Vitamin C May Not Fight the Common Cold
Finding Based on Review of Studies Done Since 1940
June 28, 2005 -- Vitamin C's reputation for fighting the common cold may not
be justified, say researchers.
They say they checked the best studies done on the topic in the last 65
years. Their findings appear in Public Library of Science
Researchers working on the review included Robert Douglas, MD, of the
Australian National University. They found hints of possible benefits in some
Those areas should be studied further, say Douglas and colleagues. But
overall, they say they didn't find proof that vitamin C thwarts colds.
Cold Prevention Questioned
The review included 55 studies.
Vitamin C did not prevent colds in people taking up to 2 grams daily, say
However, there were exceptions. In six studies, the number of colds was
halved with vitamin C.
But those studies involved rare, extreme conditions. The number of colds was
only cut in marathon runners, skiers, and soldiers exposed to cold temperatures
and/or physical stress.
Those benefits should be treated with "great caution" and probed
further, say the researchers.
In the cold-prevention studies, vitamin C didn't keep colds at bay for most
people. But it may have slightly shortened colds for kids and adults.
Children regularly taking vitamin C had cold symptoms for 14% fewer days.
For adults, days with cold symptoms fell 8% with regular vitamin C use, say the
The vitamin's cold-shortening pattern was consistent. But it may have
"questionable" significance in the real world, say the researchers.
Treating Colds With Vitamin C
Does it help to start taking vitamin C at the first sign of a cold? No, say
most of the studies exploring that question.
Seven studies covered the topic. Only one showed that colds were shorter
with vitamin C taken at the onset of symptoms.
In that large study, people took a vitamin C megadose -- 8 grams - only on a
cold's first day. The results are "tantalizing," say Douglas and
They call for studies on the value of high-dose vitamin C therapy for colds,
especially in children.