Plant Cuttings

This image of a Colgan’s Taffy Tolu Chewing Gum chromolithograph advertisement circa 1910 by an unknown artist is a faithful photographic reproduction of a two-dimensional, public domain work of art.

As promised in the previous post, this is the second (of two) on the topic of chewing-gum *. Whilst Part 1 was largely about birch-pitch, ‘gum’ of the Stone-Age variety, this post concentrates on chewing-gum in the 21^st century, and is more of a ‘chewing-gum miscellany’, or potpourri.

Having now absorbed the ancient ‘chewing-gum’ information from Part 1 – and established the product’s botanical bona fides – here’s some more modern-day chewing-gum ‘trivia’ for you to chew over.

This image of Manilkara zapota, whose stem is scored for chicle extraction, by Luis Fernández García is licensed under the Creative Commons Attribution-Share Alike 2.5 Spain license.

First, and putting information about chewing-gum in to some sort of historical context, is “A Brief History of Chewing Gum” by Amanda Fiegl. It is brief, and is a summary of the information presented by “Mayan archaeologist” Jennifer P Mathews in her book Chicle: The Chewing Gum of the Americas, from the Ancient Maya to William Wrigley. For more on the history of chewing-gum, see Elizabeth Nix, and Keith Pandolfi, and this item for more on Sapodilla, the tree that is the source of chicle.

So, much for the present and past, what about the future for chewing-gum? Well, without wishing to stick his neck on the line too much, Mr Cuttings confidently predicts that 30^th September 2024 will be the next National Chewing Gum Day – in the United States of America, that is. Who knew there’d be a day set aside for celebrating that product? In case you need it, there’s more on that national event here, and from Keira Wingate. As long as its celebrated, chewing-gum will continue to exist.

This image of a “Scientifically accurate atomic model of the external structure of the Severe Acute Respiratory Syndrome CoronaVirus 2 (SARS-CoV-2), a strain (genetic variant) of the coronavirus that caused coronavirus disease (COVID-19), first identified in Wuhan, China, during December 2019” by Alexey Solodovnikov & Valeria Arkhipova is licensed under the Creative Commons Attribution-Share Alike 4.0 International license.

Second, we have a very 21^st century role regarding reduction of spread of COVID-19 by chewing gum from Henry Daniell et al. (Molecular Therapy 30(5): 1966-1978, 2022; https://doi.org/10.1016/j.ymthe.2021.11.008). It’s a rather technical piece of work, but my understanding of it is this; some essential background first.

The part of the SARS-CoV-2 virus that allows it to infect human cells and cause COVID-19 is the so-called spike protein (Benedette Cuffari). People infected with COVID-19 have high levels of the virus in their saliva because the virus replicates in the salivary glands of an infected person. Consequently, the virus can be spread to other individuals when the infected person coughs, spits, speaks or sneezes and expels droplets of saliva. A human-produced protein known as ACE2 (angiotensin-converting enzyme 2 (Krishna Sriram et al.)), amongst its other properties (Lobelia Samavati & Bruce Uhal (2020), Front. Cell. Infect. Microbiol. 10: 317; doi: 10.3389/fcimb.2020.00317), binds to the spike protein, which prevents the virus from infecting cells and causing COVID-19.

With that as background, Daniell et al. produced a chewing-gum that contained the ACE2 protein. When mixed with saliva from a COVID-19-infected human source, the gum bound the virus particles. Binding to gum inhibited entry of the virus into the Chinese hamster ovary (CHO) cells (Christian Eberle) that were used to test whether the ACE2-enhanced gum would work as predicted. It did – in this test, in non-human cells. In fact, the ACE2 in the gum worked in two ways. First, by binding to the spike protein on the virus trapping it within the gum. Second, by blocking the ACE2 receptors on the surface of the cells (which act as the entry point for the virus) to deny access to any virus particles not stuck in the gum.

The chewing-gum approach is considered important, necessary – and additional to other COVID interventions, because, “Transmission of SARS-CoV-2 is an urgent concern around the globe due to emerging variants, inadequate vaccination, and limitation of current containment methods” (Daniell et al., 2022). In particular, although vaccinations for COVID-19 have helped (Chris Stokel-Walker, BMJ 2022;376:o298; doi: 10.1136/bmj.o298; Anika Singanayagam et al., Lancet Infectious Diseases 22(2): 183-195, 2022; https://doi.org/10.1016/S1473-3099(21)00648-4), they haven’t stopped all transmission of the virus (Chris Stokel-Walker, 2022). Furthermore, people who are fully vaccinated can still become infected with SARS-CoV-2 (Anika Singanayagam et al., 2022), and pass the virus on to others (Natasha Hinde; Carlos Franco-Paredes, The Lancet Infectious Diseases 22(1): 16-16, 2022; doi: https://doi.org/10.1016/S1473-3099(21)00768-4), and carry a viral load similar to those who are unvaccinated (Carlos Franco-Paredes, 2022).

Certainly, there is a lot more work to be done, and it is not yet known if the chewing gum approach will work in humans and block, or reduce, person-to-person COVID-19 transmission. But, it’s still a very interesting study, due in no small part to chewing-gum. Wouldn’t it be ‘ace’ if it did work though! But, something to be mindful of: with all those trapped COVID particles, that’s a very good reason to ensure that the contaminated chewing gum is appropriately disposed of, not say, stuck to the wall in an American city [See the Penultimately item below…].

Another botanical dimension to this work is the fact that the ACE2 protein was created in chloroplasts within lettuce plants that had been genetically-modified [GM] to make this compound (Henry Daniell et al., Biomaterials 233, March 2020, 119750; https://doi.org/10.1016/j.biomaterials.2019.119750). The plant-produced protein was then extracted and added to the gum for testing. An advantage of this GM plant route is that “This system has the potential to avoid the usual obstacles to protein drug synthesis: namely, an expensive production and purification process”.

For more-accessible reads on Daniell et al’’s fascinating work, see here, here, and the scicomm articles by Jeremy Booth, Elizabeth Gamillo, and Zachary Rogers. A particularly, well-written and user-friendly explanation of the study is provided by Annie Lennon.

This image, “”Apium,” (family Umbelliferae), probably Apium graveolens, (Celery), bears odd-pinnate compound leaves with dentate leaflets on a central stem” is in the public domain.

Third, have you ever wondered how much energy is used in chewing gum*? No, me neither. But, now we don’t need to, thanks to the work of Adam van Casteren et al. (Science Advances 8, eabn8351 (2022); doi: 10.1126/sciadv.abn8351). In the words of the authors’ summary of their investigation: “Any change in the energetic cost of mammalian mastication will affect the net energy gain from foods. Although the energetic efficiency of masticatory effort is fundamental in understanding the evolution of the human masticatory system, nothing is known currently about the associated metabolic costs of chewing different items. Here, using respirometry and electromyography of the masseter muscle, we demonstrate that chewing by human subjects represents a measurable energy sink. Chewing a tasteless odorless gum elevates metabolic rate by 10 to 15% above basal levels”.

In Mr Cuttings’ words, the act of chewing uses energy – and it’s now been measured. If the material that’s chewed – or the compounds it may release – are not swallowed (or, if swallowed, aren’t digested to release materials that can be metabolised by the body and contribute to a gain in energy), then it sounds like chewing as an activity is a way to burn off calories and may lead to some weight loss**. Which is fine if you have enough food. But, and linking to the previous post’s studies about ancient humans, time spent on birch-pitch chewing activity doesn’t give the body any benefit from an intake of calories point of view. However, if that activity leads to something that does – e.g. acquiring animal protein from prey killed with the axe or arrow in whose construction the pitch was used – then it can be seen as a worthwhile investment of time, and energy.

But, rather than just being a theoretical exercise in determining the energy costs associated with chewing, the study has relevance to an understanding of human evolution. For instance, van Casteren et al. recognise that, in contrast to modern humans, “for our ancestors, before the onset of cooking and sophisticated food processing methods, the costs [of chewing] must have been relatively high”. That’s not to stay that our ancestors thought to themselves, “There’s so much energy used-up in all this chewing, let’s create more-easily chewed crops and cooking to reduce the amount of chewing needed to consume meat, etc. so those previously ‘wasted’ calories can now go into bodily growth and development”. But, any developments that had the effect of reducing this ‘masticatory burden’ would act as a driver for enhanced human evolution. As van Casteren et al. say at the end of the discussion section in their paper, “While much research has focused on how food processing technologies (tools, fire, and agriculture) may have released early humans from the temporal and physical binds of oral food processing, our data suggest that there is also likely a significant energetic component to this dynamic”.

For more on this work, see the scicomm items by Margaret Osborne, Sara Loy, and Andrew Curry.

This image of an F-86 Sabre during the Heritage Flight Training Course at Davis-Monthan AFB, Tucson, Ariz., Mar 5, 2016 by JM Eddins Jr. is a work of a U.S. Air Force Airman or employee, taken or made as part of that person’s official duties. As a work of the U.S. federal government, the image or file is in the public domain in the United States.

Antepenultimately, and something that casts a whole new light on Target chewing-gum, is a question posed by the Smithsonian Magazine: What fighter pilot used gum on his windscreen as a gunsight?

The answer is Frances “Gabby” Gabreski (Todd Neikerk). Although a veteran flier of the Second World War (Thomas Hughes et al.)***, he was unfamiliar with the controls of the F-86 (the airplane he flew in the Korean War (Allan Millett)). Not a problem, he replaced the radar-controlled gunsight with a wad of chewing gum (Stephen Sherman). Which bit of conflict DIY appears to have worked because Grabski became an ‘ace’ in that conflict as well, destroying 6.5 enemy aircraft (Stephen Sherman). Which item leads to the inescapable conclusion that chewing-gum can kill: You have been warned(!)****.

This image of the Gum wall in Seattle (Washington, USA) by Diego Delso is licensed under the Creative Commons Attribution-Share Alike 4.0 International license.

Penultimately, did you know that there is such a thing as the ‘gum wall’? It’s not actually a wall made from chewing gum, but one that’s adorned with masses of the masticated material, in Seattle (USA) (Gregory Lewis McNamee), in Park Place Market*****. Famously, the wall was cleaned in 2015 (Danny Lewis) with the intention of removing the “estimated 1,000,000 pieces of chewing gum [that] are stuck to the quirky attraction”. Apparently, cleaned because “it began attracting rats”, the operation was estimated to have removed gum whose “total weight could be almost a tonne” (Rachel Blundy). However, designated an official tourist attraction by the city of Seattle in 1999 (Kay Kingsman), it didn’t take long for the bare wall to return to its former gooey, gummy glory, thanks to the visiting gum-chewing visitors. If you can face it, Kristin Kendle shares “8 Weird Facts About Seattle’s Gum Wall” [according to Mr P Cuttings, “you’ll never believe No. 4”]. For some sort of balance, it is worth mentioning that there’s another gum wall in the USA, in California*****.

This image of Stranger Visions Portraits (2012) by Heather Dewey-Hagborg is licensed under the Creative Commons Attribution-Share Alike 4.0 International license.

And, finally******, if that gum wall – the ultimate in ‘masticatory murals’? – is a little too big for your artistic appreciation, how about the much-smaller-scale artworks created by Heather Dewey-Hagborg? Artist Heather produces portraits of people whose characteristics are inspired by those revealed by analysis of the DNA that’s found in the chewing-gum (and hair, and discarded cigarette butts) found in public places (Megan Gambino). I don’t know much about modern art [so, am aware that I need to tread carefully when expressing any view on this controversial and divisive matter (Jason Kottke, Rob Alderson)], but I ‘chews’ Heather Dewey-Hagborg’s portraits. It’s my choice, and I’m … err … sticking to it.

So there you have it; chewable gum, a brilliant – but blatantly bizarre – buccal botanical (and barely a big-up of the bubble-blowing kind)******.

* Mr P Cuttings is distinguishing ‘chewing-gum’, the chewy product, from ‘chewing gum’, the act of masticating the chewy product.

** Here it would be remiss of me not to mention the notion of ‘negative calorie foods’ (Eva Hamrud). This term is applied to the consumption of foodstuffs for which the act of chewing is supposed to use more calories than the body will acquire from their digestion, absorption and assimilation by the consumer. Even though celery (Yvette Brazier) is the classic example of this sort of foodstuff, the idea of negative calories is a myth in that instance (Sarah Wells; ME Clegg & C Cooper, Proceedings of the Nutrition Society. 2012;71(OCE3):E217; doi:10.1017/S0029665112003084). Whilst celery-chewing consumes calories, the calorific value (‘energy content’) of the celery – if swallowed, and digested, etc. – is greater that the energy required to chew it (Sarah Wells). Although there probably are no ‘negative calorie’ foods (Sarah Wells), the same cannot necessarily be said for other chewing activities of materials with no food value. Accordingly, chewing – but not swallowing – chewing-gum will only use energy (e.g. Eva Hamrud). Most modern humans who chew gum will get enough calories to stay alive and healthy. However, ancient peoples – such as inhabitants of Stone-Age Scandinavia [discussed previously, in Part 1] – would need to ensure they did get sufficient calories from foodstuffs proper to replace those lost in birch-pitch tar-chewing activity to ‘keep body and soul together’.

*** And was a much-decorated fighter ‘ace’ of World War II who was credited with 28 ‘kills’ (Scot Christenson).

**** Before anybody writes in about this point, Mr Cuttings has asked me to let you know that this comment was made rather ‘tongue-in-cheek’ , as a bit of gallows or black humour. But, it remains a valid interpretation – albeit in a very limited and specific aerial combat (David MacIsaac) context, if you were flying for the ‘wrong team’, and up against Mr Gabreski, in Korea, between 25 June 1950 and 27 July 1953…

***** Iconic as they no doubt are considered to be, the scale and grossness of these magnificent ‘monolithic monuments to mastication’ raise the question of whether chewing-gum (and chewing gum)* – or, at least, its disposal in public places – should be banned. Since 1992 chewing-gum has been banned in Singapore. The ban, which includes all gum substances of vegetable or synthetic origin such as bubble gum and dental chewing-gum, carries a hefty fine and possible jail term for those caught importing, selling or manufacturing chewing-gum. However, the ban was partially lifted – in March 2004 to exempt gums with therapeutic value such as nicotine gum and oral dental gum – after the Singaporean government allowed the sale of gum under the free-trade agreement signed with the United States of America. Furthermore, in Dubai, during Ramadan (Jennifer Williams; Mohammad Hassan Khalil), you are not allowed to chew gum in public. And, ‘celebrity chef’ Jamie Oliver (Barbara Schreiber) has called for chewing-gum to be banned in the UK (Lizzie Edmonds) because people who spit it out on the streets make Britain look “like a bomb site”, and banning it would make the country a “healthier, happier, cleaner place to live.” Hard to disagree with that sentiment.

****** Mr P Cuttings apologises because, what this round-up of gummy matters hasn’t provided is the answer to the question posed by Lonnie Donegan (Billy Bragg) “Does your chewing gum lose its flavour on the bedpost overnight?” Still, isn’t it somewhat comforting that we’ve not – yet – solved all of life’s little mysteries?