By
: Ruth Howard
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Introduction
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We hear of yogis living to a
very old age. In his book Autobiography of a Yogi, Yogananda speaks of
Trailanga Swami, who was reputed to be over 300 years old, and Shankari
Mai Jiew, who was born in 1826, was still alive in 1946. Maharishi Raghuvacharya
lived to the age of 115, and Devraha Baba was believed to have lived to
over 250 years old. Yogis well known in the west who lived to a very old
age include Krishnamacharya (101), Pattabhi Jois (93) and Indra Devi
(103).
Not only are master yogis long
lived, but they also maintain excellent health e.g. BKS Iyengar is still
going strong at 91; he was in better shape at 80 than many people at 40.
Photos exist of Krishnamacharya doing full parsvakonasana at 78 years old
[13], and
Pattabhi Jois continued to teach yoga until the age of 90.
So how do we explain this?
There are several fairly
obvious physical factors in the yogic lifestyle that would influence
health and aging, as well as more subtle factors.
Calorie restriction (CR) is
widely accepted as the only method so far proven to extend longevity and
reduce the physical manifestations of aging. It has been demonstrated in a
wide variety of species, from yeast to monkeys (though not yet in
humans), that a calorie restricted diet (lowering the calorie intake by
20-30%, while providing essential nutrients), increases lifespan.
CR animals maintained youthful
appearances and activity levels longer and showed delays in a range of
age-related diseases. CR reduces age associated neuronal loss, prevents
age-associated declines in learning, psychomotor and spatial memory tasks
and improves the brain's ability for self repair [24].
We can find several parallels
between the effects of calorie restriction and the metabolic effects
associated with yoga practice.
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Physiological changes
associated with aging: These include:
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- Loss of muscle mass and
tone, decreased muscle to fat ratio
- Loss of bone density
- Loss of flexibility,
joint disorders such as arthritis
- Deterioration of lung
elasticity and capacity
- Disorders of the
circulatory system - decreased sensitivity of baroreceptors
- Degenerative disorders of
nervous system - e.g. tremor, Parkinson's disease
- Sensory and cognitive
impairment
- Psychiatric conditions -
depression, anxiety, dementia
- Reduced immune function
- Reduced reserve capacity
(slower recovery from exertion, injury or disease)
- Sleep disorders
- Impaired glucose
tolerance and insulin sensitivity, strongly linked to abdominal
obesity
- Further complications can
occur as side effects of medication, or medication may mask symptoms
of new diseases [2]
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Why do we age?
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There are many and varied
theories of aging, among them the following:
The free radical theory of
aging states that over time, cells accumulate oxidative damage caused by
free radicals which are the normal by products of metabolism. Aging is
characterised by a decline in ability to neutralise free radicals [2].
The rate of living theory
states that lifespan is inversely related to metabolic rate. It appears
to apply to many species; however a notable exception is birds.
Another theory suggests that
lack of protein turnover may cause aging.
Evolutionary theories of aging
suggest that the previous generation age and die to make way for their
offspring, maintaining genetic diversity within the population.
According to the programmed
aging theory, aging is genetically programmed, and age related changes in
cellular function result in increasing susceptibility to disease and
eventually lead to death [2].
Theories of aging based around
programmed cell death (apoptosis) imply that as people age, more of their
cells start to decide to die.The cell division limit theory
states that there is a specific limitation on the number of divisions
that somatic cells might undergo.
The telomeric theory of aging
postulates that as telomeres (regions of repetitive DNA at the ends of
chromosomes) shorten each time a cell divides; this leads damage to
essential DNA. This results in cellular damage due to the inability of
the cell to duplicate itself correctly. Elevated levels of oxidative
stress and inflammation further increase the telomere attrition rate [12], [28].
This theory ties in with the free radical theory and the cell division
limit theory. Other theories ascribe age
related problems to the accumulation of random genetic errors over time,
also decline in DNA repair capability of cells.Many of these theories are
interlinked, and all appear to have some validity, but a definitive
answer has not yet been found.
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General positive effects of a
yogic lifestyle
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There are many known benefits
to the regular practice of yoga, which would help to minimise many of the
problems associated with aging.Regular exercise (asana) can
help to maintain muscle strength and tone and bone density, joint
flexibility, and improve posture, balance and maintain mobility. Combined
with pranayama, regular practice can help to maintain circulatory and
respiratory health.Yoga has also been shown to be
beneficial in the management of stress, anxiety and depression, aiding in
the maintenance of mental health. A vegetarian diet can also aid
in extending life - it has been shown that vegetarians live longer, have
less heart disease and lower rates of cancer [4].
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Metabolic factors associated
with calorie restriction and longevity - Biomarkers of aging
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Caloric restriction in
laboratory animals has been shown to have significant impact on that
metabolism.
The biological characteristics
of animals on CR diets seem to apply to longevity in people. A continuing
study in Baltimore by George Roth of the National Institute of Aging
concluded that the same biological markers produced in CR animals are
evident in the men who are living the longest.
These markers include:
- Lower levels of blood
glucose and insulin
- Reduced body temperature
- Less fat in the blood, more
HDL (high-density lipoprotein - good cholesterol )
- A steady level of DHEA
(dehydroepiandrosterone - a steroid hormone) [14], [29]
Plasma melatonin levels may
also represent a possible biomarker of aging in primates [30].
One of the most popular
proposed theories by which CR promotes lifespan extension is the rate of living
theory. It is hypothesized that a lowering of the metabolic rate results
in lowering of reactive oxygen species (ROS) and rate of oxidative damage
to vital tissues [27].
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Parallel effects found in yoga
practitioners
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Blood glucose and insulin
Type 2 diabetes, heart
disease, arteriosclerosis, liver disease, elevated cholesterol and
hypertension are among the medical conditions associated with insulin
insensitivity and elevated blood glucose levels [2].
Calorie restricted animals
show a significantly increased sensitivity to insulin compared to freely
fed animals. CR also has a significant impact on insulin sensitivity in
humans [3], [16].
With normal aging, people tend
to develop abdominal obesity. High levels of intra abdominal fat have
been found to be predictive of heart attack risk and also linked to high
cholesterol, high blood pressure, high triglycerides. There is a strong association
between increased waist circumference, insulin insensitivity and type 2
diabetes. Yoga practice seems to weaken this link [9].
High levels of stress lead to
increased cortisol levels, which is associated with higher levels of
abdominal fat. Any form of exercise would help to reduce visceral fat and
thus reduce abdominal circumference.
It has been suggested that
relaxation and stress reduction may not cause overall weight loss, but
may result in a healthier distribution of body fat [18]. It
has been found that there were favourable metabolic changes in overweight
and underactive subjects who practiced restorative yoga [10]. The
effect of restorative yoga on body fat distribution would make an
interesting basis for further study.
A recent study found that long
term yoga practice was associated with increased insulin sensitivity, and
significantly lowered fasting plasma insulin levels [9].
In a 45 day study on people
with Type 2 diabetes, all patients continued to take conventional
medicines. The study group practiced asana and pranayama, while the
control group did not practice yoga. The yoga group showed significant
improvement in blood glucose, lipid profile and insulin levels and a
decrease in BMI (body mass index). The control group showed an increase
in weight, and non significant improvement in the other parameters [37].
Reviews of published studies
found that yoga interventions are generally effective in reducing body
weight and glucose levels [41], [20], [21].
These studies suggest that yoga can have a beneficial effect on glucose
tolerance and insulin sensitivity.
Blood
lipid profile
HDL (high density lipoprotein
- good cholesterol) helps to remove cholesterol from the blood,
protecting from cardiovascular disease. Higher levels of HDL are
correlated with better health outcomes.
LDL (low density lipoprotein -
bad cholesterol) is thought to deposit cholesterol in artery walls,
increasing the risk of heart disease. High levels of LDL are associated
with atherosclerosis. This includes VLDL (very low density lipoprotein).
Along with reductions in basal
metabolic rate (BMR), people on CR diets experienced large reductions in
LDL cholesterol, and had very high levels of HDL cholesterol [16].
In a study on normal, healthy
volunteers, after 30 days of practicing pranayama, a significant
reduction in triglycerides, free fatty acids and VLDL cholesterol along
with significant elevation of HDL cholesterol was observed in the men.
Free fatty acids were reduced in women.
After adding asana exercises
to the pranayama for another 60 days, free fatty acids increased in both
men and women, and women demonstrated a significant fall in serum
cholesterol, triglycerides, LDL and VLDL cholesterol [26].
It is of interest that free
fatty acid levels increased after the subjects started doing asana
exercises. It is possible that their bodies were breaking down fat.
Further research would aid in clarifying this somewhat contradictory
effect.
In another study on patients
with coronary artery disease, at the end of one year of yoga training,
total cholesterol was reduced by up to 23% in the yoga group of patients,
compared to 4.4% in the control group. LDL cholesterol was reduced by 26%
in study group patients as compared to 2.6% in the control group. A much
higher proportion of the yoga group showed regression and arrest of
progression of the disease than in the control group [43].
Studies indicate that
pranayama and yoga asanas can be helpful in patients with lipid
metabolism disorders [26], and
have a positive effect on blood lipid profile, reducing cholesterol [41], [20], [21].
Melatonin
Melatonin is produced by the
pineal gland, and appears to have anti aging properties [36],
likely due to its antioxidant properties. It is also a natural immune
enhancer and has been shown to extend longevity in some animal studies [22].
Higher melatonin levels are also associated with an increased sense of
well being.Melatonin is released mainly
at night during sleep. Moderate physical activity has been shown to
increase production of melatonin [35].
Calorie restriction has been
shown to prevent the usual age related decline in melatonin levels in
monkeys [30].
Yoga and meditation have been
shown to significantly increase melatonin levels, with regular meditators
found to have a higher level of melatonin than non-meditators [19], [40], [34].
In a 2004 study on normal,
healthy volunteers, a yoga group practiced asana, pranayama and
meditation while a control group did body flexibility exercises, slow
running, and played games.
Yogic practices for 3 months
resulted in an improvement in cardiorespiratory performance and
psychological profile, with an improved sense of well being. The maximum
night time melatonin levels in yoga group showed a significant
correlation with well-being score.
The yoga group showed an
increase in plasma melatonin, indicating that yoga could be used as a
psychophysiologic stimulus to increase endogenous secretion of melatonin
[19].
In another study, experienced
meditators practising either TM-Sidhi or another form of yoga showed
significantly higher plasma melatonin levels in the period immediately
following meditation compared with the same period at the same time on
control nights. It was concluded that meditation, at least in the forms
studied here, can affect plasma melatonin levels [40].
Longer term studies are
required to ascertain whether the higher melatonin levels in yoga
practitioners and meditators are sustained.
Basal
metabolic rate and body temperature
Studies measuring metabolic
rate in CR animals indicate that it lowers the BMR. CR in animals is
associated with a robust decrease in energy metabolism, including a
lowering of resting metabolic rate, lowering of the thermic effect of
meals and a decrease in the energy cost of physical activity [27], [15].
Some studies measuring
metabolic rate in CR animals give conflicting results [24], and
lowered metabolic rate does not necessarily entail a prolonged life span
[15].
However, specific metabolic
rate correlates highly with oxidative DNA damage. This is consistent with
the theory that free radical induced DNA damage may play a central role
in the aging process [1].
Body temperature, one of the
biomarkers of longevity, is linked to metabolic rate; a lowered BMR would
be associated with a slightly lowered core body temperature.
It seems logical to expect
that because yoga asana is an energy expenditure activity, it would
increase the resting metabolic rate. However, two different studies using
healthy volunteers found that the BMRs of yoga groups practicing asana,
pranayama and meditation were significantly lower than the BMRs of
control groups [7] [8].
Asanas when practiced along with pranayama and meditation over a period
of time actually significantly reduce the metabolic rate [7] [8].
The metabolic rate is an
indicator of autonomic activity. The lower metabolic rates in the yoga
subjects may have been due to decreased sympathetic nervous system
activity and probably, a stable autonomic nervous system response
achieved due to training in yoga [7] [8].
A study on alternate nostril
breathing found that breathing selectively through either nostril could
have a marked activating effect or a relaxing effect on the sympathetic
nervous system; it is possible to alter metabolism by changing the
breathing pattern [39].
Hypometabolic states have been
reported in yogic studies, and meditation has been described as a wakeful
hypometabolic state of parasympathetic dominance [44], [8].
Reports exist of yogis being buried underground in pits for many hours,
and emerging unscathed. This may be achieved by consciously and
voluntarily entering a hypometabolic state [6], [44].
This suggests not just a
general lowering of BMR as a result of practice, but in advanced
practitioners, eventually a learned ability to control normally
involuntary bodily processes [44].
Krishnamacharya was apparently able to stop his own heartbeat and breath
for several minutes with no ill effects - he demonstrated this before a
panel of doctors at the age of 76 [13].
Dehydroepiandrosterone
(DHEA)
Higher levels of DHEA are
associated with greater feelings of wellbeing, higher muscle to fat
ratios, and enhanced immune function.
DHEA also seems to increase
sensitivity to insulin. Low DHEA levels correlate with lower bone mineral
density and higher risk of osteoporosis, and also increased risk of heart
disease [23]. A
significant deficiency in DHEA in patients with several major diseases
including cancer, inflammatory diseases, type 2 diabetes,
atherosclerosis, Alzheimer's disease and cardiovascular disorders has
been described [32].
Levels of DHEA that occur
naturally in the body decline with age.
Calorie restriction has also
been shown to increase DHEA levels in animals. DHEA was found to be a
very good marker to measure the rates of aging in control versus calorie
restricted monkeys [25].
Most forms of exercise will
raise DHEA levels [35], so
practicing yoga asana would play a role in maintaining DHEA levels.
Studies have shown that
meditation is associated with increased levels of DHEA, as well as
melatonin and GABA (gamma aminobutyric acid, which reduces anxiety) [33], [17].
Older individuals practicing
meditation had higher levels of DHEA than an age-matched control group of
non-meditators. [33], [17]
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Limitations of this theory
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Results of further long term
naturalistic studies would be informative as to whether the effects
described above are sustained over time.
Many of these effects could
also result from other forms of exercise. Comparative studies measuring
these markers in yogis and athletes of a similar age would be required to
find out whether yoga practice has a greater or different effect than
other physical activity.
Larger studies are needed - at
present only relatively few exist, involving relatively small numbers of
people. More studies of diverse populations are required.
Several studies found that
yoga interventions are generally effective in reducing body weight, blood
pressure, glucose level and high cholesterol, but only a few studies
examined long-term adherence.
Animal studies cannot always
be directly correlated with humans; the results of animal experiments are
unreliable when attempting to extrapolate to humans. Although I have
referred to animal studies, personally I believe experimentation on
animals to be unethical and often very cruel. What we really need is more
human studies.
Furthermore, in her blog [31],
Sandy Szwarc points out that in a recent CR study on rhesus monkeys [11], if
deaths from factors other than age related diseases are taken into
account, there is in fact no significant difference in lifespan between
CR and non CR animals. Also, the control group were actually overfed by
20%.
Reviews of other animal CR
studies looking at causes of mortality other than old age would be
enlightening.
Finally, it may be found that
the hypothesised biomarkers of longevity actually have little or no
significance in extending longevity. For example, as we find out more
about the SIR2 gene, many currently widely accepted theories may be
discarded.
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Conclusion
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It is the side effects of CR,
the so called biomarkers of longevity , that appear to delay the onset of
age related chronic disease and extend longevity. Insulin resistance seems to be
a major factor contributing to age related disease, possibly the most
important factor. However the lowered BMR of yoga practitioners is
particularly interesting, as it is a curious and rather anomalous effect.
There is a high incidence of
obesity related disease in westerners; the average western diet is over
caloric. However the more extreme CR has associated health risks. The risks and possible
negative side effects of calorie restriction include hunger,
malnutrition, eating disorders, reproductive issues in women,
osteoporosis, sensitivity to cold, and slower healing [5]. On
top of this there may be as yet unknown long term side effects.
It has been found that some
yoga practitioners do in fact practice caloric restriction [6]. The
yogis interviewed by Dr Bushell at the Kumbha Mela festival in 2001
followed a classic Indian form of CR based on 1-2 small meals a day
consisting of legumes, milk, and augmented with fresh vegetables and
fruit. Simon Borg-Olivier lives on a
diet of mostly raw fruit and vegetables, and seems extremely strong and
healthy. He would make a particularly interesting case study; it seems
possible that he could live to a very old age.
All of the physiological
factors - a lowered BMR, with increased insulin sensitivity and lower
insulin levels, increased melatonin and DHEA, and better cholesterol
levels - appear likely contribute to longevity and health into old age
with consistent yoga practice.
The combined metabolic effect
of the practices of asana, pranayama and meditation may work in synergy
with other physical effects, possibly setting yoga practice apart from
other forms of exercise in delaying or preventing the onset of age
related disease.
Yoga practice is a natural and
healthy way to potentially achieve many of the benefits of CR, without
the associated risks, and in this manner to aid in slowing the aging
process.
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