Vitamins and supplements have always had a good reputation. Some of it is well deserved, some is not. The story of how vitamin C (from eating lemons and oranges) was discovered to be the cure for scurvy in sailors is repeatedly mentioned as an example of why we need fair tests of treatments. The story highlights how a simple dietary intervention can prevent and cure a disease. The problem nowadays is that supplements are being sold with the promise to treat all kinds of diseases.
Let’s examine a couple of common remedies for a very common condition: vitamin C and zinc for the common cold. Do they really work?
The Cochrane Systematic Review of vitamin C for the common cold included dozens of trials in adults and children. In five trials, the participants were exposed to extreme physical activity or weather conditions: they were marathon runners, skiers, swimmers and soldiers. Among these participants, vitamin C reduced the risk of developing a cold. For other participants without these backgrounds, the chance of catching a cold was about the same with or without vitamin C.
What about the duration of symptoms? It appears that vitamin C does help with symptoms, especially in children. It’s a modest effect, but the duration of the cold is reduced by almost 15%. In practical terms, this may represent a few hours or a day less of feeling under the weather.
On the other hand, the Cochrane Systematic Review of zinc for the common cold includes 16 treatment trials and 2 preventive trials. In children, zinc supplementation reduced the duration of symptoms (a few hours), school absenteeism, and also antibiotic use. This last observation is interesting because antibiotics are not indicated in common cold. It appears zinc may also reduce the number of colds if used for prevention.
Some uncertainty remains regarding both vitamin C and zinc so it doesn’t seem prudent to prescribe these supplements to all children. But if we are speaking of a child who has multiple colds a year, or an adolescent athlete who is training hard in low temperatures, it may be worthwhile to consider them. The downside of their use, however, includes infrequent mild side effects such as diarrhoea, or, in the case of zinc, some compliance issues such as bad taste.
And please, don’t forget to eat a well balanced diet.
About Dr. Giordano Pérez-Gaxiola:
Dr. Giordano Pérez-Gaxiola is a paediatrician in Culiacán, México. He works in a public paediatric hospital and also has a private practice He is currently one of the coordinators of the Mexican Branch of the Iberoamerican Cochrane Centre and is one of the Spanish editors of Testing Treatments interactive.