In my series of articles about chemical elements in the human body, and how they relate to making a planet habitable (per Michael Denton’s Privileged Species books), I added to some of Denton’s information about Earth’s supply chains for vital elements like zinc, phosphorus, potassium, copper, manganese, iron, and even boron and cobalt. But I must confess, I did not know (or had forgotten) that the body needs nickel. That is, I didn’t know until I ran across a recent update to an article at The Nutrition Source from the Harvard School of Public Health. Here’s the 5-cent version:
Nickel is a ubiquitous mineral found in soil, water, and air. In the human body, it is a component of certain enzymes involved with chemical reactions and may assist with iron absorption. The absorption of nickel can depend on specific foods it is eaten with, including milk, tea, coffee, and orange juice, which either increase or decrease its absorption. However, studies suggest that the overall absorption of dietary nickel is low, at less than 10%, and the majority of ingested nickel exits the body in urine or stool. Nickel is not stored in most tissues or organs, with the exception of the thyroid and adrenal glands. [Emphasis added.]
This sent me on a search to learn more. What enzymes need nickel, and how do they work? Does nickel occupy a central core of any enzymes, as with iron in hemoglobin? What are the food sources for nickel? What other organisms use nickel? And is nickel availability a requirement for a planet’s habitability? Does it contribute to Denton’s privileged species hypothesis and make an argument for design?
Nickel (atomic number 28) sits in the middle of the first full row in the periodic table, next to iron (26) and cobalt (27), copper (29) and zinc (30). It is among the vital “transition metals” that Denton emphasizes are uniquely fit for complex life (The Miracle of the Cell, Chapter 6). Transition metals are able to form compounds with other elements and engage in redox reactions. The 24th most abundant element in the Earth’s crust, nickel is ubiquitous but only in small amounts. The U.S. 5 cent coin with Thomas Jefferson’s image is actually 75 percent copper, says the U.S. Mint, with a nickel alloy making up the remainder. If you find a “Buffalo nickel” (minted 1913 to 1938), with the portrait of a plains Indian on one side, keep it or sell it; it can be worth from $10 to hundreds of thousands of dollars, says one coin collector source.
Nickel and Human Health
One thing I noticed was that not much research has been done on nickel in the human body. Let’s start with “The Facts on Nickel” from a Dartmouth College website about toxic metals.
Nickel has been shown to be an essential trace element in several animal species and is likely to be essential in humans. However, there is no known condition in people that has been associated with nickel deficiency, and it is likely that we get all the nickel we need from its ubiquitous presence in food and water.
WebMD agrees: “Nickel is an essential nutrient in some chemical processes in the body,” but then says, “Its precise functions in the body are not well understood.”
The amount of nickel we need is very tiny, and not hard to obtain.
Human beings unknowingly ingest a daily average of 170 micrograms of nickel, a tiny amount less than the mass of a single grain of sand. Trace amounts of nickel are present in the air we breathe, and in household products from faucets to shampoo. These amounts have no known effect on human or ecosystem health.
For those working in industries where they are exposed to nickel dust, the effects can be toxic. But, the article says, one would have to inhale some 50,000 to 100,000 times the amount most of us are exposed to. “Fortunately for most people, such chronic exposure to nickel is rare.”
Eat Your Nickel — in Moderation
What foods contain nickel? Dartmouth lists, “herring, sprouts, asparagus, peanuts, mushrooms, rhubarb, corn, cocoa, tomatoes, cabbage, oysters, beans, onions, spinach, peas, pears, raisins, tea, baking powder, whole wheat flour, foods cooked with nickel utensils, all canned foods.” WebMD adds, “nuts, dried beans, and chocolate.” The amount of nickel in these foods varies, depending on the nickel content of the soil or water in which they were grown or farmed. For these reasons, nickel deficiencies are rare, but contact dermatitis from nickel allergy affects 10-20 percent of people.
The body seems to know how much nickel to keep. “Most of the nickel in the bloodstream is removed by the kidneys and passed out of the body through urine,” says Dartmouth. “Ingested nickel passes through the gastrointestinal tract but does not get absorbed.” Nickel competes with iron for absorption, says Harvard, which can be alleviated by eating iron-rich food and taking vitamin C. But earlier, the same article says that “it is a component of certain enzymes involved with chemical reactions and may assist with iron absorption.”
One paper from 2020 attempted to establish reference levels for nickel in the internal organs. Studies from autopsies from sixty Polish people found wide variance in nickel abundance depending on the organ. Most of it was found in the liver and kidneys, somewhat less in the lungs, with the least found in the stomach and brain. It did not mention the adrenal glands and thyroid, perhaps because they didn’t look.
What About Those Nickel Enzymes?
Three years ago, in a survey of metals used in life, Casey Luskin quoted a horticultural source about some of the nickel-containing enzymes in plants, but did not mention animal enzymes. I couldn’t find any other mentions of nickel enzymes here at Evolution News, so I searched for information. I hit the jackpot with a 2020 paper in Protein Science. It says that all life uses nickel enzymes, and cells must handle and regulate it with care. Enjoy this opening paragraph:
Nickel enzymes, present in archaea, bacteria, plants, and primitive eukaryotes are divided into redox and nonredox enzymes and play key functions in diverse metabolic processes, such as energy metabolism and virulence. They catalyze various reactions by using active sites of diverse complexities, such as mononuclear nickel in Ni‐superoxide dismutase, glyoxylase I and acireductone dioxygenase, dinuclear nickel in urease, heteronuclear metalloclusters in [NiFe]‐carbon monoxide dehydrogenase, acetyl‐CoA decarbonylase/synthase and [NiFe]‐hydrogenase, and even more complex cofactors in methyl‐CoM reductase and lactate racemase. The presence of metalloenzymes in a cell necessitates a tight regulation of metal homeostasis, in order to maintain the appropriate intracellular concentration of nickel while avoiding its toxicity. As well, the biosynthesis and insertion of nickel active sites often require specific and elaborated maturation pathways, allowing the correct metal to be delivered and incorporated into the target enzyme.
The amounts may be tiny, but nickel appears to be under similar regulation as other transition metals. Nickel-iron clusters (NiFe) play a surprising variety of essential roles in the body. And in answer to my question, all life needs it: from archaea on up. An ironic conclusion of these studies is that, unbeknownst to the sculptor, both images he portrayed on Buffalo nickels had nickel inside their bodies!
Do all rocky planets have nickel? And is it available on the surface? Those were my next questions. Rocky planets that have undergone differentiation, like Mars, Earth, Venus, and Mercury, are thought to have a nickel-iron core. That’s because the heavier elements sink to the center when the planet is molten. Nickel down in the core, though, is not going to help life on the surface needing NiFe hydrogenase or Ni-superoxide dismutase. One report suggested that most of the nickel on Earth’s crust was delivered by meteorites along with iron. Volcanoes are other potential suppliers of nickel from the mantle to the surface.
This leads to another question: Can a habitable planet host life without nickel? Astrobiologists tend to focus on the abundant elements used by life as we know it (CHON: carbon, hydrogen, oxygen and nitrogen). I could not find any astrobiology sources that were worried about the availability of nickel, but maybe they should be. Astrobiologist Christopher McKay said in a 2014 PNAS paper that there was no list of essential elements.
If liquid water and biologically available nitrogen are present, then phosphorous [sic], potassium, sodium, sulfur, and calcium might come next on a requirements list, as these are the next most abundant elements in bacteria. However, there is no definitive list and any list would depend on the organism considered; for example habitability for methanogens requires high nickel levels.
Some papers like this one from Uppsala University suggest that nickel might have played a role in the origin of life, but that’s just speculation. It merely assumes that nickel would be available.
Nickel and ID
Lastly, does nickel contribute to the fine-tuning argument for intelligent design? Perhaps it doesn’t by itself, but the higher the number of chemical elements scientists find are essential for life, the more difficult it becomes to think that all of them would be available on other planets. If we can add nickel to the list, the argument becomes stronger. That’s worth at least a copper penny for thought, if not a $100,000 Buffalo nickel.