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Many people pop more vitamin pills than they need in the belief that
more is less.
This is not necessarily bad. There’s no
evidence that large amounts of vitamins have unintended side
effects. But the body needs only minute quantities; the rest is
either stored or excreted. It has been said that the sewage of New
York City is one of the richest sources of vitamin C.
Vitamins are present in natural foods. They are
either water or fat-soluble. Their absence in a person’s diet
results in abnormalities due to the derangement of particular
metabolic reactions or processes.
Vitamin B12 is water soluble and comes in four
chemical forms: cyanocobalamin, folic acid, pantothenic acid and
biotin. They can be obtained from meat, milk, liver, kidney, egg
yolk, some green vegetables, nuts, yeast and yeast extracts.
The recommended daily dose of B12 (and other
vitamins) is established by epidemiological studies. But when
scientifically designed clinical trials are performed, some of the
claims are either found false or exaggerated.
A recent 5-year study of 107 persons, 60 years
old, “linked low levels of B12 to shrinkage of the brain” (New
York Times, October 16, 2008).
It’s a fact that B12, besides preventing
anemia, also protects the nervous system. B12 deficiency could bring
on some neurological damage. But even people whose blood levels of
B12 are considerably higher than is necessary to prevent anemia have
been found to suffer from neurological deficits, prompting
researchers to wonder if the accepted dosage of B12 is really
optimal.
Many experts now say that older people probably
should increase their intake of B12 with supplements until more
definitive evidence is found through placebo-controlled clinical
trials.
Donald Jacobsen, a biochemist, told the New York
Times that B12 is needed by every cell in the body.
The body processes B12 in a somewhat complicated
way. B12 that occurs in animal foods enters the body attached to a
protein. To be absorbed, the protein must first be separated by
stomach acid. The vitamin then mixes with a substance in the gut
called intrinsic factor that enables it to pass through the small
intestines to the bloodstream.
People who do not have enough stomach acid or
intrinsic factor could develop B12 deficiency.
There are millions of such people. Many suffer
from atrophic gastritis, which reduces the stomach cells that
produce acid. Those who take acid-lowering drugs to control reflux
are also at risk.
This is further complicated by the fact that B12
can be stored temporarily in the liver thus delaying the symptoms of
the deficiency by several years.
Those who have had portions of their stomach or
intestines removed by bariatric surgery for weight loss or ulcers
have to take B12 supplements to remain healthy.
The elderly are particularly susceptible. In the
US, close to 80 percent of seniors are B12 deficient—and do not
know it.
The “normal” level of B12—160 to 250
picomoles per liter of blood serum—is not optimal, according to
Dr. J. David Spence, a neurologist, at the Robarts Research
Institute in Ontario, Canada. This level could result in chronic
ailments including cardiovascular disorders and progressive damage
to the nervous system, which could become permanent, if not
diagnosed and treated early. Dr. Spence thinks that 350 picomoles is
adequate.
A pico is 10-12; a mole is numerically
equivalent to the molecular or atomic weight of a given substance.
Clinical trials that are in progress today are
beginning to uncover the role of B12 in heart disease, stroke,
Alzheimer’s disease, dementia, frailty, depression, osteoporosis
and some cancers.
Dr. Godfrey Oakley, a research epidemiologist at
Emory University in Atlanta, USA, recommends 1,000 micrograms of B12
daily for pernicious ane-mia. For those who do not have enough
stomach acid or intrinsic factor, a daily intake of five to six
micrograms of synthetic B12 might be necessary.
However, Dr. Ralph Carmel, a hematologist and
research director at New York-Methodist Hospital, told the New York
Times. “The associations found in the studies are potentially
important, but no one has yet shown that if you give B12 it will
make a difference down the road. We need clinical trials.”
opinion@manilatimes.net
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