Why
is Niacin important to your health?
Niacin
or Vitamin B3 is a water-soluble vitamin plays. It is a powerful
antioxidant, which protects the liver from free radical damage. It
helps to regulate blood glucose levels, and lower LDL cholesterol. It
can be used to help treat circulatory disorders by improving blood flow
to the skin, heart and brain.
Physiological Functions
Niacin is an essential vitamin that supports energy metabolism
and
reactions involving biosynthesis and degradation as part of the
pyridine nucleotide coenzymes, nicotinamide adenine dinucleotide (NAD)
and nicotinamide adenine dinucleotide phosphate (NADP). The levels of
oxidized and reduced forms of these coenzymes establish the redox
potential in cells that regulates metabolic activities involving
mitochondrial electron transport and numerous enzyme reactions.
High doses of niacin are also used as a pharmacological agent
in blood lipid-lowering therapy.
Factors Affecting Availability
Because niacin is a
water-soluble vitamin, significant amounts can be lost if large volumes
of liquids are used in preparation and cooking of food sources. As with
other B vitamins, niacin is lost in the milling of grains. To
compensate for these losses, white flour and rice are enriched with the
vitamin.
Niacin can be obtained from consumption of food sources or
from
biosynthesis with the amino acid tryptophan as a precursor.
Approximately 60 mg tryptophan are required for synthesis of 1 mg of
niacin. Niacin biosynthesis from tryptophan is dependent on
availability of vitamin B6 and riboflavin.
Deficiency
Clinical evidence of niacin deficiency
includes fatigue, poor appetite, diarrhea, irritability, headache,
emotional instability and possible memory loss. Pellagra is the
clinical manifestation of advanced niacin deficiency that is
characterized by dermatitis, dementia, and diarrhea. Niacin deficiency
rarely occurs without accompanying riboflavin deficiency. Pyridoxine
deficiency may also be present.
Toxicity
Niacin toxicity is rarely observed at
doses generally consumed. Administration of pharmacological doses of
nicotinic acid (1-2 g three times a day) is used in treatment of high
blood cholesterol. At this level of intake, histamine release may be
triggered resulting in flushing of the skin which can be harmful to
patients with asthma or peptic ulcer disease. Niacin also promotes
hepatic toxicity when consumed at high doses found in some supplements.
The upper limit of safety for niacin established by the Food
and Nutrition Board of the Institute of Medicine is 35 mg daily for
adults.