Illness caused by excessive vitamin intake, almost certainly due to misuse of supplements.
Many veg*ns use some form of vitamin supplement, and such products are often not heavily regulated. Information about adequate, optimal and excessive intakes of micronutrients is not common knowledge, and high-dose products are widely available.
Just as vitamin deficiencies produce serious symptoms, excessive intakes can also cause problems, particularly the fat-soluble vitamins D and A. The preformed type of vitamin A, retinol (not present in plant foods), is known to cause birth defects in excess. Other vitamins produce less serious symptoms.
