Vitamin A - Retinoids / Carotenoids

​Function: 
Vitamin A is needed for vision, cell growth, gene expression, bone development, and the immune system. 

Deficiency: 
Vitamin A deficiency leads to the symptoms of eye dryness, night blindness, anorexia, retarded growth, increased susceptibility to infections, and hair loss. 

Absorption:
Vitamin A is a fat-soluble vitamin, meaning that it must be consumed with fat in order to be absorbed. Therefore, fat-free dairy and/or fat-free salad dressing will limit the absorption of Vitamin A and its precursors unless another source of fat is included with that meal, such as nuts, seeds, or avocado.  Excessive fiber or Vitamin E (as supplements) can reduce carotenoid absorption when consumed at the same time.
 
Sources:
Vitamin A is naturally found in liver, fat-containing dairy products, and fish, and is added to some commercial foods.  Some carotenoids are precursors of Vitamin A and are found in plants that are red, orange, yellow, and green, including carrots, sweet potato, watermelon, papayas, tomatoes, squash, pink grapefruit, pumpkins, broccoli, cantaloupe, peas, spinach, orange peppers, corn, potatoes, eggs, beets, and kiwi fruit.  As a fat-soluble vitamin, Vitamin A can be destroyed by being oxidized when exposed to varying levels of oxygen, light, heat, and some metals.  A water-soluble version of Vitamin A (Aquasol A) is available for individuals who have a hard time absorbing fat-soluble vitamins.

Toxicity:
Acute toxicity of Vitamin A, meaning an extreme amount being taken in one dose, may result in nausea, vomiting, double vision, headache, dizziness, and unusual skin shedding.  Chronic toxicity of Vitamin A, meaning that large amounts are taken daily for a given period of time, may result in anorexia, dry, itchy, and shedding skin, hair loss, coarsening of the hair, headache, bone and muscle pain, increased bone fractures, conjunctivitis, ocular pain, liver damage, and birth defects.  Do NOT self-supplement Vitamin A!

---

* This information is not intended to encourage self-supplementation.   As you will read in individual nutrient content, self-supplementation can be unnecessary or even dangerous.  I highly recommend micro-nutrient blood testing before choosing to take any supplements that are not whole-foods based.
​
References:
Gropper SS, Smith JL, Groff JL. Advanced nutrition and human metabolism. 5th ed. Belmont, CA: Wadsworth; 2009.
Mahan L, Escott-Stump S, Raymond J. Krauses's food and the nutrition care process. 13th ed. St. Louis, Missouri: Elsevier Saunders; 2012.