Vitamin A can also be made in our bodies from precursor substances called carotenoids (found in yellow and orange fruits and vegetables), however, it takes up to 24 times the amount of carotenoid to equal one unit of Vitamin A. As a consequence, the best sources of Vitamin A are animal sources.
Vitamin A is responsible for healthy:
- Immune function
- Bone metabolism
- Skin and cells (including blood and reproductive cells)
- Antioxidant activity
Because Vitamin A is fat-soluble, it can be stored in the fatty tissues of our bodies. This means it has the potential to become a toxin if too much of it is ingested so supplementation should only be undertaken on the advice of a healthcare professional. If you think you might need more Vitamin A, increase your intake of yellow/orange fruits and vegetables, such as carrots, yellow and orange bell peppers, pumpkin and other squashes.
Doses for fat soluble vitamins are often expressed in International Units or IU, and sometimes as micrograms (mcg). Adults should not exceed an intake of 10,000 IU without medical supervision. Doses for children vary according to age. Children should not take supplemental doses without medical supervision.
Vitamin A can interact with a number of drugs and medications, including: alcohol, tetracycline, demeclocycline (Declomycin), minocycline (Minocin), and tetracycline (Achromycin), retinoid skin medications, and (hepatotoxic) drugs that are hard on the liver, such as acetaminophen (Tylenol and others), amiodarone (Cordarone), carbamazepine (Tegretol), isoniazid (INH), methotrexate (Rheumatrex), methyldopa (Aldomet), fluconazole (Diflucan), itraconazole (Sporanox), erythromycin (Erythrocin, Ilosone, others), phenytoin (Dilantin), lovastatin (Mevacor), pravastatin (Pravachol), and simvastatin (Zocor). Vitamin A can also interfere with medications that affect how your blood clots, such as warfarin (Coumadin).
Vitamin A can also adversely affect people with liver disease and certain kinds of high cholesterol conditions. If you have liver disease or high cholesterol, do not take Vitamin A supplements without consulting your healthcare practitioner.