A study was published this month in the Journal of the International Society of Sports Nutrition by Kammerer et al. stating most energy drinks do not help performance in either sports or cognitive functioning in young adults. The study performed included the amount of caffeine and Taurine that normally occurs in energy drinks (caffeine 80mg and Taurine 1000mg per approx. 8oz drink).
Think again before reaching for a red bull or monster. Try getting energy from fruits, grains, proteins, leafy greens. If you are feeling fatigued or losing concentration you might be lacking essential vitamins and minerals.