September 25, 2015 5:43 pm
Updated: September 25, 2015 5:44 pm

The science behind the effects of yoga on health

WATCH ABOVE: Yoga is increasing in popularity. It's reported that more than 20 million North Americans are now practicing yoga. Many will tell you that it improves their physical and mental well-being. But are any of these effects actually proven? Dr. Samir Gupta explains in this week’s On Call.

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TORONTO — Yoga originated in India over 2,500 years ago as a part of Hindu spirituality. Its basic components are physical postures, breathing techniques, and meditation.

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This is an art that has been practiced by Indians for centuries now. However, in the last few years, yoga has gained immense popularity in North America as a form of exercise and “wellness.”

Millions of North Americans now practice yoga, and many will tell you that it benefits both their physical and mental well-being. But are these effects proven?

Today, we will explore what science actually tells us about the effects of yoga on health.

As it turns out, there are over 100 studies that have measured the impact of yoga on everything from cancer to asthma.

One of the challenges in studying and proving the benefits of yoga is that the most reliable type of study would require subjects to be “blinded” to the therapy that they are receiving (i.e. subjects should not know if they are getting the therapy being tested or getting a placebo), but for obvious reasons, it is almost impossible to “blind” participants to the fact that they are doing yoga.

This makes most studies susceptible to bias.

Although the first study on the benefits of yoga was published in 1975, and showed benefits in reducing high blood pressure, many more studies have been published quite recently, and several reviews that combine the results of these studies are now available.

Overall, although more research needs to be done, certain health benefits have clearly emerged.

Firstly, chronic low back pain is one of the most common medical problems that we deal with, and is also one of the best studied conditions when it comes to the effects of yoga.

A systematic review published in 2013 looked at 10 studies including almost 1,000 patients, and showed significant short and long term reductions in both pain and disability (when compared to just education or other exercise).

Accordingly, Viniyoga-style yoga is now recommended for lower back pain in medical guidelines.

People often tout the benefits of yoga on their state of mind. Along these lines, studies have tried to measure the impact of yoga on depression and anxiety.

A review published in 2013 looked at 12 trials including over 600 patients, and indeed found that yoga reduces the severity of depression over the short term, compared to both usual care and to other complementary treatments such as relaxation techniques and aerobic exercise.

The most obvious benefit of yoga should be on physical fitness and strength, and there is plenty of evidence that yoga does help.

Young adults have been shown to have improved strength, flexibility, and balance, whereas older adults have been found to have improved overall physical fitness through yoga.

The caveat is that the these studies compared yoga to no activity at all, and it’s hard to say whether yoga is superior to other conventional exercises for these fitness-type effects.

I have also heard yoga enthusiasts talk about how yoga “boosts” their immune system.

I must admit that this seemed rather dubious to me, but I was surprised by what I found in the scientific literature.

Although there are no long term studies looking at actual immunity, there are some fascinating findings from small short term studies.

In 2013, S Qu and colleagues drew blood from participants immediately before and after a two-hour yoga session, and showed that the expression of 97 different genes in circulating immune cells was boosted by the yoga (compared to only 24 genes boosted by a nature walk while listening to relaxing music).

Furthermore, a 2014 “meta-analysis ” combining several studies of different mind-body therapies (including 7 studies of yoga) showed that a few weeks of practicing these techniques will reduce levels of several different markers of inflammation found circulating in the blood.

Lastly, a favorite of mine is the impact of yoga on one of the most physically stressful experiences that human being can endure: childbirth.

A 2011 Cochrane Review looked at two trials reporting on the effects of Yoga as a relaxation technique during labour and demonstrated that yoga reduced labour pain intensity reported by women, increased their satisfaction with pain relief and with the overall childbirth experience and reduced the length of labour (when compared to usual labour management).

All that’s missing now is the long -term follow-up to see if the babies turn out to be more zen when they grow up.

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