You sometimes find the recommendation to use apple cider vinegar as a household remedy against reflux. The idea stems from a popular trend that it stimulates digestion. However, this is not supported by scientific evidence.
In the case of silent reflux (airway reflux), apple cider vinegar can even be harmful.
Apple cider vinegar makes LPR symptoms worse.
Acidic foods, especially drinks, activate the stomach enzyme pepsin, thereby aggravating its potential to damage mucous membranes. As long as pepsin is inside the stomach, promoting its activity by lowering the pH might stimulate digestion. In patients with silent reflux, though, pepsin also resides outside the stomach. It is carried along with the acid reflux into the throat and airways, where it sticks to the mucous membranes and may even get absorbed by the cells.,
Swallowing acidic foods, such as apple cider vinegar, activates previously refluxed pepsin. This boosts the damaging potential of pepsin, causing more irritation of the mucous membranes in the airways. As a consequence, LPR symptoms get worse. For this reason, apple cider vinegar and other acidic foods are counterproductive for silent reflux.
Confusion about the acidity of foods
A while ago, one of my readers wrote to me that it is very easy to find the pH of foods – you can just search them online. She also found the pH of lemons, which were described as alkaline (have a high pH). That is why she thought that lemons would be good for her silent reflux.
Nothing could be further from the truth, though. Lemons are very acidic. They strongly activate pepsin inside the mucous membranes, similarly to apple cider vinegar, causing damage and silent reflux symptoms.
Lemons have a pH of between 2 and 3 (pH varies among crops). At this pH, pepsin reaches around 70% of its maximal activity, and can significantly damage the mucous membranes of the airways.
People with silent reflux should avoid anything with a pH of lower than 4, or below pH 5 might be even better. This means that lemons and apple cider vinegar are far too acidic.
Where does this information come from?
As I wrote above, my reader found the misleading information online that lemons are alkaline. Why did she find this wrong information?
There are different criteria to rate the acidity of foods:
- The actual pH of food before being digested. This is the pH of the food inside the mouth, or while being swallowed.
- A food’s ability to create acids or bases (acid- or alkali-forming foods). Foods may form acids and bases during the digestive process, independent of their actual pH. For this reason, some sources suggest that eating alkali-forming foods is supposed to help to maintain a healthy acid-base balance inside the body.
For some conditions, such as rheumatism, too much acidity inside the body might be a problem. Because I am not a rheumatism expert, I am not able to judge if this is indeed the case. In general, though, the body can keep the pH constant, and therefore, following a so-called alkaline diet does not appear to offer any benefit for healthy people.
Recommending foods for silent reflux based on their alkali-forming ability is dangerous.
The problem is that many foods with a low pH happen to be alkali-forming foods.
Lemon juice and apple cider vinegar are two good examples of this. Both are alkali-forming foods but have a low pH. This means that they are acidic while drinking them and so can reactivate previously refluxed pepsin in the throat and mouth, so damaging the mucous membranes.
To clarify: For silent reflux, only the pH of the undigested food is relevant. This figure is difficult to find, and it is crucial not to confuse the information that is commonly found in health guides with the actual pH before digestion. The undigested foods pH is also the scientific definition of pH that is used in chemistry, biology, and medicine.
The most reliable way to find the pH is by measuring it, which you can do with litmus paper. In my online course about the treatment of silent reflux, I provide an extensive list of the pH of foods that I measured myself.
 Koufman JA. Low-acid diet for recalcitrant laryngopharyngeal reflux: therapeutic benefits and their implications. Ann Otol Rhinol Laryngol. 2011 May;120(5):281-7.
 Kowalik K, Krzeski A. The role of pepsin in the laryngopharyngeal reflux. Otolaryngol Pol. 2017;71(6):7-13.
 Salihefendic N, Zildzic M, Cabric E. Laryngopharyngeal Reflux Disease – LPRD. Med Arch. 2017;71(3):215–218.