Vitamin C became famous the moment that Linus Pauling (pictured), a US professor of chemistry, said he thought that vitamin C could reduce the risk of the common cold. By this time, in the early 1970s, he had already pocketed two Nobel Prizes in chemistry and peace. He could have got a third when he was working hard to determine the structure of DNA before Watson and Crick beat him to it. So, Pauling was a bloke to whom you should lend an ear.
Early reports promising Although vitamin C (ascorbic acid) wasn't first isolated, or "discovered", until 1928, for many years we knew of a vague compound that stopped you from getting scurvy. Only 10 mg a day will keep scurvy away, yet there has been long conjecture that a whole lot more than 10 mg was needed each day to be healthy. Not that long ago we found that people with high levels of vitamin C in their blood had a lower risk of heart disease and early death. Unfortunately, when we started giving people vitamin C supplements the results were less exciting.
You've heard me say this a few times - just because there is an association, we should never assume we are seeing cause and effect. High blood vitamin C is probably a "marker" of a lifestyle that includes plenty of fruit and vegetables, and of course, if you eat your veggies then there is a reasonable chance you don't smoke or drink gallons of alcohol, and probably walk the dog too. Less heart disease was more likely due to good living than being able to pin it on a single vitamin like ascorbic acid.
Vitamin C alone not that useful There is also a good chance that any one vitamin can't do a lot on its own to prevent disease and needs a whole range of other nutrients and antioxidants alongside it before a benefit kicks in.
In a new review of vitamin C, published in the British Journal of Nutrition, it states that: "It should be acknowledged that in the epidemiological studies on the relationship between vitamin C concentrations and diseases there is no evidence that the relationship is due to vitamin C itself."
Although it has long been trendy to pop 500 mg tablets of vitamin C, there is a limit to how much vitamin C our body can store. Once we have over 200 mg a day our body becomes "saturated" with vitamin C and any over this amount ends up in the loo.
And the common cold? The Cochrane Database [http://www.ncbi.nlm.nih.gov/pubmed/17636648 Systematic Review] in 2007 said: "The failure of vitamin C supplementation to reduce the incidence of colds in the normal population indicates that routine mega-dose prophylaxis is not rationally justified for community use."
And when the most powerful database in the universe says that, you better take notice. Hey, Linus was a legend and even legends are allowed to speculate and not get it right sometimes. Remember, his first crack at the DNA structure was wrong too. A brilliant human, but still a human.
What does it all mean? The daily vitamin C recommendations in the US is 75-90 mg; 40 mg in the UK; and 45 mg Australia and New Zealand.
If you can eat an orange (70mg), a small salad (100 mg), a serve of broccoli (30mg if you don't boil it to a fraction from mush), or a banana (12 mg) you can see that it is pretty easy to meet your C needs with normal good eating. If you have a very low vitamin C status (more likely in smokers) then you might benefit from a supplement (100 mg, not 500 mg or 1000 mg), but as I, and many others in the nutrition game, will tell you, a vitamin supplement ain't no substitute for getting decent feed into you.
Reference: British Journal of Nutrition 2010; 103: 1251-1259
