Vitamin A Facts
What is Vitamin A?
Vitamin A is a fat-soluble vitamin that acts as an antioxidant. Antioxidants are chemicals which may help reduce risk of cancer. Since vitamin A is fat-soluble it is not needed in daily, large quantities. Fat-soluble vitamins are stored in the body in organs such as the liver. Most of the vitamin A that we consume goes to the liver to be stored until it is needed by another part of the body. Therefore, our intake of vitamin A should be enough to replenish our liver stores.
Vitamin A, like many other nutrients, is found in different forms. The vitamin A that we obtain from animal products is called retinoids and can be used by our bodies without any modification. The form of vitamin A found in fruits and vegetables is known as carotenoids. The most common type of carotenoid is ß-carotene (beta carotene). These carotenoids are used to build the type of vitamin A used by our body.
How is Vitamin A used by the body?
Vitamin A is important to vision and the growth of the bones. Night vision is extremely dependant on vitamin A. This vitamin helps form pigments that allow our eyes to adjust to changes in light. Vitamin A plays an important role in immune system by making white blood cells, which fight off viruses and bacteria.
How much Vitamin A do I need in my diet?
The recommended daily intake of Vitamin A for adult men is around 2,333 IU (International Units) per day; for adult women, the recommended daily intake is 3,000 IU per day. Pregnant women should consume 2,566 IU per day since large amounts of vitamin A is associated with birth defects. Lactating women, on the other hand, need a slightly higher intake of 4,332 IU per day in order to make up for what is lost through breast milk.
The upper limit of vitamin A can vary depending on the sources of vitamin A consumed. See the toxicity section below for more details
What are good sources of Vitamin A?
Vitamin A is found in animal products, fruits, and vegetables. The animal sources of vitamin A typically contain a high level of cholesterol. This is due to the fact that vitamin A is found in storage tissues, like the liver, which can also be used to store cholesterol. The best fruit and vegetable sources of vitamin A are ones which are yellow, orange and dark green in color. Many food products are now fortified with vitamin A, which means that additional vitamin A was added to food item. Some good sources of vitamin A include the following:
|Fruit Sources||Vegetable Sources||Animal Sources||Fortified Foods|
|• Oranges/Juice||• Sweet Potatoes||• Liver (beef, pork, chicken)||• Fat Free Milk|
|• Cantaloupe||• Carrots||• Cereals|
|• Apricots||• Collard Greens||• Eggs||• Dried, Nonfat Milk Solids|
|• Mangos||• Spinach||• Whole Milk|
|• Pumpkin||• Kale||• Cream|| |
|• Winter Squash||• Broccoli||• Cod Liver Oil|
What is Vitamin A deficiency?
Vitamin A deficiency is more common in developing countries. This deficiency can be caused by not consuming enough vitamin A, as well as low levels of iron and zinc. Iron helps vitamin A get absorbed and metabolized by our bodies. Therefore, a low amount of iron in the body will mean that less vitamin A is absorbed and used from our diet.
Zinc, on the other hand, helps vitamin A move from the liver to other parts of the body where it is needed. Without zinc, our bodies cannot transfer vitamin A from the liver. Alcohol, liver problems, and diseases affecting the intestines also reduce vitamin A absorption into the body.
Since Vitamin A plays a large role in night vision, night blindness is a symptom of vitamin A deficiency. Other symptoms include slowed growth and bone development, inadequate immune functioning, and increased infections.
What is Vitamin A toxicity?
Too much vitamin A in the body is known as hypervitaminosis A. This occurs when vitamin A becomes toxic to the body and causes harmful effects. High levels of vitamin A can cause birth defects, osteoporosis, liver problems, and central nervous system problems. The amount of vitamin A needed to cause toxicity can vary depending on the type of vitamin A eaten. It is suggested that men and women above the age of 19 should consume less than 75,000 IU of vitamin A per day to prevent toxicity.
Vitamin A is found in the form of retinoids in animals. Since this is the form of vitamin A used by the body, it is added to our stores of vitamin A right away. On the other hand, beta carotene is derived from plant foods and needs to be converted by the body into retinoids before it can be used. If the body has enough vitamin A, then the beta carotene will not be converted. Therefore, vitamin A toxicity is usually caused by consuming excessive amounts of animal-based foods.
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