Many of our favourite tipples contain the stimulant caffeine. It has often had a bad press, but what effects does it really have and are there any health benefits to be had from our daily cuppas?
Caffeine is a drug that acts as a stimulant to the heart and central nervous system, and is also known to increase blood pressure in the short-term, although there is no conclusive evidence of long-term effects on blood pressure.
The effects on blood pressure are most likely when caffeine is taken in excessive quantities or by highly sensitive people. In particular, people who are hypertensive (have habitual high blood pressure), are advised to avoid caffeinated drinks, while pregnant women are advised to limit their intake of caffeinated drinks to less than 300mg per day.
Food Caffeine Content
Instant 61 - 70
Percolated ground 97 - 125
Tea (mg/cup) 15 - 75
Cocoa (mg/cup) 10-17
Chocolate bar 60 - 70
Cola drinks (mg/12oz can) 43 - 65
In the UK, 80 per cent of adults drink coffee every week. It's not the only bevarage to contain caffeine, but it does contain the most.
Coffee has been linked with a number of the risk factors for coronary heart disease, including increased blood pressure and high blood cholesterol levels. However, no relationship has been found between coffee drinkers and the likelihood of developing coronary heart disease.
There is good news for coffee drinkers. It has been found that coffee may be beneficial in some areas of health. Early research has found that coffee may reduce the risk of developing gallstones, kidney stones and colorectal cancer.
It's difficult to suggest a safe limit for coffee intake because of the huge variation in caffeine content of different brands and an individual's sensitivity to the drug. However, it is advised that people with high blood pressure and pregnant women limit their caffeine consumption.
For the rest of the population, however, there is no evidence that coffee does any long-term harm. Caffeine, however, does have a very mild diuretic effect, so try and include plenty of non caffeinated drinks throughout the day as well.
An estimated 196,000,000 cups of tea are drunk every day in the UK, and it's thought the average person in the UK will consume 80,000 cups of tea during their life. These figures are pretty spectacular - so what can tea do for us?
Tea does contribute slightly to our intakes of minerals, and it certainly helps to replace lost fluids, but the health interest in tea at the moment surrounds its proposed role in lowering the risk of coronary heart disease.
Tea contains antioxidant substances called flavonoids. These have been shown to help slow or inhibit the chemical reactions thought to take place during the development of coronary heart disease. So sup up! But remember that drinking water is still the best way of rehydrating our bodies, so for every cuppa you have, try to drink a glass of water too.
There has also been a lot of interest in the health advantages of green tea, with claims it can reduce blood cholesterol levels. However, scientific studies investigating its effects on blood cholesterol levels are divided. Some studies have found no effect at all; while others have found low cholesterol levels in people who consume large quantities of green tea. However, it can't be ruled out that the reason for these lower cholesterol levels is simply that people who drink green tea tend to have healthier diets generally. There is certainly no definitive evidence that green tea reduces cholesterol levels.