|Year : 2016 | Volume
| Issue : 4 | Page : 138-142
Yoga and the heart
Rahul Mehrotra MD, DNB
Department of Cardiology, Medanta The Medicity, Gurgaon, Haryana, India
|Date of Web Publication||20-Oct-2016|
Medanta - The Medicity, Sector 38, Gurgaon - 122 001, Haryana
Source of Support: None, Conflict of Interest: None
The concept of "Yoga" is currently gaining a lot of popularity worldwide owing to its various health benefits and other advantages such as safety and ease of practice. There is considerable evidence accumulating related to its benefits on health, especially cardiovascular health. There is, however, a lot of confusion related to the term "Yoga" in the various studies as it comprises several different practices. More good quality studies are needed utilizing different components of "Yoga" investigating their effects on cardiovascular disease. There is also a change in the understanding of the role of the heart in the human body.
Keywords: Cardiovascular health, heartfulness, meditation, spirituality, stress, Yoga
|How to cite this article:|
Mehrotra R. Yoga and the heart. J Clin Prev Cardiol 2016;5:138-42
"The heart of creatures is the foundation of life, the prince of all, the sun of their microcosm, on which all vegetation does depend, from whence all vigor and strength does flow."
-William Harvey, M.D., 1628
All of us have heard about "Yoga" and some of us have even practiced one or the other form of Yogic practices at some point of time. Having originated in India, "Yoga" has become very popular in the recent times even in the Occident, owing to several reasons. Ease of practice, health benefits, its ability to reduce stress, and increased awareness about fitness coupled with its spiritual benefits are some of the reasons for its increasing popularity and universal appeal. The United Nations too has declared June 21 as the International Yoga Day to promote it worldwide.
There is, however, a lot of confusion regarding the term "Yoga," what it may constitute and thus, the benefits that can be obtained. From simple physical postures (asanas), breathing exercises (pranayamas) to different types of meditations, and a combination of all these are being loosely termed as "Yoga." Actually, "Yoga" is a Sanskrit word with the root "Yuj" which means to join. "Yad jyute, anena, iti yogah." Originally, it meant the union of the individual soul (atma) with the ultimate (paramatma). Clearly, it implies the culmination, the apotheosis, of all the spiritual practices aimed at arriving at this stage and is not an activity that is performed. The Vedantists had suggested four means of achieving this (Sadhana Chatushtaya) comprising of Viveka (discrimination), Vairagya (detachment), Shat Sampatti (six ways of regulating mental tendencies), and Mumukshutva  to achieve this end. This approach required rigorous physical and mental self-discipline apart from enormous dedication, effort, and time to achieve the ultimate goal. Besides, with the passage of time, several complexities had crept up with various interpretations and approaches. There arose Japa Yoga, Tapa Yoga, Tantra Yoga, Mantra Yoga, Bhakti Yoga, Gyana Yoga, Karma Yoga, Kundalini Yoga, etc. Around 2000 years ago, Sage Patanjali removed all the confusions and gave a simplified eight step approach to God realization-Ashtanga Yoga (eight-limbed approach) in his significant work - The Yoga Sutra [Figure 1]. This system starts with morality and ethics so as to inculcate superior human qualities and ends with Samadhi-being one with the original state. It includes all the aspects required in making of a human in achieving perfection-the real the goal of human life. Broadly, the first five aspects deal with physical-mental aspects and are referred to as constituting Hatha Yoga, while the other three are concerned with finer experiences directly related to the soul and constitute Raja Yoga. 
With this background in mind, it is clear that the term "Yoga" is very vast, encompassing numerous practices. We must therefore be clear when we use the term "Yoga" as to which component or what practice we are referring to.
|Figure 1: The eight limb approach (Ashtanga Yoga) of Saint Patanjali. The green boxes on the left constitute Hatha Yoga, while the blue boxes on the right represent Raja Yoga|
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Since these practices include physical exercises, dietary regulation, and mental discipline, it is expected that they result in overall improvement in health and wellbeing. This is one of the reasons why many people are taking up yogic practices. The scientific community has also started investigating the health impact, if any, of these practices by the way of performing studies and clinical trials to evaluate the actual benefits of these practices in ameliorating disease and promoting health.
| Yoga and Health|| |
In terms of health, the benefits of these yogic practices are wholesome-encompassing the physical, mental/emotional, social, and spiritual. As mentioned earlier, the loose term "Yoga" cannot be used to denote a single type of activity. As such, the benefits also depend on the type of activity undertaken. For example, mere performance of physical asanas is unlikely to yield as much reduction in emotional stress as is expected with meditation, while asanas are likely to have more demonstrable effects on physical health as compared to meditation. Moreover, there are different types of meditation such as heartfulness, mindfulness, vipassana, and transcendental, each utilizing different techniques, and the benefits of one cannot be extrapolated on another. The temporal association of the effects with each of these is also unknown. The planning and interpretation of studies on yogic practices thus have to take into account these factors. Moreover, the studies aimed at demonstrating the tangible, physical benefits which are more easily performed than those showing the mental/emotional benefits like stress reduction for obvious reasons. The spiritual aspects cannot be evaluated by science at all since it is a different domain altogether beyond matter. In spite of these severe limitations, substantial progress has been made to study the effects of yogic practices on different aspects of health and new literature is being published from around the world with different type of yogic practices at an astonishing rate.
| Yoga and Cardiovascular Health|| |
Cardiovascular diseases (CVDs) are the leading killers of our times, and coronary artery disease (CAD) is the most important contributor to this epidemic. CAD is considered to be a lifestyle disease since the factors responsible for the development of CAD are largely related to the faulty lifestyle of the individual. Since most yogic practices involve a disciplining of the behavior, regulation in eating and drinking habits, and abstinence from smoking, it is expected that the performance of some or the other of these yogic practices would result in a change to a healthy lifestyle in general with reduced risk of development of CAD.
If one looks at the nine risk factors for myocardial infarction as brought out by the INTERHEART study, psychosocial stress emerged as a powerful risk factor.  This clearly underscores the importance of thought process influencing the metabolic factors which ultimately result in plaque rupture. It is thus clear that negative emotions described as "stress," influences the atherosclerotic plaque dynamics, perhaps through the hypothalamus-pituitary-adrenal axis. In a landmark meta-analysis published in JAMA, 47 trials involving over 3500 participants were studied. The authors concluded that mindfulness meditation programs had moderate evidence of improved anxiety and depression up to 3-6 months.  This points to the significant benefit of meditation on reducing negative emotions. The effect of positive emotions such as calmness of mind and other states produced in meditators has not been demonstrated as yet on CAD, but indirect evidence points out that these may have a protective role. In a study using Vipassana meditation, Krygier et al. demonstrated that after a brief training in meditation, the self-reported feeling of well-being improved and ill-being reduced. Moreover, there was a positive impact on measures of heart rate variability (HRV)-a psychophysiological index of health.  It is well known that HRV is a marker of cardiovascular (CV), as well as overall mortality. By influencing HRV, meditation may have a favorable impact on overall CV health and mortality. In another meta-analysis of 32 studies of Yoga,  it was shown that the practice of different types of Yoga resulted in a significant reduction in LDL cholesterol, systolic blood pressure (SBP), and body mass index. Moreover, it had a favorable impact on those who wanted to quit smoking. The meta-analysis concludes that the practice of different forms of Yoga favorably impacts several risk factors directly or indirectly influencing CAD. The major limitation of this type of analysis is that it does not discriminate the different type of practices and the effects produced for a more specific information.
There have been studies on different CAD risk factors with different type of yogic practices. Certain asanas and pranayamas are believed to lower blood pressure (BP) and are routinely prescribed for this purpose. The benefits may be by modulation of parasympathetic tone, baroreceptor sensitivity, and by reducing stress. In a systematic review of all published studies on Yoga and hypertension, which included 48 randomized controlled trials and a total of over 6600 patients, it was shown that Yoga effectively lowered BP in both normotensive and hypertensive populations.  The role of meditation in reducing BP has also been studied. Hughes et al. studied mindfulness-based stress reduction (MBSR), a structured protocol of mantra and breathing-focused meditation, in 56 male and female patients with prehypertension. Patients randomized to the MBSR arm exhibited a 4.8 mmHg reduction in systolic blood pressure (SBP) and a 1.9 mmHg reduction in diastolic BP (DBP) compared to a 0.7 mmHg reduction in SBP and an increase in DBP in the control group.  BP lowering by Yoga is a safe adjunct to diet and exercise which is free of any toxicity apart from being inexpensive. However, it is still not clear which component, asanas, pranayama, or meditation, has the maximal BP lowering effect or it is a combination of all these that works.
Lipid lowering by statins is currently the cornerstone of CVD risk reduction. However, the considerable debate is raging related to the side effects of statins on long-term use, and the practice of yogic techniques to lower lipid levels is a safe alternative which is being evaluated. In a small study, Cooper and Aygen compared 12 patients with hypercholesterolemia who regularly practiced meditation with 11 control participants who did not practice meditation and found a significant 10% (P < 0.005) reduction in fasting serum cholesterol levels in those who practiced meditation during a 13-month period.  This effect is probably mediated through a reduction in adrenergic activity and effect on serum cortisol due to the relaxation effect of meditation.
Elevated cortisol level is now being considered as an emerging risk factor for CAD. It has been shown that it is related to raised fasting glucose, cholesterol, and prevalent CAD independent of other risk factors. There are several reports of reduction in serum cortisol levels and blunting of rise in the levels in response to stress in people who meditate.  This may well be one of the mechanisms by which meditation benefits the bodily functions.
Smoking is a major risk factor for CAD worldwide, which is primarily related to human behavior. The practice of meditation being directly related to bringing about positive behavioral changes encourages healthy lifestyle choices and avoiding risky behaviors like smoking and substance abuse. Besides, it is a very safe and cost-effective means of helping people quit smoking. In a randomized trial, brief training (for 2 weeks or 5 h total) in mindfulness meditation resulted in as much as 60% reduction in smoking, and it also reduced craving, a major factor why smokers are unable to quit.  In a meta-analysis of ten studies of Yoga-based interventions, it was concluded that majority of interventions were able to enhance quitting-smoking-rates in the study participants and that Yoga-based interventions held promise as smoking cessation tools. 
Apart from the above-discussed studies related to conventional and unconventional risk factors for CAD, there have been studies which have demonstrated regression of established atherosclerotic plaques. In a study involving around eighty patients of metabolic syndrome, Yoga-based intervention (including asanas, pranayama, and meditation) was compared to control group. At the end of a year, there was a significant improvement in the parameters of metabolic syndrome along with a reduction in carotid intima-media thickness in the intervention arm as compared to the control arm.  In another prospective randomized trial involving 42 patients with angiographically proven CAD, it was shown that the intervention arm undergoing Yoga had significantly less anginal episodes, improved exercise capacity, greater lesion regression, and less lesion progression compared to the control arm at the end of 1 year. 
Another area where meditation, asanas, and pranayama can be integrated in CV health is during the period after a major CV event. Incorporation of these practices in cardiac rehabilitation programs is likely to improve adherence and retention rates rather than relying solely on diet and exercise prescription based programs, where the long-term adherence rates have been quite poor. ,
There is no straightforward mechanism which can be used to explain all the beneficial effects of different constituents of Yoga-such as asanas, pranayama, and meditation. [Figure 2] summarizes few proposed mechanisms of action of all these yogic practices based on studies carried out so far. It is not a comprehensive and complete list since new mechanisms are being revealed as our understanding is improving and new research is being undertaken.
As discussed above, there is an evolving body of evidence demonstrating the effectiveness of Yoga-based interventions in various stages of CAD prevention. However, the long-term impact of different types of meditations, asanas, and pranayamas and their relative value need to be systematically studied in a large and diverse population for more clarity on the issue. The major problem has been the small sample size in studies, the heterogeneous nature of Yogic interventions studied, short duration of follow-up, and paucity of quality data [Table 1].
|Figure 2: Proposed mechanisms by which the different yogic practices influence the body based on available evidence. BMI ody mass index, BMR asal metabolic rate, GABA amma amino butyric acid, PNS arasympathetic nervous system, SNS ympathetic nervous system|
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|Table 1: Some of the limitations of the available scientific literature on Yoga|
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| Yoga and the Role of Heart|| |
"The heart has its reasons which reason doesn't know"
The heart occupies a unique position in the human system according to the scriptures. It is not just the key organ of CV system, pumping blood to the entire body, but is also considered to be the nucleus, the center of the human body. All religious systems believe that the heart is actually the seat of divinity in the human frame. The terms such as kind hearted and soft hearted have been used since long to describe the character of an individual in the belief that heart was the seat of these traits, qualities. The heart has also been considered to have the ability to feel, communicate, and respond. This is where science and spirituality differed and diverged. Not any longer. New research is focusing on roles of the heart other than mere pumping of blood to all organs of the body.
Startling revelations by systematic experiments of heart transplant patients have compelled a rethink of rigid scientific beliefs. It has been shown that the character of the recipients changed significantly, and in many cases, the recipient recalled instances from the life of the donor, even when they had never met the donors or had any information about their lives. , Other studies have looked at the ability of the heart to communicate its feelings to the outside environment and the relationship of the heart with other organs in the body.
This is an exciting area of research for the future which may change the way we have been looking at the heart and its ailments.
Although the topic of Yoga has become quite popular in the recent times and there is a lot of excitement and expectations related to its health benefits owing to its universal appeal, simplicity, and almost no cost and side effects. Caution should however be exercised in interpreting Yogic practices and their purported health benefits since the term "Yoga" is a very heterogeneous term including, in various combinations, physical exercise component-asana, breath control-pranayama, and regulation of the mind-meditation. Besides, it should be clearly understood that the primary goal of these practices, especially meditation, is spiritual. The spiritual dimension is altogether beyond the scope of science and scientific principles, which operate within the confines of matter only. There may however result some benefits in health as a corollary, especially CV health, owing to the overall positive impact on the lifestyle of the practicant. There have been studies exploring this impact, but it is very difficult to perform and interpret these as there is no uniformity of the approach, the population studied, the duration of studies performed, the duration of exposure to these practices studied, small sample size, and the chosen end point in these studies. The effect of meditation is primarily mediated through the brain and autonomic nervous system also impacting the adrenergic system through this axis. The favorable impact has thus been shown in stress reduction, emotional stability, HRV, and metabolic parameters such as insulin resistance, cholesterol, and cortisol reduction in small-scale studies with several limitations. Having said that, the ideal of perfection as aimed for by some systems of Yoga like the Sahaj Marg  have the potential of promoting overall balanced lifestyle resulting in a holistic improvement in health including physical, mental, social, and spiritual well-being. Moreover, this approach is likely to be effective in improving compliance in the patients attending various cardiac rehabilitation programs. Prominent academic institutions are offering the practice of meditation to their patients as a scientific tool to reduce stress and improve lifestyle. As an approach to holistic health, the yogic practices have a lot to offer, and it seems their time has come, but we as scientists must be cautious before hailing it as the panacea, humanity has been looking for. A lot of information needs to be collected before this becomes a reality.
This is perhaps the best time and an opportunity to undertake systematic research to evaluate the health benefits of the various forms of yogic practices and give to the world, once again a natural, holistic approach for leading healthy, purposeful lives.
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[Figure 1], [Figure 2]