Featured Gene: NOS3

The benefits of Nitric Oxide (NO) boosting supplements are well documented, from the dilation of blood vessels to increasing levels of testosterone and growth hormone. 

And products that promote NO production is something we know quite a bit about here at FitnessGenes. After all, co-founder Mark Gilbert helped bring the first ever NO boosting sports supplement to the market.

However, as NO is produced naturally, it can’t be supplemented directly. Instead, ingredients such as L-arginine, American ginseng and folic acid are used to stimulate its production.

Whilst supplements can impact your NO levels, your DNA also plays its part. And specifically, your NOS3 gene variation.

NOS3 & Genetics

The NOS3 gene codes for the enzyme Nitric Acid Synthase 3, which naturally facilitates the production of NO.

The expression and activity levels of Nitric Acid Synthase 3 is determined by the variation of the NOS3 gene that you carry. Increased expression of the enzyme results in higher production levels of NO. So which variation results in the highest NO production, and what are the benefits?


Considering its positive impact on vasodilatation, one may assume that higher NO production would be more beneficial to endurance based athletes. However, this was not the case in a study comparing the genotypes of 110 Ukrainian power based athletes to that of 326 non-athletes. Studies into Spanish and Italian power athletes also saw similar results.Research into the NOS3 gene has shown that the T allele is associated with higher NO production, and has also been found at a higher frequency in power based athletes.

Although the association between the T allele and power based activity is not completely understood, it is possible that NO and NOS3 play a role in muscle hypertrophy. This increased muscle mass would be beneficial to power athletes, as would the resulting increase in testosterone and growth hormone.

On the other hand, research has reported health benefits in carrying two copies of the ‘reduced NOS3’ C allele, including a greater decrease in blood pressure in response to aerobic exercise, and lower triglyceride levels.

Factors affecting NO Levels

Whilst your NOS3 genotype does have an impact on NO production, it is important to remember that many other genes, as well as your diet, lifestyle and training also have a significant impact on your athletic performance.

Factors that negatively affect NO levels:

Ageing, physical inactivity, smoking, high cholesterol, a high-fat diet.

Factors that positively affect NO levels:

Moderate exercise, a low sodium, a high antioxidant intake.

Vegetables: Beets, beet greens, spinach, kale.

Legumes: Peanuts, chickpeas, soy beans.

Nuts/Seeds/Greens: Brown rice, pine nuts, sesame, pumpkin seeds, hazelnuts almonds.

And… Dark chocolate!

Your NOS3 Result

So does your NOS3 result suggest that you should be supplementing your diet with NO boosting foods and supplements? Or is your variation giving you a power based training advantage?

NOS3 is just one of the 42 genes that we test for at FitnessGenes. To discover your unique results and genetically upgrade your training, order your personalised Genetic Training System now!

Written by Alex Auld

Thursday, April 7, 2016