A series of five articles.
What is the evidence from medical research? - article 1
Gastro-oesophageal reflux disease and the variety of complications that can occur with acid reflux are extremely prevalent in United States and the West. Lifestyle and diet plays a role in the development and behaviour of GERD. A review of the medical literature and data shows conflicting findings regarding the role of a lot of these factors. Many of these studies on the pathogenesis of GERD have been carried out on small numbers of patients. Many of these studies did not fit the rigid criteria for evidence-based medicine. This means that advice regarding dietary modification and lifestyle in order to manage acid reflux is a form of empirical treatment.
A general consensus on how to treat GERD through dietary and lifestyle modification has emerged over the years. This has not been thoroughly based on rigorous medical research. In practice the treatment of acid reflux disease is orientated towards the symptoms of the individual patient and includes providing reasonable balanced advice on how to adapt and change to personal dietary intolerance and lifestyle factors.
Gastro-oesophageal reflux disease is very prevalent in the United States and Canada and Europe. In the US it is thought that about 20% of the adult population have heartburn and or acid reflux at least once a week. This figure is thought to increase to around 40% in those patients who have first-degree relatives with Barrett oesophagus or distal adenocarcinoma of the oesophagus. It seems that there is a familial background to acid reflux and the various diseases that are associated with GERD. Acid reflux disease is fairly uncommon in people of Asian origin when compared with Caucasians.
It is interesting that a study by Lagergren published in 1999 in the New England Journal of Medicine showed that symptoms of GERD precede the diagnosis of oesophageal cancer in about 60% of patients with oesophageal adenocarcinoma. The authors also found that the odds ratio for oesophageal adenocarcinoma was 43.5 in those individuals with severe and long-standing symptoms of acid reflux. There has been a very dramatic increase in the incidence of adenocarcinoma of the lower oesophagus in the Western world and there is an urgent need for acid reflux disease to be diagnosed and recognised early. There is also a need for early recognition of the diseases associated with GERD and for adequate curative and prophylactic treatment.
Many gastroenterologists and physicians have observed over the years that certain lifestyle factors and dietary factors seem to aggravate acid reflux. Because of this a type of non-pharmacological treatment has been developed to manage GERD. Many doctors offer their patients very precise advice on what they should eat and drink, and how they should modify their lifestyle. Because many of these lifestyle changes may potentially adversely affect the person's quality of life, it is important to ensure that the advice given reflects evidence-based medicine.
How GERD develops
It is worth summarising the pathological origins of acid reflux disease because every potential type of treatment including modifications of diet and lifestyle is directed at one or more of the factors that aggravate or maintain the acid reflux concerned.
With GERD there is pathological stress on the lining of the oesophagus caused by reflux of acidic stomach contents into the oesophagus because of a defective lower oesophageal sphincter (LES). It was widely believed until the 1980s that episodes of acid reflux were due to a weak resting tone in the lower oesophageal sphincter. It is now thought, that although some patients with GERD have a weak lower oesophageal sphincter, it has recently become clear that in most patients with acid reflux the pressure exerted by the LES is increased. It is now widely believed that in the majority of acid reflux patients, the main mechanism underlying gastro-oesophageal reflux is more frequent transient LES relaxations (TLESRs). These TLESRs are thought to be responsible for belching which is a physiological mechanism. Belching is thought to be a neural reflex which is stimulated by distension of the stomach, certain food types, stimulation of the pharynx, and the upright and right lateral decubitus posture. It is not known why acid reflux patients have more transient LES relaxations. It is also thought that the proportion of TLESRs which are associated with acid reflux, in addition to gas, is greater in GERD patients than in healthy people. There is speculation that hiatus hernia may have a role here. Large hiatus hernias in combination with lowered LES pressure are commonly present with moderate and severe reflux esophagitis.
Two different types of reflux patterns have been described by medical researchers. In the first, acid reflux is present more frequently during the day and in the upright position. These sufferers are known as "day burpers" or "upright refluxers". In the second type of pattern, the acid reflux takes place mainly at night and when sufferers are lying down. These acid reflux sufferers are known as "bi-positional refluxers" or "night burners". Medical researchers now know that there are two different pathological mechanisms which cause these observations. In the first pattern, which accounts for about 90% of cases, there are increased TLESRs. This is the milder form of GERD. In the more severe forms of GERD which accounts for 10% of cases the second mechanism described is responsible.
Composition of the Diet
The observations and experience of patients and doctors has led to the consensus that fatty foods cause or worsen heartburn. Therefore patients are generally advised to avoid fatty foods. Medical studies have shown that fat reduces the lower esophageal sphincter (LES) pressure. But the study by Becker et al., showed that a high fat meal caused upright acid reflux in healthy people only. Those individuals with GERD did not have an increase in postprandial (after meal) reflux when this was measured with pH-metry. Two other studies have also challenged the view that fatty meals affect acid reflux mechanisms. When they compared a fatty meal with a low-fat meal in healthy people, they found no significant differences with regard to lower esophageal pressures or the quantity of acidic fluid that was refluxed.
Many think that sweets such as candy bars cause acid reflux because of their high fat content and high osmolality. Two research studies have found that chocolate causes acid reflux by lowering LES pressure. Other researchers have commented that the sample sizes in these studies were too small for definite conclusions to be drawn.
Research into liquids has shown that fizzy drinks are thought to have a bad effect on gerd because of an increase in transient LES relaxations (TLESRs) or a reduction in the LES pressure. A research study by Crookes et al found no difference between carbonated water, regular Pepsi, or decaffeinated Pepsi. Their conclusion was that the changes in lower esophageal pressure (LES) was due to the effect of the gas rather than the caffeine level or acidity. The effect of caffeine is controversial. One study by Pehl et al comparing caffeinated and decaffeinated coffee found that decaffeinating the coffee may reduce the amount of gastroesophageal reflux.
Juices and citrus foods have been investigated. In a study by Feldman and Barnett, a survey in 1995, it was found that juices especially citrus juices provoked acid reflux symptoms in about a third of about 400 heartburn sufferers. The researchers found a significant correlation between the acidity of the drinks and the heartburn score. This data therefore suggests that citrus foods and juices should be avoided by some acid reflux disease sufferers.
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