I don’t know if it’s dangerous, but taking too much vitamin C gave me an agonizing case of diarrhea. It took me three miserable days of taking those stupid vitamins from my grandma before I figured out it was the vitamin C.
For some strange reason, I’m highly skeptical of any health product whose main quality is that it was created by a school teacher. Not that I have anything against school teachers per se (my brother being one), but that’s just not the kind of quality I’m looking for in health care products I choose to purchase. In fact, whenever I see “Created by a school teacher” on those boxes at the drug store, it’s like seeing “Batboy found birthing Bigfoot’s love child!” on the cover of a tabloid.
Anecdotal evidence for helping colds is flimsy at best since an illness with over 200 different variations can last anywhere from 2-7 days and you really can’t say with any real certainty that X helped shorten its duration. I say save your money.
What exactly does “boost your immune system” mean, anyway? That seems vague enough to mean anything.
Honestly, what’s the point of using a term like “overdose” if it applies to any ingestible substance? You can “overdose” on water more easily than you can overdose on Vitamin C.
The point is that the people who push the stuff sell more and get people to buy more with the promise that you can’t take too much. Well, you can. And the idea that taking “20,000 times the normal dose doesn’t hurt” is something that shouldn’t pass without comment.
In my experience (and that of many other people) the “feeling you get when you’re sick” is not a very reliable predictor of whether you’ll actually come down with a significant cold. Many times one will get a bit of sore throat and feel malaise - only to have it dissipate overnight. Instances where that happens and one has taken echinacea, chicken soup or Cold-fx will result in one believing that the supplement did the trick.
I read what the site had to say about those studies, and I didn’t see that any study specifically reported that Cold-fx prevents or alleviates colds. The site alludes to various effects on immune functions, like numbers of T-cells, but that doesn’t necessarily correlate with a real-world effect on colds in humans.
You have to be careful about accepting “Research/Clinical Studies Prove X!!!”
Conclusions that are based on limited evidence, badly conducted studies or poorly relevant data are not necessarily any better than “Worked for me!”