Do not smoke

Smoking causes plaque to build up in the blood. Plaque sticks to the walls of arteries (atherosclerosis), making them narrower; this reduces blood flow and increases the risk of clotting.

Smoking also narrows the arteries, making it harder for blood to flow, as well as increasing blood pressure and heart rate.

Also, chemicals in tobacco smoke increase the chance of heart problems and cardiovascular diseases.

Some of the most common are:

Coronary heart disease - narrow or blocked arteries around the heart. It is among the leading causes of death in the U.S.
Heart attack - smokers are twice as likely to have a heart attack.
Heart-related chest pain.
Carbon monoxide and nicotine in cigarettes make the heart work harder and faster; this means that smokers will find it more difficult to exercise.

Even smokers who smoke 5 or fewer cigarettes a day can have early signs of cardiovascular disease.

Immune system
The immune system protects the body against infection and disease. Smoking compromises this and can lead to autoimmune diseases, such as Crohn's disease and rheumatoid arthritis.