produced dangerous elevations in blood pressure in 45 percent of subjects.17 When a similar experiment was conducted with men at risk for hypertension, the results were even more alarming.18

  THE CALCIUM CONNECTION

  Research has identified an important connection between calcium metabolism and hypertension, accounting for the fact that calcium supplementation lowers blood pressure in about 25 percent of patients. Because caffeine is known to disturb calcium metabolism, a study was recently conducted to explore the effects of caffeine abstinence on blood pressure. The results? After two weeks off caffeine, two important measures of calcium status (serus ultrafiltrable calcium and parathyroid hormone) improved markedly in nearly all of the subjects.19 These results illustrate clearly that caffeine stresses calcium metabolism, and that those desiring to control their blood pressure would do well to get “off the bean.”

  CHECK YOUR OIL

  Scores of studies have been performed to evaluate the effects of coffee and caffeine on blood cholesterol levels. Most have found that coffee (including decaf) is associated with elevated cholesterol, and these increases are not always small.20–21, 22 In fact, blood cholesterol levels appear to rise in direct proportion

  to the number of cups of coffee consumed,23–24, 25, 26, 27, 28, 29 and we now know what causes this rise in blood cholesterol. It’s not the caffeine, as once thought, but two other chemicals (diterpene alcohols) naturally found in coffee: cufestol and kahweol.30, 31

  How does all this impact coronary artery disease? Most experts today agree that for every 5 percent increase in serum cholesterol over 200 milligrams per deciliter, there is a 10 percent increase in risk for heart attack or stroke. That means that stress and coffee can make a tremendous difference in your risk for these killer diseases. What’s more, coffee intake is associated with elevations of the most dangerous fraction of cholesterol, known as apolipoprotein B, and this correlation has been found at moderate intake of two or more cups per day.32

  BEYOND BLOOD PRESSURE

  AND CHOLESTEROL

  As I mentioned, the caffeine/cardiovascular disease debate has, until recently, been limited mainly to a discussion of blood pressure and cholesterol. Since there is no universal agreement on how much these risk factors are raised by caffeine, it has been possible for the caffeine industry to duck the entire issue.

  But no more.

  That’s because six additional risk factors are coming to light, and caffeine is involved in each and every one.

  “One point most authorities do agree on: Patients prone to cardiac arrhythmias should avoid caffeine. The amount in just a few cups of coffee can cause problems.”

  Source: Paul Cerrato, B.S., M.A., Journal for the American Association of Office Nurses.

  1. ARRHYTHMIA AND BLUES

  The proper function of the heart as a pump depends upon an intricate series of electrical impulses that contract chambers and open valves in perfect timing.

  This rhythm is the pace of life, sending blood continuously to more than 75

  trillion cells in your body.

  When the heart muscle is stimulated out of the proper ***********time sequence, pumping action becomes uncoordinated and blood flow becomes

  weak. If proper rhythm is not restored, these conduction and rhythm disturbances (collectively called arrhythmias) are usually fatal. Scientists do not understand exactly what causes arrhythmias, but they do agree that caffeine is associated with increased risk among those prone to the disorder.33, 34It is also important to note that the amount of caffeine required to disturb heart rhythm is not great. Intake of less than 300 milligrams per day has been associated with greater incidence of arrhythmias.35, 36 Since a fourteenounce mug of coffee contains around 200 milligrams of caffeine, less than two mugs can easily put you into the increased risk category.

  Even in healthy individuals, the combination of stress and fatigue has been shown to increase risk for arrhythmias.37 Think about that. When you’re feeling beat, haven’t slept well, or you’re just pushing too hard, how often do you resort to drinking coffee to get through the day? The resulting strain on your heart can be significant. Caffeine can also cause tachycardia (rapid heartbeat) and can exacerbate the symptoms of mitral valve prolapse (MVP), a common heart defect. In fact, MVP may be an important key in our understanding of the arrhythmia-caffeine connection.

  Mitral Valve Prolapse (MVP)

  The mitral valve lies within the heart, regulating the flow of blood from the left atrium to the left ventricle. When the valve is prolapsed (fallen or weakened), it malfunctions, and as the heart beats, blood may flow back into the atrium. MVP

  is rarely serious, but it does produce occasional or periodic symptoms, including shortness of breath, fatigue, light-headedness, and dizzy spells. The cause is unknown, but there is a significant genetic factor. Individuals with one affected parent have a 50 percent chance of inheriting MVP.

  While MVP can cause heart murmur, palpitations, and chest pain, most individuals with the disorder have no noticeable symptoms and are unaware of the condition. Still, MVP significantly increases one’s risk for arrhythmia,38, 39

  and the combination of caffeine and MVP can be dangerous. Interestingly, caffeine researchers often remove individuals with MVP from their investigations, presumably because such individuals would exhibit negative effects greater than the average person. But that’s bad science. Conservative estimates are that 7 to 10 percent of the population has MVP. That’s millions of Americans, and these are precisely the people who should be studied because

  they are among the most vulnerable to caffeine’s adverse effects.

  Aside from mitral valve prolapse, there are other arrhythmia risk factors that appear to operate in conjunction with caffeine intake. Caffeine can cause a sudden contraction of the aortic muscle, as well as dramatically increased stress hormone release in the heart itself. In an individual whose arteries are already partially blocked, such events can produce arrhythmia and heart attack.40

  There are also reports that caffeine can increase the incidence of paroxysmal atrial tachycardia (PAT) and ventricular beats, other types of heart rhythm disturbance. These arrhythmias are often associated with exertion, and doctors have reported increased incidence of PAT with caffeine (coffee or tea) when taken as much as twelve hours prior to exercise.41

  This brings up an important point concerning caffeine research: Long-term effects are often ignored. After all, you only see what you’re looking for. But new research using continual heart monitoring technology enables us to look at the full spectrum of caffeine effects, including something known as heart rate variability (HRV). HRV has been shown to correlate very strongly with sudden death, and while moderate caffeine ingestion appears to produce no abnormal HRV in young adults, it has been shown to aggravate abnormal HRV in overweight, middle-aged subjects.42

  “There is a two times (200 percent) greater likelihood of ventricular premature beats after coffee ingestion.”

  Source: T. K. Leonard, R. R. Watson, and M. E. Mohs, “The Effects of Caffeine on Various Body Systems: A Review,” Journal of the American Dietetic Association, 1987;87(8):1048–53.

  2. CORONARY VASOSPASM

  When an artery is blocked, tissue beyond the block is deprived of oxygen and quickly dies. If this occurs in an artery leading to the heart, it causes a heart attack (medical term: myocardial infarct or MI). If the block is in an artery leading to the brain, it causes a stroke. In both cases, the major cause of blockage is the narrowing of an artery from the buildup of plaque, a process known as atherosclerosis. Often, the fatal combination is atherosclerosis and a blood clot that lodges in the narrowe
d artery.

  But in approximately 20 percent of fatal heart attacks, an autopsy reveals that

  the victim had clear arteries. What caused the blockage of blood (and therefore oxygen) to the heart resulting in massive cell death and heart attack? Often it is a spasm of one or more arteries leading to the heart. Known as coronary vasospasm, this event can shut off blood supply as effectively as a clot or atherosclerosis.43 You need to know that the risk for such a tragedy is related in part to your intake of caffeine.

  In fact, caffeine contributes to coronary vasospasm in multiple ways. We know that caffeine, by stimulating the release of stress hormones, lowers the stress threshold (review Chapter 3) so that situations that would otherwise have been handled become distressful. With this caffeineinduced stress “magnifier,”

  the risk of vasospasm is increased.44

  Caffeine also contributes to magnesium deficiency, a condition that makes arteries more prone to spasm.45 In typical vicious-cycle fashion, the combination of caffeine and stress exacerbates the low magnesium state.46 What’s more, if there is also a buildup of plaque within the artery, the tendency for arteries to spasm increases the overall risk for heart attack tremendously.

  On the other hand, it is important to understand that the entire scenario of magnesium deficiency, elevated stress hormones, and hypersensitive arteries can be silent. You don’t feel any of these dangerous developments like you would, for example, if your arteries were being occluded by plaque. In those cases, there are often clear warning signs such as breathlessness upon exertion or chest pain.

  But research shows that a person prone to vasospasm can have a completely normal electrocardiogram and be symptom-free47—that is, until they end up facedown on the sidewalk after their morning jog.