What is vitamin C?
Vitamin C (also known as ascorbic acid) is abundant in vegetables and fruits. A water-soluble vitamin and powerful antioxidant, it helps the body form and maintain connective tissue, including bones, blood vessels, and skin.

Why is vitamin C necessary?
Vitamin C helps to repair and regenerate tissues, protect against heart disease, aid in the absorption of iron, prevent scurvy, and decrease total and LDL (“bad”) cholesterol and triglycerides. Research indicates that vitamin C may help protect against a variety of cancers by combating free radicals, and helping neutralize the effects of nitrites (preservatives found in some packaged foods that may raise the risk of certain forms of cancer). Supplemental vitamin C may also lessen the duration and symptoms of a common cold; help delay or prevent cataracts; and support healthy immune function.

What are the signs of a deficiency?
Deficiency symptoms include fatigue, muscle weakness, joint and muscle aches, bleeding gums, and leg rashes. Prolonged deficiency can cause scurvy, a rare but potentially severe illness.

How much, and what kind, does an adult need?
According to the National Institutes of Health (NIH), the recommended daily intake for adults:

is men, 90 mg per day
women, 75 mg per day
pregnant women, 85 mg per day
breastfeeding women, 120 mg per day.
Smokers may benefit from a higher intake. Dr. Weil recommends taking 250 mg of vitamin C each day.

How much does a child need?
NIH recommends Adequate Intakes (AIs):

infants 0-6 months old, 40 mg per day
infants 7-12 months old, 50 mg per day.The U.S. Dietary Reference Intakes (DRIs) for

toddlers 1-3 years old, 15 mg per day
children 4-8 years old, 25 mg
children 9-13 years old, 45 mg per day
male teens 14-18 years old, 75 mg per day
female teens 14-18 years old, 65 mg.
How do you get enough vitamin C from foods?
Vitamin C is easy to get through foods, as many fruits (especially citrus) and vegetables contain vitamin C. Good sources include: apples, asparagus, berries, broccoli, cabbage, melon (cantaloupe, honeydew, watermelon), cauliflower, citrus fruits (lemons, limes, oranges), kiwi, fortified foods (breads, grains, cereal), dark leafy greens (kale, spinach), peppers (especially red bell peppers, which have among the highest per-serving vitamin C content), potatoes, and tomatoes.

Are there any risks associated with too much vitamin C?
When obtained from food sources and supplements in the recommended dosages, vitamin C is generally regarded as safe. Side effects are rarely reported, but include nausea, vomiting, heartburn, abdominal cramps, and headache. For most healthy individuals, the body can only hold and use about 250mg of vitamin C a day, and any excess is lost though urine. At times of illness, during recovery from injury, or under conditions of increased oxidative stress (including smoking), the body can use greater amounts. High doses of vitamin C (greater than 2,000 mg/day) may contribute to the formation of kidney stones, as well as cause severe diarrhea, nausea, and gastritis.

Are there any other special considerations?
Adverse affects may occur between vitamin C and acetaminophen, antacids that contain aluminum, aspirin, and Warfarin. Nicotine products, oral contraceptives/estrogens, tetracyclines and barbiturates may decrease the effects of vitamin C.

Vitamin C may increase absorption of iron and lutein, and some evidence suggests that large doses of supplemental vitamin C may interfere with the absorption and metabolism of vitamin B12 found in food.

Credit to Dr. Weil @ http://www.drweil.com/drw/u/ART02811/facts-on-vitamin-c