Listen to your mother: eating carrots is good for your eyes. Carrots are an excellent source of carotenoids that when absorbed by the body, converts into vitamin A. In addition to promoting good vision, vitamin A also plays a strong role in reproduction, bone growth and cellular function. It also supports your immune system in the quest to fight off infections by assisting in the production of white blood cells.
Forms of Vitamin A
There are two forms of vitamin A: preformed and provitamin A carotenoid. Both animal-based and plant-based food sources contain preformed vitamin A, while provitamin A is mainly found in plants.
Preformed vitamin A is easily assimilated in the body as retinol and is found in animal products like liver and whole milk. While preformed vitamin A is more readily absorbed than provitamin A, it's possible to consume too much. Vitamin A is a fat-soluble vitamin, which means the body is able to store significant amounts (unlike water-soluble vitamins where excess is eliminated in metabolic waste). Toxic levels of preformed vitamin A can build quickly if you take in large amounts in a short period of time.
Conversely, provitamin A stops converting to vitamin A when your body has made enough. It's almost impossible to consume enough of the provitamin A to reach toxic levels. This form of vitamin A has antioxidant properties and is found mainly in plants like carrots, spinach, kale, peaches, mangos and apricots.
As with other vitamins and minerals, be mindful that naturally occurring amounts in meat, dairy, fruits and vegetables can be reduced or eliminated if the food is processed (hence why you'll see vitamin A fortified dairy products or packaged cereals at your grocery store). And, when you bring fresh vegetables home from the farmer's market and cook them, you're effectively processing them and reducing their nutritional content. Whenever possible, eat fruits and vegetables raw, blanched or lightly steamed.
Vitamin A Deficiency
Vitamin A deficiency is rarely seen in the United States and when it is, it tends to be related to diets that are severely restrictive or the excessive consumption of alcohol. However, health conditions like celiac disease (sprue), Crohn's disease and certain pancreatic disorders impair the body's ability to maintain a store of vitamin A over time. In these rare cases, vitamin A deficiency can manifest in night blindness, total blindness and immune system compromise.
Vitamin A Toxicity
When people build up toxic levels of Vitamin A (or other vitamins or minerals), it's usually the result of taking excessive supplements. Hardly ever is vitamin A toxicity caused by consuming too many foods that contain it.
When toxic levels of vitamin A are reached, the condition is called Hypervitaminosis A. When present, this condition has been linked to birth defects, disorders of the central nervous system, liver disease and decreased bone density. Early symptoms of overconsumption of vitamin A, especially from animal products, include vomiting, dizziness, headache and loss of muscle coordination.
Vitamin E is a fat-soluble vitamin comprised of eight different compounds, each with its own function and use in the body. Its most active form in humans is called alpha-tocopherol which has been associated with reducing the risk of heart disease, certain cancers and cataracts.
Keeping abreast of the latest health news can be intimidating. Everyday something changes, it seems, so taking a mulitvitamin should keep you one step ahead of the game when it comes to preventing illness and disease.