Vitamin A was first discovered around 1912. At that time, vitamins were being discovered and named at major universities throughout the country. As research became more sophisticated, it was discovered that Vitamin A was made up of a group of fat soluble retinoids that include retinol, retinal, retinoic acid and retinyl esters.
Vitamin A has many functions in areas such as, the immune system, vision, gene transcription and reproduction, bone metabolism, skin and cellular health, and antioxidant activity.
In vision, rhodopsin is a protein that absorbs light in the retinal receptors. It supports the normal differentiation and functioning of the conjunctival membranes and cornea.
Vitamin A has a role in cell growth which assists with the formation of the heart, lungs, kidney, and other organs. Not only does Vitamin A play a role in formation, but also in the maintenance of the organs throughout the life cycle.
There are two forms of Vitamin A. One form of Vitamin A is preformed vitamin A, which is found in animal sources and includes dairy products and fish. Liver is a great source of Vitamin A, but as a consumer, be aware of how the animal was fed before eating liver. The second form is pro-vitamin A or carotenoids.
Probably the most widely known precursor to Vitamin A is Beta-carotene. Other pro-vitamin A carotenoids are alpha-carotenoid and beta-crytoxanthin. Beta-carotene is the highly pigmented red, orange, and yellow fat soluble compounds, naturally presented in many fruits and vegetables. These include carrots, sweet potatoes, squash, spinach, apricots, and green peppers.
Alpha, beta and gamma carotene are all considered pro-vitamins, because they can be converted to Vitamin A in the body. The carotene has antioxidant properties. The body converts these plant pigments into Vitamin A intercellular. There are other carotenoids found in food, such as lycopene, lutein, and zeaxanthin, which are not converted into Vitamin A.
Most of the body’s Vitamin A is stored in the liver in the form of retinyl esters.
How much Vitamin A does the body need?
Intake of vitamin A is provided in the dietary reference intakes (RDI). The RDI was developed by the Food and Nutrition Board (FNB) at the Institute of Medicine of the National Academies which was formally known as the National Academy of Sciences. The DRI is used as a reference value and is used for planning and assessing the nutrient intake of healthy people. It takes into consideration age and gender.
The RDA for vitamin A is:
- 14 – 18 yr/Male 900 mcg RAE
- 14 – 18 yr/Female 700 mcg RAE, Pregnant 750 mcg RAE, Lactating 1200 mcg RAE
- 19 – 50 yr/Male 900 mcg RAE
- 19 – 50 yr/Female 700 mcg RAE, Pregnant 770 mcg RAE, Lactating 1300 mcg RAE -*RAE = Retinol Activity Equivalents
The following are some sample foods measured in mcg RAE:
- Sweet potato, baked in the skin (3 ounces) = 1403 mcg
- Spinach, frozen, boiled ½ cup = 573 mcg
- Carrots, raw, ¼ cup = 459 mcg
Vitamin A Deficiency & Overcompumtion
A deficiency of Vitamin A could possibly cause night blindness, scaly dry skin and poor growth. If a client feels they are Vitamin A deficient, they should be checked by a physician.
As a result of Vitamin A being fat soluble vitamin, you can take in too much, which could also be harmful.
Overdosing on Vitamin A causes symptoms such as headache, liver damage, bone and joint pain, vomiting, appetite loss, abnormal bone growth, nerve damage and birth defects.
Overdosing on Vitamin A generally occurs from overconsumption of high Vitamin A supplements, not an excess of fruits and vegetables that contain beta carotene.
Since Vitamin A plays a role in cell growth, there has been scientific studies that looked at the association between vitamin A and cancer. The cancer risk is not clear when looking at serum Vitamin A levels and Vitamin supplements.
There have been studies with smokers versus non-smokers looking at serum A levels and lung cancer risk. Studies continue.
As the weather changes and we move into the fall season, it may be easier to find more red, yellow and orange fruits and vegetables. Fall pumpkins, squashes and peppers are being harvested.
When dining out try baked sweet potato fries and put peppers on your salads. Instead of always having a salad made from lettuce, try a spinach salad or have half lettuce and half spinach.
Get Creative. For example, squashes can be grilled, baked or stir-fried. They add color and flavor to all dishes.