Vitamin B12 deficiency in patients with chronic-tinnitus and noise-induced
hearing loss.
Shemesh Z, Attias J, Ornan M, Shapira N, Shahar A.

Institute of Noise Hazards Research and Evoked Potentials Laboratory, IDF,
Chaim-Sheba Medical Center, Ramat-Gan, Israel.

INTRODUCTION: This study examines the incidence of vitamin B12 deficiency in
three groups of noise-exposed subjects: patients with chronic tinnitus and
noise-induced hearing loss (NIHL), patients with NIHL only, and subjects
demonstrating normal hearing. MATERIALS AND METHODS: A group of 113 army
personnel exposed to military noise was studied. The mean age was 39 years.
Chronic tinnitus and NIHL existed in 57 subjects. NIHL alone was observed in
29 subjects, and 27 subjects had normal audiograms. All subjects were
queried about noise exposure and dietary habits. Vitamin B12 serum levels
were measured. RESULTS: Patients with tinnitus and NIHL exhibited vitamin
B12 deficiency in 47% of cases (blood levels < or = 250 pg/mL). This was
significantly more (P < .023) compared with NIHL and normal subjects who
exhibited vitamin B12 deficiency in 27% and 19%, respectively. CONCLUSION:
These observations suggest a relationship between vitamin B12 deficiency and
dysfunction of the auditory pathway. Some improvement in tinnitus and
associated complaints were observed in 12 patients following vitamin B12
replacement therapy. The authors recommend that routine vitamin B12 serum
levels be determined when evaluating patients for chronic tinnitus.

PMID: 8484483 [PubMed - indexed for MEDLINE]
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Vitamin B12 (cobalamin) is an important water-soluble vitamin. In contrast
to other water-soluble vitamins it is not excreted quickly in the urine, but
rather accumulates and is stored in the liver, kidney and other body
tissues. As a result, a vitamin B12 deficiency may not manifest itself until
after 5 or 6 years of a diet supplying inadequate amounts. Vitamin B12
functions as a methyl donor and works with folic acid in the synthesis of
DNA and red blood cells and is vitally important in maintaining the health
of the insulation sheath (myelin sheath) that surrounds nerve cells. The
classical vitamin B12 deficiency disease is pernicious anaemia, a serious
disease characterized by large, immature red blood cells. It is now clear
though, that a vitamin B12 deficiency can have serious consequences long
before anaemia is evident. The normal blood level of vitamin B12 ranges
between 200 and 600 picogram/milliliter (148-443 picomol/liter). Although
deficiency is far more common than excess when it comes to vitamin B12
status cases have been reported where blood levels exceeded 3000
picograms/milliliter. Such high levels may be caused by bacterial overgrowth
as outlined in the article Vitamin B-12 Overload

A deficiency often manifests itself first in the development of neurological
dysfunction that is almost indistinguishable from senile dementia and
Alzheimer's disease. There is little question that many patients exhibiting
symptoms of Alzheimer's actually suffer from a vitamin B12 deficiency. Their
symptoms are totally reversible through effective supplementation. A low
level of vitamin B12 has also been associated with asthma, depression, AIDS,
multiple sclerosis, tinnitus, diabetic neuropathy and low sperm counts.
Clearly, it is very important to maintain adequate body stores of this
crucial vitamin.

The amount of vitamin B12 actually needed by the body is very small,
probably only about 2 micrograms or 2 millionth of a gram/day.
Unfortunately, vitamin B12 is not absorbed very well so much larger amounts
need to be supplied through the diet or supplementation. The richest dietary
sources of vitamin B12 are liver, especially lamb's liver, and kidneys.
Eggs, cheese and some species of fish also supply small amounts, but
vegetables and fruits are very poor sources. Several surveys have shown that
most strict, long-term vegetarians are vitamin B12 deficient. Many elderly
people are also deficient because their production of the intrinsic factor
needed to absorb the vitamin from the small intestine decline rapidly with
age.

Fortunately, oral supplementation with vitamin B12 is safe, efficient and
inexpensive. Most multi-vitamin pills contain 100-200 microgram of the
cyanocobalamin form of B-12. This must be converted to methylcobalamin or
adenosylcobalamin before it can be used by the body. The actual absorption
of B12 is also a problem with supplements. Swallowing 500 micrograms of
cyanocobalamin can result in absorption of as little as 1.8 microgram so
most multivitamins do not provide an adequate daily intake. The best
approach is to dissolve a sublingual tablet of methylcobalamin (1000
micrograms) under the tongue every day. That will be sufficient to maintain
adequate body stores. However, if a deficiency is actually present then 2000
microgram/day for one month is recommended followed by 1000 microgram/day.
Some physicians still maintain that monthly injections of vitamin B12 is
required to maintain adequate levels in the elderly and in patients with a
diagnosed deficiency. There is however, no scientific evidence supporting
the notion that injections are more effective than sublingual
supplementation.