vitamin_a

Vitamin A

What is vitamin A?

Vitamin A is a fat-soluble vitamin and an antioxidant that may help reduce the risk of cancer. Since the body stores fat-soluble vitamins, we do not need to consume them in large daily amounts like water-soluble vitamins.

Vitamin A comes in different forms. The vitamin A that we obtain from animal products is called retinoids. Vitamin A from retinoids is already in the form used by the body and is added to our stores right away.

Vitamin A found in fruits and vegetables is known as carotenoids, which need to be converted into retinoids before the body can use them.

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How does the body use vitamin A?

Vitamin A is important to vision and bone growth. Night vision is highly dependent on vitamin A since it is used to form pigments that allow our eyes to adjust to changes in light. Vitamin A also plays a vital role in white blood cell production and the maintenance of several organs, including the heart, lungs, and kidneys.

How much vitamin A do I need in my diet?

The recommended daily allowance (RDA) of vitamin A is measured in retinol activity equivalents (RAE), which take into account the body's ability to absorb various types of vitamin A. Retinol, a variety of retinoid, is used as the baseline since the body converts all vitamin A into retinol.

Quantity Equal to 1 mcg RAE
Vitamin A Type mcg
Retinol 1
Beta-carotene 12†
Alpha-carotene 24
Beta-cryptoxanthin 24
Source: National Institutes of Health1
† Some researchers suggestion 21 mcg of beta-carotene are needed to equal 1 mcg of retinol.2
Recommended Daily Allowances
Group RDA (mcg RAE)
Men 19+ 900†
Women 19+ 700
Pregnant Women 770‡
Lactating Women 1,300
Source: National Institutes of Health1
† Recommended daily value on new Nutrition Facts labels
‡ Pregnant women should not take high doses of vitamin A supplements or use topical retinoids, which have been linked to congenital disabilities.1
Nutrition Facts Label

Up until 2016, the US Department of Agriculture (USDA) required food manufacturers to list vitamin A on Nutrition Facts labels. The recommended daily value was 5,000 International Units (IU), which treated all sources of vitamin A as equal without regard to the body's ability to absorb the nutrient. New Nutrition Facts labels no longer require vitamin A to be listed, but food manufacturers can voluntarily include it. The new recommended daily value is 900 mcg RAE.

What are good sources of vitamin A?

Vitamin A is found in animal products, fruits, and vegetables. Animal sources of vitamin A typically contain high dietary cholesterol levels since vitamin A is located in cholesterol storage tissues, like the liver. The best fruit and vegetable sources of vitamin A tend to be yellow, orange, and dark green. Many food products are also fortified with vitamin A.

Food Serving Size mcg RAE
Beef Liver 4 oz 5,614
Sweet Potato 1 medium 1,096
Pumpkin Pie 1 slice 596
Carrots 1/2 cup 534
Cooked Spinach 1/2 cup 472
Cantaloupe 1 cup 270
Pickled Herring 3 oz 219
Mango 1 fruit 181
Source: US Department of Agriculture3

What is Vitamin A deficiency?

Vitamin A deficiency (or hypovitaminosis A) is a condition caused by low levels of vitamin A in the body.

Symptoms

  • Night blindness
  • Slowed growth and bone development
  • Inadequate immune function
  • Increased infections

Causes

  • Insufficient vitamin A consumption
  • Low iron levels. Iron helps the body absorb and metabolize vitamin A.
  • Low zinc levels. Zinc helps vitamin A move from the liver to other parts of the body.
  • Excessive alcohol consumption
  • Liver problems
  • Intestinal diseases

What is vitamin A toxicity?

Vitamin A toxicity (or hypervitaminosis A) is a condition caused by an excessive level of vitamin A in the body. Toxic levels of vitamin A can cause congenital disabilities, osteoporosis, liver problems, and central nervous system problems. Experts suggest men and women above the age of 19 should consume less than 3,000 mcg RAE of vitamin A per day to prevent toxicity.1

If reserves of vitamin A are at healthy levels, the body will not convert plant-based vitamin A (carotenoids) into the usable form (retinoids). On the other hand, the body will store animal-based retinoids regardless of the amount of vitamin A stored. As a result, vitamin A toxicity is usually caused by consuming excessive amounts of animal-based foods. Improper use of supplements can also lead to toxicity.

Additional Resources

Sources
  1. Vitamin A Fact Sheet. National Institutes of Health.
  2. West, CE, Eilander, A, & Lieshout, MV (2002). Consequences of Revised Estimates of Carotenoid Bioefficacy for Dietary Control of Vitamin A Deficiency in Developing Countries. The Journal of Nutrition, 132(9).
  3. Food Composition Databases. United States Department of Agriculture.

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