Download Summary of Chapter 8 – The Vitamins

Summary of Chapter 8 – The Vitamins
Vitamins are essential, nonkcaloric nutrients that are needed in trace amounts in the diet to help facilitate body processes.
The fat-soluble vitamins are vitamins A, D, E, and K. Vitamin A is essential to gene expression, vision, cell differentiation and integrity
of epithelial tissues, immunity, and reproduction and growth. Vitamin A deficiency can cause blindness, sickness, and death and is a
major problem worldwide. Overdoses of vitamin A are possible and dangerous. Vitamin D raises calcium and phosphorus levels in the
blood. A deficiency can cause rickets in children or osteomalacia in adults. Vitamin D is the most toxic of all the vitamins. People
exposed to the sun make vitamin D in their skin; fortified milk is an important food source. Vitamin E acts as an antioxidant in cell
membranes and is especially important in the lungs where cells are exposed to high concentrations of oxygen. Vitamin E may protect
against heart disease, but evidence is not conclusive yet. Vitamin E deficiency is rare in healthy human beings. The vitamin is widely
distributed in plant foods. Vitamin K is necessary for blood to clot and for bone health. The bacterial inhabitants of the digestive tract
produce vitamin K, but people need vitamin K from foods as well. Dark green, leafy vegetables are good sources of vitamin K.
The B vitamins and vitamin C are the water-soluble vitamins. Each B vitamin is part of an enzyme helper known as a coenzyme. As
parts of coenzymes, the B vitamins assist in the release of energy from glucose, amino acids, and fats and help in many other body
processes. Folate and vitamin B12 are important in cell division. Vitamin C’s primary role is as an antioxidant. Historically, famous B
vitamin–deficiency diseases are beriberi (thiamin) and pellagra (niacin). The vitamin C–deficiency disease is known as scurvy.
Vitamin Name
Chief Functions
Deficiency Symptoms
Toxicity Symptoms
Significant Sources
Vitamin A (Retinol,
retinal, retinoic acid;
main precursor is betacarotene)
Vision, maintenance of
cornea, epithelial cells,
mucous membranes,
skin; bone and tooth
growth; reproduction;
regulation of gene
expression; immunity
Infectious diseases,
night blindness,
blindness
(xerophthalmia),
keratinization
Reduced bone mineral
density, liver
abnormalities, birth
defects
Retinol: milk and milk
products; eggs; liver
Beta-carotene: spinach
and other dark, leafy
greens; broccoli; deep
orange fruits (apricots,
cantaloupe) and
vegetables (carrots,
winter squashes, sweet
potatoes, pumpkin)
Vitamin D (Calciferol,
cholecalciferol,
dihydroxy vitamin D;
precursor is
cholesterol)
Mineralization of bones
(raises blood calcium
and phosphorus by
increasing absorption
from digestive tract,
withdrawing calcium
from bones, stimulating
retention by kidneys)
Rickets, osteomalacia
Calcium imbalance
(calcification of soft
tissues and formation of
stones)
Synthesized in the body
with the help of
sunshine; fortified milk,
margarine, butter, and
cereals; eggs; liver;
fatty fish (salmon,
sardines)
Vitamin E
(Alphatocopherol,
tocopherol)
Antioxidant
(stabilization of cell
membranes, regulation
of oxidation reactions,
protection of
polyunsaturated fatty
acids [PUFA] and
vitamin A)
Erythrocyte hemolysis,
nerve damage
Hemorrhagic effects
Polyunsaturated plant
oils (margarine, salad
dressings, shortenings),
green and leafy
vegetables, wheat
germ, whole-grain
products, nuts, seeds
Vitamin K
(Phylloquinone,
menaquinone,
naphthoquinone)
Synthesis of
bloodclotting proteins
and bone proteins
Hemorrhage
None known
Synthesized in the body
by GI bacteria; green
leafy vegetables;
cabbage-type
vegetables; milk; liver
Vitamin Name
Chief Functions
Deficiency Symptoms
Toxicity Symptoms
Significant Sources
Thiamin (Vitamin B1)
Part of a coenzyme
used in energy
metabolism
Beriberi (edema or
muscle wasting),
anorexia and weight
loss, neurological
disturbances, muscular
weakness, heart
enlargement and failure
None reported
Enriched, fortified, or
whole-grain products;
pork
Riboflavin (Vitamin B2)
Part of coenzymes
used in energy
metabolism
Inflammation of the
mouth, skin, and
eyelids; sensitivity to
light; sore throat
None reported
Milk products; enriched,
fortified, or whole-grain
products; liver
Niacin (Nicotinic acid,
nicotinamide,
niacinamide, vitamin
B3; precursor is dietary
tryptophan, an amino
acid)
Part of coenzymes
used in energy
metabolism
Pellagra (diarrhea,
dermatitis, and
dementia)
Niacin flush, liver
damage, impaired
glucose tolerance
Milk, eggs, meat,
poultry, fish, wholegrain and enriched
breads and cereals,
nuts, and all proteincontaining foods
Biotin
Part of a coenzyme
used in energy
metabolism
Skin rash, hair loss,
neurological
disturbances
None reported
Widespread in foods;
GI bacteria synthesis
Pantothenic acid
Part of a coenzyme
used in energy
metabolism
Digestive and
neurological
disturbances
None reported
Widespread in foods
Vitamin B6 (Pyridoxine,
pyridoxal,
pyridoxamine)
Part of coenzymes
used in amino acid and
fatty acid metabolism
Scaly dermatitis,
depression, confusion,
convulsions, anemia
Nerve degeneration,
skin lesions
Meats, fish, poultry,
potatoes, legumes,
non-citrus fruits,
fortified cereals, liver,
soy products
Folate (Folic acid,
folacin, pteroylglutamic
acid)
Activates vitamin B12;
helps synthesize DNA
for new cell growth
Anemia; smooth, red
tongue; mental
confusion; elevated
homocysteine
Masks vitamin B12
deficiency
Fortified grains, leafy
green vegetables,
legumes, seeds, liver
Vitamin B12
(Cobalamin)
Activates folate; helps
synthesize DNA for
new cell growth;
protects nerve cells
Anemia; nerve damage
and paralysis
None reported
Foods derived from
animals (meat, fish,
poultry, shellfish, milk,
cheese, eggs), fortified
cereals
Vitamin C (Ascorbic
acid)
Synthesis of collagen,
carnitine, hormones,
neurotransmitters;
antioxidant
Scurvy (bleeding gums,
pinpoint hemorrhages,
abnormal bone growth,
and joint pain)
Diarrhea, GI distress
Citrus fruits, cabbagetype vegetables, dark
green vegetables (such
as bell peppers and
broccoli), cantaloupe,
strawberries, lettuce,
tomatoes, potatoes,
papayas, mangoes