Table of Contents
How is vitamin A calculated?
Example: A diet contains 1,666 IU of retinol and 3,000 IU of β-carotene. (1,666 ÷ 3.33) + (3,000 ÷ 20) = 650 μg RAE. Example: A supplement contains 5,000 IU of vitamin A (20 percent as β-carotene). 5,000 ÷ 3.33 = 1,500 μg RAE.
What is the daily allowance for vitamin A?
The recommended daily amount of vitamin A is 900 micrograms (mcg) for adult men and 700 mcg for adult women.
What is the upper limit for vitamin A?
Can vitamin A be harmful?
| Ages | Upper Limit |
|---|---|
| Children 4–8 years | 900 mcg |
| Children 9–13 years | 1,700 mcg |
| Teens 14–18 years | 2,800 mcg |
| Adults 19 years and older | 3,000 mcg |
How is vitamin A formed?
In foods of animal origin, the major form of vitamin A is an ester, primarily retinyl palmitate, which is converted to retinol (chemically an alcohol) in the small intestine. The retinol form functions as a storage form of the vitamin, and can be converted to and from its visually active aldehyde form, retinal.
What does vitamin A re mean?
Vitamin A intakes or requirements are generally expressed in terms of retinol equivalents (RE). One RE is defined as the biological activity associated with 1 µg of all-trans retinol.
What is the best form of vitamin A?
Concentrations of preformed vitamin A are highest in liver and fish oils [2]. Other sources of preformed vitamin A are milk and eggs, which also include some provitamin A [2]. Most dietary provitamin A comes from leafy green vegetables, orange and yellow vegetables, tomato products, fruits, and some vegetable oils [2].
Can you overdose vitamin A?
Vitamin A is a fat-soluble nutrient that is naturally present in many foods, like beef, eggs and many fruits and vegetables. An overdose of this vitamin can lead to problems with confusion, hair loss, liver damage and bone loss.
Where is vitamin A metabolized?
The liver is the major site of retinoid metabolism and storage in the body [3,4,5,6]. There are two hepatic cell types important to these processes: the parenchymal cells (also known as hepatocytes) and the stellate cells (also known as fat-storing cells, lipocytes, Ito cells, and perisinusoidal cells).
What is function of vitamin A?
Vitamin A helps form and maintain healthy teeth, skeletal and soft tissue, mucus membranes, and skin. It is also known as retinol because it produces the pigments in the retina of the eye. Vitamin A promotes good eyesight, especially in low light. It also has a role in healthy pregnancy and breastfeeding.