Coffee: Health Drink, Drug, or Delivery System for Whatever is in the Soil?
Coffee has had a strange medical career. For decades it occupied roughly the same nutritional territory as cigarettes and whisky: a pleasurable vice that respectable health advice suggested we should cut down. Now the epidemiological tables have turned. Coffee increasingly looks less like a guilty pleasure and more like one of those rare cases where something people actually enjoy may also be associated with better health.
The evidence is impressive, although it needs the usual epidemiological qualifications. A major BMJ umbrella review examined more than 200 meta-analyses of observational research and found that coffee consumption was associated with benefit more often than harm. The apparent sweet spot was around three to four cups per day. Compared with drinking none, that level was associated with lower all-cause mortality, cardiovascular mortality and cardiovascular disease. Coffee consumption has also repeatedly been associated with lower rates of type 2 diabetes and several liver, neurological and metabolic disorders.
The liver findings are particularly striking. Coffee consumption has been associated with lower risks of cirrhosis and liver cancer, while the broader literature also reports favourable associations for Parkinson's disease and type 2 diabetes. Another umbrella review concluded that coffee could form part of a healthy diet, although it stressed that coffee and caffeine are not quite the same exposure. Coffee contains hundreds of compounds besides caffeine, including chlorogenic acids and other polyphenols. Some benefits are also seen with decaffeinated coffee, suggesting that caffeine cannot take all the credit.
That distinction matters because caffeine is unquestionably a psychoactive drug. It blocks adenosine receptors and makes us feel less tired, which is why civilisation has somehow arranged for millions of people to medicate themselves with it before speaking to anybody in the morning. In sensible quantities this may improve alertness and performance. In susceptible people or excessive quantities, however, caffeine can produce anxiety, tremor, palpitations, sleep disturbance and transient increases in blood pressure. Randomised evidence confirms an acute blood-pressure effect from caffeine.
Sleep is perhaps the most routinely ignored downside. A person can drink coffee late in the day, fall asleep normally and conclude that caffeine has no effect on him. That does not necessarily follow. Caffeine has a half-life measured in hours, varies considerably between individuals and may affect sleep quality even when sleep still comes. Someone using coffee to compensate for inadequate sleep can therefore construct a neat biological circle: caffeine compensates for tiredness while contributing to the conditions that make caffeine necessary.
There are also groups for whom the reassuring general picture needs qualification. Pregnancy is the clearest example. The World Health Organization recommends that pregnant women consuming more than 300 mg of caffeine a day reduce their intake because high consumption is probably associated with pregnancy loss and low birth weight. The large BMJ review likewise found pregnancy to be one of the conspicuous exceptions to coffee's otherwise favourable epidemiological profile.
How the coffee is made matters as well. Coffee contains the diterpenes cafestol and kahweol, which can raise LDL cholesterol. Paper filtering removes much of them, whereas boiled, Turkish, Greek and some espresso-style coffees retain considerably more. European cardiovascular-prevention guidelines specifically caution about large quantities of unfiltered coffee. Thus "coffee" is not really a single nutritional exposure. A paper-filtered black coffee, a large unfiltered brew and a giant flavoured coffee containing several hundred calories of sugar and cream may share a name while being quite different biological propositions.
Then there is an issue that receives much less attention in cheerful stories about coffee's health benefits: what was in the soil in which the coffee grew?
Plants do not know whether a substance in the soil has been approved by a health-food shop. They take up minerals and other substances according to plant physiology, soil chemistry, acidity, water availability and the particular contaminant involved. Coffee is grown across an enormous geographical range, under very different volcanic, agricultural and industrial conditions. Consequently, beans can contain varying concentrations of trace elements and contaminants.
This is where the comparison with chocolate becomes instructive. Cocoa has acquired an almost saintly nutritional reputation because of its flavanols, yet cacao plants can accumulate cadmium from soil. The US Food and Drug Administration notes that cadmium concentrations in chocolate depend partly upon the geographical growing area and the proportion of cocoa solids in the finished product. Organic certification does not magically remove naturally occurring cadmium from the earth. An organic cacao tree growing in cadmium-rich soil can still absorb cadmium.
That does not mean chocolate is poisoning everybody. Indeed, the FDA notes that international assessments generally find cocoa products to be a relatively minor contributor to total dietary cadmium exposure. But it illustrates a broader principle that deserves much more attention: "organic" describes agricultural practices; it is not a laboratory certificate saying that the finished food contains no undesirable elements.
The same caution should be applied to coffee without exaggerating the danger. Studies have detected metals including lead and cadmium in coffee beans and coffee products, with concentrations varying according to origin and processing. Detection alone tells us remarkably little about health risk. Modern analytical equipment can detect substances at concentrations far below harmful doses. The relevant questions are how much is present, how much transfers into the brewed drink, how frequently it is consumed and what the total exposure is from the rest of the diet.
There is another contaminant with a quite different origin. Coffee can be contaminated by ochratoxin A, a mycotoxin produced by certain fungi, particularly when harvesting, drying and storage conditions allow fungal growth. Roasting and processing can reduce exposure, and commercial food-safety controls are intended to keep concentrations within regulatory limits, but the phenomenon is real rather than a health-blog invention. Reviews of coffee contamination identify growing, harvesting, drying, storage and processing as points at which the eventual ochratoxin concentration can be affected.
This introduces an interesting paradox into modern food culture. Consumers will pay considerably more for beans labelled organic, single-origin, shade-grown, fair-trade or artisan roasted, yet those labels do not necessarily tell them the information most directly relevant to contamination: what was actually measured in the beans?
The ideal premium coffee producer would therefore provide something less romantic and more useful than a photograph of a mist-covered mountain plantation. It would periodically laboratory-test representative batches for relevant heavy metals, mycotoxins and pesticide residues and make the results available. "Tested" is not the same thing as "organic," and neither term should be substituted for the other.
None of this overturns the increasingly favourable evidence on coffee. Quite the contrary. If coffee consumption at ordinary levels were producing a large net health burden, it would be difficult to reconcile that with the repeated observational association between coffee drinking and lower all-cause mortality. The famous umbrella review found the largest apparent benefit at roughly three to four cups daily, although that should not be converted into a medical instruction that non-coffee drinkers must immediately buy an espresso machine. Association is not causation, and people differ greatly in caffeine metabolism and susceptibility.
A more sensible conclusion is that for most healthy adults who tolerate it, moderate coffee drinking appears to be compatible with good health and may confer benefits. Paper-filtered coffee has advantages where cholesterol is a concern. Drinking it earlier rather than later protects sleep. Loading it with sugar can turn a virtually calorie-free drink into dessert. Pregnancy requires greater caution, and anyone who develops palpitations, anxiety or other symptoms after caffeine has better evidence from his own body than an epidemiological average.
Finally, quality matters. Coffee begins not in the café but in soil. The health-conscious consumer who worries about pesticides while ignoring metals and fungal contamination has understood only half the problem. The lesson from cocoa applies equally well here: a plant cannot read the organic label attached to it. It simply absorbs and accumulates according to its biology and environment.
Coffee therefore deserves neither the old demonisation nor a new health-food halo. The evidence increasingly suggests that a few cups of well-prepared coffee may be one of life's pleasures we do not have to apologise for. But if we are going to become particular about what goes into the cup, we should be particular all the way back to the ground from which the bean came.
https://www.trialsitenews.com/a/the-impact-of-drinking-coffee-on-health-1f6b5112
