Nitrogen oxide: an air pollutant or a health promoter?
The news and the controversy over nitrogen have naturally not escaped your attention in recent weeks. The farmers’ protests and the protests from the construction sector have firmly put this topic on the map—and on the Malieveld. Nitrogen has two faces! It is more than just an environmental and health issue. It is an indispensable nutrient for all living organisms, found in air, water, soil, plants and animals. Nitrogen is therefore a fundamental building block of nature. An adult human weighing 70 kg has 2 kg of nitrogen in the body.
The different forms of nitrogen
Why does part of the nitrogen on Earth cause us so much concern? Nitrogen (N) is a gas, has no color, no smell and no taste, and occurs in different forms. About 50% of the nitrogen on our planet is in gaseous form, because our atmosphere consists of 78% nitrogen compounds. Most atmospheric nitrogen takes the form \(N_2\). This is a very stable, non-reactive form of nitrogen that most living beings cannot use. Besides stable nitrogen, there is also reactive nitrogen. Reactive nitrogen can bind with both organic and inorganic substances. All living beings depend on reactive nitrogen, because it is needed as a building block for DNA or proteins. But it can also affect chemical and physical processes in water, the atmosphere or the soil. These can in turn affect all living beings.
Reactive nitrogen occurs in the following compounds:
- Nitrate (\(NO_3^-\))
- Nitrite (\(NO_2^-\))
- Nitrous oxide (\(N_2O\))
- Ammonia (\(NH_3\))
- Ammonium (\(NH_4^+\))
There are only a few processes in which atmospheric, stable nitrogen (\(N_2\)) is converted into a reactive form. For example, lightning can convert \(N_2\) into nitrogen oxides (\(NO_x\)). Some bacteria, especially root nodule bacteria, are able to bind nitrogen and make it available to plants. Human activities also convert \(N_2\) into reactive compounds. This conversion takes place, on the one hand, in the production of fertilizer and, on the other, in the use of fossil and renewable fuels. In both cases, reactive nitrogen is released. Not only is stored nitrogen released during combustion, but \(N_2\) in the air is also converted into nitrogen oxides (\(NO_x\)).
The main source of reactive nitrogen release is agriculture, which contributes more than 50%. Nitrogen is crucial for agriculture because it affects crop yields, which is why agriculture uses nitrogen-based fertilizers. On the one hand, reactive nitrogen is important on farmland, but on the other hand it can be harmful in other areas. For example, reactive nitrogen endangers human health through nitrogen oxides (\(NO_x\)), affects groundwater quality through nitrate (\(NO_3^-\)), and nitrous oxide (\(N_2O\)) contributes to climate change. In addition, reactive nitrogen compounds lead to overfertilization and acidification of ecosystems and thus to biodiversity loss. Buildings are also slowly damaged.
What is this pollution?
- Natural ecosystems can be damaged, water can become polluted, and this contributes to the thinning of the ozone layer and to global warming. This is because they can retain heat in the atmosphere 300 times more effectively than carbon dioxide!
Transport, industry and energy production each also contribute 15% to emissions. Industries we all use, so—fair is fair—everyone contributes. Us too, you too. But what has recently been overshadowed are the positive sides of nitrogen. It is not “just a pollutant”; it is also very useful. In our own biochemistry, nitric oxide plays an important role.
Nitric oxide and human health
The human body produces nitric oxide, and it plays an important role in many essential processes, both at the cellular level and at higher levels. It acts as a neurotransmitter, because it passes signals to cells in all vital systems, including the cardiovascular, nervous and immune systems. Nitrogen is therefore essential for our existence because without it we cannot live. It influences almost every function in our body.
NO plays a role in, among other things:
- Relaxation of blood vessels (vasodilation)
- Regulation of circulation
- Release of hormones, including insulin and growth hormone
- Cell and nerve survival
- Memory and cognitive learning
- The immune system
Unfortunately, the body’s own nitrogen production gradually declines as you get older. Around the age of forty, the body produces more than half as much nitrogen as it did at twenty. In women, this difference is greater than in men.
Maintaining optimal nitric oxide levels can therefore be an important strategy for a healthy and long life. Below you can read ways to effectively keep your own nitrogen balance at a good level.
- Nitrogen is also called the “miracle molecule,” and the discovery of the role of nitrogen in the cardiovascular system earned Robert Furchgott, Ferid Murid and Louis Ignarro the Nobel Prize in 1998.
1) Add these foods to your diet
Your body can convert nitrates—a substance commonly found in vegetables—into nitric oxide. If you want to increase NO production, increase your intake of nitrate-rich foods such as celery, cress, chervil, lettuce, beetroot, spinach and arugula. In addition, the antioxidants they contain can prevent free radicals from breaking down the NO that is formed and thereby lowering its level. So add these antioxidants to your diet: vitamin C (bell pepper, broccoli, blackcurrant, grapefruit), vitamin E (nuts, sunflower seeds, flaxseed, kale, asparagus) and various polyphenols (cloves, dark chocolate, blueberries, blackberries, strawberries, nuts, artichokes, chicory).
2) Exercise!
Nitric oxide is produced in the inner, thin layers of blood vessels: the endothelium. Exercise improves this endothelial function. In addition, physical activity stimulates antioxidant activity in the body, which means less nitric oxide is broken down at the same time.
A 15-minute intense workout (HIIT: High Intensity Interval Training) increases NO production better than 150 minutes of moderate-intensity training. A specific exercise program has even been developed for this by Dr. Zach Bush in the United States: the Nitric Oxide Dump program is a new variation of HIIT training specifically designed to stimulate the release of NO.
3) Consider supplements
The two best-known supplements for this purpose are L-arginine and L-citrulline. L-arginine is a semi-essential amino acid. It is the only precursor of nitric oxide that is converted into NO via a process called the L-arginine-NO pathway. Your body naturally produces L-arginine, but taking extra daily can be a sensible choice, especially as you get older.
L-citrulline is a non-essential amino acid, which means your body can make it from other substances. L-citrulline is important as a precursor for the formation of L-arginine. Our body converts L-citrulline into L-arginine in the kidney. The conversion process also produces some nitric oxide and thus contributes to the body’s NO production.
4) Breathe through your nose
Specific enzymes in your nose and sinuses help produce nitric oxide. Therefore, breathing through your nose (i.e. not through your mouth) can increase nitric oxide production in the sinuses and improve oxygen delivery. Nasal breathing can lead to better blood circulation, healthier blood pressure levels, improved sleep and a reduced risk of heart disease, asthma, allergies and inflammation. One approach you can consider here comes from the Buteyko breathing method, which is taping your mouth shut while sleeping. Sounds intense, but look it up.
5) Limit mouthwash
As discussed earlier, nitrate from food can be converted into nitric oxide. However, this cannot happen without the help of special bacteria in our mouth. Mouthwash kills all bacteria in the mouth, including those essential for NO production. So do not use mouthwash unless specifically advised by your dentist.
6) Go sunbathing!
The skin contains a lot of nitrite, and when exposed to sunlight, this nitrite enters the blood. This eventually, just like nitrate-rich vegetables, leads to an increase in nitric oxide.
Exposure to the summer sun without sunscreen for about 30 minutes produces a good increase in nitrogen.
The conclusion?
Nitric oxide is a molecule produced by our own body and is absolutely essential for our physiological functioning. If your NO production is no longer optimal, you can fortunately apply simple strategies to stimulate it: physical activity, supplements, nitrate-rich vegetables, nasal breathing, limiting mouthwash use and sunlight. Perhaps you can now also look at all the alarming news about the environment, farmers, construction and the “nitrogen crisis” in a different way. Because although nitrogen is a real nuisance in some sectors, without that tiny substance we would not be able to live healthily at all.