Nitric oxide is a trending search term on TikTok, as voices in the wellness space tout the efficacy of supplements for enhancing physical performance, muscle recovery and endurance.
But dietitian Amber Core, of The Ohio State University Wexner Medical Center told Newsweek: "In general, nitric oxide supplements are not recommended. These supplements do not contain nitric oxide, but rather are intended to increase nitric oxide production."
Typically, these supplements contain L-citrulline, L-arginine or both: amino acids (protein fragments) that support nitric oxide production in the body.
"While there are some studies that suggest these supplements could improve cardiovascular health, the research is limited and doctors typically do not recommend them," said Core.
One such doctor who does recommend the supplements for some of his patients is cardiologist Dr. Chris Davis from a nitric oxide supplement company called Humann, who told Newsweek: "I recommend supplements that help support nitric oxide (NO) production to my patients.
"For many, particularly those focused on cardiovascular health or athletic performance, a nitric oxide supplement can be beneficial.
"As we age, our body's natural ability to product nitric oxide declines and lifestyle factors like stress and poor diet can further impact [nitric oxide] levels."
The gas impacts blood flow, blood pressure, immunity and exercise performance, said Core, helping our blood vessels relax so blood pressure decreases, and helping fight off infections.
Research does indicate that nitric oxide has a relaxing, widening effect on blood vessels, but supplements for nitric oxide deliver mixed results.
For instance, an animal study from 2014 found that nitric oxide supplements improved blood flow for rats and rabbits, and research from 2005 found that they could be a safe an effective way to improve blood vessel function and lower blood pressure in women with pre-eclampsia—a condition that affects pregnant women.
There has also been research that suggests nitric oxide supplements could help treat erectile dysfunction, and this may be one reason why Viagra is effective.
Research on the effectiveness of nitric oxide supplements for physical performance is limited and inconclusive. They seem to improve the exercise tolerance and recovery of some young men, but to have no effect on athletes, and little research has been done on women and older people.
"For those looking to improve endurance in sport, of if you have a health condition and your doctor has recommended nitric oxide, then it can be obtained in supplement form," said Core.
However, she warned that it was important to carefully read labels on nitric oxide supplements, as some versions could be "harmful to those with certain cardiac conditions," for instance if they contained caffeine.
Indeed, one study from 2006 found that heart attack survivors were more likely to die if they took nitric oxide supplements, so the effects may not always be beneficial.
Both Core and Davis agree that those who wish to support blood flow and blood pressure without supplements, increasing your intake of some foods might help.
"We can get an increase in nitric oxide production in our bodies from the foods we eat," she said. "Some foods that increase nitric oxide include spinach, beets, bok choy, cauliflower, carrots and collard greens." Davis added kale and arugula to the list.
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