What seems to have gotten lost in the enthusiasm for vitamins is the fact that too much of vitamin intake can, indeed, be bad.

Risks include:

• Liver abnormalities
• Birth defects
• Reduced bone density
• Nerve damage to the arms and legs (from very high intake of supplements)
• Nausea
• Cramps
• Diarrhea
• Kindey stones
• High calcium levels in the blood
• Hemorrhage (only from supplements and fortified food)
• Kidney stones from supplements; renal insufficiency

Source: Oprah.com