Can You Overdose on Vitamins?
Many vitamins are water-soluble, meaning any excess is flushed out of the body. But some minerals and fat-soluble vitamins such as A, D and E if taken in excess of recommended daily allowances (RDAs) can build to dangerously high levels in the body.
- Large doses of beta carotene (equivalent to six carrots a day) has been found to increase the risk of lung cancer among smokers.
- Gorging on vitamin A compound in doses of more than 25,000 IUs (five times the RDA) can lead to liver damage, hair loss, blurred vision and headaches. Vitamin A in large doses can also accelerate osteoporosis and can cause birth defects.
- Ingesting more than 400 mg a day (200 times the RDA) of vitamin B6 can cause numbness in the mouth and hands and difficulty in walking.
- Doctors prescribe doses of 2,000 mg (100 times the RDA) of vitamin B3 (niacin) to help lower cholesterol. But patients who take that much should be monitored for possible symptoms of jaundice and liver damage.
- High vitamin E doses can increase your chance of a heart attack.
- Large doses of iron can be fatal in children; in adults it can bring on nausea, constipation and stomach pain. Daily doses higher than 100 mg (six times the RDA) could also interfere with absorption of zinc, a mineral that speeds wound healing and helps regulate the immune system.
The most current expert advice is to improve your diet and take note of established, safe RDAs. "If you're concerned that you're not getting enough vitamins in your diet, choose a multivitamin that will provide a spectrum of 100% of your RDA," says Frankie Phillips, a registered dietician.