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Nitric Oxide in the Body: Benefits and Dangers

Updated on April 1, 2017
AliciaC profile image

Linda Crampton is a teacher with a first class honors degree in biology. She writes about human biology and the scientific basis of disease.

Beets are a good source of nitrates, which the body turns into nitrites and then into nitric oxide.
Beets are a good source of nitrates, which the body turns into nitrites and then into nitric oxide. | Source

A Simple and Important Molecule

Nitric oxide is a simple little molecule with big effects inside our body. Many biological molecules have a complex structure, but nitric oxide contains just two atoms—a nitrogen atom and an oxygen atom—and has the formula NO. It's sometimes called nitrogen monoxide.

NO has many important biological functions. It relaxes the walls of blood vessels, causing vasodilation (widening of the vessels). This allows more blood to flow into the heart and other organs. It also acts as a signaling molecule between nerve cells. In addition, it plays an important role in our immune system and helps it to fight infections.

Research suggests that nitric oxide may have an effect on aging and longevity. The possession of intestinal bacteria that make NO enables Caenorhabditis elegans to live for significantly longer than members of its species without the bacteria. C. elegans (the abbreviated scientific name) is a roundworm and a popular organism in anti-aging studies. What applies to a roundworm may not apply to us, but it is known that the level of nitric oxide in our body decreases as we age. The idea that bacteria producing nitric oxide could be added to our intestine in order to help us live longer is a tantalizing thought.

Green vegetables such as romanesco broccoli contain nitrates.
Green vegetables such as romanesco broccoli contain nitrates. | Source

Nitric oxide shouldn't be confused with nitrous oxide, which is commonly known as laughing gas. A nitrous oxide molecule contains two nitrogen atoms and one oxygen one. It acts as an anesthetic and is not a normal component of our body.

Nitric Oxide and the Heart

Role of NO in the Circulatory System

Nitric oxide in blood plays a vital role in keeping our circulatory system healthy. It causes vessels to widen and open up, allowing large quantities of blood to be transported. Blood without nitric oxide doesn't cause vessels to expand. This means that the blood can't flow as easily through the vessels.

Researchers have noticed that the longer that blood is stored before a blood transfusion, the more dangerous it is for the recipient. This seems to be due to the biochemical changes that take place as the blood ages, including loss of nitric oxide gas. Without nitric oxide, the donated blood may block the circulatory system because it can't move through the vessels properly. One scientist has shown that in lab animals adding nitric oxide to blood before a transfusion prevents blockage and allows the blood to flow freely.

Nitric oxide also lowers blood pressure. We have some control over this action via the food that we eat. A diet high in leafy green vegetables and beets (or beetroot) is known to lower high blood pressure. These vegetables are a good source of nitrates. Inside the body, the nitrates are converted to nitrites. The nitrites are then converted to nitric oxide. The nitric oxide expands blood vessels, which lowers blood pressure. The body also makes nitric oxide from an amino acid called L-arginine.

Blood Transfusions and Nitric Oxide Depletion

Three researchers—Robert F. Furchgott, Louis J. Ignarro, and Ferid Murad—discovered that NO acts as a signaling molecule in the circulatory system. In 1998 these scientists won the Nobel Prize for Medicine for their work with nitric oxide.

Nitroglycerin, NO, and Angina

In 1977, a researcher discovered that nitroglycerin causes the production of nitric oxide in the body. Nitroglycerin (or nitroglycerine) is one medicine given to people suffering from angina. During an angina attack, a person experiences chest pain due to a lack of oxygen in the heart, usually due to the narrowing of a coronary artery. Nitroglycerin expands the artery. The nitric oxide made from the nitroglycerin is responsible for the vasodilation.

A synapse is the region where one neuron ends and another begins.
A synapse is the region where one neuron ends and another begins. | Source

Neurotransmission

Nerve cells, or neurons, communicate with each other by means of chemicals. These chemicals are known as neurotransmitters. A neurotransmitter is produced in advance and stored in small sacs called synaptic vesicles, which are located at the end of a neuron.

The region where one neuron ends and another begins is called a synapse. When a nerve impulse arrives at a synapse, the neurotransmitter is released from the first neuron into the tiny gap that is present between neurons. The neurotransmitter travels through the gap and attaches to receptors on the membrane of the second neuron. Once this union takes place, the second neuron is stimulated (or in some cases inhibited). Stimulation generates a nerve impulse. After it has done its job, the neurotransmitter is broken down or reabsorbed into a nerve cell.

Nitric oxide is a neurotransmitter, but it behaves differently from other neurotransmitters. It isn't produced in advance or stored but is made when it's needed. It does travel across the gap between neurons, but it travels into the second neuron instead of attaching to receptors and staying at the neuron's surface. It may also enter more than one neuron.

Nitric oxide isn't very stable and only exists for a short time. It's sometimes called a "gasotransmitter"—a gas that is made in the body and acts as a signaling molecule.

Radishes contain nitrates that the body uses to produce nitric oxide.
Radishes contain nitrates that the body uses to produce nitric oxide. | Source

Functions in the Nervous System

Nitric oxide has many functions in the central nervous system (the brain and the spinal cord). It plays a role in:

  • learning and memory
  • controlling body temperature
  • regulating food intake
  • controlling the sleep-wake cycle
  • regulating hormone release
  • protecting nerves

The peripheral nervous system is made of nerves that leave the central nervous system and travel to the rest of the body. In the peripheral nervous system nitric oxide does the following:

  • relaxes the muscles in the lining of the gastrointestinal tract
  • relaxes the muscles in the lining of the urinary and reproductive tracts

Neuroprotection and Neurotoxicity

Although nitric oxide is very important in the nervous system, it's present in tiny quantities in our body. These quantities are neuroprotective— they protect the nerves from damage. Large amounts of nitric oxide kill nerve cells and are said to be neurotoxic, however. This might explain why the results of some research studies involving nitric oxide disagree with the results of other studies. For example, some research suggests that NO administered to a patient after a stroke helps the patient, while other research suggests that excess NO produced during strokes damages brain cells.

A macrophage extending its pseudopods, which it uses to engulf pathogens
A macrophage extending its pseudopods, which it uses to engulf pathogens | Source

What Role Does Nitric Oxide Play in the Immune System?

Nitric oxide is made by macrophages, which are a type of white blood cell in our immune system. The NO kills bacteria and inhibits the replication of viruses.

Nitric oxide is part of our innate immune response. This is a rapid, general, and non-specific response, which is the same for any pathogen (organism that causes disease). Our other type of immunity is the acquired immune response, which involves an attack that is specific for each pathogen.

Nitric oxide is a controversial chemical with respect to cancer. Some evidence suggests that it helps the immune system fight cancer, while other evidence suggests that it can actually cause cancer.

C. elegans Swimming and Clumping

Aging and Longevity

Caenorhabditis elegans is a transparent roundworm that lives in soil. Like humans, the roundworm has bacteria that live in its intestine and produce substances that provide health benefits.

C. elegans feeds on a bacterium called Bacillus subtilis. Some of the bacterial cells survive and live in the animal's intestine, where they produce nitric oxide. The worms also eat Escherichia coli, another bacterium that lives in their intestine. Escherichia coli can't make nitric oxide, however.

Worms fed Bacilus subtilis live for about 50 percent longer than worms fed Escherichia coli. This is believed to be at least partly due to the presence or absence of nitric oxide.

One research experiment discovered that C. elegans worms fed normal B. subtilis lived for 15 percent longer than those fed a mutant form of the bacterium that lacked the gene for nitric oxide production. The experiment also confirmed a previous discovery that C. elegans can't produce nitric oxide itself.

C. elegans with a stain added to show its internal anatomy
C. elegans with a stain added to show its internal anatomy | Source

Nitric Oxide Use in the Future

In the future, nitric oxide may be very useful as a medicine. A major problem will be ensuring that the concentration of the nitric oxide is high enough to be helpful but low enough to be safe, however.

In addition, researchers need to learn more about nitric oxide's effects on the body before it's used medicinally. It's a simple molecule but is involved in complex reactions. If NO is administered to treat one health problem, it's important that it doesn't cause another one.

References

The Vital Role of Nitric oxide from Oakland University

Nitric Oxide and Longevity from ScienceDaily

© 2013 Linda Crampton

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    • billybuc profile image

      Bill Holland 4 years ago from Olympia, WA

      Although I'm not a big vegetable eater, I do like broccoli, so I'm feeling pretty good about that right now. :) Great information, Alicia. Thanks for making me feel good about my eating habits.

    • AliciaC profile image
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      Linda Crampton 4 years ago from British Columbia, Canada

      I like broccoli too! It's great that it has so many health benefits. Thanks for the comment, Bill.

    • prasetio30 profile image

      prasetio30 4 years ago from malang-indonesia

      Very informative and useful for us. Thanks for always renew great information about health. I think we should know about this. Keep it up and my vote always for you. Cheers :-)

      Prasetio

    • bdegiulio profile image

      Bill De Giulio 4 years ago from Massachusetts

      Hi Alicia. This was very interesting. I always knew that leafy, green veggies were good for us but I guess I never really knew exactly why and how this all works. Great job explaining all of this.

    • AliciaC profile image
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      Linda Crampton 4 years ago from British Columbia, Canada

      Thank you very much, Prasetio. I appreciate your comment and vote, as always!

    • AliciaC profile image
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      Linda Crampton 4 years ago from British Columbia, Canada

      Thank you for the visit and the comment, Bill. Leafy green vegetables are so healthy - I'm glad that I like them!

    • Mhatter99 profile image

      Martin Kloess 4 years ago from San Francisco

      Fascinating. Thank you for this.

    • AliciaC profile image
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      Linda Crampton 4 years ago from British Columbia, Canada

      Thank you very much for the comment, Martin.

    • aviannovice profile image

      Deb Hirt 4 years ago from Stillwater, OK

      So nitric oxide introduced into out bodies will help us sleep better, vs. wasting money on sleeping aids, I trust?

    • AliciaC profile image
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      Linda Crampton 4 years ago from British Columbia, Canada

      I wish it were that simple, Deb! Much more research into nitric oxide's behavior is needed, as well as research into the correct amount that is needed for treating health problems. It may be very helpful in the future, though. Thanks for the visit.

    • drbj profile image

      drbj and sherry 4 years ago from south Florida

      Fascinating information about nitric oxide, Alicia. Guess I should not say NO to adding more cabbage, beets and broccoli to my diet. Yes?

    • AliciaC profile image
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      Linda Crampton 4 years ago from British Columbia, Canada

      Thank you, drbj. I would say yes to NO in vegetables! Vegetables are healthy foods for many other reasons, too.

    • Fossillady profile image

      Kathi 4 years ago from Saugatuck Michigan

      Your hubs are always so informative and go into depth with added photos and illustrations! Quality information and work! Congrats, Kathi :O)

    • AliciaC profile image
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      Linda Crampton 4 years ago from British Columbia, Canada

      Thank you so much for such a lovely comment, Kathi! I appreciate it very much.

    • kashmir56 profile image

      Thomas Silvia 4 years ago from Massachusetts

      Hi my friend great article, was very interesting and informative and so well written. Well done !

      Vote up and more !!! Sharing !

    • Peggy W profile image

      Peggy Woods 4 years ago from Houston, Texas

      Hi Alicia,

      This is a very interesting article about Nitric Oxide in our bodies. It is good to know some of the natural health benefits and that we can get them from eating our veggies. Also interesting research being done on possible medical applications. It sounds as though much more research needs to be done since there are conflicting conclusions at the current time...but exciting to know. Up, useful and interesting votes.

    • AliciaC profile image
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      Linda Crampton 4 years ago from British Columbia, Canada

      Thank you the kind comment and the vote, Tom. I appreciate the share, too!

    • AliciaC profile image
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      Linda Crampton 4 years ago from British Columbia, Canada

      Hi, Peggy. Thanks for the comment and all the votes. The nitric oxide research is exciting. It will be interesting to see how the substance is used in the future!

    • livingsta profile image

      livingsta 4 years ago from United Kingdom

      So much useful information which I never knew. Thank you for sharing! Voted up and sharing!

    • AliciaC profile image
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      Linda Crampton 4 years ago from British Columbia, Canada

      Thank you very much for the comment, the vote and the share, livingsta! I appreciate them all.

    • jimmythejock profile image

      James Paterson 4 years ago from Scotland

      Lol That broccoli looks like David Haslehoff side on.

    • AliciaC profile image
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      Linda Crampton 4 years ago from British Columbia, Canada

      I hadn't thought of that before! Thanks for the visit, Jimmy.

    • mary615 profile image

      Mary Hyatt 4 years ago from Florida

      Very interesting and informative Hub. Guess we folks just never think of nitric oxide in our bodies. I do love green veggies (except cucumbers!)

      Voted Up, etc. and will share.

    • profile image

      nicket 4 years ago

      mmmmm very good information, great share!

    • Darknlovely3436 profile image

      Annie 4 years ago from NewYork

      one of my favorite vegatables.............

    • AliciaC profile image
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      Linda Crampton 4 years ago from British Columbia, Canada

      Thanks for the comment, nicket!

    • AliciaC profile image
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      Linda Crampton 4 years ago from British Columbia, Canada

      I like green vegetables too, Darknlovely3436, especially broccoli. Thanks for the visit.

    • AliciaC profile image
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      Linda Crampton 4 years ago from British Columbia, Canada

      Thank you very much for the comment, the votes and the share, Mary! I appreciate them all. I like green veggies as well - including cucumber!

    • JCielo profile image

      JCielo 4 years ago from England

      Well researched and very well presented. And I love broccolli! Voted up, useful and shared.

    • AliciaC profile image
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      Linda Crampton 4 years ago from British Columbia, Canada

      Thank you very much, JCielo. I appreciate your comment, as well as the votes and the share!

    • teaches12345 profile image

      Dianna Mendez 4 years ago

      I love broccoli and am so glad to hear of this additional health benefit. Thanks for the information on how nitric oxide can be good for a body.

    • AliciaC profile image
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      Linda Crampton 4 years ago from British Columbia, Canada

      Thanks for the comment, Dianna. It is good to know that broccoli is so healthy!

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