House plants - There was a surge in the 70’s to bring the outdoors in, use them as a major feature of the home. Hanging plants, ferns, crawlers, and palms – part of that Feng Shui movement we saw come through in conversation of every household back in the day.

If your mum didn’t have a crispy leafed Bonsai that she had either overwatered or left to die that was then moved into a hidden spot on the patio out the back, did you even take part in the Feng Shui trend!?

Making a Comeback!

Now, as with all fashion trends we are seeing a huge come back of the indoor houseplant – much like pokemon for adults, there is rare types, common types, and collectors’ pieces that are flexed on social media in their fancy pots. Some have indoor jungles almost – and many lay claim that they have a ‘calming effect’ on the atmosphere of their indoor space and that they feel they have actual health benefits on mood, air quality and sleep.

Is this anecdotal or is there some substantiating evidence to this effect of having plants around us inside? We turned a new leaf to find out the science behind these effects that were being spoken about in the masses.

Humble House Plant and our Connection with Nature

Humans and animals have a very close connection with nature, but we have also adapted to survive from nature as she is a wild beast and we have evolved to build shelter from her lashings and storms. The modern human spends around 80-90% of their time indoors now [1], under artificial lighting and around plastic, metal and four walls containing us in a space. It’s any wonder we begin to crave some greenery!

But do these green machines actually assist us while indoors with the following?

• Air purification?
• Sleep?
• Psychological health?

• Cognitive Performance?

Let’s first break down the function of plants in the environment as a whole first…

Plants have an important list of jobs to do!

Photosynthesis – this is a process by which plants convert carbon dioxide in the air (CO2), Light received in and water into energy and we get oxygen (O2) as a result! Oxygen as we know is essential for all living organisms to live and thrive.

Introducing negative air ions – you might have heard or potentially not, that when we go to the beach that the experience feels so euphoric because we get more ‘negative ions’. There is genuine method to this madness of why we feel so good when we visit the beach, but we are looking at plants more specifically today. Photosynthesis by plants produces negative air ions (NAIs), these have been documented for the effects on human and animal health for over 100 years now and there is machinery in the industrial world we live in now that provides these in the air quality knowing their effects [2].

Air Ions are electrically charged molecules or atoms that exist in the atmosphere around us, and to get slightly nerdier (for the justification later of buying more indoor plants), an ion in the air or air ion as it is termed is formed when a gaseous molecule or atom receives enough high energy that it actually ejects an electron. To get weirder, a negative air ion actually takes up that ejected electron and positive ions actually are the ones that lose it. Cool huh! The energy sources that utilise this action are [2]:

• Radiant or Cosmic Rays in the atmosphere.
• Sunlight and that which especially denoting to Ultraviolet.
• Thunder and lightning in the atmosphere.
• Fast-moving water. (there is your beach explanation)
• Plants.

How does something ‘negative’ impact us positively?

Kruger and Reed hypothesized and reviewed data in 1976 on the biological effects that small negative air ions had on human health [3]. Particularly in regards to Serotonin levels interestingly, a very important and powerful neurohormone in humans. Its reach for effects in the body expand to Neurovascular, endocrine, and metabolic effects in our body – This includes both mood and sleep regulation [4,5].

More substantiating evidence around mood and anxiety/depressive states is required to draw a line in the sand on this one as a definitive factor around house plant benefits, but there is promising data emerging to give weight to the anecdotal feelings that people state they feel when having interactions with nature on their mood and mental health. Interestingly though, if you were to look deeper down the rabbit hole of Negative Ion aspects for internal habitat, they do appear to be produced by plants more so in and around electric field submersion [6] and in particular the wide blade variety [7]!

To house plant or not to house plant – That is the question…

Houseplant. Simple, if you love having plants and they make you feel great – then why not build an indoor jungle!? As for the negative air ions – they do have proven effects on the capacity to absorb dust, clean the air around you by efficiently controlling super fine aerosols and pollutants [8]. Measuring the yield from indoor plants is the challenge here however. Again, if you love having them as we do in the office, our office is packed with plants! Then, you collect that rare monstera and don’t let anyone tell you otherwise!

References

1. Ferguson, K. T., Cassells, R. C., MacAllister, J. W., & Evans, G. W. (2013). The physical environment and child development: an international review. International journal of psychology : Journal international de psychologie, 48(4), 437–468. https://doi.org/10.1080/00207594.2013.804190
2. Jiang, S. Y., Ma, A., & Ramachandran, S. (2018). Negative Air Ions and Their Effects on Human Health and Air Quality Improvement. International journal of molecular sciences, 19(10), 2966. https://doi.org/10.3390/ijms19102966
3. Biological impact of small air ions. Krueger AP, Reed EJ Science. 1976 Sep 24; 193(4259):1209-13.
4. Environmental influences on serotonin and cyclic nucleotides in rat cerebral cortex.Diamond MC, Connor JR Jr, Orenberg EK, Bissell M, Yost M, Krueger A Science. 1980 Nov 7; 210(4470):652-4.
5. The effect of exposure to negative air ions on the recovery of physiological responses after moderate endurance exercise. Ryushi T, Kita I, Sakurai T, Yasumatsu M, Isokawa M, Aihara Y, Hama K Int J Biometeorol. 1998 Feb; 41(3):132-6.
6. Tikhonov V.P., Tsvetkov V.D., Litvinova E.G., Sirota T.V., Kondrashova M.N. Generation of negative air ions by plants upon pulsed stimulation applied to soil.  Plant Physiol. 2004;51:414–419. doi: 10.1023/B:RUPP.0000028690.74805.e2.
7. Changes in negative air ions concentration under different light intensities and development of a model to relate light intensity to directional change.Wang J, Li SHJ Environ Manage. 2009 Jun; 90(8):2746-54.
8. Steffan, Joshua & Brevik, Eric & Burgess, Lynn & Cerdà, Artemi. (2018). The effect of soil on human health: An overview. European Journal of Soil Science. 69. 159-171. 10.1111/ejss.12451.