Consumed by hundreds of millions of people every day, the caffeinated drink is the world’s most commonly used psychoactive substance.

Having a cuppa has become a day-saving part of many people’s early morning routines. It helps to wake you up and it keeps you going, one cup at a time.

Consumed by hundreds of millions of people every day, the caffeinated drink is the world’s most commonly used psychoactive substance. In Western society at least 80 percent of the adult population consume caffeine on a daily basis, and the popularity of coffee culture is growing across Asia.

But while scientists debate its potential positive and negative health effects, there is a loose consensus on what is the maximum amount of caffeine you should gulp down in one day.

Dr Samson Fong of the Hong Kong Society of Sleep Medicine says that you should limit caffeine intake to a moderate amount – one or two cups of coffee – and drink it before noon.

“Consuming these drinks in the afternoon and evening can make it hard to fall asleep or cause you to wake up during the night,” she said.

Up to 400 milligrams of caffeine a day appears to be safe for most healthy adults, according to the Mayo Foundation for Medical Education and Research. That’s roughly the amount of caffeine in four cups of brewed coffee, ten cans of cola or two energy drinks.

If you drink more than four cups a day you might experience side effects, the Mayo Clinic said, including nervousness, fast heart rate, muscle tremors, upset stomach and inability to control urination. Caffeine can have withdrawals symptoms, including fatigue, sleepiness and headache, in habitual users.

Some say you should not drink coffee until after 9:00am and this video explains that theory:

Other research suggests that dark coffee, like espresso of French roast, is better for the stomach than other blends. Dark roasts contain a substance (N-methylpyridium, NMP) that tells the stomach to reduce the production of acid.

Adding milk to the coffee is also a common way to relive stomach pain. But it may have opposite effect, as milk also stimulates acid production.

Some 40 million people in the United States either avoid coffee, or cannot drink as much as they would like, due to stomach irritation.

Dark-roasted, without milk, is probably the most stomach-friendly.

The medical world seems to agree that coffee should not be used as a substitute for rest. Instead of always reaching for yet another cup of coffee – especially when you feel you already have reached your daily dose – go out for a walk and get some sunlight on your face. Dehydration also leaves us feeling tired so a glass of water might be the best pick-me-up.

“Caffeine cannot replace sleep” adds Samson Fong. “It only works as a central nervous system stimulant by blocking the effect of adenosine in our brain which make us feel sleepy.”

Quick facts about caffeine

• Sweden, Denmark, and Norway consumes most caffeine per capita – around 400mg of caffeine per person per day, mostly coffee. (That’s about double Dr Samson Fong’s recommended limit).

• The US consumes 168mg of caffeine per person per day. It’s the biggest market in total tonne of coffee.

• China consumes only 16mg of caffeine per person per day, mostly tea.

• South American countries, such as Argentina and Brazil, get most of their caffeine from Yerba Maté tea.

• Japan has the world’s most expensive coffee.
Source: Caffeine Informer 

In search of the perfect cup… Photo: Johan Nylander