9p21 isn’t a gene per say, but rather a genetic marker at a location within your genetic manual (your genome) that is largely associated with cardiovascular disease risk.
A major risk factor for cardiovascular disease is the tendency of the lining of your blood vessels (referred to as your vasculature) to become inflamed caused by toxins/pollutants etc, dissolved in your blood.
If you have the ‘increased sensitivity’ version of the 9p21 marker, your blood vessels might be overly sensitive to inflammatory agents/toxins (such as the chemicals found in cigarette smoke).
Components that may be beneficial to individuals with the ‘increased sensitivity’ version of 9p21 are: Omega 3 Fatty Acids, and Tocotrienols.
Test your genomic profile to see your version of the 9p21 gene marker.