Alternative Medicine Review 2001 (Feb); 6 (1): 61–77 ~ FULL TEXT
Debra B. Kettler, MS, DC
Introduction
The National Institutes of Health Consensus Development Conference Statement
on Osteoporosis Prevention, Diagnosis and Therapy, published in March 2000
states:
"Osteoporosis, once thought to be a natural part of aging among
women, is no longer considered age or gender-dependent. It is largely preventable
due to the remarkable progress in the scientific understanding of its causes,
diagnosis and treatment. Optimization of bone health is a process that
must occur throughout the lifespan in both males and females. Factors that
influence bone health at all ages are essential to prevent osteoporosis
and its devastating consequences." [ 1 ]
In the United States today, eight million women have osteoporosis and
15 million more have osteopenia, placing them at increased risk for osteoporosis.
One out of two women will have an osteoporosis-related fracture in their
lifetime. Osteoporosis is responsible for more than 1.5 million fractures
annually, with an associated cost for direct expenditures in 1995 (hospitals
and nursing homes) of $13.8 billion. [ 2 ] The
most typical sites of osteoporosis related fractures are the thoracic and
lumbar vertebral bodies (T8 through L3), the proximal femur, distal radius,
humerus, pelvis, and ribs. Of all osteoporotic fractures, those at the
hip are associated with the highest risk of morbidity and mortality. [ 3 ]
Many factors contribute to the lifetime accumulation or decline in bone
mineral density (BMD), including levels of the nutrients vitamin D, calcium,
sodium, and protein, as well as lifestyle factors such as body mass index,
exercise, drug and alcohol use, and smoking. [ 1,2 ]
Remodeling of bone takes place throughout adult life, with osteoclasts
resorbing old bone and osteoblasts creating new bone. These cells continuously
renew the skeleton while maintaining its strength and density. Normally,
in the adult skeleton, three percent of cortical bone and 25 percent of
trabecular bone is remodeled each year. The primary characteristic of osteoporosis
is a reduction in bone mass due to an increase in bone resorption over
bone formation. Postmenopausal osteoporosis is characterized by an accelerated
loss of bone tissue (2-4% per year on average) that begins after natural
or surgical menopause, and lasts 5-10 years in the absence of treatment.
Fractures are most likely to occur within 15-20 years after ovarian function
ends. [ 4 ]
Postmenopausal bone loss is associated with an increase in both the
number and activity of osteoclasts in trabecular bone. This rapid decline
in BMD at menopause is often followed by a gradual decline in BMD, known
as age-related osteoporosis (1-2% per year on average), which may persist
indefinitely and may accelerate once more after the age of 70. [ 5 ]
The rapid decline in BMD at menopause is the major factor contributing
to the high rate of disabling bone fractures in postmenopausal women. [ 6 ]
Review of Fatty Acids
There are two classes of essential fatty acids (EFAs): omega-3 and omega-6.
Humans (like all mammals) are unable to synthesize EFAs so they must be
provided in the diet. [ 17 ] EFAs are required
for membrane integrity, visual and neurological function, and their deficiency
is associated with neurological and immunological disease. [ 18 ]
Small changes in the fatty acid composition of the cell membrane can significantly
alter cell function. [ 19 ]
The parent compound in the omega-6 fatty acid family is linoleic acid
(LA), while the parent compound of the omega-3 fatty acid family is a-linolenic
acid (ALA). These parent compounds are metabolized to longer-chain fatty
acids (which play other, more important roles in the body) by a series
of elongation and desaturation steps (Figure
3). LA is first converted to gamma-linolenic acid (GLA), then to dihomogamma-linolenic
acid (DGLA) and arachidonic acid (AA), while ALA is converted to eicosapentaenoic
acid (EPA) and docosahexaenoic acid (DHA). [ 19 ]
Although the omega-3 and omega-6 fatty acids compete for the desaturation
enzymes, the D 4 and D 6 desaturases favor the omega-3 fatty acids. [ 17 ]
Generally, the desaturation steps are slow and rate limiting, while the
elongation steps usually proceed rapidly. Factors known to inhibit fatty
acid desaturation are aging, smoking, diabetes, high sodium intake, and
biotin deficiency, whereas calcium deficiency can impair essential fatty
acid elongation. [ 19 ]
Fatty fish are the major source of EPA and DHA in the U.S. diet, while
vegetable oils, especially soybean and canola oils, are the primary sources
of ALA. Although flaxseed oil contains approximately 57-percent ALA, it
is not commonly used in food preparation. Nuts, seeds, vegetables, and
some fruit, as well as egg yolk, poultry, and meat contribute small amounts
of omega-3 fatty acids to the diet.
The typical American diet has a high ratio of omega-6:omega-3 fatty
acids. [ 20 ] Studies show that the consumption
of increased amounts of fish, [ 21 ] fish oil, [ 22-25 ]
flaxseed oil, [ 25,26 ] or canola oil [ 27 ]
will result in the incorporation of the longer-chain omega-3 fatty acids
EPA and DHA into the plasma and cell membranes of platelets, erythrocytes,
neutrophils, monocytes, and liver cells. This leads to a change in the
ratio of omega-6:omega-3 fatty acids in the membranes, [ 28,29 ]
a change in the function of the membranes, [ 29 ]
and a decrease in the production of IL-1, IL-6 and TNFa. [ 22-25 ]
![[SWIRL 2]](../GRAPHICS/SWIRL-2.GIF)
