It’s natural and perfectly safe. While you wouldn’t want to have a diet that consisted of kefir and nothing else, it is safe to consume it on a daily basis. Ideally, you should set a limit for yourself and have just one serving of kefir each day. If you do that, you shouldn’t have to worry about many issues.
Dried or frozen grains can take a week to 2 at the most. Kefir grains may not start growing right away, but they should be properly kefiring the milk they are in by 5-14 days. Growth can start happening right away, or it may take up to 3 weeks before you start noticing growth (usually the case with dried, not live).
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