Vitamin A
Vitamin A that comes from animal sources in the form of retinoic acid, retinal and retinol is fat soluble. The Vitamin A found in fruits and vegetables is in the form of carotenoids and must be converted by the body into retinoids. This form of vitamin A does not have the toxicity risk as the other form. There are also supplemental forms of vitamin A that are water soluble.
Vitamin A is a group of compounds or retinoids that play several important roles for our body such as vision, bone growth, reproduction, cell division, and cell differentiation
Vitamin A that comes from animals and is called preformed vitamin A and vitamin A that comes from colorful fruits and vegetables is called provitamin A carotenoid.
Benefits of Vitamin A
Vitamin A supports several important roles for our body’s immune system and cell development. This vitamin helps prevent or fight off infections by making white blood cells that destroy harmful bacteria and viruses. Below is a list of the several benefits that vitamin A provides for our body.
- Important for Vision
- May help with Coronary Artery Disease
- Improves the Immune System
- Keeps Skin and Mucous Membrane cells healthy
- Inhibits the production of DNA in Cancerous Cells
- Helps fight against Viruses
- Helps improve Skin Disorders
Symptoms of Vitamin A Deficiency
Vitamin A Deficiency is common in developing countries but is not commonly seen in the United States. There are approximately 250,000 to 500,000 malnourished children in the developing world that become blind each year from vitamin A deficiency. Zinc is required to make retinol binding protein which transports vitamin A. So, a deficiency in Zinc limits the body’s ability to move vitamin A from the liver to body tissues.
- Night Blindness
- Dry Eyes
- Increase in Respiratory and Diarrheal Infections
- Rough Skin
- Growth Retardation in Children
- Pruritus
People at Risk for Vitamin A Deficiency
Toddlers and young children are most at risk for vitamin A deficiency.
- Alcoholics*
- Toddlers and preschoolers
- Children living below poverty level
- People with diseases of the pancreas or liver
- People with diseases of the intestines
- People with inadequate fat digestion or absorption
- People that have Chronic Diarrhea
- People who have Iron Deficiency
- People with Crohn’s Disease
- People with Celiac Disease
- Vegetarians who do not consume eggs or dairy foods
*Alcoholics should talk with their doctor before starting Vitamin A supplements because their liver is more susceptible to toxicity from high doses of Vitamin A
Best Vitamin A Supplements
Vitamin A and Zinc supplementation work best to help the body distribute Vitamin A to the rest of the body. Most experts recommend avoiding supplemental vitamin A as retinol or retinoic acid. Experts suggest taking Plant-derived vitamin A such as Beta-Carotene (in addition to other mixed carotenoids) to reduce the risk of toxicity. Some experts suggest avoiding concentrated animal sources of vitamin A such as cod liver oil.
Vitamin A Foods
Foods with the highest amounts of Vitamin A are listed first
- Carrots and Carrot Juice
- Beef Liver
- Chicken Liver
- Spinach
- Kale
- Cantaloupe
- Apricots
- Papaya
- Mango
- Peas
- Tomato Juice
- Peach
- Milk, Eggs
Vitamin a Toxicity and Overdose
High levels of Vitamin A can build up in the body and cause birth defects, liver abnormalities, and reduced bone mineral density leading to osteoporosis. Central nervous system disorders have also been found with Vitamin A Toxicity.
Signs of acute toxicity include nausea, vomiting, headache, dizziness, blurred vision, and incoordination. Most toxicity cases come from supplemental intake but eating high quantities of liver have also been found to cause toxicity.
Vitamin A Interactions
Ethanol in alcoholic beverages and in some psychoactive drugs, such as painkillers or antidepressants may cause adverse effects with Vitamin A supplementation. The mix of these can cause liver damage.
Neomycin can slow the body’s ability to absorb vitamin A
Tetracycline interacts with vitamin A and can raise blood pressure causing hypertension.
Recommended Daily Allowance of Vitamin A
- 0-6 months: 400mcg (1,320 IU)
- 7-12 months: 500mcg (1,650 IU)
- 1-3 years: 300mcg (1,000 IU)
- 4-8 years: 400mcg (1,320 IU)
- 9-13 years: 600mcg (2,000 IU)
- 14-18 years: Males 900mcg (3,000 IU); Females 700 mcg (2,310 IU)
- 19+ years: Males 900mcg (3,000 IU); Females 700mcg (2,310 IU)
- Pregnancy 14-18 years: 750mcg (2,500 IU); Lactating: 1200mcg (4,000 IU)
- Pregnancy 19+ years: 770mcg (2,565 IU), Lactating: 1,300mcg (4,300 IU)
Tolerable Upper Intake Levels (ULs) for Retinol
- 0-1 years: 600mcg (2,000 IU)
- 1-3 years: 600mcg (2,000 IU)
- 4-8 years: 900mcg (3,000 IU)
- 9-13 years: 1,700mcg (5,610 IU)
- 14-18 years: 2,800mcg (9,240 IU)
- 19+ years: 3,000mcg (10,000 IU)
- Pregnant 14-18 years: 2,800mcg (9,240 IU), Lactating: 2,800mcg (9,240 IU)
- Pregnant 19+ years: 3,000mcg (10,000 IU), Lactating: 3,000mcg (10,000 IU)
Consult with your doctor before taking Upper intake levels of vitamin A. Synthetic retinoids similar to vitamin A are prescribed for acne, psoriasis, and other skin disorders. The medication Acutane contains high levels of retinoids and has been known to cause birth deffects in infants.