PUFAs for Bone Growth and Repair

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excerpt:

>

> Bone strength is not normally associated with conditions such

> as osteo- and rheumatoid arthritis, inflammatory bowel

> diseases, severe food allergies, Lyme disease or the autoimmune

> condition known as ankylosing spondylitis. However, these

> conditions are known to interfere with the absorption and

> utilization of nutrients needed to construct healthy bone and

> cartilage.1 Moreover, some biochemical messengers associated

> with these chronic inflammatory conditions directly interfere

> with bone growth and repair.2

> http://www.healthwellexchange.com/nutritionsciencenews/nsn_backs/Mar_

> 01/pufa.cfm

>

> From The March 2001 Issue of Nutrition Science News

>

> ( For the references, click on the link )

>

>

> PUFAs for Bone Growth and Repair

>

> by C. Leigh Broadhurst, Ph.D

>

> The omega-3 polyunsaturated fatty acids linoleic acid and

> alpha-linolenic acid can help increase bone formation and

> reduce bone resorption

>

> Bone strength is not normally associated with conditions such

> as osteo- and rheumatoid arthritis, inflammatory bowel

> diseases, severe food allergies, Lyme disease or the autoimmune

> condition known as ankylosing spondylitis. However, these

> conditions are known to interfere with the absorption and

> utilization of nutrients needed to construct healthy bone and

> cartilage.1 Moreover, some biochemical messengers associated

> with these chronic inflammatory conditions directly interfere

> with bone growth and repair.2

>

> In addition, all nonsteroidal anti-inflammatory drugs (NSAIDs)-

> as well as scores of medicinal plants used to relieve the pain

> and inflammation associated with conditions such as arthritis,

> headaches, sports injuries and tendinitis - work wholly or

> partly by inhibiting cycloxygenases such as prostaglandin E2

> (PGE2). And high levels of PGE2 may do more than simply

> aggravate aching joints. Evidence exists that lowering PGE2

> levels can actually help increase bone formation and reduce

> bone resorption rates.3

>

> Investigation into this aspect of inflammation has revealed

> that balancing essential fatty acids in the body can prevent

> abnormalities in bone protein matrix growth and/or

> mineralization.

>

> In the case of mammals, essential fatty acids are

> conventionally defined as the polyunsaturated fatty acids

> (PUFA) linoleic acid and alpha-linolenic acid. Both have 18

> carbons in the fatty acid chain. Linoleic acid is the head of

> the n-6 PUFA family, and alpha-linolenic is the head of the n-3

> PUFA family. These two families are not interchangeable. They

> are like men and women-both sexes are humans, but one sex can

> never replace the other, and both are needed to continue the

> species.

>

> When ingested and metabolized in the body, linoleic and

> alpha-linolenic acids are converted with enzymes to the more

> biochemically active long-chain polyunsaturated fats

> (LC-PUFAs). After years of laboratory studies, however,

> researchers have found that in humans this conversion is often

> slow or incomplete. Presumably this is because we are omnivores

> and evolved eating diets containing LC-PUFAs, thus we did not

> have to create them. Hence, some researchers now consider some

> LC-PUFAs as essential or conditionally essential.4

>

> The 20-carbon n-6 LC-PUFA arachidonic acid (AA) is one such

> fatty acid that could be considered essential. Arachidonic acid

> is found in cell membranes throughout the body because it is

> necessary for numerous body processes. It also makes up about

> half of the PUFAs in our brains and nervous systems. The

> placenta and sperm are rich in AA. Infants, growing children,

> and pregnant and nursing women in particular appear to require

> arachidonic acid in the diet in order to achieve optimal growth

> and health.

>

> Arachidonic acid is best known as the substrate for the

> series-2 eicosanoids. Eicosanoids are hormonelike biochemicals

> that control activities locally where they are produced. There

> are three series of eicosanoids, which all function in

> virtually the same manner.

>

> The biochemical reactions required to make series-2 eicosanoids

> from arachidonic acid are controlled by the sister enzyme

> systems cycloxygenase and lipoxygenase. Cycloxygenases are well

> known for their ability to change arachidonic acid into

> eicosanoids such as prostaglandin E2 (PGE2). PGE2 production is

> an important reaction to trauma and injury, which increases

> inflammatory mediators as the body tries to react to the

> damage. Unfortunately, in many chronic conditions this process

> becomes unbalanced and an overproduction of PGE2 results in a

> chronic inflammatory response. Such a response can have

> long-term effects on bone health.

>

>

> Bone Modeling and Remodeling

>

> The human skeleton is not static. Bone is a highly active

> metabolic tissue, continually changing throughout life. The

> process of bone modeling is associated with body growth in

> children, teenagers, and young adults, when 100 percent of

> their bone surface is active. Modeling adds length, width, and

> weight to bones and increases overall skeletal mass. Bone

> remodeling, on the other hand, is the process of bone growth

> associated with maintaining a fixed adult bone mass. In

> remodeling, only about 20 percent of the bone surface is

> active. Older bone tissue is destroyed (resorption) and

> replaced by new bone tissue (formation) in a cyclical process.5

> In the case of osteoporosis, the basic problem is that

> resorption gets ahead of formation, resulting in a net bone

> loss.

>

> Bone supports and protects, manufactures various immune and

> blood cells, and is a " metabolic reservoir " for calcium,

> magnesium, and phosphorus. While minerals such as calcium and

> magnesium are necessary for bone formation, they do not supply

> enough to produce bone. For example, calcium intake beyond

> dietary requirements does not stimulate bone formation.

> Instead, bone metabolism is under the control of many hormones

> and growth factors, including activated vitamin D, estrogen,

> growth hormone, insulin, insulinlike growth factor, parathyroid

> hormone, and various eicosanoids-with PGE2 playing a major

> role.6

>

> At low levels, PGE2 apparently stimulates bone formation. The

> mechanism for this may be that PGE2 increases the production of

> insulinlike growth factor, a powerful " master " growth

> stimulator for bone, cartilage, and muscle. Surprisingly, high

> or excessive levels of PGE2 swamp this effect, and bone

> formation is reduced and resorption is increased.7 In bone

> modeling, this pattern leads to reduced skeletal growth. In

> bone remodeling, this pattern leads to osteoporosis. Growth

> opportunity lost in childhood can never be fully compensated

> for in adulthood and may put an individual at greater risk for

> osteoporosis later in life. Therefore, it is important to

> maintain low levels of PGE2 throughout one's lifetime.

>

>

> Nutritional Strategy for Lowering PGE2

>

> Just as the n-6 LC-PUFA arachidonic acid gives rise to series-2

> eicosanoids, eicosapentaenoic acid (EPA) and

> dihomogammalinolenic acid (DGLA) serve as substrates for the

> series-1 and -3 eicosanoids, respectively. DGLA and EPA compete

> with arachidonic acid for the cycloxygenase and lipoxygenase

> enzymes, thereby reducing-but not eliminating-the production of

> series-2 eicosanoids. High intakes of fish, black currant,

> evening primrose, and borage oils have been shown to moderately

> increase production of series-1 and -3 prostaglandins at the

> expense of PGE2; therefore, specialized PUFA supplementation

> may help optimize bone modeling and remodeling.12

>

> In a 2000 study conducted at Purdue University in West

> Lafayette, Ind., this nutritional approach was tested on bone

> modeling in growing rats.8 For 42 days, groups of 15 rats were

> fed identical diets except that the n-6 to n-3 PUFA ratios

> differed. Fish oil and safflower oil were mixed to produce n-6

> to n-3 ratios of 23:8, 9:8, 2:6, and 1:2. Rat liver and bone

> tissue samples showed both PGE2 levels and serum alkaline

> phosphatase decreased as the proportion of n-6 to n-3

> decreased. High levels of alkaline phosphatase indicate bone is

> being resorbed. Moreover, rats fed the 1:2 ratio diet had

> slightly higher rates of bone formation.

>

> Only a single 1995 South African human study has specifically

> examined the effects of LC-PUFA supplementation on

> osteoporosis.9 Forty elderly women with age-related

> osteoporosis were divided into four groups. They received one

> of four treatments daily for 16 weeks: 4 g evening primrose

> oil; 4 g fish oil; 4 g of a fish and evening primrose oil

> mixture; or 4 g olive oil placebo. The women took no other

> medications, supplements, or special foods. In this study fish

> oil increased serum calcium, osteocalcin and collagen, and

> decreased alkaline phosphatase. Evening primrose oil alone had

> no significant effects, but the positive results from the fish

> oil group were also seen in the fish oil plus evening primrose

> oil group. According to the research team, evening primrose oil

> may have potentiated the effects of fish oil.

>

>

> Mood and Bone

>

> Clinical depression in both women and men has been correlated

> with reduced bone density. In a 1997 National Institutes of

> Health study, 24 women with a history of major depression were

> compared to 24 controls. Subjects were matched for age, race,

> body-mass index, and menopausal status. Upon testing, various

> bone sites showed densities 6.5 to 13.6 percent lower in the

> depressed women.10 Clinical depression is known to be

> associated with strongly reduced levels of n-3 LC-PUFAs, and

> clinically depressed people have been found to respond to fish

> oil supplementation. Deficiencies of n-3 PUFA may be a common

> link between depression and reduced bone density, both

> prevalent in older people.11

>

> Bone is a complex tissue whose health and maintainence needs a

> great deal of nutritional support. Yet many postmenopausal

> women still take excessive amounts (1.5 to 2 g) of calcium per

> day-often at their doctor's recommendation-without any

> complementary supplements such as magnesium, silicon, boron,

> protein and vitamin D. Even in the natural products industry we

> actively push menopausal women toward soy milks and cheeses

> that do not naturally contain vitamin D and are not necessarily

> fortified with vitamin D like their dairy counterparts are.

> With the insights that the n-3 to n-6 PUFA ratio directly

> affects bone modeling, and that fish oil may increase the rate

> of bone formation, perhaps we can broaden our thinking beyond

> single " bone health " products and toward an integrated protocol

> approach.

>

> Doses of 2 g per day of fish oil, evening primrose, or black

> currant or borage oil are reasonable and safe, and may enhance

> bone formation, especially when used on a long-term, preventive

> basis.12 We can expect that those in the medical community

> interested in bone health will embrace these nutrients in the

> next five years, as was calcium in the 1990s. For those who

> create and dispense such supplements, the time is now.