True, false or utterly absurd? Vitamin C
It's vitamin C's protective effect on the body's immune system that is thought to ward off an impending cold. Photo: Quentin Jones
My mother was a strong believer in herbal remedies to prevent all manner of maladies - echinacea* to thwart sore throats, ginger* to relieve an upset stomach, and thin slices of raw garlic* swallowed whole to ward off vampires (bacteria).
As a child, the only remedy I took obligingly was the sugar-free chewable vitamin C tablet mum prescribed daily to stave off the common cold. Sweet like a lolly, you can imagine my joy when I turned 12 and was allowed two tablets each morning.
Although it is referred to as a common cold, the name includes 200 or so virus strains and some bacteria, which combined are the biggest cause of sick days in the First World.
Inside the body, vitamin C, an organic compound known as ascorbic acid, works as an antioxidant, mopping up molecules called free radicals that are generated by ageing, smoking and infections and can damage cells. It is the vitamin's protective effect on the body's immune system that is thought to ward off an impending cold.
But the virtues of vitamin C for both preventing and treating a cough and sniffles have been debated for more than 70 years.
It became especially popular from the late 1960s when Nobel prize-winning chemist Linus Pauling published studies that found doses well above the recommended daily allowance reduced the incidence of colds. Subsequent research found the vitamin had no such effect.
The controversy continued when, in the decades that followed, the veracity of several large studies that refuted Pauling's link between vitamin C and the common cold was found to be lacking. What appears to be the most reliable evidence to date, a review of placebo-controlled trials (half the subjects were given vitamin C, half were given a placebo) was published by the Cochrane Collaboration in January.
The first part of the study examined 29 trials with more than 11,000 participants and found regular vitamin use (from two weeks to five years) did not reduce the number of colds in the general population.
If, however, you take part in marathons, are a keen skier or engage in other types of extreme physical activity, regular vitamin C can halve your risk of a cold, a conclusion that was based on five studies of almost 600 individuals.
When the reviews look at 31 studies with more than 9000 ''cold episodes'', they also found regular ingestion did reduce the duration of symptoms.
When it came to vitamin C as a cold treatment, the review found no significant effect on the length or severity of the cold, but few studies have tested the remedy.
* The health benefits to be evaluated in future columns.