Vitamins are organic compounds (compounds that contain carbon), and of the 13 that your body needs, 4 are called fat-soluble (A, D, E, and K). Fat-soluble vitamins do not dissolve in water and are stored in your body's fat and liver. As a result, these vitamins can build up in the tissues and become toxic (specifically vitamins A and D).
Vitamins fall into two classes: fat-soluble and water-soluble.
|Fat-Soluble Vitamins||Water-Soluble Vitamins|
|Vitamin D||Thiamin||Vitamin B-12|
|Vitamin E||Riboflavin||Pantothenic acid|
|Vitamin B-6||Vitamin C|
Vitamin A (Retinol)
Like Mom always said, eat plenty of carrots and you'll see in the dark. That's because carrots contain beta-carotene, a substance that is converted into vitamin A by your body. Vitamin A promotes good vision, as well as healthy skin and the normal growth and maintenance of your bones, teeth, and mucous membranes. What Mom didn't tell you was that beta-carotene is also found in most orange-yellow fruits and vegetables, along with dark green vegetables.
Your body converts beta-carotene into vitamin A only when you need it, so eating foods rich in beta-carotene cannot cause vitamin A toxicity. However, eating huge amounts might turn your skin slightly orange. Not to worry, this condition isn't serious. Simply lay off the orange veggies for a few days and the color will disappear.
Although your body controls the creation of vitamin A from beta-carotene, it has no control when you ingest straight vitamin A, which can be found in vitamin tablets. Over-supplementation can be extremely toxic, resulting in general fatigue and weakness, severe headaches, blurred vision, insomnia, hair loss, menstrual irregularities, skin rashes, and joint pain. In extreme cases, there can be liver and brain damage. Huge doses taken in the prenatal period can cause birth defects.
What happens if you don't get enough? Vitamin A deficiency can cause night blindness, total blindness, and lowered resistance to infection because vitamin A plays a key role in the structural integrity of your cells. Here come the germs!
Foods rich in vitamin A include: liver, eggs, milk, butter, and cheese.
Foods rich in beta-carotene include: cantaloupes, carrots, sweet potatoes, winter squash, spinach, and broccoli.
More on: Children's Nutritional Needs
Excerpted from The Complete Idiot's Guide to Total Nutrition © 2005 by Joy Bauer. All rights reserved including the right of reproduction in whole or in part in any form. Used by arrangement with Alpha Books, a member of Penguin Group (USA) Inc.
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