There are many products available in the market which claim to help you dealing with the side effects of quitting smoking, especially cold turkey. Most of these people list indigestion, flatulence, gas, diarrhea, constipation, sinus congestion, voice hoarseness, phlegm production as some of the side effects of quitting smoking cold turkey.
There is a great list of side effects of quitting smoking listed in many websites which I do not want to repeat here. There are times when I quit smoking up to two weeks in the past. Apart for strong urge to smoke, there were no side effects of quitting on my body.
Most of the side effects which are quoted by these internet markets are actually the side effects of smoking not quitting smoking. For example voice hoarseness and sinus congestion. The strong side effect of smoking which affects you negatively is only the strong uneasiness which your body feels which makes you desperate to smoke. Other than this I don't think there are any major side effects. Few side effects like headache and numbness and tingling in the fingers are actually psychosomatic where you try to fool yourself to smoke.
I also belief that it is the availability of the smoke which plays all the tricks on your mind and body to convince yourself to smoke. Once I spent about fifteen days in an ashram where there is no chance of smoking or coming out of the ashram. I had no side effects as my mind clearly knows that smoke is available only fifty miles away and almost impossible.
Do try cold turkey keeping in mind that all the tricks your mind plays on body is because of the fact that smoke is available in the vicinity. See if you get any of the so called side effects of quitting smoking.