I have titled my post “Betel nut quid chewing & ischaemic heart diseases: where is the missing link?” for several reasons.
Betel nut chewing is widespread in the Asia-Pacific Region, including Papua New Guinea. The method of chewing varies from country to country. In Asian countries betel nut is chewed with tobacco and spices wrapped in betle piper leaf, whereas in PNG betel nut is chewed with the betle piper inflorescence (flower) dipped in lime powder. Lime powder in PNG is made from heated corals or sea shells. After chewing the mixture turns red and is chewed, lasting about one hour.
What drives this habit? Betel nut is chewed mainly for its mild euphoric and stimulatory effects. It is also relaxes the intestines and after a full meal, most people in PNG go for a betel nut. The last 10 years has seen the habit of chewing betel nut reach wide proportions in PNG largely due to income the selling of betel nut generates for growers and retail sellers in PNG towns and cities. In fact betel nut has been found to be a sensitive indicator for the consumer price index (CPI) in PNG by the Central of Bank of PNG. And it is the only market food item listed as an indicator of a rise or a fall in CPI in PNG!
Betel nut chewing is strongly linked to mouth cancer, a topic that has been widely researched and WHO now recognises betel nut as a carcinogen.
However, the link between betel nut chewing and heart diseases is just emerging and that is the area of my interest and this post. I did a study on betel nut chewers in PNG as a third year medical student at the Sir Buri Kidu Heart Institute under the supervision of Sir Professor Isi Kevau, professor of internal medicine and director of the institute (Sir Kevau was not a knight back then). What I found out was 2 things:
- Betel nut chewing increases the resting heart rate significantly which lasts for 7 minutes and returns to normal after 20 minutes. This effect was observed in both novices and habitual chewers.
- Betel nut chewing produces variable effect on the blood pressure – where we saw either a decrease or no response in blood pressure in chewers and non-chewers. In a subset of hypertensive patients we studied also had variable response after chewing betel nut.
After I left the Sir Buri Kidu Heart Institute after one year of betel nut research, Dr Jochita Jothimanickam worked with Professor Kevau and showed that betel nut chewing induces chest pain and ischaemia (low blood supply) to the heart muscles.
Our hypothesis: we proposed in 1998 that betel nut chewing causes paradoxial vasoconstriction (narrowing of blood vessels) in patients with coronary artery diseases probably via a mechanism similar to observed in rats after the injection of acetylcholine (arecoline & acetylcholine have a similar chemical structure). Arecoline is the main chemical compound in betel nut thought to produce effects in chewers. You can download (BETEL NUT CAUSES PARADOXICAL VASOCONSTRICTION IN PATIENTS WITH) a PDF copy of the abstract our paper here. The paper was presented at the 1998 Asia-Pacific Cardiac Society in Auckland, New Zealand.
Recent evidence from epidermiological studies in several Asia countries are now seeing an association between betel nut chewing and heart diseases. There is also association between betel nut chewing and diabetes, metabolic syndrome, hypertension and subclinical ischaemic heart disease. However, statistical association does not mean causal relationship. In other words, the epidemiological association does not necessarily translate to a biological cause-effect relationship! But from experience, epidemiological evidence precedes our molecular understanding of disease cause-effect relationships. The smoking and lung cancer story showed us that.
So the question remains: “what is the link between betel nut chewing and heart diseases?”
That is the next phase of my betel nut research project.
I am looking for potential collaborators and if you read this post and you are interested, email me.
Very interesting post Rodney. I am diabetic but luckily don’t chew betel nut. I tried it once and hated how it dried my mouth.
Cheers Brian
Yes, very interesting. I am working on a rat model to test my hypothesis..good you did not try it!
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Hi Rodney,
Your BMedSci. research findings are interesting.
As many things in life, betel nut chewing may only be one factor amongst multiple associates of coronary heart diseases. Therefore, finding a link between betel nut chewing and heart diseases would be an enormous project requiring a multifactorial approach and substantial logistics and funding support. Furthermore, studies on mice models may not add much value. For instance, if you give arecoline (or its metabolite) to one group of mice compared to an arecoline non-treated group, the dosage you would require to see an effect that is clinically relevant in humans may be very high and the results may be difficult to translate or extrapolate to human.
A simpler cost-effective but clinically relevant study design would be to conduct a randomised controlled trial further examining point 2 of your BMSci findings. To conclusively determine if betel nut chewing has variable effects on blood pressure, you might consider doing an open label randomised controlled trial on hypertensive versus non-hypertensive patients (with and without betel nut). Prior to that, define your groups, sort out definitions, do a proper samples size calculation based on your BMedSci. work in order for your study to have appropriate power and also determine a primary endpoint for the clinical trial. Then get MRAC ethical approval and do serial BP checks in patients over determined periods (preferable similar to the time-points in your previous studies with Sir Isi Kevau or similar studies in the literature (if there’s any), but the point is- to make your findings comparable, if possible. This may give you a conclusive finding on the effects of betel nut on BP and lead you on to other questions that have important clinical implications for our setting.
On another note, well done on your posts, they are very informative. Keep it up.
Moses.
Thanks Moses for the tips.
Rodney
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