People with sensitive stomachs may find that energy gels cause gastrointestinal problems, specifically nausea. Anyone, even those who don’t have sensitive stomachs, may experience nausea from consuming too many gels in too short a timeframe. Remember, your body can digest and process a maximum of 60 grams of glucose and 30 grams of fructose per hour3. Consuming more than that doesn’t do any good and can cause an upset stomach.