Coffee culture is ingrained in our everyday lives. Once a nation of tea drinkers, coffee is now the beverage of our desire, a pick-me-up that few of us can manage without. Seven British adults out of ten drink it on a regular basis, guzzling an average of three to four cups a day, often from one of the 3,000 high street coffee shops, which contributes to an industry worth £700 million.

For many people, no working day begins without a slurp of an Americano, no social catchup complete without a cappuccino. But while we have long been warned that one caffeine hit too many is unhealthy, experts are now claiming it is how we choose to drink coffee that is cause for concern.

Emerging research reveals that the way coffee is made impacts on our health. Studies have already proved that the boiled coffee drunk in Scandinavian countries – made by boiling unfiltered coffee beans in water, often for long periods – can raise levels of blood lipids (fats). But now it has been found that coffee made in a cafetière does the same. Substances in coffee called cafestol and kahweol, which are retained by a filter paper in some processes, raise serum concentration of cholesterol and triglycerides in drinkers of espresso and cafetière coffee.

Professor David Moor, a researcher in molecular and cellular biology at the Baylor College of Medicine, Texas, showed how five daily cups of cafetière coffee resulted in a 6 to 8 per cent increase in blood cholesterol. Oddly, for a drink that was once considered a dieter’s dream because of its low-energy content, experts are also concerned that the way we drink coffee is an increasingly significant contributory factor to obesity and its related illnesses.

Last week research by the consumer group Which? found that coffee sold at high street chains often contain more than 500 calories each – almost a third of the daily recommended intake for women. Indeed, when the Centre for Science in the Public Interest (CSPI), a nutritional advocacy organisation in Washington, looked at types of coffee in popular chains it found some contained as much fat and as many calories as a fast-food meal.

“While most people wouldn’t dream of eating a quarter-pounder between breakfast and lunch, they wouldn’t realise it is possible to get more than 500 calories from a drink at Starbucks,” says Jayne Hurley, a CSPI nutritionist. It is easy for coffee calories to mount up. Whipped cream on top of a mocha adds 80 to 120 calories and seven grams of saturated fat; sugar contains ten calories a sachet and flavoured syrups 70 calories a shot. And, says Joanne Lunn, a nutrition scientist at the British Nutrition Foundation, fat created by coffee calories seem to have a greater potential to settle on the hips than that from food.

“The latest research suggests that the body is not good at compensating for calories obtained from beverages such as these coffee drinks and may not process them in the same way as food,” Lunn says. “There is a psychological element in that people are not aware of the calories in these drinks and continue to eat as normal when drinking them,” she explains. “But some researchers are suggesting there is a physiological mechanism that means the body reacts differently to calories obtained from drink to that in food. At present they do not know the reason.”

The best choice for waistline and health, says Lunn, is a single-shot espresso or Americano (espresso with water added), preferably black, but with a shot of skimmed milk at the most.

Research carried out in 2004 backs this up. Dr Chiara Trombetti and a team of nutritionists at the Humanitas Gavazzeni institute, Bergamo, found espresso to be the best coffee source of tannin and antioxidants – good for the heart and arteries – and they also say that some small studies suggest a shot could cure headaches.

Switching to decaf won’t negate potentially harmful effects. Caffeinated and decaffeinated coffees are often derived from different species of beans. Usually, caffeinated coffee comes from the Arabica bean but as decaffeination extracts flavonoids and ingredients that give coffee its flavour, a stronger bean, such as the Robusta, is often used. That difference appears to impact on blood fats.

A study presented to the American Heart Association two years ago by Dr Robert Superko, chair of molecular and preventative cardiology at the Fuqua Heart Centre, Atlanta, found that decaf coffee increased blood pressure and harmful LDL cholesterol. After three months, drinkers of decaf in the trial experienced a rise in fatty acids and cholesterol by 8 per cent. “It’s not caffeinated but decaf that might promote risk factors associated with metabolic syndrome,” Superko says. “People should think twice about drinking it.”

Professor Bruce Goldberger, the study’s co-author, says decaf should not be mistaken for “caffeine-free”. “If someone drinks five to ten cups of decaf coffee, the dose of caffeine could easily reach the level present in two cups of regular, caffeinated coffee,” Goldberger says. “This is of particular concern to people advised to cut their caffeine intake.”

Too much of any type of coffee (more than six cups a day) has been linked to the excretion of calcium through urine, leading to potentially compromised bone density.

Bridget Aisbitt, a nutrition scientist at the British Nutrition Foundation, says that compounds in coffee are also known to inhibit absorption of some minerals, such as calcium and iron. For that reason it shouldn’t be drunk with meals. “There’s no conclusive evidence that it raises risks of osteoporosis,” she says, “but it is wise to limit your intake if you’re susceptible.”

Despite the mounting evidence against coffe, findings about how much we should or shouldn’t drink remain inconclusive and have divided the medical and scientific community. Professor Roland Griffiths, a neuroscientist at The Johns Hopkins School of Medicine, Baltimore, has shown how as little as 100mg of caffeine a day – the amount found in half a cup of instant coffee and only a third of the estimated total daily intake in the UK (280mg) – can lead to a physical dependence on caffeine that is difficult to wean yourself off.

It is impossible to prescribe “healthy” limits of caffeine, Aisbitt says. “People metabolise caffeine at different rates and, while a few cups are tolerable for one person, they can cause side-effects, such as restlessness and anxiety, in another,” she says. “However, it is similar to other drugs in that the more you drink, the more you need to get the stimulatory effect. To be safe, stick to five cups or less and don’t rely on coffee to keep your energy levels peaked.”

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