Depends really on the acidity of your stomach and the resistance of the strain. Home grown already better. But a lot of kefir I see is lab grown over industrialilized source. Already. These pampered babies don't do the job.

That's why invested in building a relationship with them. Fungi / bacteria. Now for 15years I have multiple strains hand trained in various media. They can all survive PH 1 and even a red kefir strain that is completely impervious to Iron! But this takes time! And this quality on the market is very valuable.

My cure for COVID? Cannabis golden milk with my best strain.! By the slime! It will be fine!