A moderate caffeine intake boosts metabolism and elevates moods. Long term effects of caffeine however, can cause heart palpitations, hypertension and insomnia. It is best to keep your daily caffeine intake to less than 400mg. One serving of espresso (1 oz.) has 40mg of caffeine. A cup of brewed coffee (8 oz.) contains up to 133mg of caffeine. Decaf coffee has less than 5mg of caffeine. Energy drinks and soft drinks are high in caffeine too - Red Bull (12 oz) has about 80mg of caffeine while a diet Pepsi has 36mg!