Biological Function Found in Cyanide

Refuting the toxin myth: 
Cyanide turns out to be
an essential compound
(in tiny amounts)

 

by Jerry Bergman, PhD

One myth that persists no matter what evidence is presented is the myth that some chemicals are toxic regardless of the amount. And the converse is that some chemicals are safe except at extreme levels. In fact, as correctly stated by the Swiss physician and chemist, Paracelsus (1493-1541), the dose is the poison. In other words, all chemicals are safe in small amounts, and all are dangerous in large amounts.

Tiny Amounts of Arsenic

This fact was discovered by an event that occurred 300 years ago. The event began with a wedding. The wedding was a community event. The bride was gorgeous and the groom handsome. Not long after the wedding, rumors spread about the groom’s infidelity. Soon, he died from poisoning. The medical examination showed large amounts of the metal arsenic in his body. The bride claimed she was innocent, but the jury thought otherwise, and she was convicted of murder and sentenced to life in prison. On her deathbed, she admitted she did poison her husband, but with strychnine, not arsenic.

Due to similar experiences, the medical staff eventually realized that many very healthy people have measurable amounts of arsenic in their body. The medical community then researched the issue by evaluating a large sample of persons and discovered that a significant percent of the world population has measurable amounts of arsenic in their bodies.[1] It was also widely believed for the past century that poisons, such as arsenic, have no function in the body. It seemed logical to assume that a dangerous toxin which harms the body could not have functions that confer benefits in the human body.  However, this conclusion has been proven incorrect. Research has now documented that, in certain plants and animals, arsenic does have important uses.[2]

How Do We Determine the Function of Chemical Compounds in Humans?

The difficulty in experimentally determining the functions of compounds, such as arsenic, in humans is problematic in view of the fact that arsenic is found in small amounts in all we eat and drink. The main way we learn the function of a molecule is to deprive the body of the compound and then determine what effects result from its deprivation. Furthermore, because humans require only very small amounts, it is difficult to totally deprive them of the molecule. A common method used to determine the function(s) of elements or compounds which only small amounts are required in the body is to recruit subjects, often students, then feed them a diet that does not contain the element or compound being tested. Then, careful health examinations are completed to determine the effects of its lack.  This review brings me to a new discovery, namely that the dangerous poison cyanide, in contrast to the wisdom of the last century, plays a major role in the health of the human body.

Cyanide As A Toxin

Cyanide is a highly toxic chemical that is fatal in small amounts. The lethal dose in humans is 0.5-1.5 mg/kg body weight. It can be taken into the body by ingestion, inhalation, or skin absorption. Symptoms, which typically begin to appear within minutes, include headaches, dizziness, nausea, vomiting, seizures, coma, and death.

Cyanide inhibits cellular respiration by binding to the Cytochrome C Oxidase enzyme. The result is that cells are prevented from using oxygen, leading to tissue damage and death. It has been used as a poison in war, mass homicides, and suicides. And for centuries it was believed that cyanide had no useful functions in humans.[3]

New Research Overturns Years of Beliefs About Cyanide

The claim that cyanide serves no useful function in humans has now been refuted. In a global study published in Nature Metabolism by Karim Zuhra et al., a research team from seven countries and 12 universities has upended the world’s former consensus on cyanide.[4]

The researchers found that it plays a critical role in normal cell functions. Human cells actually produce cyanide, specifically hydrogen cyanide. Its specific function is as a crucial signaling molecule.[5] The discovery was the result of the observation that hydrogen cyanide was found to be present in most cells and entire organisms, including the liver and bloodstream of both mice and humans.

The researchers demonstrated that cyanide was produced naturally, evidence that it had a role in fundamental physiological processes. Experiments conducted during the Zuhra et al. study have documented that hydrogen cyanide can enhance cell survival during oxygen deprivation events, such as during a stroke or heart attack. For this reason, cyanide plays an important role in the body’s protective mechanisms against conditions such as strokes.

This finding should not be too surprising because cyanides are naturally produced in some types of bacteria, fungi, algae, and even in certain plants. Zuhra et al. also found that the amino acid glycine stimulates cyanide production in liver cells.

The question this research has raised is Why doesn’t the cyanide produced in the body poison the human? The reason is that the Rhodanese enzyme rapidly converts hydrogen cyanide into thiocyanates, which are nontoxic salts that are effectively eliminated from the body.[6]

Another Example of Irreducible Complexity

This finding by Zuhra et al. is yet another example of irreducible complexity. To achieve cyanide’s role in fundamental physiological cellular processes without killing the person the production of both the cyanide and the Rhodanese is required. Without the Rhodaneses, the cyanide build-up would kill the person; thus, both systems must co-exist must exist as a system set in the human body.

This research is another example of the principle Paracelsus formulated in the 1500s because the findings support Paracelsus’s conclusion that the dose determines whether cyanide acts as a poison or has beneficial effects.[7] The Zuhra et al. research also supports the fact that, as our understanding of the body progresses, discoveries, such as the cyanide-Rhodanese system, are another example of the complexity of life. As our understanding of the body progresses, discoveries like the cyanide-Rhodanese system provide further support for the complexity of life.

References

[1] Forney, Robert. 1998. Class notes Medical Toxicology. Toledo: Medical College of Ohio.

[2] Biologic Effects of Arsenic on Plants and Animals. Washington (DC): National Academies Press (US); 1977. https://www.ncbi.nlm.nih.gov/books/NBK231025/

[3] Graham, Jeremy. “Cyanide toxicity,” https://www.ncbi.nlm.nih.gov/books/NBK507796/, 2023.

[4] Zuhra, Karim, et al., “Regulation of mammalian cellular metabolism by endogenous cyanide production,” Nature Metabolism 7:531-555.

[5] Zuhra, et al., 2025.

[6] Zuhra, et al., 2025

[7] DeHaven, Addison, “Cyanide plays a major role in the human body, study reveals,” https://medicalxpress.com/news/2025-03-cyanide-plays-major-role-human.html, 27 March 2025.

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Dr. Jerry Bergman has taught biology, genetics, chemistry, biochemistry, anthropology, geology, and microbiology for over 40 years at several colleges and universities including Bowling Green State University, Medical College of Ohio where he was a research associate in experimental pathology, and The University of Toledo. He is a graduate of the Medical College of Ohio, Wayne State University in Detroit, the University of Toledo, and Bowling Green State University. He has over 1,900 publications in 14 languages and 40 books and monographs. His books and textbooks that include chapters that he authored are in over 1,800 college libraries in 27 countries. So far over 80,000 copies of the 60 books and monographs that he has authored or co-authored are in print. For more articles by Dr Bergman, see his Author Profile.