Coffee or tea? Science investigates
Coffee or tea? Scientific investigations on coffee and tea are reported at a dizzying pace, for the most part focussing on coffee and its impact on our health. While it now appears tea is getting some attention, coffee keeps coming up smelling like roses – or at least chock full of aromatic health-promoting substances. Gradually, the waters have become less muddied. For example, coffee is a major source of caffeine. And it was thought caffeine caused a loss of calcium from bones resulting in osteoporosis. But a well-conducted study of over 35,000 post-menopausal women done by the University of Minnesota vindicated caffeine as not a bone-thinning substance.
But before you celebrate by brewing up a big pot of java, there are other considerations:
Caffeine is found in both coffee and tea, as well as other beverages, such as soft drinks. The amount in coffee, however, can be significantly more than in tea, but much depends upon preparation.
- Drip coffee contains 140 milligrams of caffeine per five-ounce cup.
- Instant has just 60 milligrams.
- Tea provides only 30 milgrams if brewed for one minute and 45 milligrams for a five-minute steep for a five-ounce cup.
- Decaffeinated varieties of both coffee and tea are almost caffeine-free.
- Alternating decaffeinated brews with regular ones can help you keep within the recommended caffeine quotas – the amount contained in three to four five-ounce cups of coffee.
Caffeine affects people in different ways, and reactions to its stimulant effect are greatly influenced by a person’s weight and body size. This explains why, for one person, a cup of coffee in the afternoon can lead to a sleepless night, while for another an after-dinner double espresso can be a bedtime beverage.
Impact on heart
Besides being linked to irritability and sleeplessness, caffeine-containing beverages may lead to:
- Irregular heart rhythms, such as tachycardia
- Indigestion (both regular and decaffeinated varieties of coffee contain potentially irritating acids).
- Tea, on the other hand, is considered by many to be a soothing beverage – but caffeine counts quickly add up for those who sip all day long.
- Using both regular and decaf tea may be preferable for caffeine-sensitive drinkers.
When it comes to heart-health, coffee and tea have been the subject of numerous scientific studies. A scientific review of a number of studies, published in the journal Hypertension, looked at the effect of regular consumption of coffee and its effect on blood pressure and found that:
- As coffee consumption increased, so did blood-pressure levels.
Age, hypertension link
An Australian study evaluated what happened to blood pressure levels after two weeks on a caffeine-free diet for people with normal blood pressure and others with hypertension.
- In subjects with normal blood pressure readings, there was no difference.
- In those with high blood pressure, especially older subjects, readings were higher after the coffee.
Consequently, researchers were able to recommend that coffee intake be reduced for older individuals, particularly those with hypertension.
Rheumatoid arthritis link
Recent research also shows a connection between coffee and the risk of rheumatoid arthritis. In the 15-year study, reported in the Annals of the Rheumatic Diseases, the amount of coffee consumed on a daily basis was strongly associated with the presence in the blood of a substance called rheumatoid factor.
This compound can usually be detected in the blood years before the actual development of rheumatoid arthritis.
- Researchers found that four or more cups of coffee a day doubled the likelihood of testing positive for rheumatoid arthritis. While scientists don’t as yet know what compounds in coffee are responsible for this effect, they do suggest it’s yet another good reason to practice moderation.
Tea as antioxidant
As for tea, it has shown great potential on the health-front due to the antioxidant effects of compounds called flavonoids. These substances are also abundant in fruits and vegetables.
- They help prevent cholesterol from being deposited in the arteries and reduce the tendency of blood to clot.
- Scientists have even suggested drinking a cup of tea a day could provide the equivalent antioxidant quota as a full serving of vegetables.
The much talked about French Paradox, which promotes red wine’s ability to protect against heart disease, is mainly about the flavonoids found in that beverage.
Although many people turn to their medicine chest for antioxidant supplements, brewing up a pot of tea may be more effective – and cheaper.
Heart and homocysteine
High blood levels of a substance called homocysteine have recently emerged as a major risk factor for heart disease and stroke.
- Tea contains lower levels of homocysteine.
- Coffee has not fared as well. In a study of over 16,000 Norwegian adults, increased homocysteine readings were found in coffee, whether filtered, boiled or instant.
- There was no association between decaffeinated coffee and blood levels of homocysteine.
Because tea can also contain caffeine without boosting homocysteine levels, it’s thought the trick lies within the decaffeination process. The offending substance, which may boost homocysteine readings, is likely removed as well.
The study also found that drinking coffee and smoking cigarettes seems to be a particularly potent combination associated with boosting homocysteine levels.
A recent study from the University of Toronto published in the International Journal of Cancer looked at both coffee and tea consumption and beverages such as alcohol and cola, to see if there was a connection to prostate cancer.
Only tea showed a relationship.
- Men who drank more than two cups a day had a lower risk of prostate cancer.
Research has also indicated other benefits to consuming tea. A study group involving post-menopausal women in Iowa showed that as tea consumption rose, rates of certain cancers – such as that of the stomach, mouth and kidney – actually fell.
- Women who drank more than two cups of tea a day were 60 per cent less likely to have cancers of the urinary tract than those who consumed none.
At Rutgers University, black and green tea and their decaffeinated counterparts have all demonstrated an ability to suppress skin tumour growth in mice. Other research showed the protective effect of black tea against both the onset and progress of lung cancer in mice.
While more research into tea’s effects on humans is needed, studies from China show promising results. Subjects diagnosed with pre-cancerous lesions in the mouth appeared to benefit from tea. In one study, tea was both consumed and applied topically and seemed to delay the progression of the lesions into oral cancer.
Milk in tea
Some research shows that when tea contains milk, the beneficial compounds or flavonoids are likely absorbed in smaller amounts. This may explain why green tea has traditionally had a more healthful reputation.
In countries such as Britain, where black teas are thought of as a national beverage, they’re usually served with milk. Research on black tea and its link to disease rates may have been clouded by the addition of milk.
That’s not to say you have to have your tea without milk, but if you’re seeking tea’s healthful benefits, vary how you drink it.