Poor intake of vitamin
C-containing vegetables and fruits. One-third of all Americans get less
vitamin C from their diet than is recommended, and 1 out of every 6 adults
gets less than half the amount recommended.
Smoking
Pregnancy
Illness
The use of oral
contraceptives/birth control pills, NSAIDs (non-steroidal
anti-inflammatory drugs including aspirin and acetaminophen),
corticosteroids (like cortisone), sulfa drugs (often used as antibiotics
or in cancer treatment), and barbiturates.