I started making my own raw cow's milk kefir about 4 weeks ago. The first week I drank about 4-8oz daily and experienced bloating and a little gas. I had been mostly no dairy prior to kefir.
After that first week, I stayed with it and now for the past week or so had been consuming on the order of 16oz daily completely symptom-free.
A question: You said "last night for the first time". What was the "first time"? You straining it at night, and drinking it immediately after? Do you normally strain it at night and drink in the morning? Or do you normally strain in the morning and drink in the morning? It would be helpful if you could clarify, because this "first time" might be making the difference.
Some thoughts that I have that could help narrow it down:
- Did you eat any fruit in a similar timeframe as drinking the kefir? I have definitely noticed a gas/bloat correlation in myself b/w drinking kefir and eating fruit. Or maybe you had something else sweet in the same timeframe, dessert maybe?
- What was different about this batch from the way you have normally made kefir?
- How long have you been making goat's milk kefir? If this is relatively new for you, your body could be adjusting to it, as mine did, or perhaps you are discovering that you do have a lactose intolerance.
- Has anything about your kefir-making environment changed recently? I'm thinking a swing upward in temp, either from ambient temp changes or maybe you moving the kefir to a different, warmer location. This could significantly increase bacterial activity and CO2 creation. The CO2 gas is what gives kefir the "fizzy" taste/consistency.
- How long did this batch ferment compared to your other batches? If it fermented for less time than usual, there might be more lactose than usual since the bacteria didn't have enough time to consume most of it. An indicator that it didn't ferment for enough time would be that the consistency was thin, closer to "milk" than "kefir".
- Do you normally let the kefir refrigerate, but this time you drank it right after straining? Maybe letting it rest for 24h would make a difference.
You may want to try going off kefir for a week to see if the flatulence resolves, especially since it seems that's an existing condition for you. Or play with some of the variables above.