Women in the U.S. who live in homes surrounded by more vegetation appear to have significantly lower mortality rates than those who live in areas with less vegetation, according to a new study

We like plants-and-people stories in the Plant Cuttings collections – especially those that demonstrate the benefits of Man’s association with our vegetable co-habitants of planet Earth. We also like slightly unusual tales, too. This item delivers on both scores. Firstly this is a nice study whose main message is elegantly summarised thus: ‘Women in the U.S. who live in homes surrounded by more vegetation appear to have significantly lower mortality rates than those who live in areas with less vegetation, according to a new study’.

That new study – of 108,630 women in the USA – by Peter James et al. demonstrates that those living in the greenest areas (chlorophyll levels were determined by a satellite image-based vegetation index) had a ‘12% lower rate of all-cause non-accidental mortality’.

Although the team acknowledge that more research is required to determine the nature of this relationship between other natural environmental factors and health, the results do at least show that green vegetation has some ‘protective effect’ on humans. Well, at least for the study’s cohort, who were primarily white, non-Hispanic women of normal weight, but with low levels of physical activity living in metropolitan areas of the USA. However, Mr Cuttings suspects this green advantage can be found for all peoples – even men – but is enough of a scientist to acknowledge that we ought to await evidence-based reports before we can conclude that definitively.

The second part of this item is an article by McGill University (Canada)’s Faculty of Dentistry member Louis Z. G. Touyz and presents his musings on the role of trees and their relationship to human health, in particular oral health and human teeth.* Amongst the items covered is the importance of ‘oral biofilms’ (‘three-dimensional structured bacterial communities … embedded in an exo-polysaccharide matrix’) that can develop on teeth.**

This malevolent microbial mantle contributes to several dental problems such as removal of calcium from the mineral hydroxyapatite, which comprises >95% of enamel (the hard protective outer layer of the tooth), and the diseases gingivitis (‘gum disease’) and periodontitis (a condition affecting the tissues and bone that support the teeth, and which can develop from gingivitis).

Miswak used for dental health. Photo: Iqbal Osman / Wikipedia
Miswak used for dental health. Photo: Iqbal Osman / Wikipedia

A plant-related way of removing this bacterial build-up – revealed to me in Touyz’s paper – is the oral hygiene practice of chewing miswaak (‘a teeth cleaning twig made from the Salvadora persica tree’). Apparently this natural alternative to the toothbrush has been in use for thousands of years, and features prominently in Muslim hygienical jurisprudence, and has many benefits compared to synthetic toothbrushes. Although this plant-people relationship might not lead you to live longer, you should at least reach the end of your days with a full set of teeth – which must be something to smile about (and to smile with)!

*This intriguing article – which also discusses elephants and beavers, herbivores that use their teeth to eat trees to survive in nature – was brought to my attention by Dr Peter Barlow (School of Biological Sciences, University of Bristol, UK). Cheers, Peter!

**Also known commonly as ‘plaque’.

[Ed. – if you’re now itching to try out miswa(a)k for yourselves, there’s a rather charming ‘how to do it’ video on YouTube.]

Further reading

Peter James, Jaime E. Hart, Rachel F. Banay, Francine Laden, 2016, 'Exposure to Greenness and Mortality in a Nationwide Prospective Cohort Study of Women', Environmental Health Perspectives, vol. 124, no. 9

Vincent Zijnge, M. Barbara M. van Leeuwen, John E. Degener, Frank Abbas, Thomas Thurnheer, Rudolf Gmür, Hermie J. M. Harmsen, 2010, 'Oral Biofilm Architecture on Natural Teeth', PLoS ONE, vol. 5, no. 2, p. e9321

Akhilanand Chaurasia, Ranjit Patil, Amit Nagar, 2013, 'Miswak in oral cavity – An update', Journal of Oral Biology and Craniofacial Research, vol. 3, no. 2, pp. 98-101

MuhammadS Zafar, Fayez Niazi, Mustafa Naseem, Zohaib Khurshid, Khalid Almas, 2016, 'Role of Salvadora persica chewing stick (miswak): A natural toothbrush for holistic oral health', European Journal of Dentistry, vol. 10, no. 2, p. 301

Ruchi Banthia, Rita Chandki, Priyank Banthia, 2011, 'Biofilms: A microbial home', Journal of Indian Society of Periodontology, vol. 15, no. 2, p. 111