Wednesday October 2 2013
Tightening your belt is more likely to cause indigestion than cancer
"Wearing your belt too tight can raise your risk of getting throat cancer…as it increases your chance of suffering acid reflux," is the unnecessarily alarmist headline in The Daily Telegraph.
In fact, in an experiment which asked people to wear a weightlifter’s belt, researchers found changes in the cells at the junction between the stomach and the oesophagus.
These changes can cause acid to leak back up (acid reflux) from the stomach and into the junction. However, it is unlikely that this will trigger the onset of throat cancer.
Researchers also found that volunteers wearing a waist belt had more signs of acid reflux in this area than those who did not, and that this was more marked in those wearing a waist belt who also had a large waist circumference.
This was a very small, experimental study which lasted only a few days. It did not measure cancer as an outcome. While obesity is a risk factor for several cancers, wearing a waist belt is unlikely to be harmful – particularly if it is not too tight.
Where did the story come from?
The study was carried out by researchers from the University of Glasgow, Universiti Sains Malaysia, the University of Strathclyde and Southern General Hospital, Glasgow. There is no information about external funding.
The study was published in the peer-reviewed medical journal, Gut.
Both The Daily Telegraph’s and the Mail Online’s references to throat cancer are misleading. The research looked in particular at where the lower part of the oesophagus joins the stomach. The study did not find that wearing a tight belt “can give you throat cancer” – it did not look at cancer outcomes.
It appears that the media interpretations of the study’s findings were influenced by the comments of the lead author of the study, Professor Kenneth McColl. Prof McColl highlighted the risk of cancer in an interview with the Scottish Daily Record. Unfortunately, the professor's point about a small increase in risk has become a simplistic, "tight belts equal cancer" headline. This should serve as a warning for any academic discussing their findings with the media.
What kind of research was this?
This was an experimental study involving 24 volunteers, which aimed to look at the effects on the gastro-oesophageal junction (where the oesophagus opens into the stomach) of wearing a belt and increased waist circumference (a measure of obesity).
The researchers point out that in the developed world there is a high incidence of adenocarcinoma – a type of cancer that develops in the lining of certain organs and areas of the body. Adenocarcinoma of the stomach is largely a result of infection with H. pylori – a common bacteria thought to infect up to half of the world’s population.
In contrast, adenocarcinoma of the oesophagus is often the result of damage to cells brought about by acid reflux – when the acid the stomach uses to digest food escapes from the stomach, back into the oesophagus.
Researchers suggest that similar to the oesophagus itself, the vast majority of these cancers in the gastro-oesophageal junction are probably due to cell changes caused by chronic acid reflux. The puzzle is that patients with cancers in this area do not have the usual symptoms of reflux (such as heartburn or a burning feeling in the chest). The researchers thought that these cells may still be damaged by stomach acids, even in the absence of reflux symptoms.
The researchers say they have found in previous studies that healthy volunteers without reflux symptoms can develop inflammation in this area and that this type of cancer is already associated with increased body mass index and waist circumference. They suggest another lifestyle factor which might be important is the use of waist belts.
What did the research involve?
The researchers recruited 24 healthy volunteers without any history of reflux. Twelve of the volunteers had normal size waists (defined as less than 94cm in men and 80cm in women) and 12 had increased waist circumference (more than 102cm in men and more than 88cm in women).
Using an endoscope (a thin, long, flexible tube with a light source and a video camera at one end) researchers checked that none of the volunteers had hiatus hernia (where the stomach squeezes into the chest through an opening in the diaphragm).
They then asked each volunteer to swallow a special probe consisting of a magnet and clip. This was secured to the area where cells change from looking like the lining of the mouth (squamous cells) to becoming the lining of the stomach (columnar cells) – known as the squamo-columnar junction (SCJ).
In healthy people, the SCJ is found at the junction between the oesophagus and the stomach. However, in people who have acid reflux, the squamous cells that line the oesophagus change to become like the gland cells of the stomach, meaning the SCJ occurs higher up in the oesophagus. The presence of gland cells in the oesophagus is known as Barrett’s oesophagus. People who have this are more likely to develop cancer of the oesophagus.
Researchers say the movement of the clip during swallowing reflects any movement of the gastro-oesophageal junction. Over the next two or three days, subjects fasted and three further probes were inserted into various parts of the oesophagus. The aim was to monitor the location of the SCJ and to study any changes at the junction between oesophagus and stomach.
On one study day, the experiment was performed without volunteers wearing a waist belt. They consumed a meal of battered fish and chips over 15-20 minutes and were asked to eat until full. After the meal, the researchers continued recording for 60 minutes as volunteers sat in the upright position.
On the second study day the procedure was repeated but volunteers wore waist belts throughout the recording period. This was a weight-lifter belt with a blood pressure cuff beneath it. The order of study days with and without belt was alternated at random between the obese and non-obese groups. Any upper gastrointestinal symptoms were also recorded.
The researchers recorded and analysed various changes at the gastro-oesophageal junction, including the movement of the SCJ, the pressure of the lower oesophagus – which can increase in the presence of cell changes – and the pH content, which can indicate the presence of acid reflux.
What were the basic results?
Researchers found that both the waist belt and increased waist circumference were each associated with “displacement” of the junction between stomach and oesophagus, which moved higher up in the oesophagus. These findings, they say indicate partial hiatus hernia – the intrusion of stomach type cells in the oesophagus.
They also found the waist belt was associated with the occurrence of acid reflux just above the SCJ and this was most marked with a combination of waist belt and increased waist circumference. Waist circumference alone was not associated with acid reflux.
How did the researchers interpret the results?
The researchers say the findings are likely to explain the high prevalence of inflammation and cancer at the junction between oesophagus and stomach. The compression produced by a waist belt they suggest could be responsible for cell abnormalities in this region.
This was a small, short-term, and highly technical study which measured certain changes in the junction of the oesophagus and stomach in volunteers, half of whom were obese.
It found that wearing a weight-lifter’s belt and a greater waist circumference was associated with changes in the lining of the oesophagus at the junction between the oesophagus and the stomach.
These changes are associated with an increased risk of cancer, but the researchers did not set out to find if belts or obesity caused cancer.
The researchers also found that volunteers wearing a waist belt had more signs of acid reflux in this area than those who did not, and that this was more marked in those wearing a waist belt who also had a large waist circumference.
It is hard to know what to make of this study. Acid reflux is thought to be more prevalent among obese people, so it makes sense that researchers found cell changes which might lead to cancer in people with bigger waist circumferences.
Whether wearing a belt for such a short study can induce any such changes with the implied long-term effects is unclear. And it is unclear how many people – even weightlifters – choose to regularly wear a weightlifter’s belt.
The study did not prove that wearing a belt can give you oesophageal cancer. The best available evidence about reducing your risk of oesophageal cancer (as well as other types of cancer) is to quit smoking if you smoke, drink alcohol in moderation and try to maintain a healthy weight.
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter.