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(HealthNewsDigest.com) – Reserach published in the Journal of Neuroscience, from the Oregon Health & Science University, shows that nerve cells in the eye require vitamin C to work properly. The retina of the eye, which is part of the central nervous system, needs to be bathed in vitamin C to function correctly. This could have implications for glaucoma which is caused by the dysfunction of nerve cells in the retina. It is possible that a vitamin C rich diet could be protective of the retina and prevent deterioration.
What else does vitamin C do? It plays a critical role in the formation of collagen, which is the connective tissue that holds together the structures of your body. Lack of vitamin C was the downfall of early ocean explorers. At sea for many months, with no fresh fruits and vegetables, the sailors often developed and died from scurvy. The sailors suffered from bleeding gums and aching joints because they were unable to make collagen. It’s found in most of the tissues throughout your body especially in the heart, brain, pancreas, adrenal glands, thymus, lungs, pituitary gland, and lens of the eyes. Vitamin C also protects many other nutrients — vitamin E, folic acid and iron — so they can work effectively.
The vitamin is found mainly in fruits and vegetables, but Americans eat far too few of them, so we may not be getting enough of this important vitamin daily. Foods high in vitamin C include: cabbage, chili peppers, green leafy vegetables, peppers, potatoes, tomatoes, acerola, grapefruit, guava, kiwis, mango, oranges, orange juice, strawberries, watermelon and vitamin-C fortified fruit juices.
How much vitamin C do you need each day? The Dietary Reference Intakes (DRIs) for vitamin C set by the Institute of Medicine for both Americans and Canadians recommends: 90 milligrams a day for men 19 and older (125 milligrams for men who smoke); 75 milligrams for women 19 and older (110 milligrams for women who smoke); 85 milligrams for pregnant women; and 120 milligrams a day during breastfeeding. Smokers are encouraged to get extra vitamin C each day because smoking depletes the body’s stores of the vitamin. Smoking produces damaging free radicals and vitamin C is used up when it helps to remove these dangerous substances.
Does vitamin C cure colds? Vitamin C and the common cold have been linked for decades. Though the evidence is inconclusive, some studies do report a slightly lower incidence of colds in those people who regularly get enough vitamin C. The vitamin helps the immune system function properly which in turn keeps you healthy. What is conclusive is that vitamin C actually can shorten a cold’s duration and make the symptoms more tolerable. The vitamin has antihistamine properties like those found in cold medications.
Very large daily doses of vitamin C – megadoses — have often been suggested. Do you truly benefit from these large amounts? Many people firmly believe that large amounts of vitamin C will keep them healthy. Research, however, has never proven this.
There are a few reasons why you may want to rethink taking large amounts of vitamin C daily. When you take in 100 milligrams of vitamin C, your body absorbs 80 to 90% of the vitamin. As vitamin C intake increases, absorption decreases, with most of the excess being excreted through the urine. So, when you take in very large amounts at one time, the absorption can be as low as 20%. Some experts also believe that large amounts of vitamin C can reverse its normal protective antioxidant effect. Instead of protecting you from free radical damage too much vitamin C may promote the formation of free radicals, the exact opposite of what you want.
Very large amounts of vitamin C — over 2,000 milligrams daily — may cause nose bleeds, abdominal cramps, and diarrhea. High levels of vitamin C can also cause a false-positive result when testing for diabetes. In people prone to kidney stones, high intakes may contribute to the problem. And, for people with hemochromotosis, a condition that causes excess accumulation of iron, too much vitamin C, which enhances iron absorption, is a problem. The UL (tolerable upper limit) for vitamin C has been set at 2,000 milligrams daily.
Bottom line: Keep in mind that you need vitamin C each day and the best way to get it is by eating fruits and vegetables. But, too much of a good thing may not be good for you. It is hard to overdose on nutrients by eating, but it is easy to take too much as a supplement.
© NRH Nutrition Consultants, Inc.
Jo-Ann Heslin, MA, RD, CDN is a registered dietitian and the author of the nutrition counter series for Pocket Books with 12 current titles and sales of more than 8.5 million books. The books are widely available at your local or on-line bookseller.
Current titles include:
The Diabetes Counter, 4th Ed., 2011
The Protein Counter, 3rd Ed., 2011
The Calorie Counter, 5th Ed., 2010
The Ultimate Carbohydrate Counter, 3rd Ed., 2010
The Complete Food Counter, 3rd ed., 2009
The Fat Counter, 7th ed., 2009
The Healthy Wholefoods Counter, 2008
The Cholesterol Counter, 7th Ed., 2008
For more information on Jo-Ann and her books, go to TheNutritionExperts
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