Results of the very few randomized controlled trials that look at how yoga affects symptoms of type 2 diabetes point to no ill but wide uptake of the practice is a stretch.
Research suggests various health benefits for the practice of yoga, including improvements in chronic back pain, obesity, cardiovascular disease, asthma, quality-of-life (QOL) issues related to cancer and stress management, relaxation, and depression. Could yoga also have a role in the management of type 2 diabetes mellitus (T2DM)?
Research into effects of the ancient practice seems to indicate that yoga has some benefits for people with T2DM, albeit through indirect mechanisms such as improved weight management, reduced anxiety, and enhanced overall fitness. Evidence for more direct effects on glycemic control comes from small, short-term studies of limited quality. Variations among studies in types of yoga used in the intervention (of which there are many) also hinders comparison of outcomes.
There are, however, several randomized controlled trials that have examined the role of yoga in various aspects of T2DM prevention and management and they merit a look.
A 48-week randomized trial conducted from 2009-2012 at the University of California, San Francisco, and University of California, San Diego, compared restorative yoga vs stretching among 180 adults with metabolic syndrome and low activity levels. Researchers looked at fasting plasma glucose (FPG) and 2-hour glucose, HbA1c (A1c), triglycerides, HDL-cholesterol (HDL-C), insulin, systolic blood pressure, visceral fat, and quality of life.1
♦ Completion: 75% of participants completed the trial.
♦ At 6 months: The yoga group had favorable but nonsignificant reductions in FPG, insulin, and A1c and increases in HDL-C. None of these changes were durable at 1 year except FPG.
♦ At 12 months: The yoga group continued to have lower levels of FPG, compared with the stretching group (P = .002); no other significant between-group differences were noted.
♦ Conclusion: “Restorative yoga was marginally better than stretching for improving fasting glucose but not other metabolic factors.”
Cardiac Autonomic Function
In a study conducted in New Delhi, researchers randomized 120 patients with diabetes who were receiving standard treatment with oral medication and lifestyle management to continued 6 months of standard treatment or standard treatment plus a comprehensive yogic breathing program with monitored yoga practice. They tested cardiac autonomic function with the deep breathing test using ECG monitoring, and blood pressure changes during Valsalva maneuver, sustained handgrip, the cold pressor test, and the lying-to-standing test.2
♦ Quality of life and postprandial glucose level: Significantly improved in the yoga compared with control groups (P = .06 and P = .02, respectively).
♦ FPG, A1c: No significant differences.
♦ Sympathetic cardiac autonomic function: Significantly improved in the yoga compared with the control group (P = .01)
♦ Total and parasympathetic cardiac autonomic functions: No significant differences.
♦ Conclusion: “This randomized controlled trial points toward the beneficial effect of a yogic breathing program in preventing progression of cardiac neuropathy. This has important implications because cardiac autonomic neuropathy has been considered as one of the factors for sudden cardiac deaths.”
This study was conducted in Mangalore, India, and looked at measures of oxidative stress in 123 patients with T2DM and microvascular complications, macrovascular complications, peripheral neuropathy, or without complications. They randomized participants to either standard diabetes care (n=63) or standard care along with yoga (3 classes/week) for 3 months (n=60).3
♦ Average class attendance: 82% to 88%
♦ FPG, A1c, BMI, malondialdehyde level (a measure of oxidative stress): Significantly reduced for yoga vs standard care (P < .001 for all)
♦ Glutathione, vitamin C (measures of antioxidant status): Significantly increased for yoga vs standard care (P < .001 and P < .002, respectively)
♦ Waist circumference, waist to hip ratio, blood pressure, vitamin E, superoxide dismutase: No significant between-group differences.
♦ Conclusion: “Yoga can be used as an effective therapy in reducing oxidative stress in type 2 diabetes.”
Feasiblity of Yoga: Role of Culture and Environment
This study took place in 2 mutli-ethnic boroughs of London with average or low socioeconomic levels. Researchers identified participants from general practice clinics. They randomized 59 participants with diabetes not requiring insulin to 12 weeks of twice-weekly 90-minute yoga classes or a control group assigned to a wait-list for yoga. Both groups received counseling on healthy lifestyle and exercise.4
♦ Participation: 90% of eligible participants chose not to participate. The 59 persons who did had a mean age of 60 ± 10 years.
♦ Intervention: Only 50% of participants attended yoga practices. No participants regularly practiced yoga at home.
♦ Barriers: When interviewed, yoga teachers believed that most participants were “unsuitable” for “standard” yoga, as a result of limited flexibility, poor fitness, comorbidity, and low confidence.
♦ A1c: Fell slightly in the yoga group, but change was nonsignificant and not sustained over 6 months.
♦ Outcome measures: No significant changes seen in weight, waist circumference, lipids, blood pressure, measures of cardiovascular risk, diabetes-related QOL, self-efficacy.
♦ Conclusion: “The benefits of yoga in type 2 diabetes suggested in some previous studies were not confirmed. Possible explanations (apart from lack of efficacy) include recruitment challenges; practical and motivational barriers to class attendance; physical and motivational barriers to engaging in the exercises; inadequate intensity and/or duration of yoga intervention; and insufficient personalisation of exercises to individual needs. ”
Just Say Om
Though limited evidence suggests that yoga could play a role in the prevention and management of T2DM, several barriers exist. Socioeconomic disadvantage, cultural attitudes affecting acceptability of yoga, and physical limitations could all play roles. Personalizing regimens to the limitations and abilities of individual patients may go a long way in getting them off the couch and moving.