Those reading some of the major newspapers looking for health and science news will have stumbled onto some extraordinary claims over the past week. Apparently, the latest saving grace from the looming threat of cancer is, that’s right, yoga. As always, the Daily Mail’s headline is especially interesting: Yoga and meditation reduce the risk of cancer by changing our DNA: Relaxation techniques boost the way our genes protect the body from illness. That does indeed sound amazing. Being able to change your DNA, the essential molecular code detailing how each cell in the body lives, behaves and dies – through the simple act of attending a yoga class. This sounds almost too good to be true – and definitely demanded at least some fact checking.
First of all, the original research itself is not actually original research at all. The articles refer to a review of other articles, recently published in Frontiers in Immunology. Of course, this is in itself no bad thing – reviews are a very common type of article in science, summarizing recent important results from different authors and pointing out emerging trends. It is, however rather misleading that the Mail article refers to it as a study, whereas what they are referring to is a systematic review. While this might seem a point of petulant semantics, it is actually quite important to understand the difference. A study is a piece of original research presenting new findings. A review looks at pre-existing findings. So no new information has been added by the article referenced by the Mail. Either way, the paper in question suggests that people who practice yoga and other relaxation techniques lower their expression of certain molecules associated with inflammation. The connection with cancer is made not in the original paper, but in the Mail article itself. While inflammation and cancer are very closely related, the relationship between the tow is extremely complex. While inflammation is associated with an increased risk of cancer and metastasis, cells in the immune system also have the power to aggressively tackle and destroy cancer cells once they are able to recognize them. Therefore, the tabloid is doubly misleading – this is not a study proving that yoga protects you from cancer, but a review suggesting that yoga (and other relaxation practices) lower the levels of certain inflammatory markers.
Or does it?
While there is nothing wrong or unreliable about systematic reviewing, there are definitely some interesting questions to be asked of this review in particular. First of all, it puts no restriction on the size of the study – which means that it includes studies that include a very small number of cases. For instance, it includes this study from 2005, which only looks at 6 patients. Studies with such a small number of patients are widely considered completely unreliable by the scientific community – and are most often referred to as “observations”, not carrying even nearly as much weight as studies with a more significant number of patients. In fact, none of the studies included in the systematic review includes more than 50 cases, which is an extremely low threshold. Most reliable studies include hundreds, if not thousands, of patients.
A second serious problem with this review is that it includes studies like this one, where there is no control group. A control group is one of the most important things in a study – it’s a group of cases that is virtually identical to the group being studied in all but the key component. This is not just good scientific practice, it’s very much common sense. A comparison only makes sense if there is something to compare to. Some studies try to get around the need for a control group – and these studies are always considered far less reliable than those with a valid control group. Even those who do have a control group don’t always have the right control group. For instance, the majority of the studies considered by the review deal with “experienced practitioners” – i.e. those who have been practicing relaxation techniques for years – and compare them to patients that do not have that kind of experience. This does not account for what statisticians call confounding factors – elements that can “muddle the waters”. For example, it is not completely unthinkable that people who regularly practice relaxation techniques might have a different diet and follow alltogether a different lifestyle than those who do not. So how do we know if the differences that were measured are due to the meditation – or to any of these other possible things?
The third serious problem with this review is with what it considers to be a change in inflammatory markers. The Mail deadline promises a change in DNA. That is, of course, fiction. DNA is where the hard-wired information in the body is stored – the only way to change the DNA of an adult is through mutation (which is what happens when regular cells turn into cancer). What the review references is a change in gene expression, which is a measure of how much a gene is actually translated into a molecule that can affect the behavior of the cell. While every single gene is present in every cell in the body, not all genes are expressed in all cells. This explains why while all cells carry the same DNA, not all cells look and behave the same: cells that line the stomach, for instance, are completely different from cells that make up the eye. What the review is suggesting is that people who do practice relaxation practice express less of genes that are associated with inflammation. However, while some of the studies cited do indicate that there is a regulation in genes genuinely related to inflammation, some show regulation of factors that have nothing or very little to do with it (such as this paper, which shows regulation in NFkB – a gene that is involved in virtually every process in the body, including inflammation).
In conclusion, no – meditation certainly does not change your DNA and there is no current scientific evidence that it protects anyone from cancer. However, yoga is a form of exercise and we do know that maintaining a healthy weight and staying active do protect us from a variety of conditions, including cancer. So get those yoga mats out – but don’t throw out your running shoes just yet.