Got Salt? Yoga, the immune system, and the problem with some scientific studies

by Nina

Currents in Salty Water by Brad Gibson

So I’ve been seeing these articles about a particular scientific study circulating in the blogosphere that claimed the study was proof that yoga improved your immune system system. One example is from Can Yoga Boost Your Immune System? at salon.com, which claimed:

“This latest study confirms those findings, links them to the body’s immune system, and suggests this effect may be instantaneous.”

Naturally, as a dedicated yoga blogger, I decided I needed to check these articles out because I need to share the good news with our readers, too, right? But my initial readings left me scratching my head a bit (for example, “a comprehensive yoga program rapidly produces internal changes on a genetic level”), so I decided to consult with my handy scientist co-bloggers to find out more, specifically what the relationship is between changes in gene expression and the immune system.

Dr. Ram Rao put it this way:

“The article describes effects of Yoga on genes that influence the immune system. There are so many factors that affect gene expression (environment, diet, pollutants, stress etc) and so the authors looked to see if Yoga did the same.”

That makes sense, right? So far, so good. But Dr. Brad Gibson said it this way:

OK, what they were measuring was gene expression profile changes in PBMC.

"Right before and after each regimen, 20 ml blood was drawn, PBMCs were immediately isolated, total RNA was recovered and used in gene expression profiling experiments interrogating >47,000 independent transcripts in two hybridization runs"

First, PBMCS (according to Wikepedia) are "peripheral blood mononuclear cell (PBMC) is any blood cell having a round nucleus. For example: a lymphocyte, a monocyte or a macrophage. These blood cells are a critical component in the immune system to fight infection and adapt to intruders."

So, what they are suggesting is that the observed changes in the gene expression profiles in blood immune cells (PBMCs) in Yoga practioners is correlated with an improved immune function. However the second bit is pure speculation.  They see a change, but it's anybody's guess if this represents a better or healthy immune system.  They provide some guesses, but….

Okay, I admit it, that phrase “the second bit is pure speculation” was a bit disappointing. I’d just wasted my time (and theirs) on an idea for a blog post that I couldn’t really use because, after all, on this blog anyway, we try to back up our claims with good science. But a few days later I realized I actually had more of a contribution to make on the topic than some of the other blogs because while everyone else was simply parroting some kind of good news about yoga they didn’t really understand, I had an actual real-life scientist weighing in on the significance of the study and he said to take it with a giant BUCKET OF SALT.

However, before writing the post, I decided to do a bit more research by looking an the original scientific journal article that everyone was quoting from Rapid Gene Expression Changes in Peripheral Blood Lymphocytes upon Practice of a Comprehensive Yoga Program—you know, just in case. And here is the abstract from the study:

One of the most common integrative medicine (IM) modalities is yoga and related practices. Previous work has shown that yoga may improve wellness in healthy people and have benefits for patients. However, the mechanisms of how yoga may positively affect the mind-body system are largely unknown. Here we have assessed possible rapid changes in global gene expression profiles in the peripheral blood mononuclear cells (PBMCs) in healthy people that practiced either a comprehensive yoga program or a control regimen. The experimental sessions included gentle yoga postures, breathing exercises, and meditation (Sudarshan Kriya and Related Practices – SK&P) compared with a control regimen of a nature walk and listening to relaxing music. We show that the SK&P program has a rapid and significantly greater effect on gene expression in PBMCs compared with the control regimen. These data suggest that yoga and related practices result in rapid gene expression alterations which may be the basis for their longer term cell biological and higher level health effects.

Whoa, I’m thought, somehow we went straight from “wellness” and “benefits” to specific claims about the immune system. Then there were all those vague words like “suggest” and “may.” But, of course, I’m not scientist, so again, I consulted with Brad. Here is what he said: 

Look at their last sentence:
"These data suggest that yoga and related practices result in rapid gene expression alterations which may be the basis for their longer term cell biological and higher level health effects."

That is, they don't know whether the change in gene expression patterns they observed has anything to do with the yoga practice, let alone a more healthy immune system.  This is a general problem of small correlative studies of this type.  At best I would say this is an intriguing pilot study (low N, not really statistically significant enough to establish even correlation), which will need considerably more work to establish:
(1)  'causation' (i.e., yoga practice causes these genetic expression changes as opposed to some random or other variable that wasn't accounted for)
(2) 'benefit' (the expression changes that are observed are actually beneficial and lead to an improved immune system)
(3) 'mechanism' (why these gene changes lead to a more healthy or robust immune system).

My translation? The number studied was so low that correlation couldn’t be established. Causation definitely was not established. And then there was a bunch of speculation. So, yes, get out the salt everyone, and sprinkle liberally! (For you non-American readers out there, we have an expression “take it with a grain of salt” that means you should be skeptical about something. So I like to joke about buckets of salt, when I think a lot of skepticism is warranted. And, as much as we love yoga, this is not the first time we’ve looked at scientific studies of yoga that indeed warrant quite a bit of skepticism.)

Note: I’m pretty sure that yoga is good for the immune system, however. Stress compromises the immune system—this is known medical fact—and yoga reduces stress. Spending more time in Rest and Digest mode (where your body restores itself) rather than Fight or Flight mode (where your body depletes itself) is therefore good for your immune system.