The seeds and leaves of the guarana plant, a climbing shrub native to Brazil and Uruguay, are high in caffeine, theobromine and theophylline, just like coffee. But there are mitigating factors. The plant itself contains saponins, compounds also found in ginseng that have tonic or balancing properties with a mild and long-lasting effect. These are less irritating to the gastrointestinal tract than coffee - probably because of the presence of fats and oils in the seeds, which prolong absorption. Guarana also reduces fluid retention and appetite, relieves tension headaches and period pains, and gives your energy a boost.

The problems with guarana lie in the processing. With many commercially prepared guarana products, the caffeine is absorbed and used up in the body as quickly as with a cup of coffee. So in this form guarana is over-stimulating, much like tea and coffee, and has the same ill effect on you. Like all stimulants it raises your blood sugar level, giving you a short-term lift in energy followed by a drop. I' d suggest going for a diluted, milder form of guarana, and only as an occasional pick-me-up. Supplements come in 500mg strengths, with a recommended intake of l,000mg, which provides 35mg of caffeine - roughly that found in a cup of tea or a weak cup of coffee.