Posted by Blog Thursday, March 3, 2011

Excess preformed vitamin A from animal products or supplements taken during pregnancy is known to cause birth defects. Provitamin A carotenes are not known to cause birth defects. Intake levels by pregnant women below 10,000 IU daily have not been associated with an increase of birth defects. However, many foods are fortified with preformed vitamin A that can add to the other dietary sources of vitamin A. For this reason, pregnant women are advised to keep their preformed vitamin A levels below 5000 IU daily, for example, from prenatal vitamins.

To avoid any possibility of increasing birth defects, a diet rich in vegetables and fruit is an alternative to preformed vitamin A sources. One medium-sized carrot provides a safe alternative vitamin A source and contains about 16,000 IU.

Osteoporosis and Vitamin A
In older men and women, long-term intakes of preformed vitamin A can be associated with increased risk of osteoporotic fracture and decreased bone mineral density. Levels of only 5000 IU (1,500 mcg) are enough to increase risk. This is well below the upper limit set at 10,000 IU (3000 mcg) per day. Only high intakes of preformed vitamin A, not beta-carotene, are associated with any increased adverse effects on bone health.

Older men and women may want to limit their supplemental vitamin A intake or take only the beta-carotene form of vitamin A. Many fortified foods such as cereal contain significant levels of preformed vitamin A. The vitamin Ain fortified foods should be added to the vitamin Ain any supplements to find the total intake. On the other hand, low levels of vitamin Acan adversely affect bone mineral density. In older people, an intake of preformed vitamin A close to the RDA is safest.

The best way to assure safe levels of vitamin A is to eat plenty of fruits and vegetables and, if supplements are needed, to use the beta-carotene form.

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