If it really is that you need a beverage to stimulate you to stay awake, then the caffeine in coffee will do the job. For a feeling of alertness, with out the overstimulation then try having it in the form of a cup of tea instead. Tea contains L-theanine, an amino acid that helps increases alpha brain waves that help you to feel calm, but alert. L-theanine also damps down the stimulating effects of caffeine.

The main danger of caffeine is when you are using it to try and override your body’s need for sleep. Getting at least 7 hours sleep is a part of helping you achieve a healthy weight. Caffeine takes 4 hours for your liver to metabolise and clear from your body. This can be as long as 7 hours in a child. So aim to have no caffeine, at least 4 hours before you intend to sleep.

The best way to find out if you are caffeine dependent is to spend at least half a day without it and see if you develop a headache that is then relieved by a cup of tea or coffee. You can use decaffeinated or the cereal based coffee alternatives found in the supermarket to help reduce your consumption. 

Are you Australia's healthiest eater? Try the Healthy Eating Quiz developed by the School of Health Sciences in the Faculty of Health at the University of Newcastle.

Dr Clare Collins is a Professor in Nutrition and Dietetics at the University of Newcastle and consultant for The Biggest Loser