High-Dose Side Effects. Excessive consumption of Garcinia cambogia extract can cause gastrointestinal side effects, according to EMedTV and Green Herbal Remedies. People taking large amounts of this herb might experience stomach or intestinal pain, nausea, vomiting and diarrhea.Headaches are another possible side effect.igh-Dose Side Effects. Excessive consumption of Garcinia cambogia extract can cause gastrointestinal side effects, according to EMedTV and Green Herbal Remedies. People taking large amounts of this herb might experience stomach or intestinal pain, nausea, vomiting and diarrhea.