Hey, Emanresu. It used to be very standard procedure for people who believed in vitamin supplementation/protection to recommend beta carotene supplements as a protection for smokers, meaning cigarette smokers.

But in the mid-1990s, all that changed. The results of two large studies (one in Finland and one in the U.S.) on beta carotene supplementation and lung cancer risk came out about that time. Both studies found a strong link with increased lung cancer risk in people who took beta carotene supplements when compared with people who took a placebo drug. So we now know beta carotene increases smokers' risk of lung cancer, and frankly, smokers don't need any additional risk. They face high enough cancer risks just from cigarette-smoking alone.
http://www.cancer.gov/clinicaltrials...inal-CARET1204

Whoever advised you against taking beta carotene supplements knew what he was talking about. You should not take those if you smoke--and the truth is, you probably shouldn't take extra beta carotene anyway. There are studies currently underway to see whether it increases cancer risk in non-smoking people. Definitely stop taking those beta carotene supplements now--and then do yourself another favor and stop smoking cigarettes, too. They're bad news.

I'll be moving this thread to our Medical area.