not know why citrus fruit was essential to health (it is
high invitamin C, and scurvy is caused by vitamin C
deficiency), he recognized that it contained some sub-
stance that the sailors needed.
Water-soluble vitamins
Humans need nine water-soluble vitamins. These
vitamins dissolve inwaterand are not stored in the
body for long periods. Most excess water-soluble vita-
mins are removed by the kidneys and leave the body in
urine. Below is a list of the water-soluble vitamins and
a very brief description of their importance to health.
For details on how these vitamins function, see the
specific entries for each vitamin. In general, B vitamins
tend to be involved in reactions that convert nutrients
to energy and reactions that synthesize new molecules.
There are gaps in the numbering of the B-complex
vitamins, because compounds originally named as
vitamins, such as B4 (adenine), were renamed after
further research showed that they did not meet the
definition of a vitamin.
Vitamin B 1 (thiamin): needed to convert carbohy-
drates to energy
Vitamin B 2 (riboflavin): helps breakdown proteins,
fats, and carbohydrates and make other vitamins
and minerals available to the body
Vitamin B 3 (niacin): helps the body process fats and
proteins
Vitamin B 5 (pantothenic acid): helps regulate the
chemical reactions that produce energy
Vitamin B 6 (pyridoxine): involved in the transmis-
sion of nerve impulses, formation and functioning of
red blood cells, and creation of new cells
Vitamin B 12 (cobalamin): necessary for healthy red
blood cells, creating new deoxyribose nucleic acid
(DNA), and in maintaining nerve cells
Vitamin C (ascorbic acid): helps form cartilage and
connective tissue; as an antioxidant protects cells
from free radical damage
Vitamin H (biotin): joins with enzymes that regulate
the breakdown of foods and their use in the body
Folic acid (folate): helps make new cells; important
in development of the fetal nervous system
Fat-soluble vitamins
Humans need four fat-soluble vitamins. Unlike
water-soluble vitamins, fat-soluble vitamins can be
stored in the body. High levels of these vitamins can
cause health problems. Below is a list of the water-
soluble vitamins and a very brief description of their
importance to health. In general the fat-soluble vita-
mins have antioxidant activity that helps protect cells
from damage. For details on how these vitamins func-
tion, see the specific entries for each vitamin.
Vitamin A (retinol): needed for vision, a healthy
immune system, development of the fetus, tissue
repair; as an antioxidant protects cells from free
radical damage
Vitamin D (calciferol): involved in building bones,
muscle contraction, and nerve impulse transmission.
Vitamin E: (tocopherol) acts as an antioxidant to
protect the body against damage caused by free
radicals
Vitamin K: needed for blood clottingvitamin supplements
Before the twentieth century, all vitamins had to
come from food. Often individuals on limited diets with
little variety developed vitamin deficiency diseases. The
period from the 1920s to the 1940s was a time of active
research on vitamins. Out of this research came a food
fortification program in the United States that contin-
ues today. Beginning in the late 1930s, the addition of
vitamins to common foods such as flour, milk, andKEY TERMS
B-complex vitamins—A group of water-soluble vita-
mins that often work together in the body. These
include thiamine (B 1 ), riboflavin (B 2 ), niacin (B 3 ),
pantothenic acid (B 5 ), pyridoxine (B 6 ), biotin (B 7 or
vitamin H), folate/folic acid (B 9 ), and cobalamin (B 12 ).
Dietary supplement—A product, such as a vitamin,
mineral, herb, amino acid, or enzyme, that is intended
to be consumed in addition to an individual’s diet
with the expectation that it will improve health.
Free radical—A molecule with an unpaired elec-
tron that has a strong tendency to react with other
molecules in DNA (genetic material), proteins, and
lipids (fats), resulting in damage to cells. Free rad-
icals are neutralized by antioxidants.
Functional Food—Also called nutraceuticals, these
products are marketed as having health benefits or
disease-preventing qualities beyond their basic
supply of energy and nutrients. Often these health
benefits come in the form of added herbs, minerals,
vitamins, etc.
Mineral—An inorganic substance found in the earth
that is necessary in small quantities for the body to
maintain a health. Examples include zinc, copper, iron.Vitamins