Nutrient Information: Vitamin A, IU

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Nutrient Key Information 
Nutrient Name: Vitamin A, IU
Nutrient Category: Vitamins and Other Components
Unit Name: IU
Nutrient Summary: Vitamin A is important for vision, skin tissues, reproduction, embryonic development, bone growth, and immune function.
Nutrient Function: The main forms of Vitamin A are:

  1. Preformed (active form) Vitamin A: retinol, retinal, and retinoic acid (collectively called retinoids). They are naturally exists in meats, fish, and dairy products. Body can convert retinol to retinal, and convert retinal to retinoic acid.
  2. Provitamin A carotenoids: beta-carotene, an orange pigment. It is a precursor of Vitamin A. It is converted into retinol in the intestine and liver. Beta-carotene exists in vegetables, fruits, and plant-based oils. The absorption and conversion rate from beta-carotene to retinol is not that efficient. The conversion rate from plant based beta-carotene to vitamin A RAE is 12 mcg beta-carotene to 1 mcg RAE. In addition to be a Provitamin A, beta-carotene also acts as an antioxidant in the body.
  3. Body storage form of retinol: retinyl ester. Most of Vitamin A are stored in liver in the form of retinyl esters for later use. Retinyl esters are often used in the supplements, and fortified foods.

RAE stands for Retinol Activity Equivalents. RAE value is used as the recommended daily value for Vitamin A. 1 microgram (mcg or µg) of retinol is 1 RAE. 12 mcg of dietary beta-carotene is 1 RAE.

Each form of vitamin A performs a specific function in the body.

Benefits to eye health:
1) Retinal is required by the eye to transduce light into the neural signals necessary for color vision and low-light vision.
2) Retinoic acid is required to maintain crystal-clear cornea and conjunctiva membranes (which covers the surface of your eye), thus to prevent xerophthalmia.

Benefits to skin tissue health:
Outside and inside body is covered by epithelial cells.
1) Outside skin epithelial cells: vitamin A and beta-carotene help protect against skin damage from sunlight. It can stimulate skin cell growth.
2) Inside body epithelial cells: mucous membranes for mouth, stomach, intestines, lungs, various passageways, etc. Vitamin A helps to maintain their integrity and health.

Supporting reproduction:
1) For men, retinol for of Vitamin A participates in sperm development.
2) For women, vitamin A supports normal embryonic development during pregnancy.

Role in bone growth:
Bone growth includes 2 steps: 1) dismantle old bone cells (osteoclasts) 2) generate new bone cells (osteoblasts). Vitamin A participates in the old bone cell dismantling process.

Other functions:
• Support immune function: retinoic acid form of Vitamin A may support the creation, growth and distribution of T-cells which is a type of white blood cell that protects your body from infection.
• Help red blood cell formation: Vitamin A helps iron mobilization from stores, thus improves hemoglobin concentrations.

Vitamin A is a fat-soluble vitamin. Taking with a meal containing fats can increase its absorption.


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Food Sources

Preformed Vitamin A (retinol) exists naturally in animal-based foods. The efficiency of preformed vitamin A absorption is higher (from 70 to 90%). The primary food sources are:
• Liver
• Fish: such as bluefin tuna fish, king mackerel, trout, salmon
• Dairy products: such as various cheese
• Egg yolk

Dietary Provitamin A carotenoids exist in vegetables, fruits, and plant-based oils. The efficiency of Provitamin A carotenoids absorption and conversion is relatively lower (~ 9-22%). The primary food sources are:
• Sweet potatoes
• Carrots
• Orange color pumpkin and butternut squash
• Deep orange fruits: such as cantaloupe, apricots, and mangos
• Dark green leafy vegetables: such as spinach, Swiss chard, kale, and broccoli
• Red peppers

Foods fortified with vitamin A:
• Low-fat and nonfat milk
• Fortified grains and cereals
• Margarine

Notes:
• Dietary fat may enhance the absorption of Vitamin A.
• Cooked carrots and spinach has greater absorption rate of Vitamin A.
• Alcohol consumption may negatively affect vitamin A stores in liver.

Sample Foods High in: Vitamin A, IU
View Additional Food Sources
Food Description Nutrient Amount1 Daily Value%2
Beef, variety meats and by-products, liver, cooked, braised
Category: Beef Products
31,714 IU 634.28%
Sweet potato, cooked, baked in skin, flesh, without salt
Category: Vegetables and Vegetable Products
19,218 IU 384.36%
Carrots, cooked, boiled, drained, without salt
Category: Vegetables and Vegetable Products
17,033 IU 340.66%
Mustard greens, cooked, boiled, drained, without salt
Category: Vegetables and Vegetable Products
12,370 IU 247.40%
Squash, winter, butternut, cooked, baked, with salt
Category: Vegetables and Vegetable Products
11,155 IU 223.10%
Spinach, cooked, boiled, drained, without salt
Category: Vegetables and Vegetable Products
10,481 IU 209.62%
1 Nutrient amount is in 100 gram food
2 Use FDA 2000 calorie diet as Daily Value reference



Additional Nutrient Information
Nutrient Summary Vitamin A is important for vision, skin tissues, reproduction, embryonic development, bone growth, and immune function.
Deficiency Health Effects A person's Vitamin A status depends on the level of Vitamin A storage and the retinol-binding protein which transports retinol from storage to target tissues. People will not notice the Vitamin A deficiency until their Vitamin A stores are depleted. Here are possible health problems caused by Vitamin A deficiency:

  • Blindness (Xerophthalmia): the initial symptom is not able to see well in low lights. Xerophthalmia is the most specific clinical effect of vitamin A deficiency. It has various stages including night blindness, conjunctival xerosis (dry cornea), Bitot’s spots (triangular gray spots on eye), corneal xerosis (dry and hazy appearance of the cornea), corneal ulceration and scarring, and then corneal degeneration and blindness. The night blindness is caused by a lack of vitamin A at the retina in the back of the eye; total blindness is caused by a lack of vitamin A at the cornea in front of the eye.
  • Outside and inside body surfaces: Vitamin A deficiency causes the body's outer surface skin to become dry, rough, and scaly, and causes inside body's epithelial tissues weaken, as a result, the the respiratory tract, the GI tract, etc. will more likely to get infection.
  • Reduced immune function: Vitamin A deficiency decreases immune function, so increases the risk of infectious morbidity and mortality, such as respiratory infection, diarrhea, and measles virus.
  • Vitamin A deficiency impairs iron mobilization from stores.
Effects if Above Upper Limit As a fat-soluble vitamin, vitamin A is not readily excreted, so the risk of toxicity is relative high when eating large amount of preformed vitamin A animal foods (such as beef liver), fortified foods, or supplements. The excessive vitamin A not used can potentially damage cells. Preformed vitamin A toxicity (hypervitaminosis A) may be acute or chronic.

Beta-carotene from fruits and vegetables is not so efficiently converted to the active form of vitamin A retinol, so the toxicity risk is low, though over consumption may turn the skin to yellow. However, overconsumption of beta-carotene supplements will make it act as a prooxidant which induces oxidative stress and damages cells and tissues.

Vitamin A toxicity effects:
• Excessive vitamin A may stimulate bone-dismantling activity that reduces bone density and weaken the bones. This contributes to fractures and osteoporosis.
• High doses of Vitamin A (≥ 7,800 mg/day) during the first trimester of pregnancy may cause infant birth defects such as teratogenicity.
• High doses of vitamin A (5,500-6,750 mg/day) may cause intracranial and skeletal abnormalities for infants.
• Liver is the main storage of vitamin A, excessive vitamin A may cause liver abnormalities.

Vitamin A acute toxicity symptoms:
• Blurred vision
• Nausea and vomiting
• Headache and dizziness
• Muscular incoordination

Note: People with high alcohol intake, pre-existing liver disease, hyperlipidemia, or severe protein malnutrition should lower the intake Upper Limit.
External References



Daily Value Age Group Recommended Daily Values
Female 31 to 50 years old: 5,000 IU
FDA (Based on 2000 calorie daily diet): 5,000 IU
Notes:
As of 02/25/2022, FDA decreased Vitamin A Daily Value from 5000 IU to 900 mcg RAE (3000 IU).
0.3 mcg RAE = 1 IU
900 mcg RAE = 3000 IU
International Units (IU) was used to measure vitamin A's biological effect.
Learn more from FDA website.


Dietary Reference Intakes The nutrient Dietary Reference Intakes and nutrition facts is from Institute of Medicine of National Academies 2006. Dietary Reference Intakes: The Essential Guide to Nutrient Requirements. Washington, DC: The National Academies Press. https://doi.org/10.17226/11537
US FDA Nutrition Education Nutrition facts knowledge are based on U.S. FOOD & DRUG Administration Nutrition Education Resources & Materials. https://www.accessdata.fda.gov/scripts/interactivenutritionfactslabel/
National Institutes of Health Nutrition facts knowledge are based on National Institutes of Health Dietary Supplement Fact Sheets. https://ods.od.nih.gov/factsheets/list-all
Disclaimer The nutrient information provided here should not take the place of medical advice. We encourage you to talk to your healthcare providers (such as your doctor) about your dietary requirements which are best for your overall health. We also recommend you to read organization or professional reference documents or articles mentioned, but not limited to, in this page. Any mentions and reference links in this page don't represent our endorsement of their services and advice.


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