In Experiment 001, Sun Powered, I wrote that nitric oxide does an enormous amount of work in your body, and that I would come back to it. This is me coming back.

Nitric oxide is a gas: one atom of nitrogen, one of oxygen. Its main job is to tell your blood vessels to relax and open. Wider vessels mean lower blood pressure and more blood and oxygen reaching your muscles, your brain and everything else.

Your body makes it two ways. The first is built in. The cells lining your blood vessels make it on their own, and they make more every time blood rushes past them, which is a big part of why exercise works. The second runs through your food and your mouth, and it is the one you can feed directly.

An explosive story.

Alfred Nobel made his fortune from dynamite, which is built on nitroglycerin. Late in his life, sick with heart disease, his doctor prescribed him nitroglycerin. He wrote: "It is ironical that I am now ordered by my physician to eat nitroglycerin."

It took a hundred years to find out why it helped. Nitroglycerin releases nitric oxide. In 1998 three American scientists, Robert Furchgott, Louis Ignarro and Ferid Murad, won the Nobel Prize, the prize Nobel's own fortune pays for, for showing that nitric oxide is a signal in the heart and blood vessels. That same year, the FDA approved Viagra, which works by keeping the nitric oxide signal switched on longer.

Beets and greens.

Beets, arugula, spinach and other leafy greens are full of nitrate. Nitrate needs help. Bacteria living on your tongue turn it into nitrite. You swallow that, and your body turns it into nitric oxide. No bacteria, no nitric oxide from your food.

Arugula carries the most nitrate by weight: German food safety testing found about 4,700 milligrams per kilo, more than beets. But you would need a big bowl of it. Beets are the easy way to a real dose, which is why most of the research uses beet juice. I eat a lot of beets. Nitrate dissolves in water. When you boil them, part of it ends up in the red cooking water, so I always drink it.

The evidence for beets is some of the best in nutrition. In a 2015 trial, people with high blood pressure who drank 250 milliliters of beet juice a day for four weeks lowered their blood pressure by about 8 points, and their arteries became more flexible. At the University of Exeter in 2009, cyclists who drank beet juice for six days lasted 16 percent longer before exhaustion. notes that an international sports medicine consensus lists nitrate among the few supplements with strong evidence. The effect is real. Nathan Bryan, a nitric oxide researcher, believes in beets so much that he wrote a whole book about them and called it Beet the Odds.

Protect the bacteria.

Strong antiseptic mouthwash wipes out the good bacteria with the bad. It does not pick sides. In a 2013 study in London, a week of it cut the nitrite coming from people's mouths by about 90 percent, and their blood pressure went up. In a study in San Juan, Puerto Rico, adults who used mouthwash twice a day or more had a 55 percent higher risk of developing prediabetes or diabetes over three years. That study shows a link, not proof, but the pathway behind it is real.

I stopped using mouthwash a few years ago, and started using a tongue scraper around the same time. A scraper cleans your tongue without wiping out the good bacteria you need. A small 2019 study found that people who cleaned their tongue every day carried more of the nitrate-turning bacteria, not fewer. Tongue scrapers have other benefits too, and I will write about them soon.

The rest of the list.

1. Breathe through your nose.

Your sinuses make nitric oxide all day, in very high concentrations. Breathe through your nose and every breath carries it down into your lungs, where it opens the vessels that pick up oxygen. Breathe through your mouth and you skip it. Plenty of people who breathe through their nose all day breathe through their mouth at night, and miss it for hours. I wrote about mouth taping in Experiment 002, Take a Breath.

2. Hum.

In that Experiment, I also wrote that humming raises nasal nitric oxide about 15 fold, and I promised to explain the vibration. Humming makes the air in your nose shake, and that pumps air in and out of your sinuses, where the nitric oxide is made. Quiet breathing barely moves the air in there at all.

3. Practice your breathing.

A few minutes of slow breathing through the nose each day trains you to breathe that way without thinking, and every one of those breaths carries nitric oxide down with it. Experiment 002, Take a Breath walks through the practices.

4. Get sun on your skin.

Your skin holds its own store of nitric oxide. The UVA in sunlight releases it straight into your blood, with no eating, digesting or converting. I wrote more about it in Experiment 001, Sun Powered.

5. Sweat.

In Finland, one 30 minute sauna session lowered people's blood pressure from 137 over 82 to 130 over 75, and their arteries were less stiff afterward. I never skip the chance for a sauna session. Sauna has many other benefits, which I will cover in the Experiment on heat and cold.

6. Train hard.

This is the built-in route. When your heart pumps harder, blood rushes along your vessel walls, and the cells lining them answer by making more nitric oxide. Regular exercise is the main thing shown to protect that system as you age. My go-to is high intensity interval training, which is known to switch on nitric oxide. A review of seven trials found that interval training improved how well arteries widen about twice as much as steady cardio did.

7. Eat the other helpers.

A review of 42 trials found that cocoa flavanols, the compounds in dark chocolate, helped arteries widen and lowered blood pressure. In a review of 20 trials, garlic lowered blood pressure by about 9 points in people with high blood pressure. Across 14 trials, pomegranate juice lowered it by about 5. I always have fresh garlic in my pantry, a big collection of dark chocolate, and pomegranate molasses, which I wrote about in Experiment 006, Well Preserved.

8. Citrulline and arginine.

Arginine is the raw material your vessels use to make nitric oxide, and citrulline is an amino acid your body turns into arginine. Watermelon is the richest food source of citrulline, and pumpkin seeds are among the richest in arginine. Get them from food, and skip arginine pills: your body breaks most of them down before they reach your blood.

A bonus for men.

An erection is a blood flow event, and it runs on nitric oxide. That is how Viagra works. Every habit in this Lab Note raises nitric oxide, so they all feed the same system.

Here is what you can do this week. Skip the antiseptic mouthwash, unless your dentist prescribed it, and start using a tongue scraper. Eat a beet or a big bowl of arugula every day. Breathe through your nose, day and night. Get some sun, without burning. Get your heart rate up. Your body already knows how to make this molecule. Feed it, and get out of its way.

Georges

Usually one Experiment on Sunday. Lab Notes in between. Free.

If you enjoyed it, leave me a like or a comment.

Subscribe now

I am a professional walker. I try to walk almost every afternoon, often with friends. I live on a canal, and there is a path along the water where I can walk for kilometers. When I am in Europe, I walk everywhere for hours, and somehow I never get tired. My father has walked all his life. He never played a sport and never went to a gym. Walking is his only workout. He is 89 now, in good shape for his age, and his mind is still sharp.

Most people do not count walking as exercise. The research says they should.

The number.

The 10,000 steps goal did not come from a lab. It came from a Japanese pedometer sold in 1965 called manpo-kei, which means "10,000 steps meter."

The real numbers are friendlier. In 2025 The Lancet Public Health pooled 57 studies. People who walked 7,000 steps a day had a 47 percent lower risk of dying during the studies than people who walked 2,000. Their risk of dementia was 38 percent lower, death from cancer 37 percent lower, and symptoms of depression 22 percent lower. In a Harvard study of women in their seventies, about 4,400 steps a day already went with about 41 percent lower mortality.

How you take the steps matters too. In a 2025 study of more than 33,000 people who walked less than 8,000 steps a day, the ones who walked in stretches of 15 minutes or more had a much lower risk of dying than the ones who only walked in bursts of five minutes or less. One real walk beats a day of shuffling.

What it does to your brain.

At Stanford in 2014, people came up with 60 percent more creative ideas while walking than while sitting. "We're not saying walking can turn you into Michelangelo," the lead researcher, Marily Oppezzo, said. "But it could help you at the beginning stages of creativity."

In a trial with 120 older adults, a year of walking three days a week grew the hippocampus, the brain's memory center, by 2 percent. The researchers wrote that this effectively reversed one to two years of age-related shrinking. The people who only stretched lost volume.

For mood, a 2024 review in the BMJ pooled 218 trials on exercise and depression. Walking or jogging had the biggest effect of any type of exercise.

points to something else that happens on a walk. As you move forward, the world streams past your eyes. He calls it optic flow and says it "has this incredible property of lowering activity in the amygdala," the brain's alarm. The study behind it tested eye movements in a scanner, not walks, so take it as a lead, not a law.

Where you walk counts. At Stanford, people who walked for 90 minutes through nature dwelled less on their worries afterward, and the part of the brain tied to brooding quieted down. People who walked the same time along a busy road saw no change. The neuroscientist , who wrote a whole book on walking, puts it this way: "Our sensory systems work at their best when they're moving about the world."

We were built to walk.

Mark Sisson, the founder of and one of the best known voices of the primal movement, puts it plainly: "Humans are the best walkers on the planet." His rule is to move often at a slow pace, with your heart rate around 180 minus your age. At 50, that is about 130 beats a minute.

The Hadza, hunter gatherers in Tanzania, still live much as hunter gatherers have for thousands of years. Measured by GPS, the men walk about 11 kilometers a day and the women about 6.

The thinkers knew it. Charles Darwin walked a sand path behind his house every day until the last weeks of his life, and called it his thinking path. Nietzsche wrote: "Only thoughts reached by walking have value." Steve Jobs held his serious conversations on long walks. And in 1847 the philosopher Søren Kierkegaard wrote in a letter: "Every day I walk myself into a state of well-being and walk away from every illness; I have walked myself into my best thoughts, and I know of no thought so burdensome that one cannot walk away from it."

How to make it count.

Walk after you eat. When your muscles work, they pull sugar out of the blood without needing insulin. In a study in New Zealand, in people with type 2 diabetes, a ten minute walk after each meal lowered blood sugar more than one thirty minute walk a day. I went deeper on this in Experiment 008, Sugar Rush.

Walking also heals. In a 2024 trial in The Lancet, 701 people who had recovered from low back pain were put on a walking program. They went a median of 208 days before the pain came back, against 112 days for people who did nothing.

To make a walk work harder, the Japanese have a method. Researchers at Shinshu University had people in their sixties walk three minutes slow, then three minutes fast, five rounds, four days a week. After five months their leg strength was up 13 to 17 percent and their blood pressure down 9 points, more than people who walked 8,000 steps at a steady pace.

, the longevity doctor, adds weight. He walks hills with a 60 pound pack and says walking downhill trains "the brakes," because "most people fall because they lose the brakes." He suggests starting at about a tenth of your body weight.

Walking is not the lesser version of running, and it could be considered the better one. You get much of the same benefit with far less wear. Moderate running is good for you, and recreational runners even have healthier knees than people who sit. The trouble starts with long, hard mileage, year after year. Sisson knows this from the inside. He ran marathons at the national level and finished fourth at the Ironman World Championship in 1982. Today he calls himself an "anti-chronic cardio" guy: walk every day, lift a few times a week, and sprint now and then.

Here is what you can do today. One walk of at least 15 minutes without stopping, outside if you can. Three minutes easy, three minutes fast. And ten minutes after dinner.

Kierkegaard had it right. There is no thought so heavy that you cannot walk away from it.

Georges

Usually one Experiment on Sunday. Lab Notes in between. Free.

If you enjoyed it, leave me a like or a comment.

Subscribe now