[Clinical Problem] Diarrhoea [Potentially Harmful Nutrient] Magnesium usually >150 mg Iron usually >17 mg/day Vitamin C >1000 mg/day. Chewable supplements containing sorbitol or xylitol [Reasons for Caution] 
Supplements of these three nutrients can cause or aggravate diarrhoea especially at high dose. The artificial sweeteners sorbitol and xylitol can sometimes cause diarrhoea.