Nutrition Science and Everyday Application - beta v 0.1

478 ALICE CALLAHAN, PHD, HEATHER LEONARD, MED, RDN, AND TAMBERLY POWELL, MS, RDN
VITAMIN C
Vitamin C, also called ascorbic acid, is a water-soluble vitamin essential in the diet for
humans. Interestingly, most other mammals can readily synthesize vitamin C and don’t
require it in their diets. Vitamin C’s ability to easily donate electrons makes it a highly
effective antioxidant. Since it is water-soluble, it acts both inside and outside cells to protect
molecules in aqueous environments. Vitamin C also plays a vital role in regenerating vitamin
E after it has acted as an antioxidant, allowing it to be recycled and used again.
Figure 8.15. After vitamin E donates an electron to neutralize a free radical, it can be
regenerated by an electron from vitamin C. Vitamin C is then regenerated by antioxidant enzymes.
In addition to its role as an antioxidant, vitamin C is a required part of several enzymes
involved in the synthesis of collagen, a protein important to the strength and structure of
muscles, bones, tendons, ligaments, connective tissue, and skin. Vitamin C is also required
to synthesize neurotransmitters important for signaling in the brain, some hormones, and
amino acids. It also plays a role in immune function and improves the absorption of dietary
iron.
The body’s vitamin C status is tightly controlled to maintain steady tissue and plasma
concentrations. This means that if you consume high doses of vitamin C, you’ll absorb less
from the intestine and excrete more in urine to prevent excessive concentrations in the
body. Vitamin C is not stored in any significant amount in the body, but once it has reduced
a free radical, it is very effectively regenerated and therefore can exist in the body as a
functioning antioxidant for many weeks.
Food Sources of Vitamin C
Fruits and vegetables are great sources of vitamin C. Some of the best sources include bell
pepper, citrus, broccoli, strawberries, Brussels sprouts, and cantaloupe. 4