Vitamin A is a fat-soluble vitamin that can be stored in the body and need not be replenished every day.
It requires fats as well as minerals to be properly absorbed by the digestive tract.
Fat-soluble means that if taken in large doses it will build up in the body tissue.There are two types of vitamin A that are found in the diet.
- Preformed vitamin A, called retinol is found in animal products such as meat, fish, poultry and dairy foods.
- Pro-vitamin A, known as carotene is found in plant-based foods such as fruits and vegetables. The most common type of pro-vitamin A is beta-carotene. Pro-vitamin A must be converted into active vitamin A by the body.
Vitamin A is also available in dietary supplements. It most often comes in the form of retinyl acetate or retinyl palmitate (preformed vitamin A), beta-carotene (pro-vitamin A) or a combination of those.
Function of Vitamin A (1)
Vitamin A helps form and maintain healthy skin, teeth, skeletal and soft tissue, and mucus membranes. It is also known as retinol because it produces the pigments in the retina of the eye. Vitamin A promotes good vision, especially in low light. It may also be needed for reproduction and breast-feeding. Retinol is an active form of vitamin A. It is found in animal liver,butter, cheese, whole milk, egg yolks, fish liver oils and some fortified foods.
- Beta-carotene is an antioxidant. Antioxidants protect cells from damage caused by substances called free radicals. Free radicals are believed to contribute to certain chronic diseases and play a role in the aging processes.
- Diets containing food sources of carotenoids such as beta-carotene have been shown to reduce the risk for cancer.
- On the other hand have beta-carotene supplements (isolated Beta-carotene in concentrated form) not seemed to reduce cancer risk.
Foods rich in vitamin A
Carotenoids are pigments found in plant foods that can turn into a form of vitamin A. There are more than 500 known carotenoids. One such carotenoid is beta-carotene. Beta-carotene is found in all red orange yellow and dark green fruits and vegetables as:
- sweet potatoes
- tomatoes and more
Here is a full list of foods that are high in vitamin A
Beta-carotene is powerful antioxidant protecting cells from oxidative damage, that later could lead to cancer. Beta-carotene can be converted into vitamin A as we need it. Unlike preformed vitamin A (retinol) beta-carotene does not exhibit the same clear toxic effects if excess doses are consumed.
In a study referred to as the AREDS study, “A randomized, placebo-controlled, clinical trial of high-dose supplementation with vitamins C and E, beta carotene, and zinc for age-related macular degeneration and vision loss.”
It was concluded that persons older than 55 years that fit a certain criteria should consider taking a supplement of antioxidants plus zinc such as that used in the study.
Signs of vitamin A deficiency (2)
Dry eyes and night blindness, loss of appetite, fatigue, recurring infections, bad skin,
Signs of vitamin A excess (3)
Hair loss, Diarrhea , vomiting, dry and flaky skin, blurred vision, eczema, bone aches, irregular menstruation, fatigue, headache, and swollen liver
Recommended daily dosage of vitamin A (4)
- Adult males 900 mcg/day
- Adult females 700 mcg/day
- Children and adolescents 300-600 mcg/day