Category Archives: Omega-6

High Omega-6:Omega-3 Ratios Increase Fracture Risk and Doubles Risk for Ratios > 6


The association of red blood cell n-3 and n-6 fatty acids with bone mineral density and hip fracture risk in the women’s health initiative.

Omega-3 (n-3) and omega-6 (n-6) polyunsaturated fatty acids (PUFA) in red blood cells (RBCs) are an objective indicator of PUFA status and may be related to hip fracture risk. The primary objective of this study was to examine RBC PUFAs as predictors of hip fracture risk in postmenopausal women. A nested case-control study (n = 400 pairs) was completed within the Women’s Health Initiative (WHI) using 201 incident hip fracture cases from the Bone Mineral Density (BMD) cohort, along with 199 additional incident hip fracture cases randomly selected from the WHI Observational Study. Cases were 1:1 matched on age, race, and hormone use with non-hip fracture controls. Stored baseline RBCs were analyzed for fatty acids using gas chromatography. After removing degraded samples, 324 matched pairs were included in statistical analyses. Stratified Cox proportional hazard models were constructed according to case-control pair status; risk of fracture was estimated for tertiles of RBC PUFA. In adjusted hazard models, lower hip fracture risk was associated with higher RBC α-linolenic acid (tertile 3 [T3] hazard ratio [HR]: 0.44; 95% confidence interval [CI], 0.23-0.85; p for linear trend 0.0154), eicosapentaenoic acid (T3 HR: 0.46; 95% CI, 0.24-0.87; p for linear trend 0.0181), and total n-3 PUFAs (T3 HR: 0.55; 95% CI, 0.30-1.01; p for linear trend 0.0492). Conversely, hip fracture nearly doubled with the highest RBC n-6/n-3 ratio (T3 HR: 1.96; 95% CI, 1.03-3.70; p for linear trend 0.0399). RBC PUFAs were not associated with BMD. RBC PUFAs were indicative of dietary intake of marine n-3 PUFAs (Spearman’s rho = 0.45, p < 0.0001), total n-6 PUFAs (rho = 0.17, p < 0.0001) and linoleic acid (rho = 0.09, p < 0.05). These results suggest that higher RBC α-linolenic acid, as well as eicosapentaenoic acid and total n-3 PUFAs, may predict lower hip fracture risk. Contrastingly, a higher RBC n-6/n-3 ratio may predict higher hip fracture risk in postmenopausal women.

Orchard TS, Ing SW, Lu B, Belury MA…
J. Bone Miner. Res. Mar 2013
PMID: 23018646 | Free Full Text

The full text has a nice chart showing the hazard ratios for the various fatty acids they looked at.

The Omega-6:Omega-3 ratios and their respective hazard ratios were:

Omega-6:Omega-3 Ratio 1.48–5.00 5.01–6.07 6.08–10.59
Hazard Ratio 1.00 1.28 (0.71–2.30) 1.96 (1.03–3.70)

[Hazard Ratios] for hip fracture by tertiles of RBC FAs with multivariate adjustment for risk factors per Robbins and colleagues37 are reported in Table 3. No significant associations were found between RBC total SFA, MUFA, or PUFA and risk of hip fracture. However, there was a significant inverse linear association between hip fracture risk and total n-3 FAs in RBCs (p for linear trend 0.0492). When examining individual n-3 FAs, there was a 56% lower relative risk of hip fracture with highest RBC ALA (tertile 3 [T3] hazard ratio [HR]: 0.44; 95% CI, 0.23–0.85; p for linear trend 0.0154), and a 54% lower hip fracture risk with highest EPA levels (T3 HR: 0.46; 95% CI, 0.24–0.87; p for linear trend 0.0181) compared to T1. Neither DHA nor the n-3 index was significantly associated with risk of fracture. In contrast, hip fracture risk nearly doubled in women in the highest tertile of the n-6/n-3 FA ratio (HR T3: 1.96; 95% CI, 1.03–3.70; p for linear trend 0.0399). Because the n-6/n-3 FA ratio in RBCs primarily reflects the ratio of AA to EPA and DHA, we further examined the relation of the AA/EPA + DHA ratio to hip fracture risk. Similar to the n-6/n-3 FA ratio, a higher AA/EPA + DHA ratio produced higher HR for hip fracture, but the association was not significant (T3 HR: 1.69; 95% CI, 0.86–3.31; p for linear trend 0.1242). Although the direction of association between total n-6 FAs, AA, and hip fracture was toward harm, there was no significant relation of either total n-6 FAs or AA with hip fracture. There was an inverse direction of association between LA and hip fracture risk, but again, this was not statistically significant (T3 HR: 0.77; 95% CI, 0.40–1.49; p for linear trend 0.5140). Inclusion of additional potential confounders (alcohol consumption, total energy intake, total calcium intake, total vitamin D intake, and multivitamin use) in the model produced similar results….

Fish Oil or Borage Oil Improve Bone in Mice


Borage and fish oils lifelong supplementation decreases inflammation and improves bone health in a murine model of senile osteoporosis.

Fats are prevalent in western diets; they have known deleterious effects on muscle insulin resistance and may contribute to bone loss. However, relationships between fatty acids and locomotor system dysfunctions in elderly population remain controversial. The aim of this study was to analyze the impact of fatty acid quality on the age related evolution of the locomotor system and to understand which aging mechanisms are involved. In order to analyze age related complications, the SAMP8 mouse strain was chosen as a progeria model as compared to the SAMR1 control strain. Then, two months old mice were divided in different groups and subjected to the following diets : (1) standard “growth” diet – (2) “sunflower” diet (high ω6/ω3 ratio) – (3) “borage” diet (high γ-linolenic acid) – (4) “fish” diet (high in long chain ω3). Mice were fed ad libitum through the whole protocol. At 12 months old, the mice were sacrificed and tissues were harvested for bone studies, fat and muscle mass measures, inflammation parameters and bone cell marker expression. We demonstrated for the first time that borage and fish diets restored inflammation and bone parameters using an original model of senile osteoporosis that mimics clinical features of aging in humans. Therefore, our study strongly encourages nutritional approaches as relevant and promising strategies for preventing aged-related locomotor dysfunctions.

Wauquier F, Barquissau V, Léotoing L, Davicco MJ…
Bone Feb 2012
PMID: 21664309

High Omega-6 to Omega-3 Ratio is Associated with Lower Bone Density


Ratio of n-6 to n-3 fatty acids and bone mineral density in older adults: the Rancho Bernardo Study.

Several lines of evidence suggest that n-3 fatty acids reduce the risk of some chronic diseases, including heart disease, diabetes, and cancer. Other research, mainly in animals, also suggests a role in bone health.
We aimed to investigate the association between the ratio of dietary n-6 to n-3 fatty acids and bone mineral density (BMD) in 1532 community-dwelling men and women aged 45-90 y.
Between 1988 and 1992, dietary data were obtained through self-administered food-frequency questionnaires, and BMD was measured at the hip and spine with the use of dual-energy X-ray absorptiometry. A medical history was obtained and current medication use was validated. Age- and multiple-adjusted linear regression analyses were performed.
There was a significant inverse association between the ratio of dietary linoleic acid to alpha-linolenic acid and BMD at the hip in 642 men, 564 women not using hormone therapy, and 326 women using hormone therapy; these results were independent of age, body mass index, and lifestyle factors. An increasing ratio of total dietary n-6 to n-3 fatty acids was also significantly and independently associated with lower BMD at the hip in all women and at the spine in women not using hormone therapy.
A higher ratio of n-6 to n-3 fatty acids is associated with lower BMD at the hip in both sexes. These findings suggest that the relative amounts of dietary polyunsaturated fatty acids may play a vital role in preserving skeletal integrity in older age.

Weiss LA, Barrett-Connor E, von Mühlen D
Am. J. Clin. Nutr. Apr 2005
PMID: 15817874 | Free Full Text

Omega-3 Inhibits Osteoclasts In Vitro


The omega-6 arachidonic fatty acid, but not the omega-3 fatty acids, inhibits osteoblastogenesis and induces adipogenesis of human mesenchymal stem cells: potential implication in osteoporosis.

Arachidonic fatty acid (AA) induces adipogenesis in human mesenchymal stem cells cultures, and high concentrations inhibit osteoblastogenesis; whereas eicosapentaenoic and docosahexaenoic fatty acids do not induce adipogenesis and do not inhibit osteoblastogenesis. In mesenchymal stem cells, omega-6 arachidonic polyunsaturated fatty acid promotes the differentiation of adipocytes and inhibits the osteoblast differentiation. While omega-3 fatty acids do not affect the adipogenic differentiation their effects on osteoblastogenesis are less relevant. An increased ratio of omega-3/omega-6 fatty acid consumption can prevent bone mass loss.
Consumption of omega-3 may protect against osteoporosis since they may inhibit osteoclastogenesis. However, with aging, MSC in bone marrow are increasingly differentiated into adipocytes, reducing the number of osteoblasts. Products derived from omega-6 and omega-3 metabolism may affect MSC differentiation into osteoblasts and adipocytes.
Human MSC have been differentiated into osteoblasts or adipocytes in the presence of omega-6 (AA), or omega-3 (DHA and EPA), and osteoblastic and adipocytic markers have been analyzed.
AA decreases the expression of osteogenic markers and the osteoprotegerin/receptor activator of nuclear factor kappa β ligand gene expression ratio (opg/rankl). High concentrations of AA inhibit the mineralization and cause the appearance of adipocytes in MSC differentiating into osteoblasts to a higher extent than DHA or EPA. In MSC differentiated into adipocytes, AA increases adipogenesis, while DHA and EPA do not affect it. AA caused the appearance of adipocytes in undifferentiated MSC. The lipoxygenase gene (alox15b) is induced by omega-3 in MSC induced to osteoblasts, and by omega-6 in MSC induced to adipocytes.
An increase in the intake of omega-3 respect to omega-6 may provide protection against the loss of bone mass, since omega-6 favors the osteoclastic activity by diminishing the opg/rankl gene expression in osteoblasts and promotes MSC differentiation into adipocytes, thus diminishing the production of osteoblasts.

Casado-Díaz A, Santiago-Mora R, Dorado G, Quesada-Gómez JM
Osteoporos Int May 2013
PMID: 23104199

Fish Oil, EPA + DHA Correlated with Bone Mass in Postmenopausal Korean Women


Positive correlation between erythrocyte levels of n-3 polyunsaturated fatty acids and bone mass in postmenopausal Korean women with osteoporosis.

Osteoporosis, a major health problem among postmenopausal women, is influenced by dietary factors. The purpose of the present study was to evaluate the hypothesis that erythrocyte levels of n-3 polyunsaturated fatty acid (PUFA) and the dietary intake of fish are associated with risk of osteoporosis and correlate with bone mass in postmenopausal Korean women with the disease.
Fifty cases and 100 controls were recruited. Osteoporosis was defined according to the International Society for Clinical Densitometry guideline as a score lower than -2.5 SD below the T-score for lumbar vertebrae L₁-L₄, femoral neck or femoral total.
The T-score of the femoral neck was positively correlated with erythrocyte levels of n-3 PUFA, eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and the intake of fish, and was negatively correlated with the ratio of n-6/n-3 PUFA after adjusting for age, years after menopause and height. In addition, the risk of osteoporosis was positively associated with erythrocyte levels of saturated fatty acids but negatively associated with EPA + DHA.
Erythrocyte levels of n-3 PUFA and the intake of fish were positively correlated with bone mass. In particular, erythrocyte levels of EPA + DHA reduced the risk of osteoporosis in postmenopausal Korean women.

Moon HJ, Kim TH, Byun DW, Park Y
Ann. Nutr. Metab. 2012
PMID: 22507833

Review: Fish Oil Effects on Bone


The impact of omega-3 fatty acids on osteoporosis.

The essential polyunsaturated fatty acids (PUFAs) comprise 2 main classes: n-6 and n-3 fatty acids. The most common source of n-6 fatty acids is linoleic acid (LA) which is found in high concentrations in various vegetable oils. Arachidonic acid (AA), the 20-carbon n-6 fatty acid, is obtained largely by synthesis from LA in the body. The n-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic (DHA) are found in fish and fish oils. Long-Chain polyunsaturated fatty acids (LCPUFAs) and lipid mediators derived from LCPUFAs have critical roles in the regulation of a variety of biological processes including bone metabolism. There are different mechanisms by which dietary fatty acids affect bone: effect on calcium balance, effect on osteoblastogenesis and osteoblast activity, change of membrane function, decrease in inflammatory cytokines such as interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF-alpha), modulation of peroxisome proliferators-activated receptor gamma (PPARgamma). Animal studies have shown that a higher dietary omega-3/omega-6 fatty acids ratio is associated with beneficial effects on bone health. In spite of increasing evidence of the positive effects of dietary fats on bone metabolism from animal and in vitro studies, the few studies conducted in humans do not allow us to draw a definitive conclusion on their usefulness in clinical practice.

Maggio M, Artoni A, Lauretani F, Borghi L…
Curr. Pharm. Des. 2009
PMID: 20041817

EPA + DHA Have Favorable Effect on Bone Density and Strength in Mice


Femur EPA and DHA are correlated with femur biomechanical strength in young fat-1 mice.

Evidence suggests that n-3 polyunsaturated fatty acids (PUFA) are beneficial for maintenance of bone health and possibly bone development. This study used the fat-1 mouse, a transgenic model that synthesizes n-3 PUFA from n-6 PUFA, to determine if outcomes of bone health were correlated with n-3 PUFA in femurs. Control and fat-1 mice were fed an AIN-93G diet containing 10% safflower oil from weaning through 12 weeks of age. Femur bone mineral content (BMC) and density were determined by dual-energy X-ray absorptiometry, and biomechanical strength properties, surrogate measures of fracture risk, were measured by a materials testing system. Femur fatty acid composition was determined by gas chromatography. At 12 weeks of age, femur n-3 PUFA were higher among fat-1 mice compared to control mice. The n-6/n-3 PUFA ratio in the femur was negatively correlated with BMC (r=-.57, P=.01) and peak load at femur midpoint (r=-.53, P=.02) and femur neck (r=-.52, P=.02). Moreover, long-chain n-3 PUFA, eicosapentaenoic acid, and docosahexaenoic acid were significantly and positively correlated or displayed a trend suggesting positive correlations, with BMC and peak load. In conclusion, the results of the present study suggest that n-3 PUFA have a favorable effect on mineral accumulation and functional measures of bone in fat-1 mice at young adulthood.

Lau BY, Ward WE, Kang JX, Ma DW
J. Nutr. Biochem. Jun 2009
PMID: 18708283

Fish Oil Decreases Bone Loss in Ovariectomized Mice


Dietary n-3 fatty acids decrease osteoclastogenesis and loss of bone mass in ovariectomized mice.

The mechanisms of action of dietary fish oil (FO) on osteoporosis are not fully understood. This study showed FO decreased bone loss in ovariectomized mice because of inhibition of osteoclastogenesis. This finding supports a beneficial effect of FO on the attenuation of osteoporosis.
Consumption of fish or n-3 fatty acids protects against cardiovascular and autoimmune disorders. Beneficial effects on bone mineral density have also been reported in rats and humans, but the precise mechanisms involved have not been described.
Sham and ovariectomized (OVX) mice were fed diets containing either 5% corn oil (CO) or 5% fish oil (FO). Bone mineral density was analyzed by DXA. The serum lipid profile was analyzed by gas chromatography. Receptor activator of NF-kappaB ligand (RANKL) expression and cytokine production in activated T-cells were analyzed by flow cytometry and ELISA, respectively. Osteoclasts were generated by culturing bone marrow (BM) cells with 1,25(OH)2D3. NF-kappaB activation in BM macrophages was measured by an electrophoretic mobility shift assay.
Plasma lipid C16:1n6, C20:5n3, and C22:6n3 were significantly increased and C20:4n6 and C18:2n6 decreased in FO-fed mice. Significantly increased bone mineral density loss (20% in distal left femur and 22.6% in lumbar vertebrae) was observed in OVX mice fed CO, whereas FO-fed mice showed only 10% and no change, respectively. Bone mineral density loss was correlated with increased RANKL expression in activated CD4+ T-cells from CO-fed OVX mice, but there was no change in FO-fed mice. Selected n-3 fatty acids (docosahexaenoic acid [DHA] and eicosapentaenoic acid [EPA]) added in vitro caused a significant decrease in TRACP activity and TRACP+ multinuclear cell formation from BM cells compared with selected n-6 fatty acids (linoleic acid [LA] and arachidonic acid [AA]). DHA and EPA also inhibited BM macrophage NF-kappaB activation induced by RANKL in vitro. TNF-alpha, interleukin (IL)-2, and interferon (IFN)-gamma concentrations from both sham and OVX FO-fed mice were decreased in the culture medium of splenocytes, and interleukin-6 was decreased in sham-operated FO-fed mice. In conclusion, inhibition of osteoclast generation and activation may be one of the mechanisms by which dietary n-3 fatty acids reduce bone loss in OVX mice.

Sun D, Krishnan A, Zaman K, Lawrence R…
J. Bone Miner. Res. Jul 2003
PMID: 12854830

Higher Omega-3, but Especially DHA, Preserve Bone in Ovariectomized Rats


Dietary ratio of n-6/n-3 PUFAs and docosahexaenoic acid: actions on bone mineral and serum biomarkers in ovariectomized rats.

Hypoestrogenic states escalate bone loss in animals and humans. This study evaluated the effects of the amount and ratio of dietary n-6 and n-3 polyunsaturated fatty acids (PUFAs) on bone mineral in 3-month-old sexually mature ovariectomized (OVX) Sprague-Dawley rats. For 12 weeks, the rats were fed either a high-PUFA (HP) or a low-PUFA (LP) diet with a ratio of n-6/n-3 PUFAs of 5:1 (HP5 and LP5) or 10:1 (HP10 and LP10). All diets (modified AIN-93G) provided 110.4 g/kg of fat from safflower oil and/or high-oleate safflower oil blended with n-3 PUFAs (DHASCO oil) as a source of docosahexaenoic acid (DHA). Fatty acid analyses confirmed that the dietary ratio of 5:1 significantly elevated the amount of DHA in the periosteum, marrow and cortical and trabecular bones of the femur. Dual-energy X-ray absorptiometry measurements for femur and tibia bone mineral content (BMC) and bone mineral density showed that the DHA-rich diets (HP5 and LP5) resulted in a significantly lower bone loss among the OVX rats at 12 weeks. Rats fed the LP diets displayed the lowest overall serum concentrations of the bone resorption biomarkers pyridinoline (Pyd) and deoxypyridinoline, whereas the bone formation marker osteocalcin was lowest in the HP groups. Regardless of the dietary PUFA content, DHA in the 5:1 diets (HP5 and LP5) preserved rat femur BMC in the absence of estrogen. This study indicates that the dietary ratio of n-6/n-3 PUFAs (LP5 and HP5) and bone tissue concentration of total long-chain n-3 PUFAs (DHA) minimize femur bone loss as evidenced by a higher BMC in OVX rats. These findings show that dietary DHA lowers the ratio of 18:2n-6 (linoleic acid)/n-3 in bone compartments and that this ratio in tissue correlates with reduced Pyd but higher bone alkaline phosphatase activity and BMC values that favor bone conservation in OVX rats.

Watkins BA, Li Y, Seifert MF
J. Nutr. Biochem. Apr 2006
PMID: 16102959

Fish or Fish Oil No Association With Fracture – 2010


Fish consumption, bone mineral density, and risk of hip fracture among older adults: the cardiovascular health study.

Marine n-3 polyunsaturated fatty acids (PUFAs) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) may be beneficial for bone health, but few studies have investigated the association with fish consumption. Our aim was to study associations of fish and EPA + DHA consumption with bone mineral density (BMD) and hip fracture risk and determine whether high linoleic acid (LA) intake, the major dietary n-6 PUFA, modifies the associations. The study population consisted of 5045 participants aged 65 years and older from the Cardiovascular Health Study. Data on BMD were available for 1305 participants. Food-frequency questionnaire was used to assess dietary intake, and hip fracture incidence was assessed prospectively by review of hospitalization records. After multivariable adjustment, femoral neck BMD was 0.01 g/cm(2) lower in the highest versus lowest tuna/other-fish intake category (p = .05 for trend). EPA + DHA intake (higher versus lower median of 0.32 g/day) was associated with lower femoral neck BMD (0.66 versus 0.71 g/cm(2), p < .001) among those with LA intake greater than the median 12.1 g/day (p = .03 for interaction). No significant associations were found with total-hip BMD. During mean follow-up of 11.1 years, 505 hip fractures occurred. Fish or EPA + DHA consumption was not significantly associated with fracture incidence [hazard ratio (HR) for extreme categories: HR = 1.23, 95% confidence interval (CI) 0.83-1.84 for tuna/other fish; HR = 1.16, 95% CI 0.91-1.49 for fried fish; and HR = 0.98, 95% CI 0.71-1.36 for EPA + DHA]. High LA intake did not modify these associations. In this large prospective cohort of older adults, fish consumption was associated with very small differences in BMD and had no association with hip fracture risk.

Virtanen JK, Mozaffarian D, Cauley JA, Mukamal KJ…
J. Bone Miner. Res. Sep 2010
PMID: 20572022 | Free Full Text