The blood vessels of smokers do not respond as well as those of nonsmokers when the heart needs more blood flow during physical exertion. The heart beats faster during physical exertion, requiring the coronary arteries to dilate or widen to increase the flow of oxygen-rich blood to the heart muscle to keep it pumping properly. Researches found that the arteries of smokers do not dilate adequately, possibly increasing smokers' blood pressure and their risk for heart attack or stroke. smokers averaged about 14-precent less blood flow to the heart than nonsmokers when both groups underwent cold pressor testing, a brief exposure to ice water that stressed their hearts and caused them to beat faster.

Cigarette smoke also contains a number of cell-damaging toxins, and smoking increases the production of angiotensin II, which reduces activity of nitric oxide, a substance in the blood that instructs the blood vessels to expand.

Furthermore, smoking fills your blood vessels with carbon monoxide, a lethal gas. Smokers have 4 to 15 times more carbon monoxide in their blood than nonsmokers.

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