What is kefir? Great question.
It is a symbiotic system of healthy bacteria and yeast. The kefir is small grains, kind of like tapioca balls.
There are two types of Kefir I'm aware of, commonly referenced to as milk kefir and water kefir. The water kefir grows in a sugar water solution while the milk kefir thrives in simple milk. Water kefir is comprised of a blend of different strands of bacteria. Each culture will vary in number and type, but typically less than 10 strands. Milk kefir will have much more upwards of 45 strands of bacteria.
So who cares about the bacteria right? Well with the probiotic industry being a $35 billion dollar industry, obviously a lot of people care (http://www.grandviewresearch.com/industry-analysis/probiotics-market). However the probiotic industry usually markets only lactobacillus bacteria. Kefir uses that and many more.
I have had my milk kefir grains for 3 years now and my water kefir for 1 and a half years. I prefer the milk over the water because I see more benefit in the amount of bacteria. FYI, I paid about $10 for each, the water and milk kefir grains.
But with a $35 billion dollar industry in probiotics, why have most people never heard of Kefir? Because kefir would shut down the probiotics industry. For $10 and a gallon of milk, I can make 3 weeks worth of Kefir. After that it is just the price of milk every three weeks.
Best of all is how simple it is to make. For 2 minutes a day I have fresh kefir.
First you will need a glass container, a nylon (not steel) mesh strainer, milk (I use whole because I like the end consistency), and the kefir grains.
Then place the nylon strainer over a cup.
Pour the milk kefir over the strainer and into the cup. Notice the kefir grains that look like tapioca balls.
Now I clean out the glass jar with a bottle brush. NO SOAP! I know it sounds strange, but the bacteria in the Kefir will overpower any other bacteria.
Then return the kefir grains to the jar and refill with milk.
I find a clump of grains the size of a marble will work for a quart size jar. No more than a clump the size of a quarter.
Finally, cover with a coffee filter and secure the coffee filter with a rubber band.
Now set it out on the counter for 12 to 24 hours. I do 24 because I prefer it thicker. Then repeat the whole process. It will taste like a drinkable plain yogurt. You can flavor it with anything you want after you have removed the grains. I have done pumpkin pie flavor, egg nog flavor, Apple pie, orange juice, vanilla and brown sugar, etc.
Every two weeks or so, the kefir grains will double in size and you will need to get rid of some. They are edible and shareable with friends or family.
Also, I almost forgot to note, the bacteria eat the sugar in the milk, so there will be less lactose and lower calorie count than regular milk.
Our family has noticed kefir works wonders for upset stomachs, heartburn, and regularity. Also, with the increased bacteria in our guys, it is quite rate anyone ever gets sick around here.
Hope you find this useful! Any questions, let me know.