Winter is just around the corner, so I’ll start with the health claim we all know best: vitamin C prevents colds and flu and alleviates the symptoms of these irritating ailments.
There is little evidence to support much of a case for vitamin C supplements, despite the publication of enough research papers to build a small hill.
Cochrane Collaboration scientists, after systematically reviewing all the well-designed studies they could lay their hands on, concluded that there is no evidence that supplements of vitamin C prevent colds. There is, they conclude, a small reduction in the severity and duration of colds in those taking regular supplements.
It is possible, they go on to say, that massive doses (e.g. 8 grams), at the onset of a cold may help symptoms but there are too few trials to be sure. The jury is still out on this and doses of this size can cause diarrhoea. And remember the effects that are found in some (but not all) studies are minor, not curative.
There is some evidence that for those indulging in arduous physical activity – marathons and so on - vitamin C can help to reduce their incidence of colds. So if you are entering a triathlon or climbing a mountain then make sure your diet contains plenty of fruit and veg.
So what are the other facts?
Severe deficiency of vitamin C causes scurvy. This is a disease in which the walls of blood vessels cannot repair themselves. Sufferers eventually die from bleeding (and not, apparently, from infections). So we are certain that vitamin C is essential to the body if it is to carry out repairs. It is also used by cells, including immune cells, but they only seem to need a small amount.
You have to be eating a terrible diet for several weeks to get scurvy – one that contains no fresh food. If you are an Arctic hunter eating plenty of fresh meat you will be fine. If you eat chips and burgers and nothing else, you will not get scurvy. If you ate only cake and sweets you might.
There is circumstantial evidence that people who eat lots of fruit and vegetables tend to be healthier but there is no reason to think that vitamin C is the magic ingredient. When we eat fruit and veg we get a range of benefits and extracting pure vitamins and consuming them as supplements does not seem to be the same thing at all.
So, my conclusion is that we should not be seduced into buying products that claim to have added vitamin C or wasting our money on vitamin C supplements. Spend money on fruit and veg instead and you will get your vitamin C along with the other nutrients.
Here’s the link to the Cochrane article.