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(RIBOFLAVIN)
DESCRIPTION
Vitamin B-2 (Riboflavin) is a water soluble, stable
vitamin. It plays an important role in several enzymes and coenzymes as a
hydrogen atom acceptor in various metabolic roles, including protein
metabolism. It is a constituent of coenzymes involved in the release of energy
from glucose and fatty acids in the mitochondria. It is important in DNA
synthesis, and in the formation of red blood cells. Riboflavin also takes part
in the activation of vitamin B-6 and conversion of folacin to its coenzymes.
METHOD OF ACTION
Riboflavin is absorbed through the walls of the small
intestine. Food in the gastrointestinal tract increases the absorption of
riboflavin; when ingested without food, only about 15% of riboflavin is
absorbed. Within the intestinal cells, much of the absorbed riboflavin is
phosphorylated to flavin mononucleotide (FMN) and, subsequently, is carried by
the blood to the tissues.
Free riboflavin is transported by blood albumin to the
liver, where it is converted to flavin-adenine dinucleotide (FAD). Both FAD and
FMN play important roles in catalyzing oxidation-reduction reactions in the
cells, and are essential coenzymes in the oxidative phosphorylation which
occurs in cellular mitochondria.
Riboflavin is a component of the enzymes L- and D-amino
acid oxidase, which catalyze the oxidation of amino acids, thereby involving
the vitamin in protein metabolism. Riboflavin plays a primary role in the
conversion of folacin to its coenzymes, some of which are needed for DNA
synthesis and cell proliferation. It also activates vitamin B-6 and may
participate in red blood cell formation.
Loss of protein from the body is accompanied by a loss in
riboflavin. Riboflavin is not stored in the body and must be supplied in the
diet, as any excess is excreted in the urine.
PROPERTIES AND USES
Riboflavin has been used effectively in treating the
following symptoms of deficiencies: soreness and burning of the lips, mouth,
and tongue; fissures and cracks in the lips, a purple, swollen tongue; and
possible anemia.
Riboflavin needs increase during growth, pregnancy, wound
healing, and lactation. This phenomenon is related to the fact that riboflavin
plays a role in protein metabolism, which is increased during these periods.
CONSEQUENCE OF DEFICIENCY
Early signs of riboflavin deficiency are: soreness and
burning of the lips, mouth, and tongue; fissures and cracks in the lips; a
purple, swollen tongue; burning and itching of the eyes; photophobia; a loss of
visual acuity; and possible anemia. Individuals who ingest a diet devoid of
animal protein sources and green leafy vegetables are prone to ariboflavinosis,
a severe riboflavin deficiency.
If the intake of riboflavin is low for several months,
the following symptoms will appear: cheilosis; angular stomatitis (cracks in
the skin at the corners of the mouth); a greasy eruption on the skin of the
nasolabial folds and scrotum; capillary overgrowth around the cornea of the
eye; and a purplish, swollen tongue.
Riboflavin deficiency rarely appears alone; most often it
appears in conjunction with multiple nutritional deficiencies. This makes
diagnosis quite difficult, especially as niacin, iron, and pyridoxine
deficiencies mimic the symptoms of riboflavin deficiency.
Ocular manifestations such as photophobia and itching,
burning, and redness of the eyes, are believed to be the earliest signs of
riboflavin deficiency. Urinary excretion of riboflavin can confirm diagnosis.
TOXICITY FACTORS
Riboflavin has no known toxicity level.
RECOMMENDED DIETARY ALLOWANCES
RDA for men: 1.7 mg
RDA for women: 1.3 mg
RDA for children: 1.2 mg
RDA for infants 0.5 mg
RDA for pregnancy: 1.8 mg
RDA for lactation: 1.8 mg
The body's riboflavin requirement is related to total
energy needs, body size, metabolic rate, and rate of growth, all of which are
related to protein intake. The lower the protein intake, the more riboflavin is
excreted and lost. For practical purposes, the general RDA standard for
riboflavin is stated as 0.6 mg per 1,000 kilocalories for all ages. Persons in
certain risk groups or clinical situations may require increased riboflavin.
This includes persons living in poverty or with bizarre food habits, with
gastrointestinal tract diseases or chronic illnesses where appetite is poor and
malabsorption exists, during wound healing, and during growth periods such as
in childhood, pregnancy, and lactation.
FOOD SOURCES
· Almonds
· Breads
· Brewer's yeast
· Cereals (enriched)
· Cheese
· Eggs
· Milk
· Organ meats
· Yogurt· Green leafy
vegetables
SUMMARY OF RIBOFLAVIN DEFICIENCY
SYMPTOMS:
· Cracks At Corners of Lips
· Inflammation of Lips and Tongue
· Burning And Itching Eyes
· Photophobia
· Blurred Vision
· Anemia
· Conjunctivitis
· Blood Shot Eyes
· Cataracts
· Insomnia
· Dizziness
· Loss of Mental Alertness
· Impaired Reproduction With Congenital
Malformations In The Offspring
· Unhealthy Scalp and Sometimes Hair Loss |
