The principal form of vitamin A found in the body.
A. (See APPENDIX 5: VITAMINS.)
Vitamin A is absorbed by the body in the form of retinol. This is found in liver, fish-liver oils, egg yolk, dairy produce, and is added to margarines. Carotene, which the body converts into retinol, is found in various vegetables and fruits.
Vitamin A deficiency is rare in developed countries. In most cases, it is due to malabsorption. Vitamin A deficiency may also result from long-term treatment with certain lipid-lowering drugs. Deficiency is common in some developing countries due to poor diet. The first symptom of deficiency is night blindness, followed by dryness and inflammation of the eyes (see xerophthalmia), keratomalacia, and eventually blindness. Deficiency also causes reduced resistance to infection, dry skin, and, in children, stunted growth.
Prolonged excessive intake of vitamin A can cause headache, nausea, loss of appetite, skin peeling, hair loss, and irregular menstruation. In severe cases, the liver and spleen become enlarged. Excessive intake during pregnancy may cause birth defects. In infants, excessive intake may cause skull deformities, which disappear if the diet is corrected.
The drug tretinoin (a derivative of vitamin A) is used to treat severe acne.... vitamin a
Nutritional Profile Energy value (calories per serving): Low Protein: Moderate Fat: Low Saturated fat: Low Cholesterol: None Carbohydrates: High Fiber: High Sodium: Moderate Major vitamin contribution: Vitamin A Major mineral contribution: Potassium
About the Nutrients in This Food Carrots are high-fiber food, roots whose crispness comes from cell walls stiffened with the insoluble dietary fibers cellulose and lignin. Carrots also contain soluble pectins, plus appreciable amounts of sugar (mostly sucrose) and a little starch. They are an extraordinary source of vitamin A derived from deep yellow carotenoids (including beta-carotene). One raw carrot, about seven inches long, has two grams of dietary fiber and 20,250 IU vitamin A (nine times the R DA for a woman, seven times the R DA for a man).
The Most Nutritious Way to Serve This Food Cooked, so that the cellulose- and hemicellulose-stiffened cell walls of the carrot have partially dissolved and the nutrients inside are more readily available.
Diets That May Restrict or Exclude This Food Disaccharide-intolerance diet (for people who are sucrase- and /or invertase-deficient) Low-fiber diet Low-sodium diet (fresh and canned carrots)
Buying This Food Look for: Firm, bright orange yellow carrots with fresh, crisp green tops. Avoid: Wilted or shriveled carrots, pale carrots, or carrots with brown spots on the skin.
Storing This Food Trim off the green tops before you store carrots. The leaf y tops will wilt and rot long before the sturdy root. Keep carrots cool. They will actually gain vitamin A during their first five months in storage. Protected from heat and light, they can hold to their vitamins at least another two and a half months. Store carrots in perforated plastic bags or containers. Circulating air prevents the for- mation of the terpenoids that make the carrots taste bitter. Do not store carrots near apples or other fruits that manufacture ethylene gas as they continue to ripen; this gas encourages the development of terpenoids. Store peeled carrots in ice water in the refrigerator to keep them crisp for as long as 48 hours.
Preparing This Food Scrape the carrots. Ver y young, tender carrots can be cleaned by scrubbing with a veg- etable brush. Soak carrots that are slightly limp in ice water to firm them up. Don’t discard slightly wilted intact carrots; use them in soups or stews where texture doesn’t matter.
What Happens When You Cook This Food Since carotenes do not dissolve in water and are not affected by the normal heat of cooking, carrots stay yellow and retain their vitamin A when you heat them. But cooking will dissolve some of the hemicellulose in the carrot’s stiff cell walls, changing the vegetable’s texture and making it easier for digestive juices to penetrate the cells and reach the nutrients inside.
How Other Kinds of Processing Affect This Food Freezing. The characteristic crunchy texture of fresh carrots depends on the integrity of its cellulose- and hemicellulose-stiffened cell walls. Freezing cooked carrots creates ice crystals that rupture these membranes so that the carrots usually seem mushy when defrosted. If possible, remove the carrots before freezing a soup or stew and add fresh or canned carrots when you defrost the dish.
Medical Uses and/or Benefits A reduced risk of some kinds of cancer. According to the American Cancer Society, carrots and other foods rich in beta-carotene, a deep yellow pigment that your body converts to a form of vitamin A, may lower the risk of cancers of the larynx, esophagus and lungs. There is no such benefit from beta-carotene supplements; indeed, one controversial study actually showed a higher rate of lung cancer among smokers taking the supplement. Protection against vitamin A-deficiency blindness. In the body, the vitamin A from carrots becomes 11-cis retinol, the essential element in rhodopsin, a protein found in the rods (the cells inside your eyes that let you see in dim light). R hodopsin absorbs light, triggering the chain of chemical reactions known as vision. One raw carrot a day provides more than enough vitamin A to maintain vision in a normal healthy adult.
Adverse Effects Associated with This Food Oddly pigmented skin. The carotenoids in carrots are fat-soluble. If you eat large amounts of carrots day after day, these carotenoids will be stored in your fatty tissues, including the fat just under your skin, and eventually your skin will look yellow. If you eat large amounts of carrots and large amounts of tomatoes (which contain the red pigment lycopene), your skin may be tinted orange. This effect has been seen in people who ate two cups of carrots and two tomatoes a day for several months; when the excessive amounts of these vegetables were eliminated from the diet, skin color returned to normal. False-positive test for occult blood in the stool. The active ingredient in the guaiac slide test for hidden blood in feces is alphaguaiaconic acid, a chemical that turns blue in the presence of blood. Carrots contain peroxidase, a natural chemical that also turns alphaguaiaconic acid blue and may produce a positive test in people who do not actually have blood in the stool.... carrots
In Greenland, where much oily fish is eaten, heart disease is scarcely known. Each year over 200,000 people in Britain alone die of heart disease. Western affluence-diseases from a diet of excess saturated fat (from meat, butter, etc) may be reduced by modest amounts of oily fish.
A daily intake of 800 milligrams of essential fatty acids as contained in herring, mackerel, cod, etc., can play a decisive role in cardiac treatments. Such fish may be eaten twice weekly. On days when not taken, supplement with pure fish oil or fish oil capsules. As little as 1oz (30 grams) of mackerel, herring or other similar fish is sufficient.
When eating oily fish only twice a week a teaspoon of pure fish oil or dessertspoon cod liver oil daily is sufficient.
Labels of fish oils should be carefully studied for their DHA and EPA content in milligrams. Add together to a total 800 milligrams – average daily dose.
Fish oils can lower the level of triglycerides and reduce ‘stickiness’ of the blood – its tendency to clot and possibly block coronary vessels. As fish oil Vitamin A contains 10,000iu of Retinol, it should not be taken for extended periods without the advice of a practitioner. ... fish oils
Health Encyclopedia