Waking Up to the Effects of Caffeine
By Jeff Novick, M.S., R.D., L.D./N.
How innocent is that morning cup of coffee? Maybe not so innocent for your health.
Believe it or not, according to a new study presented recently at the European Society of Cardiology Congress, the amount of caffeine in just one cup of coffee could be enough to harden a person's arteries for several hours afterward; Hardened arteries, or atherosclerosis, put extra pressure on the heart and increase the risk of heart attack and stroke, researchers said. They noted that their findings could have implications for people already at risk of these conditions.
“People must be careful with caffeine, especially if they have high blood pressure,” said Dr. Charalambos Vlachopoulos from the Cardiology Department of the Henry Dunant Hospital in Athens, Greece. ”After drinking a cup of coffee, blood pressure can rise up to five or even 10 millimeters of mercury. The amount depends on the individual and dose. Regular rises of this magnitude are important in a person's long-term prognosis and could increase their risk of suffering from a stroke or heart attack,” Vlachopoulos said. “I think that people with high blood pressure...should consider reducing their caffeine intake or having caffeine-free drinks.”
The researchers gave a group of 10 healthy volunteers either inactive placebo capsules or capsules containing 100 milligrams of caffeine — a quantity equivalent to one cup of coffee. On another day, the volunteers received the opposite capsule from the previous dosage. Neither the volunteers nor the testers knew the sequence in which the volunteers had been given the capsules. Caffeine consumption caused an increase in wave reflection — a measure of arterial stiffness — for at least two hours, according to the study results.
In other research, Dr. M. O'Rourke and colleagues at St. Vincent's Hospital, Sydney, Australia, presented data at the 22nd Congress of the European Society of Cardiology linking caffeine consumption with alterations in the aorta, the main artery supplying blood to the body. In this study, 18 middle-aged healthy volunteers consumed 250 mg of caffeine (equivalent to two or three cups). The results showed that caffeine led to a loss of aortic elasticity, and raised blood pressure. The elasticity of the aorta is linked to heart function and coronary blood flow, the researchers say.
In yet another study of 15 healthy volunteers, Dr. Georg Noll and colleagues at the University Hospital of Zurich, Switzerland, showed for the first time that coffee drinking results in a pronounced blood pressure increase in non-habitual coffee drinkers, but did not apparently have the same effect in regular coffee drinkers. In the study, blood pressure, heart rate and other measurements were continuously recorded before and after drinking coffee (triple espresso), decaffeinated triple espresso, an intravenous infusion of caffeine, or placebo.
Other bad news about caffeine... According to a study conducted in Finland, those people who drank four or more cups of coffee a day had twice the risk of developing rheumatoid arthritis, compared with people who drank less coffee. Rheumatoid arthritis is an autoimmune disease in which the body's defenses attack its own tissues. It is more common in women, tends to strike between the ages of 36 and 50, and results in a chronic destruction and deformity of the joints. Smoking, high cholesterol, being overweight and certain dietary factors have also been linked with a higher risk of the disease, according to the report in the Annals of the Rheumatic Diseases (Annals of the Rheumatic Diseases 2000;59;631-635).
Dr. Maarku Heliovaara of the National Public Health Institute in Helsinki and colleagues looked at data from nearly 19,000 healthy men and women who entered a study in the early 1970s and were followed for 15 years. In that time, 126 people developed rheumatoid arthritis and 89 of those people had detectable levels of rheumatoid factor — an antibody that is often found in the blood years before the onset of rheumatoid arthritis. Coffee drinkers were at higher risk of developing rheumatoid factor-associated rheumatoid arthritis.
The results “should be viewed as the first step in support of the hypothesis that coffee consumption has a causative role in the development of rheumatoid factor positive rheumatoid arthritis,” the researchers write. Currently rheumatoid arthritis affects more than two million people in the US, according to the American College of Rheumatology. Too much caffeine has also been shown to raise women’s risk for incontinence.
According to a report in the July issue of Obstetrics and Gynecology (Obstetrics and Gynecology 2000;96:85-89), women who drink more than four cups of brewed coffee a day — or consume a lot of caffeine from other sources — may be putting themselves at risk for urinary incontinence. These women may be more than twice as likely to suffer from a weakened bladder muscle — known as unstable bladder — as women who consume less caffeine. Unstable bladder is a major cause of urinary incontinence, especially in older women.
The researchers from Brown University in Providence, Rhode Island, compared fluid and caffeine intake in 131 women with an unstable bladder and 128 women without the condition. Patients measured and recorded their daily intake of tea, cola, cocoa and coffee — both caffeinated and decaffeinated, which contains a small amount of caffeine, and brewed and instant. Women who consumed an average of 484 milligrams (mg) of caffeine a day, or about three to four cups of coffee, were more likely to have an unstable bladder compared with women who consumed an average of 194 mg caffeine, or one to two cups of coffee a day. Although caffeine is a diuretic — a drug that increases urinary output — the women who were high-caffeine consumers tended to have signs of unstable bladder even when drinking water. While women who smoked and those older than 55 years were also more likely to suffer from urinary incontinence, caffeine consumption remained a risk factor regardless of these other variables. “Based on the present findings, it would be prudent to advise women to avoid excessive caffeine intake...more than 400 mg/day (equivalent to four cups of brewed coffee),” Arya and colleagues conclude. Women who are suffering symptoms of incontinence, such as uncontrolled leakage of urine when laughing or coughing, may want to limit caffeine even further, the authors add.
Additionally, another recent study reported in the journal Diabetes Care (Volume 25, Number 2, February 2002) looked at the effect of caffeine and insulin sensitivity. In a randomized double blind, crossover design study, 12 healthy volunteers were administered caffeine or a placebo intravenously in a dose that equaled moderate consumption. Results showed that moderate consumption of caffeine reduced insulin sensitivity in healthy subjects 15%. Caffeine also increased catecholamines, plasma free fatty acids, and both systolic and diastolic blood pressure. The moderate consumption of caffeine caused a five fold increase in epinephrine. Epinephrine increases the production of glucose in the liver and interferes with the ability of muscle and fat cells to use glucose.
Found in coffee, tea and soft drinks, caffeine is the most widely used drug in the world. In the Western world, eight out of 10 adults consume caffeine in some form. Based on a 5-ounce cup, brewed coffee contains 128 mg of caffeine, instant coffee contains 66 mg, decaffeinated coffee contains 3 mg, non-herbal tea contains 38 mg, and hot chocolate contains 4 mg of caffeine. Based on an 8-ounce glass, iced tea contains 47 mg of caffeine, and cola drinks contain about 24 mg. Do yourself a favor, wake up to the negative effects of caffeine and avoid it.
©Copyright 2002. All Rights Reserved. Health Science is the publication of the National Health Association. This article reprinted from the Spring 2002 issue.