A deficiency of vitamin C causes the disease scurvy, which is rare in the United States.

Toxicity does not normally occur, since vitamin C is water soluble and is regularly excreted by the body. Recent studies have shown, however, that excessive doses of vitamin C (many times more than the recommended amount) can lead to toxicity.

The most common manifestations of vitamin C toxicity are kidney stones, and in very rare circumstances, anemia (caused by interference with vitamin B12 absorption).

Diarrhea is also a possible but uncommon symptom associated with massively increased intake of vitamin C.

Recommended dietary allowances (RDAs) are defined as the levels of intake of essential nutrients that, on the basis of scientific knowledge, the Food and Nutrition Board judges to be adequate to meet the known nutrient needs of practically all healthy persons.

The best way to get the daily requirement of essential vitamins is to eat a balanced diet that contains a variety of foods from the food guide pyramid.

Vitamin C should be consumed every day, since it is not a fat-soluble vitamin and cannot be stored for later use.

Specific recommendations for each vitamin depend on age, gender, and other factors (such as pregnancy). The U.S. Department of Agriculture offers a PDF file that lists these recommendations.

There has been much debate regarding the use of vitamin C in cancer and heart disease prevention. Although the evidence is mixed regarding a definitive benefit of vitamin C in this regard, it is still encouraged that individuals maintain adequate intake. On the other hand, the majority of current evidence does not support vitamin C's role in the prevention or treatment of the common cold.

Vitamin C is an antioxidant, which means that it quenches free radicals that can damage organs, tissues, and cells. Free radicals are believed to be one of the causes of the degenerative changes seen with aging, but it is not yet known whether consumption of additional antioxidants like vitamin C can help.