Federal health officials have released a set of videos featuring the scientific research of how yoga works, the safety of yoga and whether yoga can help treat certain health problems.

The National Center for Complementary and Alternative Medicine (NCCAM), part of the National Institutes of Health (NIH) says that the videos can help viewers make informed decisions if they're interested in practicing the ancient Hindu meditation practice.

Researchers say for instance that there is accumulating scientific evidence that while yoga may be beneficial for lower back pain, the meditation practice has not been proven to help treat asthma and research into yoga for helping to treat arthritis have had mixed results.

Experts say that that while yoga is generally considered safe in healthy people when practiced appropriately under the direction of a well-trained instructor, people with high blood pressure, glaucoma, sciatica and pregnant women should modify or avoid some yoga poses.

They also stress that because everybody is different, yoga postures should be modified based on individual abilities and that people should inform their trainers about any medical conditions they may have as well as ask about the physical demands of yoga.

The NIH also advises that people who are thinking about practicing yoga should talk to their health care providers and give their doctors a "full picture" of what they do to cope with their health.

About 13 million, or 6 percent, of American adults report practicing yoga, according to the most recent survey conducted by the U.S. Centers for Disease Control and Prevention in 2007, and the number is on the rise as alternative mind and body therapies are becoming increasingly integrated into the nation's health care system.

Because of the accumulating scientific evidence for the benefits of yoga, the American College of Physicians and the American Pain Society now include a number of mind and body approaches, including yoga, in their 2007 clinical practice guidelines for managing common difficult-to-treat chronic low-back pain.

"This video provides important information on the safety and usefulness of yoga and also insights into how scientists study this commonly used health practice," Dr. Josephine P. Briggs, director of NCCAM, said in a statement released by the NIH.

"What we're seeing from our researchers — through the application of rigorous scientific methods — is evidence suggesting that yoga may help people manage certain symptoms while it may not help with others. We're also learning more about the safety of yoga, particularly when it is used in populations who are at increased risk for injury," she adds.

The videos are available at NCCAM's video page and it highlights the work of two renowned yoga researchers: Dr. George Salem of the University of Southern California and Dr. Karen Sherman of the Group Health Research Institute in Seattle.

Salem's research focuses on using advanced technology to examine how older adults use their muscles and joints in certain yoga postures, and Sherman's research highlights how yoga may be a beneficial supplementary health practice for people with chronic low-back pain.