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Little protection from cold seen in Vitamin C

July 17, 2007
Courtesy U.S. Center for the 
Advancement of Health
and World Science staff

Un­less you run mar­a­thons, you probably won’t get much pro­tec­tion from com­mon colds by tak­ing extra vit­a­min C daily, ac­cord­ing to a new re­view of 30 stud­ies.

Vitamin C is found in many fruits and ve­ge­ta­bles, as well as sup­ple­ments.
Con­ducted over sev­er­al dec­ades and in­clud­ing more than 11,000 peo­ple who took daily doses of at least 200 mil­ligrams, the re­view found that vit­a­min C, or ascor­bic ac­id, does lit­tle to re­duce the length or sev­er­ity of a cold, ac­cord­ing to the in­ves­ti­ga­tors.

But they found that peo­ple ex­posed to pe­ri­ods of high stress — such as mar­a­thon run­ners, skiers and sol­diers on sub-arctic ex­er­cises — were 50 per­cent less likely to catch a cold if they took a daily dose of vit­a­min C. 

For most peo­ple, the ben­e­fit of the pop­u­lar rem­e­dy is so slight when it comes to colds that it’s not worth the trou­ble, the sci­ent­ists say. “It does­n’t make sense to take vit­a­min C 365 days a year to less­en the chance of catch­ing a cold,” said Har­ri Hemilä of the Un­ivers­ity of Hel­sin­ki in Fin­land, one of the authors of the review.

The work ap­pears in the lat­est is­sue of The Cochrane Li­brary, a pub­lica­t­ion of The Cochrane Col­la­bora­t­ion, an in­terna­t­ional or­gan­iz­a­tion that eval­u­ates med­i­cal re­search. 

Vitamin C is thought to have an array of benefits, in­clud­ing pro­tect­ing cells from dam­age, strength­en­ing blood ves­sels, main­tain­ing heal­thy gums, and help­ing absorb iron. Nonetheless, since the vitamin’s disco­very in the 1930s, contro­versy re­gard­ing its ef­fi­ca­cy in treat­ing ail­ments from lung in­fec­tions to colds has sur­rounded it. 

In the 1970s, No­bel Prize-winning chem­ist Li­nus Paul­ing pop­u­larized its reg­u­lar use. His book, “Vi­ta­min C and the Com­mon Cold,” en­cour­aged peo­ple to take 1,000 mil­ligrams of the vit­a­min dai­ly. The cur­rent U.S. rec­om­mended daily al­low­ance of vit­a­min C is 60 mil­ligrams. An eight-ounce glass of or­ange juice has about 97 mil­ligrams of vit­a­min C.

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Unless you run marathons, you probably won’t get much protection from common colds by taking a daily supplemental dose of vitamin C, according to an updated review of 30 studies. Conducted over several decades and including more than 11,000 people who took daily doses of at least 200 milligrams, the review also shows that vitamin C, or ascorbic acid, does little to reduce the length or severity of a cold, according to the researchers at the Australian National University and the University of Helsinki. But they found that people exposed to periods of high stress — such as marathon runners, skiers and soldiers on sub-arctic exercises — were 50 percent less likely to catch a cold if they took a daily dose of vitamin C. For most people, the benefit of the popular remedy is so slight when it comes to colds that it’s not worth the trouble, the authors say. “It doesn’t make sense to take vitamin C 365 days a year to lessen the chance of catching a cold,” said co-author Harri Hemilä, a professor in the Department of Public Health at University of Helsinki in Finland. The review appears in the latest issue of The Cochrane Library, a publication of The Cochrane Collaboration, an international organization that evaluates medical research. Since vitamin C’s discovery in the 1930s, controversy regarding its efficacy in treating ailments from lung infections to colds has surrounded it. In the 1970s, Nobel Prize-winning chemist Linus Pauling popularized its regular use. His book, “Vitamin C and the Common Cold,” encouraged people to take 1,000 milligrams of the vitamin daily. The current recommended daily allowance of vitamin C is 60 milligrams. An eight-ounce glass of orange juice has about 97 milligrams of vitamin C.