“Role of Yoga for Patients with Type II Diabetes” and Lack of Methodological Rigour in Yoga Research

If you have a copy of “Light on Yoga” by Iyengar, in it you will find a whole index of asana and pranayama suggestions for a wide range of ailments. For example, if you are suffering from diabetes, Iyengar suggests that you do inversions, seated and standing forward folds, backbends, and twists (Yes, that’s right! All kinds of yoga poses)*. The point is that traditional notion assumes yoga practice is healing for “obvious” reasons. Exciting as it may sound, I would say that unless such claims are supported by solid scientific evidence, they should be taken with a large dose of scepticism.

According to WHO, Type II diabetes “results from the body’s ineffective use of insulin. Type II diabetes comprises the majority of people with diabetes around the world, and is largely the result of excess body weight and physical inactivity.”** Those who have been diagnosed with Type II diabetes are recommended to have a healthy diet, regular physical activity, to maintain a normal body weight and avoiding tobacco use, in addition to pharmaceutical treatment, which is very effective in treating Type II diabetes.

Yoga is amongst the accessible types of physical exercise that people try when they are told to change their lifestyle. So it doesn’t come as a surprise that the efficacy of yoga in managing Type II diabetes have been subject to empirical studies.

A few systematic reviews depicting the efficacy of yoga for type II diabetes have shown promising results of this intervention on blood glucose levels, insulin sensitivity, oxidative stress, lipid profile, anthropometric measures, pulmonary measures, nerve conduction and quality of life.

A new review and systematical meta-analysis by Kumar et al. contains interesting findings and conclusions that reflect general issues with empirical study of yoga and the misguidance it encourages.

Kumar et al. begin by database searches with relevant keywords. Of the 193 publications they had extracted through their search, they had to remove 118 for various reasons such as duplication, or that the publications were reviews or conference proceedings. The remaining 75 full text papers were re-evaluated and only 17 of these were randomised control trials (RCT) and only these were take into review. This is one of the major issues in yoga research as I have mentioned before. Without an experimental design that involves randomised control and experimental groups, it is hard to reach to reliable and valid results that can be generalised to general public.

The analyses revealed that “evidence in favour of yoga as an effective complementary treatment for patients with type II diabetes in comparison to standard care is evident, though its robustness cannot be emphasised due to high risk of bias and possibility of publication bias.”

And then they go on to list these possible study biases as well as publication biases. Here is a list combining their comments and my observations:

  1. Majority (14/17) of the studies in the review were of Indian origin and the authors think the fact that yoga is a part of Indian tradition and culture may have contributed to the ease in understanding the intervention, leading to better performance and results.
  2. In yoga studies with Indian origin, the interventions are more intense than non-Indian trials. e.g. 6 days a week etc. This can also be interpreted as a shortcoming as there is hardly any evidence regarding the appropriate length and intension of the yoga intervention.
  3. Most people who are diagnosed with diabetes are on diabetes medication and the participants in the reviewed studies are no exception. Therefore it is difficult to predict if the effect or no-effect is due to the pharmaceutical treatment or the adjunct yoga treatment. A couple of ways to get around this issue is to increase the number of participants or to recruit people who are not on diabetes medication for yoga trials for control comparison. And remember most yoga research does not even employ randomised controls.
  4. Pharmaceutical treatment for Type II diabetes works effectively. So, why introduce yoga in the studies? Further why yoga and not other types of exercise? What is so special about yoga? “Future randomized controlled studies could consider providing yoga as an alternative treatment to either severe cases of diabetes who have not improved with pharmaceutical treatment, or to mild-moderate cases of diabetes who have shown to be more sensitive to the blood glucose changes than the severe cases.” A further issue in general yoga research is that (when they do) most studies compare the yoga group to a non-exercising, passive group. Until we figure out what is so special about yoga practice, the comparisons have to involve other types of exercises. This would, of course, require a modern, reformed and quantified definition of yoga!
  5. And then, there is the question of the safety of yoga interventions, which has not been addressed in yoga studies generally.
  6. Mostly due to publication pressure, most of the time non-significant results do not find their way to refereed-journals. There is a publication bias towards significant results. As the popularity of yoga expands, it becomes harder to disqualify yoga as an aid in treating ailments, or its effectiveness. Unfortunately, popularity of a topic goes a long way in receiving funding and publishing the results.

In conclusion, yoga may or may not be an effective complementary aid for management of Type II diabetes. My personal experience is that yoga is a nice, accessible gateway exercise that helped me to transform my less active life to what it is now. We need to be able to show this with more confidence, so there is a need for studies with solid methodology.

Thanks for reading this long entry. If you have anything to contribute, please comment below. ❤

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Ref: Kumar, V., Jagannathan, A., Philip, M., Thulasi, A., Angadi, P., & Raghuram, N. (2016). Role of yoga for patients with type II diabetes mellitus: A systematic review and meta-analysis. Complementary Therapies in Medicine, Vol. 25. pp. 104-112. doi: 10.1016/j.ctim.2016.02.001

* Iyengar does name specific asanas however the list is about 100-asana long encompassing the those asana families above.

**Detailed WHO report on diabetes  here

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