Acid and Alkali foods
The acidity or alkalinity of what we consume actually has little or no bearing on the acid production of the stomach.
Stomach acid is produced by the parietal cells in the stomach in response to action of neurotransmitters histamine and acetylcholine. It is highly concentrated hydrochloric acid that can dissolve metal.
If you pour vinegar (an acid) on your hand, it will feel wet. Pour battery acid on your hand and it will cause damage. Pour vinegar on the damaged area and it will hurt; it's not the vinegar that's caused the problem but the concentrated acid.
Despite the many articles on "health" websites extolling the values of alkaline diets, they do nothing to reduce stomach acid.
Acidity is measured in terms of pH. pH7 is neutral: anything below is acid and anything above is alkaline.
Stomach acid "at rest" is usually pH4 but can reach pH1 when "active". (Vinegar is pH4.)
You can measure pH values using indicator papers but, whereas saliva or urine may be easily measured, stomach acid cannot.
Foods that may cause reflux
Some drugs (like caffeine and alcohol) may cause the muscles of the lower oesophageal sphincter to relax which could exacerbate reflux. However, for those experiencing frequent reflux, their sphincter is obviously malfunctioning anyway and the drugs' actions may make little difference.
Anything causing a build up of gas in the stomach may cause reflux.
This includes beans, brassicas (cabbage, cauliflower, etc), salad vegetables (cucmbers, radishes etc), fruits, grains, dairy products, breads and cereals etc.
Perhaps sounding counter-intuitve, sipping plain soda water can help by permitting a controlled burp to release the gas.
Know your triggers
Some acid refluxers may be affected by some foods. They are their trigger foods. However, as everyone is different, not everyone is affected in the same way by the same foods. We don't know why some foods act as a trigger for some and not others. It could be to do with the foods we were weaned on, our environment or even the food choice of our mothers whilst we were still in the womb.
To determine your food triggers, you should keep a food diary writing down the components and times of meals and recording any possible consequences. Analysing your log after a week or two may identify common elements that caused your reflux.
These items are frequently found on people's trigger foods lists but they may not affect you. If unaffected, you don't need to avoid them:
Spicy Foods, Citrus fruits, tomatoes, dairy products, fatty foods, soda, coffee.
Some food myths
Coffee. Although the caffeine content may relax the sphincter, research has shown that for most acid refluxers, coffee need not be avoided.
There have been a number of studies looking at the effects of coffee.
A study of over 8000 patients in Japan in 2012 [fd-i] found "No association of coffee consumption with gastric ulcer, duodenal ulcer, reflux esophagitis, and non-erosive reflux disease."
And a study published by American Gastroenterological Association in May 2016 [fd-ii] found "Coffee or Tea, Hot or Cold, Are Not Associated With Risk of Barrett’s Esophagus."
Alcohol. A search through the Barrett's Wessex accumulated archive of research links relevant to reflux, Barrett's etc, from all reputable journals over the last 5+ years [fd-iii], found 9 studies showing alcohol had no harmful effect on Barrett's Oesophagus:
"alcohol consumption is not a risk factor" (Gut 2005)
"No significant effects of alcohol consumption" (Digestive Diseases & Sciences 2013)
"Alcohol drinking is not associated with risk of neoplastic progression in Barrett's esophagus." (PLoS one 2014)
"we found no evidence that alcohol consumption increases the risk of Barrett's esophagus." (American Journal of Gastroenterology 2014)
"alcohol consumption ... [did] not seem to have any impact" (Gastroenterology Research & Practice 2014)
"Alcohol consumption ... [is] not associated with the condition." (Gastrointestinal Tumors 2016)
In fact 2 studies seemed to show it may actually have a beneficial effect.
"Significant inverse association was observed between alcohol consumption and BE," (Medicine Baltimore 2016)
"The limited data available on alcohol consumption supports a tentative inversion of alcohol consumption with BE risk in women" (Scientific Reports 2015)
(Alcohol was, however, considered to have a detrimental effect on the development of squamous cell cancer.)
Alkaline Water. Heavily promoted by those who hope to profit from its sale, only one study has shown any positive effects from alkaline water [fd-iv]. It was not replicated by peer review and not produced by a gastroenterologist but an ENT specialist who may be a beneficiary of companies selling the product.
These articles have debunked any claims alkaline water may provide:
Alkaline Water Hoax [fd-v]
Alkaline Water Helps neutralize Heartburn Symptoms? Doctors Debunk Claims [fd-vi]
The Doctor is in: Water, water everywhere - which drop should we drink? [fd-vii]
How we eat is important
Our modern lifestyle is much to blame for an increase in acid reflux and its associated problems.
We are prone to eat too much and too quickly and probably the wrong foods, too. (For instance fatty or processed meats need longer to break down in the stomach so should not be eaten in a rush, "on the go".)
When we eat, we need to eat small portions to avoid over-filling the stomach. We should eat slowly to permit each food bolus to enter the stomach and start being processed before the next is sent on its way.
Chewing each mouthful well will stimulate secretion of saliva and mucous to protect and lubricate the oesophagus to facilitate peristalsis to the stomach.
Keeping upright whilst eating is important for gravity to help.
A 1999 study on The role of diet and lifestyle measures in the pathogenesis and treatment of gastroesophageal reflux disease [fd-viii] stated, "A general consensus on the control of GERD through alterations in diet and lifestyle factors could hardly be based on the results of clinical or outcome studies."
This was further supported by a 2017 study Diet and GERD: Role in Pathogenesis and Management [fd-ix] stating, "Although anecdotal evidence has suggested associations with certain foods (fats, nonvegetarian, fried foods, and beverages) with reflux symptoms, objective evidence based data in this field remain unclear. Recent evidence points to the increasing importance of lifestyle in disease development as well."
And this item [fd-x] said, "It's Not Food Causing Your Heartburn—Here Are The 5 Real Culprits"
Exercise after food
After eating, the stomach should be allowed to empty before any activity which would result in it being squeezed, tilted or shaken.
It is probably best to abstain from activities like sit-ups, heavy lifting, bending down, running, swimming etc for an hour after eating.
However, gentle upright exercise is encouraged like walking which will help the food move from the stomach into the duodenum quicker.