Reflux symptoms in the esophagus, such as heartburn, are primarily caused by rising stomach acid. Consequently, the diet has a heavy influence on gastroesophageal reflux disease.[1]
Chronic acid exposure leads to sensitized pain receptors in the esophagus. They become hypersensitive and respond to stimuli that would typically not cause any problems, and as a consequence, people get heartburn.[2]
Acidic Foods Can Cause Heartburn.
Once the pain receptors are sensitive, they can also react to acid in foods.
Many foods are very acidic, especially fruits. In addition, many processed foods like canned foods and refrigerated foods, are often acidic. Acid is a cheap preservative that manufacturers add to many packaged foods.
Many drinks are also acidic. This includes sodas such as Coke, lemonade, or iced tea. They contain acid because it adds fresh taste. Because sodas contain a lot of sugar, though, they do not taste sour. Fruit juices are acidic as well, but usually to a lesser extent than the typical soda drink.
The acidity of foods is measured by its pH. You probably learned about pH in school.
Reflux patients should avoid acidic foods, especially those within the red area of the scale. Where to draw the line on the pH scale mainly depends on symptoms. For patients who only have esophageal symptoms, it is typically sufficient to avoid concentrated acid sources. However, even small amounts of acid can aggravate symptoms of airway reflux, like asthma, cough, and hoarseness.
The pH of Foods can be Misleading.
It is not easy to find the pH of foods. It can be easily measured, but the pH of foods is not usually written on the packaging.
To make things even more difficult, the pH of foods is sometimes confused with something else. A while ago, one of my readers told me that it was very easy to find the pH of foods. She said that they could be found online. She also discovered the pH of lemons, which is apparently high, meaning that lemons are alkaline. The same seemed to be true for other fruits.
As a result, she thought that squeezing lemons and drinking the juice would reduce her reflux, similarly to other sour-tasting foods.
Since then, I’ve noticed that this is a common fallacy – nothing could be further from the truth. Lemons are very acidic and damage the already-irritated mucous membranes. The acid in lemons can also aggravate heartburn.
So where does the information about lemons being alkaline come from?
The Concept of Acid-Forming Foods
You might expect that the reported pH of food refers to its actual pH before being digested. The pH at this stage is relevant for the treatment of reflux, and this is also the official scientific definition of pH that is used in chemistry, biology, and medicine.
In addition to the actual pH of foods, there is the concept of acid- or alkali-forming foods. While the food is digested and metabolized, it may form acids and bases. This means that acidic food can still create alkalis, or soluble bases, inside the body. This is commonly what is meant when talking about alkali-forming foods. Alkali-forming foods are thought to maintain a healthy acid–base balance in the body.
Acid-forming foods, on the other hand, are thought to cause problems for patients with certain conditions, such as rheumatism. For this reason, some dietary approaches try to restore a healthy acid–base balance. Whether avoiding acid-forming foods is of benefit for these patients is controversial.[3]
One thing is for sure: For reflux, the only pH that matters is the pH before digestion. As the food passes the throat during the swallowing process, acids can activate pepsin and cause damage. At this stage, lemons and most other fruits are acidic.
Unfortunately, because of this alkaline diet trend, the actual pH of undigested foods is difficult to find. When you find the information that a specific food item is acidic or alkaline, it refers to the phenomenon of acid- and alkali-forming foods.
For this reason, eating foods that are commonly known as “alkaline” is dangerous for people with reflux.
How to find out whether something is too acidic
When you have only heartburn and not LPR (with symptoms such as hoarseness, cough, and asthma), you can rely on the taste of foods[4] – whatever tastes sour is likely too acidic. If it causes heartburn, it is too acidic for sure. Some items are a bit misleading because the sugar they contain masks the acidity. This applies to most sodas, such as Coke, lemonade, and iced tea. All of those are highly acidic.
When you have LPR symptoms, you need to be more careful. You should try to avoid anything with a pH lower than 5. This includes foods that do not taste sour but are still mildly acidic.[5],[6],[7] To be on the safe side, you should either look up the pH (read below for more information) or measure it yourself.
The Myth of Apple Cider Vinegar
In agreement with the alkaline diet food trend, some poorly researched health guides recommend apple cider vinegar for treating reflux. They advise you to drink it either undiluted or diluted with water.
Apple cider vinegar is often pushed by populistic authors as a miracle cure for all kinds of health problems. I am not sure how the recommendation of apple cider vinegar for reflux started. I assume it is based on the assumption that any alkali-forming foods are inherently healthy. The human body is, however, able to regulate its pH because this is vital for all biochemical reactions to take place. The assertion that we all have to eat more alkali-forming foods to stay healthy is not well supported by scientific evidence.
Another apparent benefit of apple cider vinegar is that it is supposed to increase the acidity level of the stomach, thereby promoting digestion. This sounds feasible at first glance, but only before having a closer look at the pH scale. The pH scale is logarithmic.[8] This means that each number on the scale corresponds to a 10-fold change in acid content; so pH 4 is 10 times as acidic as pH 5, pH 3 is 100 times as acidic (10 x 10), and pH 2 1,000 times more.
This means that you would have to drink highly concentrated apple cider vinegar to significantly raise the pH in the stomach. Drinking such concentrated vinegar would burn your throat and esophagus while swallowing. The throat is even more sensitive to acid than the esophagus. Conversely, drinking diluted vinegar would have no effect, because it is not the amount of acid taken that matters but its final concentration.
As you can see, the topic of digestion and stomach acid is more complicated than you might think.
Esophageal Sensitization Can Recover
Many of my readers are afraid that they may never get rid of their reflux symptoms because the pain receptors in the esophagus have been sensitized.
There is, however, no reason to worry about this. Once the reflux is under control, pain receptors return to their normal state. They become less sensitive towards pain so that mild and sporadic reflux does not cause any symptoms, and heartburn disappears.
The reason why many people suffer their whole life from reflux symptoms is that they do not eliminate the cause of the disease; they merely suppress the symptoms.
Experimentation with Foods Has Its limits.
In general, it makes sense to experiment with one’s diet. Everybody reacts differently to certain foods, but this does not mean that you should follow every trend. Some trends have no scientific basis and may indeed cause more harm than good.
In my book about the treatment of heartburn, I put a particular focus on dietary approaches that are known to be of benefit. The book also contains a list with the pH of many foods and a list of recommended foods for avoiding reflux.
References
[1] Bennett JR. What is physiological gastroesophageal reflux? OESO foundation.https://www.hon.ch/OESO/books/Vol_3_Eso_Mucosa/Articles/ART008.HTML. Mai 1994. Assessed on Oct 08, 2019.
[2] Yamasaki T, Fass R. Reflux hypersensitivity: A new functional esophageal disorder. J Neurogastroenterol Motil. 2017;23(4):495-503.
[3] Khanna S, Jaiswal KS, Gupta B. Managing rheumatoid arthritis with dietary interventions. Front Nutr. 2017;4:52.
[4] Salihefendic N, Zildzic M, Cabric E. Laryngopharyngeal reflux disease – LPRD. Med Arch. 2017;71(3):215-218.
[5] Koufman JA. Low-acid diet for recalcitrant laryngopharyngeal reflux: therapeutic benefits and their implications. Ann Otol Rhinol Laryngol. 2011;120(5):281-7.
[6] Koufman JA, Huang S., et al. Dr. Koufman’s Acid reflux diet: With 111 all new recipes including vegan & gluten-free: The never-need-to-diet-again diet. Katalitix. 2015.
[7] Koufman JA, Jordan S, Bauer MM. Dropping acid: The Reflux Diet cookbook & cure. Reflux Cookbooks; 1st ed. 2010.
[8] pH Scale. Virtual Chembook, Elmhurst college. http://chemistry.elmhurst.edu/vchembook/184ph.html. Accessed on Oct 04, 2019.