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Yoga Research: Yoga Reduces Risk Factors for Type 2 Diabetes
Type 2 diabetes is a leading global public health crisis, with the number of adults diagnosed with the condition more than doubling in the past 30 years. A systematic review of controlled yoga trials for adults with Type 2 diabetes (DM2) published in the Journal of Diabetes Research suggests that regular yoga practice may help to reduce a number of key risk factors and outcomes of the disease.
DM2 is the leading cause of death and disability worldwide. In addition to its role in heart and renal disease, DM2 is also associated with many serious, chronic conditions including depression, dementia, diabetic neuropathy and blindness. The primary symptoms of diabetes include hypertension, elevated cholesterol levels, chronic inflammation and increased oxidative stress.
Although the incidence of DM2 tends to be higher in certain ethnic and racial groups such as African Americans, Native Americans and Pacific Islanders, modifiable lifestyle factors including physical inactivity, poor diet, obesity, chronic stress, impaired sleep and smoking are major contributors to the rapid growth of this disease and its high mortality rate.
Yoga for Type 2 Diabetes
Yoga has been widely studied as a potential ancillary treatment for DM2. Because of its mind-body emphasis and its ability to address not only physical risk factors for DM2 such as hypertension and dyslipidemia, but also psychological factors like perceived stress, depression and emotional wellbeing, yoga may be an important addition to DM2 prevention and management.
To better understand the evidence for the use of yoga for DM2 management, researchers examined all of the published controlled trials in which yoga was used as a primary intervention for DM2 symptom reduction. They identified 33 articles detailing the outcomes of 25 original studies in which the effects of a yoga-based intervention was tested on one or more of the following: glycemic control, insulin resistance, lipid profiles, blood pressure, oxidative stress, cardiopulmonary function, mood, sleep impairment, body weight or composition, and medication use.
As is typical for yoga research, their review found that yoga interventions varied greatly in their frequency, duration, content and intensity with some including weekly classes and others requiring participants to practice six to seven times per week for 12 months. A total of 92% of students incorporated yoga poses (asanas) into their interventions some of which also included yoga nidra, pranayama (rhythmic breathing), and all used some form of active control group (exercise, group education, special diet, medication etc.).
Yoga Improves Glycemia and Insulin Resistance
Of the studies reviewed, 24 (12 randomized controlled trials [RCTs]) included some measure of glycemia and insulin resistance. Of these, all but two used yoga postures in their intervention. Treatment length varied from 15 days to 12 months. Of the 12 RCTs and 12 non-randomized controlled trials (N-RCTs) reviewed, 92% reported statistically and clinically significant improvements in glucose readings. These findings suggest that regular yoga practice may be highly beneficial in reducing these two symptoms for adults with DM2.
Yoga Improves Lipid Profiles
A total of 16 of the studies included in the systematic review examined the effects of yoga practice on lipid profiles. A lipid profile refers to a blood test that screens for cholesterol and triglycerides, two key risk factors for DM2. Yoga programs offered in these 16 studies varied in length from 40 days to 12 months. With the exception of one program, participants were expected to practice yoga three days per week.
Of these studies, 94% reported clinically and statistically significant reductions in lipid levels following participation in the yoga intervention. These results provide support for regular yoga practice as one method for reducing cholesterol and triglyceride levels among adults with DM2.
Yoga May Reduce Hypertension
Only five of the 25 controlled trials examined blood pressure as an outcome variable. Each of these studies included some form of active asana practice, and they ranged in duration from 40 days to three months. Of these studies, three reported significant reductions in systolic and diastolic blood pressure in the yoga group compared to standard care of active controls. Neither of the remaining two studies found statistically significant changes in blood pressure following the yoga intervention.
Yoga May Help to Reduce Body Weight
Nine of the studies reviewed included some measure of change in body weight and/or composition. All of these trials included active yoga postures as a key component of their intervention, which lasted from 40 days to six months. Participants were asked to practice yoga three days per week in all but one of the studies.
While the findings were mixed, 89% of studies noted some improvements in weight, body mass index (BMI), or waist-hip ratio for the yoga group compared to inactive or light exercise controls. One study found no differences in weight or BMI following the yoga program, however, their lack of positive findings may be due to poor treatment adherence. The extent to which regular yoga practice may facilitate changes in body composition for adults with DM2 may depend on the length, duration and intensity of the asana component of the practice. More research will be required to test that proposition.
Yoga May Provide Important Benefits on Other DM2-Related Symptoms
A number of other important variables were considered in some of these controlled trails including oxidative stress, mood, sleep disturbance, and pulmonary and nervous system function. Although only a few of the 25 studies examined these factors, overall results provide general support for yoga as a means to decrease stress and sympathetic nervous system activation, depression and sleep impairment, and improve pulmonary and nervous system functioning and perceived quality of life.
The authors of this review conclude that stress reduction may be one of the major mechanisms by which yoga impacts health factors including metabolic function, cardiovascular function and mood. They go on to note that although these findings are encouraging, the methodological limitations, poor analytic methods and factors such as considerable variability in yoga program duration, intensity, design and delivery, make it difficult to draw any definitive conclusions regarding the benefits of yoga for the prevention and complementary treatment of DM2.
Learn ways to reduce diabetes risk. Study online with YogaU and Dr. Baxter Bell, Yoga and Metabolic Syndrome: The Positive Possibilities!
More on Yoga and Diabetes from YogaUOnline and Elaine Gavalas: 3 Ways Yoga and Meditation Can Help with Diabetes.
B Grace Bullock, PhD, E-RYT 500 is a psychologist, research scientist, educator, author, yoga and mindfulness expert and creator of BREATHE: 7 Skills for Mindful Relationships. Her mission is to reduce stress, increase health and wellbeing and improve the quality of relationships. She offers classes, workshops, writing and research that combine the wisdom of applied neuroscience, psychophysiology, psychology and contemplative science and practice. Her goal is to empower individuals, groups, leaders and organizations to reduce chronic stress and increase awareness, attention, compassion, mindfulness and effective communication to strengthen relationships, release dysfunctional patterns and unlock new and healthy ways of being. Dr. Bullock is a Certified Viniyoga Therapist and Faculty at the Integrated Health Yoga Therapy (IHYT) Training program. She is the former Senior Research Scientist at the Mind & Life Institute and former Editor-in-Chief of the International Journal of Yoga Therapy. For more information see www.bgracebullock.com
Innes, K.E. & Selfe, T.K. (2015). Yoga for adults with Type 2 Diabetes: A systemic review of controlled trials. Journal of Diabetes Research. Article ID 526967