Q. We learned in Chulin 105b that the froth produced by various drinks is detrimental to one's health. One of the liquids is beer, another is water.
Question 1: Is the froth of today's beer also detrimental?
Question 2: What froth is there in water?
Question 3: Is the froth of carbonated drinks detrimental?
And last, Question 4: Is the froth of diet carbonated drinks (as I've noticed diet cola produces significantly more froth) detrimental?
A. Mishna Berura (179: 18) quoting Magen Avraham mentions that there is a well known principle in Halacha that with the passage of time “Nishtanu Hatevaim” or many things in nature have changed (See Tosafos Moed Kattan 11a). Therefore, we usually maintain in regard to diseases, medical procedures and medicinal issues that applied in Talmudic times, do not necessarily apply today. (See question 1982).
Horav Shlomo Miller's Shlit'a opinion is that the same may pertain in the case of foams and the effervescence of beer and soft drinks in our days, as they are not the result of dangerous or unwanted decomposition or decay processes, and therefore not detrimental to one's health.
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit'a