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OSTEOPOROSIS: Diet, Acidity and Calcium |
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by Aftab J. Ahmed, Ph.D.
Over the past several years, a perceptible
shift in healthcare paradigm has
emerged. No longer are chronic diseases
seen as fait accompli to be awaited passively and
treated willy-nilly only when the symptoms
present themselves with uncompromising
ferocity. Rather, preventive measures have
assumed central importance in avoidance of
disease. The broader emphasis on nutritious
diet is but one index of this changing mind-set
as individuals more assertively take control
of their health. In a sense, it is coming full
circle for the role of diet in traditional societies
was seen for eons as the basic insurance
against debilitating disease, irrespective of
chronological age.
Diet as a critical factor in management of
health and disease has a long history.
Supplementation with vitamins was deemed
appropriate several decades ago with the implication
that diet alone does not supply all the
nutrients necessary for good health.
Extrapolation of this basic premise has brought
metals, trace minerals, herbals, antioxidants
and metabolic cofactors (such as COQ10) with
rather complex biochemistry under the
umbrella of nutritional supplementation. It is
understandable, therefore, that an estimated 72
percent of consumers have changed their diet
for health reasons.
Literally, a fundamental evolution is afoot,
the signs of which include calcium-fortified
orange juice to help prevent osteoporosis,
herbal tea with antioxidants to lower the risk of
cancer, eggs with fish-derived fatty acids to
manage heart disease and, among many others,
phytochemicals in oats to mitigate muscle
soreness after heavy workout.1 These so-called
functional foods contrast from the foods previously
marketed, which touted having lower fat,
cholesterol and salt as the “lesser-evil” foods.
Accordingly, the focus in the design of functional
foods is more pragmatic—namely, to
enhance the “good” and minimize the “bad.”
In spite of these encouraging trends and
availability of reasonably wholesome choices,
the health benefits of supplemental nutrients
differ from individual to individual. That is to
a large extent due to the genetic makeup of a
given person along with age, the state of general
health and, in fact, dietary habits. Increasing
evidence suggests that diet is considerably
more important in maintenance of health than
is normally discerned. Indeed, in a rather odd
coalescence, the technology-intense molecular
biology, as the human genome is deciphered,
and technology-insensitive nutrition have
joined hands to help better understand human
health and disease. This is a fitting tribute to
Hippocrates, the father of allopathic medicine,
who said: “Let your food be your medicine and
let your medicine be your food.”
Intense research efforts continue to
establish causal links between nutrition and
degenerative diseases. In fact, recent scientific
and clinical research has shed light on how
nutrition itself may be the culprit in the onset
of chronic diseases.2 While it may appear
counter-intuitive, it is actually not. It is widely
appreciated that the risk of cardiovascular
disease can be lowered by sensible nutrition
and dietary habits. As a counterpoint, there is
ample evidence suggesting a strong correlation
between the consumption of “junk food” and
type II diabetes, even in teenagers. Thus the
role of nutrition in the onset of degenerative
diseases is being critically re-examined.
Osteoporosis is one of the few human
diseases which proves that people truly
are what they eat. Many a time eloquent
case has been made that a deficiency in
each and every nutrient involved in bone
metabolism could contribute to the onset, or
aggravate the severity, of osteoporosis. One
aspect of this debilitating disease however, has
been neglected—namely, the effect of nutrition
on bone health and integrity. Thus the
findings that even nutritious foods may have
deleterious effects have only now begun to be
more completely understood. How so?
Evidence suggests that commonly ingested
foods—such as meat, grains and dairy
products, including cheese—precipitate osteoporosis
by increasing systemic acidity in the
body. As acidity increases, physiological mechanisms
are triggered that leach out minerals
from bone, especially calcium, to increase
alkalinity. These observations corroborate
what has been known for quite some time now
that “acidic” nutrients—for example, caffeine
and carbonated beverages—increase the rate of
mineral leaching from the bone with a concomitant
increase in the risk of osteoporosis.
How does that come about? It has been
well within the precinct of classical nutrition
that foods do produce acid in the body.3 Thus,
carbonic and lactic acids are produced by the
aerobic and anaerobic metabolism of glucose,
respectively. Likewise, acidic ketone bodies
accumulate during the incomplete breakdown
of dietary fats. These compounds increase the
acidity in varying amounts in the extracellular
fluid bathing the cells and influence acid-base
balance. Toxic accumulation of acidic ketone
bodies, for instance, is a common complication
in untreated diabetes mellitus.
Minerals that remain after the food has
been metabolized are referred to as either acidic
or basic, depending upon whether they contribute
to formation of an acid or basic
medium in solution. Acid-forming elements
include chlorine, sulfur and phosphorus, and
are quite abundant in high-protein foods such
as meat, fish, poultry and eggs. Accordingly,
these foods are designated as acid-forming
foods. After metabolism is complete, most
mixed diets contain a surplus of acid-forming
minerals that must be continually buffered to
maintain the acid-base balance. On the other
hand, minerals such as potassium, calcium,
sodium and magnesium are alkaline, or basic.
All of these minerals are found in vegetables
and fruits, which nutritionists term as baseforming
foods. These predominantly basic
residues that result after metabolism of a strict
vegetarian diet may tax the body’s ability to
maintain optimal acid-base balance or pH.
Ordinarily, the body has the ability to
maintain the balance by controlling
the pH of body fluids. The symbol
pH indicates the degree of acidity or
alkalinity; thus as the pH goes down, the
acidity goes up and, conversely, as the pH
goes up, the alkalinity is increased. The most
poignant evidence of the effectiveness of the
pH control mechanism is the quite narrow
range of blood pH, which varies between the
values of 7.36 to 7.41. Irrespective of that,
physiological buffering against untoward
escalation of acidity and alkalinity is accomplished
by the respiratory system, which
presents itself as hyper- or hypo-ventilation,
and the kidney excretion of acids and bases.
Inasmuch as physiological response is rather
slow, rapid changes in the buffering can be
achieved by chemical buffers, such as sodium
bicarbonate or calcium carbonate that are
used in antacids.
Even though disturbances in the acidbase
balance, from a clinical standpoint, can
be considered largely dependent upon the
relative amounts of carbonic acid and bicarbonate,
persistent imbalances can induce
metabolic acidosis or alkalosis. If allowed to
fester, either of these conditions can pose
serious consequences for general health.
Again, osteoporosis provides a compelling
example of the contribution of diet-induced
acidity in the pathogenesis of a chronic
disease. In essence, persistent acidity can
cause alkaline minerals, such as calcium, to
begin to be leached out of the bone. In such
cases as much as 60 milligrams of alkaline
minerals can be extracted every day from the
skeleton to neutralize blood pH. That computes
to a loss of roughly 250 grams of alkaline
metals over a decade, which is equivalent
to the mineral content of an arm or leg bone.
If the skin is a model of external flexibility,
the human skeletal structure embodies
internal rigidity. It allows mobility while
simultaneously protecting internal organs. To
accomplish this task, the bone consists of
mineral deposits, principally calcium taking
about 45 percent of its volume, in addition to roughly 30 percent of soft tissue and 25 percent
water. The bone, although extremely strong, is
nary a static structure. In fact, the inner scaffold
of the bone is continuously resculpted, whereby
the older components are replenished with
newer ones. Two types of cell in the bone carry
this out: Osteoclasts generally degrade (resorb or
demineralize) solid bone matter whereas
osteoblasts build the bone anew (Fig. 1). The
equilibrium between demineralization and remineralization
is central in maintenance of bone
integrity, regardless of what mechanisms trigger
its disintegration.
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Osteoblasts
Make Bones |
Osteoclasts
Erode Bones |
These Activities
Remodel the Skeleton |
| Figure 1: The Dynamics of Bone Growth |
The loss of bone strength is not a smooth
process as it progresses rather nonuniformly.
Even though women, particularly those in
menopause, are more susceptible to bone thinning,
the onset of bone loss is quite slow and typically
starts around the age of 39. After that there
is a progressive increase in bone loss with time.
With the caveat that osteoporosis is a
multi-factorial disease with several physiological
pathways contributing to its etiology, progressive
loss of calcium is the most obvious factor
amenable to intervention. As such, calcium
supplementation appears the most effective
modality to fend against and delay bone loss.
Importantly, recent observations underscore
the fact that calcium supplementation as early as
the teen years helps individuals to strengthen the
bones sufficiently to retard bone loss when it
does eventually start. It is for this reason that
calcium supplementation continues to be a
subject of intense research—in part, because it
is the first mineral approved by the FDA in
prevention of a specific disease.
While the recommended daily amount of
calcium supplementation is broadly agreed
upon, the requisite amounts are
apparently not being absorbed. The sheer numbers
of people suffering from osteoporosis bears
testimony to that. Much has been said about the
various chemical forms and sources of calcium.
The discussion has revolved mostly around solubilization
of calcium with the tacit assumption
that an easily soluble salt is more readily
absorbed. This assumption is being reconsidered,
however, as the amounts of elemental
calcium ingested do not correlate with adequate
levels of calcium in the body.
An intriguing approach to increase calcium
absorption and its enhanced bioavailability
would be to couple its mode of absorption with
the gastrointestinal (GI) tract. Two mechanisms
account for calcium absorption: An active transport
that takes place in the upper intestine, and
absorption by passive diffusion, which is largely
operative in the lower intestine (the colon). It
stands to reason then that if fermentative ability
of the colon were to be increased, the amount of
calcium absorbed would escalate as well.
Latest research demonstrates that calcium
supplementation is substantially increased
when taken in conjunction with inulin, a prebiotic.5 A prebiotic is a substrate for the so-called
beneficial bacteria resident in colon. Inulin
specifically initiates the multiplication of beneficial
colonic flora. Thus, when calcium
supplementation in teenaged female athletes
was fortified with inulin, the amount of
calcium absorbed exceeded that of the group
administered calcium alone.6
These results persuasively corroborate the
concept that absorption of calcium can be maximized
by jumpstarting proliferation of colonic
flora. In that sense, active uptake of calcium
complements its absorption by passive diffusion
and, therefore, delivers this critically crucial
mineral to the body. The more complete the
absorption of elemental calcium, the more
robust the bone remineralization to maintain its
integrity.
It could be correctly argued that other
factors such as vitamin D may be required for
calcium absorption. While that is true, it can be
safely assumed that in a vast majority of people
there is dietary adequacy of vitamin D and other
minerals or biomolecules. A balanced, nutritious
diet along with an optimally functional GI
system ensures a requisite supply of additional
factors to enhance the preventive function of
calcium supplementation. While many types of
diets claim to confer a variety of benefits, if a
balance is not struck between the acid-forming
and base-forming foods, serious long-term
consequences for health is inevitably the result.
For instance, a dietary regimen skewed toward
either protein exclusively or composed solely
of carbohydrates, despite lucrative promises,
cheats the body of nutrients required to mobilize
its innate healing potential. There is a
measure of wisdom, after all, to the maxim that
health begins in the gut. Perhaps the time is
ripe for a redefinition of a food pyramid that
helps maintain the body fluids within
physiological pH range as one way to hold
degenerative diseases at bay.
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