What about the common advice to take zinc supplements?

Mostly bullshit. A couple of studies on multivitamins that include zinc in developing nations showed a very small reduction in the incidence of an upper respiratory infections-approximately 8%. In studies of zinc supplementation and the zinc nasal spray in first world countries the effects of zinc have largely been disproven. It’s just marketing crap.

Its not bullshit. Taking vitamin C + zinc is much more then anecdotal, there is planty of evidence in medical journals, some people for some reason like to cherry pick negative ones (that is, there are no negative ones, even 8% is still better, given that treatment is chepaer then watter).

Those supplements work, they changed life of my entire family. I personally find it ridiculous for people to object. Yes, some may not get full blown effect just like with anything but in majority of cases they work. Personally, they changed my life and I didn't measure on a one year sample.

>>Mostly bullshit.

I don't know. I've noticed that if I take zinc pills along with vitamin C pills on the first or second day of the cold I start feeling better within two or three days and within a week the cold is almost gone. If I do not then the cold can easily last a couple of weeks.

I’ve often thought about this argument. However, you have no way of knowing how long that particular case of the cold would have lasted if you hadn’t taken pills. Plus placebos are an amazing thing.

It gets biased because a single positive feeling is enough to get the human mind to think there is a causal connection between the pill and the "cure".

There are hundreds of variants of the common cold virus, and you are at any time more or less immune to a subset of them, so many times after you're exposed you just feel ill for half a day. If you pair one of those occurances with your magic pill intake, you'll truly believe the pill caused you to get better, and then you'll keep buying that pill every time you feel a cold coming up for the rest of your life.

A real medical study is 10,000-100,000 patients, it's not possible to draw any conclusions from a single human's observation in this regard... but people keep trying, it's due to the nature of the human mind and its analysis of causality :)

I honestly thought you were setting up a joke. “If I take zinc the cold lasts a week, if I don’t...”

Colds last a week. That’s normal.

Not in my case. I can suffer for an entire month with a runny nose, cough or sore throat. Of course, this is all anecdotal and it could all just be the placebo effect.