Vitamin C may be the nutrient that is the most famous for providing a little extra immune support. Interestingly enough, evidence does not support this nutrient being all its reputation suggests. Per an article on this topic from Harvard Med School’s website, many studies have looked at this nutrient, but they have often been poorly designed.
In research of this topic, I went deep down into the "Vitamin C + Immunity" vault, and found an article from way back in the 1940s. Even this pre-Linus Pauling study was unable to conclusively say that Vitamin C had any significant impact on our immune systems, or ability to fight disease.
Pauling, or "King of the Vitamin C Argument" as I alone refer to him, started his research back in the 1960s, publishing Vitamin C and the Common Cold in 1970, where he shared the results he believed to prove that this lil water soluble nutrient was the cure-all we had been looking for. This dude felt Vitamin C was the answer for treating, not just the common cold, but cancer. It turns out Pauling's studies were pretty poorly designed, and medical boards later deemed his theories "quackery". But Pauling decided "Hey, what do they know," and continued to recommend megadoses to his cancer patients anyway. One of the primary differences noted between Pauling's research and that of said medical boards, and institutions like the Mayo Clinic, is that Pauling was often studying intravenous Vitamin C dosing, whereas these other institutions were focused more on oral supplementation. So, it may not be fair to bash Pauling's theories and throw them away all together. But I'll have to research that more one day... For now, our focus will be on large amounts of oral Vitamin C, and its effect on our immune system.
Some studies have shown us that larger doses of Vitamin C may help shorten the duration of the common cold. However, this is certainly inconclusive, and warrants further observation. While there is a large body of research out there around this topic, it seems hard to separate people from their biases. Many studies are double blind (meaning the researcher AND the subject are both blind to whether they are receiving the intervention or a placebo) - so that's awesome. But it bares noting the potential bias.
Effect of vitamin C on common cold: randomized controlled trial
This randomized, controlled, double blind, 5 year study had its subjects take either 50 mg (low dose) or 500 mg (high dose) of Vitamin C.
It should be noted that the initial purpose of this study was to look at the effects of beta carotene and vitamin C supplementation on the incidence of gastric cancer. About 1 year into this study, results of other trials were showing that beta carotene had no benefit for gastric cancer patients, and so the study was asked to cease this intervention. The study was redesigned, and the focus shifted to Vitamin C supplementation, and its effect on various markers which would help determine the effect on incidence, duration, and severity of the common cold. The expectation was that Vitamin C would have a "preventative or therapeutic effect on the common cold through effects of the immune system".
This study concluded that no apparent reduction was seen for the severity and duration of the common cold, although frequency of the common cold was significantly decreased.
One major limitation of this study was that there was no definition or criteria for "the common cold," and whether symptoms indicated such a diagnosis was left up to the subjects to self report. As you can imagine, there is a ton of room for error in this, opening up results to subject interpretation.
Additionally, you may have noticed that this study had no group that received a placebo. I feel that this is a major area lacking in this study, as it seems placebo effect is a huge factor in Vitamin C having any kind of positive effect on immune health.
One thing I really liked about this study is that they took into account Vitamin C in the diet - not just supplementation- with a food frequency questionnaire at the start of the study, and another 5 years in.
So as not to drag out this post too far, I will only cover the one study here. But, to summarize, it seems most of the studies out there say the same thing:
Supplementation of this nutrient seems to have a more significant effect on children than it does on adults. Additionally, it seems unlikely that supplementation would benefit someone who already has adequate Vitamin C status – that is, if you are not deficient in Vitamin C, a supplement will likely not do anything for you. It is true that our bodies utilize vitamin C to help fight off illness. But your body does that perfectly well if your cells already have enough vitamin C to do so. Our wonderful little bodies are so good and efficient that if you give it extra Vitamin C, it will just go right ahead and excrete it. So mega-dosing is just not effective. You can find out if you are deficient by asking your MD to run a blood test. If you are, you might want to discuss trying out supplementation. But otherwise, I'd suggest spending your money on good whole foods, like fresh fruits and vegetables, that will give your body the tools it needs to fight off illness, rather than spending it on supplements that we aren't sure actually do anything.
Stay well, little nerdies.