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Old 07-03-2006, 02:25 AM   #2
R.B.
Senior Member
 
Join Date: Mar 2006
Posts: 1,843
More possible reasons fro balancing the omega threes and sixes.

RB


Ratio of n–6 to n–3 fatty acids and bone mineral density in older adults: the Rancho Bernardo Study1,2,3



http://www.ajcn.org/cgi/content/full/81/4/934


ABSTRACT

In this cohort, an increasing ratio of dietary n–6 to n–3 fatty acids was significantly associated with lower BMD. The most consistent association was seen with the ratio of LA, the predominant n–6 fatty acid, to ALA, the predominant n–3 fatty acid, where an increasing ratio of n–6 to n–3 fatty acids was associated with lower BMD at the hip in men and in women regardless of HT status and at the lumbar spine in women not using HT. In addition, the ratio of total n–6 to n–3 fatty acids was inversely associated with BMD at the hip in both groups of women and at the lumbar spine in women not using HT. These associations were independent of other bone-related variables, such as age, lifestyle, and medication use.................

There are a plethora of biologically plausible pathways whereby PUFAs may regulate the factors involved in bone metabolism, such as prostaglandins, cytokines, insulin-like growth factor I, and calcium. Reviewers have suggested that one or a combination of these factors may have an effect on bone (5, 6, 13, 23). For example, PGE2, the major prostaglandin involved in bone metabolism, is synthesized from n–6 fatty acids, whereas n–3 fatty acids inhibit its production (1, 13). Normal or moderate concentrations of PGE2 support bone formation, whereas greater quantities promote bone resorption (5). Fatty acids are also involved in calcium metabolism. Higher n–3 fatty acid intake enhances calcium absorption, decreases calcium loss, and increases bone calcium (13, 20,23). In addition, the inhibition of cytokine production has been implicated as a potential mechanism of the favorable effects of fatty acids on bone, with higher intakes of n–3 fatty acids inhibiting the synthesis of proinflammatory cytokines, such as interleukin 6, interleukin 1, and tumor necrosis factor {alpha} (24, 25). Kettler (6) suggested that bone loss is mediated by cytokines, and n–3 fatty acid supplementation in animals and humans reduces cytokine synthesis and increases calcium absorption............
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