It's an enzyme-rich food filled with friendly micro-organisms that
help balance your "inner ecosystem" to maintain optimal health and
strengthen immunity.

Kefir's tart and refreshing flavor is similar to a drinking-style
yogurt, and it contains beneficial yeast as well as the friendly
'probiotic' bacteria found in yogurt. When used regularly, the
naturally occurring bacteria and yeast in Kefir combine symbiotically
to help balance your intestinal flora and boost your immunity.

Among its many beneficial powers, Kefir:

* Provides supplemental nourishment for pregnant and nursing women*

* Contributes to your healthy immune system help fortify patients
suffering from AIDS, chronic fatigue syndrome, herpes, and cancer.

* Promotes a relaxing effect on the nervous system and benefit many
who seek a restful night's sleep, and who suffer from depression, and
ADHD (attention deficit hyperactivity disorder).

* Helps support your normal intestinal tract function, promote bowel
movements and your healthy digestive system -- and is an absolute must
after the use of antibiotics to restore balance to the digestive tract

* Curbs unhealthy food cravings by making your body more nourished and
balanced

Source and recommended site for making better kefir :
http://www.howtomakekefir.com