Avoid Acidic foods (eg. Tomatoes and Tomato-based Preparations

Efficacy of Avoiding Acidic Foods as a Lifestyle Change According to GRADE* Ranking: 

Gastro-Oesophageal Reflux Disease (GORD or GERD) [1]:

Recommendation: Weakly in favor (Acidic foods may trigger or worsen GORD/GERD)

Grade of Evidence: Low level of evidence 

Stomatitis/Recurrent Aphthous Stomatitis [2]:

Recommendation: Weakly in favor (Acidic foods may trigger or worsen stomatitis

Grade of Evidence: Low level of evidence 

Xerostomia [3]:

Recommendation: Weakly in favor (Acidic foods may worsen xerostomia)

Grade of Evidence: Low level of evidence 

* www.gradeworkinggroup.org 

References: 
1.  https://www.niddk.nih.gov/health-information/health-topics/digestive-diseases/ger-and-gerd-in-adults/Pages/overview.aspx

2. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4002348/

3. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4278738/