CITRIC ACID

A question:
what is it about citric acid that harms ketosis?
The reason I ask is, I was in Asda purchasing a 2 litre bottle of Still Perfectly Clear, the flavours were Lemon n Lime, Summer Fruits and Red Apple. The latter two flavours (possibly all 3 - can't remember) had both 'CARB FREE' & 'SUGAR FREE' written on them. Now I quite fancy tasting the Summer Fruits and thus picked it up. However the ingredients listed 'citric acid'. Now if this drink is being mooted as carbohydrate and sugar free then it should be OK to drink, no? So what is it about Citric Acid in this context that makes it the devils own ingredient?
thank you in advance
C-C

Basically when you restrict carbs the citric acid cycle is inhibited, which increases the rate of oxidation of fatty acids, leading to ketosis. The addition of citric acid to the diet will stimulate the cycle and in some people this can take them out of ketosis. Hope that helps

Plus it can kick off cravings for some, now some people get away with it, but I never tried it, I stuck to Malic Acid which works in a different way, but only as a saturday night treat, Bottle of Fanta Apple Zero and a choped up peanut bar!!

I drink it every day, as a treat.