In a recent contribution to these pages, titled `Caffeine risk interview may be a storm in a teacup' December, 21st 2000), Dr William Reville was disbelieving of comments I made during an interview on national radio about the possible harmful effects of caffeine beverages such as coffee, tea, cola drinks and some so-called `energy' drinks.
In light of his scientific training and background, it is understandable that Dr Reville might have been wary of the views I expressed. Wariness and scepticism are the stock in trade of scientists. Dr Reville's commentary, however, is far from what one would expect from a professional scientist faced with new and unexpected information.
Dr Reville referred to research of mine which shows that moderate caffeine use produces sustained elevations in blood pressure, a finding that has since been repeated by others. He likened these blood pressure elevations to those that accompany physical activity.
Because moderate physical activity is harmless, Dr Reville suggested there is no need to be concerned about the blood pressure increases caused by caffeine.
In the case of physical exercise, increased blood pressure is a response to increased metabolic demand in the body. No such increase in metabolic demand is associated with ingestion of caffeine which exerts its influence on blood pressure through an entirely different mechanism.
The medical evidence is very clear: even modest increases in blood pressure, which do not serve a metabolic purpose and are sustained over time, contribute directly to increased incidence of heart disease and stroke.
There are other important health concerns about caffeine beverages. There is strong evidence that caffeine use during pregnancy can contribute to lower birth weight, and increase the risk of miscarriage. For older consumers, caffeine is suspected of speeding up the development of osteoporosis. Daily usage of caffeine also produces physical dependence. Many consumers find that going without their usual intake of caffeine for a day or so leaves them tired, irritable, unable to concentrate and possibly gives them a headache. These are the symptoms of caffeine withdrawal.
Manufacturers of caffeine beverages know about, and make use of, physical dependence on caffeine. Most caffeine consumers know the desire for coffee and tea is often most pronounced first thing in the morning, the time of day when most people have been longest without caffeine.
After your first caffeine beverage of the day you feel revived, but this obvious "benefit" is an illusion.
Because of physical dependence, that first caffeine beverage merely restores you to how you would have felt if you were not a caffeine consumer in the first place.
Caffeine is an ingredient in some popular medications for relieving pain, but it has no pain-relieving properties in its own right. So why is it used in combination with pain relieving compounds?
The pharmaceutical companies claim the effectiveness of pain-relieving drugs is improved when combined with caffeine. While this is supported by the drug companies' own research, there is little independent scientific evidence to support such claims.
One of the main reasons people use pain medications is to relieve headache, and headache is a common symptom of caffeine withdrawal. So, it's all very neat.
Unbeknownst to you, the medication may be both the cause and the cure of your problem.
If caffeine use is not risk free, why do most people think that it is? The answer may have something to do with big finance - caffeine is the core business of some of the biggest companies in the world. One economist estimated that coffee is the world's most widely traded commodity after oil and eight out of 10 people around the world consume caffeine drinks daily.
The caffeine industry has invested hugely in efforts to counter damage to its profits by unfavourable scientific findings. There is nothing new in this. History shows that when conflict arises between commercial interests and the public interest, commercial enterprises frequently act to protect the former at the expense of the latter.
One example is the tobacco industry, which for decades actively confounded evidence on the harmful effects of tobacco smoke. Like the tobacco industry before it, the caffeine industry has created heavily funded "institutes" and other such "research centres", which regularly disseminate claims via the Internet and other media, including at times scientific literature. Such claims serve to create a false public impression that caffeine is safe.
Prof Jack James is head of the Department of Psychology, NUI, Galway. He co-ordinates an EU- funded research programme examining the effects of dietary caffeine on health in Europe.
Prof Jack James, of the NUI, Galway, who is co-ordinating a EU-funded research programme on the effects of caffeine