Julia read over 50 books and takes a critical eye to some of the claims that are typically made in Yoga classes. Her post has an excellent list of links to major academic studies over the past few decades.
There are some known benefits, like reducing inflammation, helping with back issues, improving flexibility, and increasing body awareness (which has many other benefits).
However the research on Yoga is overall still weak. Most studies suffer from bias and there is no clean firm definition of what ‘Yoga’ actually is.
We still don’t have firm evidence on which types of Yoga are the best, and if and how it can flush our organs or stimulate digestions as some Yogis claim.
However, the good news is that the quality and quantity of studies is improving over time.