alcoholism, END-STAGE RENAL DISEASE (ESRD) with
RENAL DIALYSIS, serious BURNS, major surgery, GAS-
TRECTOMYor BARIATRIC SURGERY, and chronic CIRRHO-
SIS. People who smoke and women who take oral
contraceptives (birth control pills) are at high risk
for pyridoxine deficiency.
Vitamin B 7 (biotin) Biotin works in close
alliance with folic acid and pantothenic acid, and
is important in metabolizing macronutrients, espe-
cially carbohydrates and fats, from food during
digestion. Sulfa-based ANTIBIOTIC MEDICATIONS can
prevent the body from absorbing biotin from foods
during digestion.
Vitamin B 9 (folic acid) Folic acid, also called
folate, is essential for the formation of new blood
cells (HEMATOPOIESIS) and works in conjunction
with cyanocobalamin to repair DNA. Folic acid is
crucial for normal development of the neurologic
system in the early EMBRYO; prophylactic folic acid
decreases NEURAL TUBE DEFECTSby up to 80 percent.
Folic acid also participates in cellular energy con-
version cycles.
FOLIC ACID PREVENTS NEURAL TUBE DEFECTS
Folic acid is so effective at preventing NEURAL
TUBE DEFECTSthat doctors urge all women who
could become pregnant, regardless of whether
they are planning PREGNANCYand especially if
they are taking oral contraceptives (which
deplete folic acid), to take a folic acid supple-
ment that delivers 400 micrograms daily. Folic
acid is crucial for the closure of the neural tube,
the rudimentary CENTRAL NERVOUS SYSTEM that
develops in the EMBRYOabout 14 days after CON-
CEPTION.Vitamin B 12 (cyanocobalamin) Cyanocobal-
amin, also called cobalamin, is essential for the
formation of myelin, the protein coating that pro-
tects NERVEfibers. It also participates in DNA repair
(nucleic acid synthesis), erythropoiesis (formation
of new red blood cells), and folic acid metabolism.
Intrinsic factor, which the stomach produces, is
essential for absorption of cyanocobalamin. Health
conditions that diminish intrinsic factor produc-
tion, such as PEPTIC ULCER DISEASE, and circum-
stances such as bariatric surgery or gastrectomy,
significantly reduce the body’s ability to absorb
cyanocobalamin and often require supplementa-
tion via vitamin B 12 injections. The ability to pro-
duce intrinsic factor diminishes with age, increas-
ing the risk of deficiency.Vitamin C (Ascorbic Acid)
The body requires vitamin C to create collagen, a
protein critical for the formation of connective tis-
sue and in healing (the formation of scar tissue).
Collagen forms the foundation of the SKELETONover
which the bones develop. Vitamin C is also neces-
sary for production of serotonin, a vital neurotrans-
mitter, and aids in the dismantling of cholesterol for
excretion in the BILE. The body absorbs significantly
more iron in combination with vitamin C; health
experts recommend eating combinations of foods
that contain these substances and taking iron sup-
plements with a glass of orange juice. Citrus fruits
are the primary dietary source of vitamin C.LIMEYS
British sailors of the 19th century acquired the
nickname “limey” when the British Navy began
including limes in sailors’ rations while at sea.
Citrus fruits are high in vitamin C, which pre-
vents SCURVY. Limes hold up better in storage
than other citrus fruits. Before this practice, half
or more of a ship’s crew often died before return-
ing home from a long sea voyage.Long-term vitamin C deficiency results in
scurvy, a condition of collagen depletion with
symptoms that affect the musculoskeletal, neuro-
logic, and immune systems. Vitamin C deficiency
is rare in modern times. Increasing dietary con-
sumption of foods high in vitamin C is usually
adequate to restore vitamin C levels and reverse
symptoms. Though vitamin C is a water-soluble
vitamin, it can accumulate to toxic levels with
excessive supplementation. The symptoms of vita-
min C toxicity (NAUSEA, DIARRHEA, and sometimes
anemia) improve immediately when vitamin C
consumption returns to normal.
Vitamin C is also a powerful ANTIOXIDANTwith
roles in healing and preventing diseases. Much
research has explored these roles in recent
decades, and numerous studies support vitamin
C’s ability to expedite recovery from viral infec-
tions such as COLDS(though vitamin C cannot pre-
vent such infections). Doctors may recommend206 Nutrition and Diet