you can have an overdose of vitamins, it may cause: Cirrhosis of the Liver, loss of bone mass & Osteoporosis, decrease in mental alertness, abnormalities of the skin & hair and Birth Defects.
here's is a list (from here) of the maximum amount a body should get from each vitamin:
Vitamin A
Gorging on this vitamin compound in doses of more than 25,000 IUs (five times the RDA) can lead to liver damage, hair loss, blurred vision and headaches.
Bitamin B-6
Ingesting more than 400 mg a day (200 times the RDA) can cause numbness in the mouth and hands and difficulty in walking.
Vitamin C
It was once believed to cause kidney stones, but experts now say there is no solid evidence of dangerous side effects from vitamin C. High doses can produce stomachaches and diarrhea.
Vitamin D
In daily doses of 50,000 IUs (125 times the U.S. RDA), the sunshine vitamin can cause the buildup of calcium deposits that can interfere with the functioning of muscles, including heart tissue. While sunbathing will never create an overdose, taking too many supplements can.
Niacin
Doctors prescribe doses of 2,000 mg (100 times the RDA) to help lower cholesterol. But patients who take that much should be monitored for possible symptoms of jaundice and liver damage.
Iron
Those who want to bolster their red blood cell count, especially elderly people and menstruating women, have been taking iron supplements for years. Daily doses higher than 100 mg (six times the RDA) could interfere with absorption of zinc, a mineral that speeds wound healing and helps regulate the immune system.
I really can't think of any cereal which contain vitamins above the limit.
