Zinc
acetate lozenges may increase the recovery rate from the common cold by
three-fold
University of Helsinki
According to a meta-analysis of three randomized controlled
trials zinc acetate lozenges may increase the rate of recovery from the common
cold three fold.
On the fifth day, 70% of the zinc lozenge patients had recovered
compared with 27% of the placebo patients.
The
effect of zinc acetate lozenges was not modified by age, sex, race, allergy,
smoking, or baseline common cold severity. Therefore the 3-fold increase in the
recovery rate from common cold may be widely applicable.
While some zinc lozenges have an unpleasant taste, the zinc
acetate lozenges used in these three randomized trials did not suffer from such
a problem.
The
dose of zinc in the three studies was between 80 to 92 mg/day. Such doses are
substantially higher than the recommended daily zinc intake in the USA, which
is 11 mg/day for men and 8 mg/day for women.
Furthermore, 150 mg/day zinc is a standard treatment for
Wilson's disease that requires treatment for the rest of a patient's life.
Therefore, it seems highly unlikely that 80-92 mg/day of zinc
for one to two weeks, starting very soon after the onset of the first cold
symptoms, might lead to long-term adverse effects.
None of the three analyzed zinc lozenge studies observed serious
adverse effects of zinc.
Even
though there is strong evidence that properly formulated zinc acetate lozenges
can increase the rate of recovery from the common cold by 3 fold, many zinc
lozenges on the market appear to have either too low doses of zinc or they
contain substances that bind zinc ions, such as citric acid.
Therefore, the findings of this meta-analysis should not be
directly extrapolated to the wide variety of zinc lozenges on the current
market.
Although
the lead author, Dr. Harri Hemilä from the University of Helsinki, Finland,
suggests that the optimal formulation of zinc lozenges and the best frequency
of their administration should be further investigated.
He also instructs
common cold patients to test individually whether zinc lozenges are helpful for
them: "given the strong evidence of efficacy and the low risk of adverse
effects, common cold patients may already be encouraged to try zinc acetate
lozenges not exceeding 100 mg of elemental zinc per day for treating their
colds."