NOS3 produces the enzyme nitric oxide synthase responsible for making nitric oxide, known to be protective in our blood vessels and to be involved in vasodilation (opening of the blood vessels).
Variants result in low nitric oxide production which has been associated with cardiovascular disease. Recent research has shown that omega-3 fat has a positive impact on cardiovascular risk in people with NOS3 variants by lowering another kind of fat called triglycerides which is also linked to lower HDL (good) cholesterol.
The T- allele is associated with increased cardiovascular risk markers and increased risk of high blood pressure. With reduced NO production relaxation of smooth muscles surrounding blood vessels will be reduced leading to increased blood pressure.
If you carry the risk allele you may benefit from adding in the 3 co-factors associated with NOS3 function; namely B2, iron, and tetrahydrobiopterin (production increased by methyl folate, Vitamin C, and curcumin).