If you are sensitive to the effects of caffeine and are using products with higher caffeine content, then take into consideration your total amount of caffeine you are taking in throughout the day. (healthadviceworld.com)
Just a note about Guarana - it actually has a very high caffeine content and many people I know (myself included) find it very jittery and as stressful on the adrenals and nerves as coffee. (affairsofliving.com)
Many companies tend to sell an inferior Green Coffee supplement containing higher caffeine content. (perfect-supplements.com)