Flaxseed oil and bone development in growing male and female mice

A comprehensive review of the health benefits of flaxseed oil in relation to its chemical composition and comparison with other omega-3-rich oils

Flaxseed (Linum usitatissimum L) is an ancient perennial plant species regarded as a multipurpose plant owing to its richness in omega-3 polyunsaturated fatty acids (PUFA) including α-linolenic acid (ALA). The extensive biochemical analysis of flaxseed resulted in the identification of its bioactive, i.e., lignans with potential application in the improvement of human health. Flaxseed oil, fibers, and lignans exert potential health benefits including reduction of cardiovascular disease, atherosclerosis, diabetes, cancer, arthritis, osteoporosis, and autoimmune and neurological disorders that have led to the diversification of flaxseed plant applications. This comprehensive review focuses on flaxseed oil as the major product of flaxseed with emphasis on the interrelationship between its chemical composition and biological effects. Effects reviewed include antioxidant, anti-inflammatory, antimicrobial, anticancer, antiulcer, anti-osteoporotic, cardioprotective, metabolic, and neuroprotective. This study provides an overview of flaxseed oil effects with the reported action mechanisms related to its phytochemical composition and in comparison, to other PUFA-rich oils. This study presents the most updated and comprehensive review summarizing flaxseed oil's health benefits for the treatment of various diseases.

A mechanistic review of chinese medicine polyphenols on bone formation and resorption

Bone reconstruction includes a steady state system of bone formation and bone absorption. This tight coupling requires subtle coordination between osteoblasts and osteoclasts. If this balance is broken, it will lead to bone mass loss, bone density reduction, and bone metabolic diseases, such as osteoporosis. Polyphenols in Chinese herbal medicines are active ingredients in plant extracts with high safety and few side effects, and they can play a role in affecting bone formation and bone resorption. Some of these have estrogen-like effects and can better target bone health in postmenopausal women. The purpose of this review is to provide comprehensive information on the mechanisms underlying the relationship between traditional Chinese medicine polyphenols and bone formation or bone resorption.

n-3 fatty acids fed to ISA brown and Shaver white breeders and their female progeny during rearing: Impact on egg production, eggshell, and select bone attributes from 18 to 42 weeks of age

The impact of feeding sources of n-3 fatty acids (FA) to ISA brown and Shaver white breeders and their female offspring during rearing on egg production, eggshell, tibia, and keel bone attributes was examined. Breeders were fed Control (CON) or CON + 1% dried microalgae (DMA: Aurantiochytrium limacinum) as the source of docosahexaenoic acid or CON + 2.6% of a coextruded mixture of full-fat flaxseed (FFF) and pulses as a source of α-linolenic acid. Day-old offspring were fed 1) breeder CON-pullet CON (CON-CON), 2) breeder CON-pullet DMA (CON-DMA), 3) breeder CON-pullet FFF (CON-FFF), 4) breeder DMA-pullet CON (DMA-CON), 5) breeder DMA-pullet DMA (DMA-DMA), 6) breeder FFF-pullet CON (FFF-CON), and 7) breeder FFF-pullet FFF (FFF-FFF). At 18 wk of age (WOA), pullets were fed a common layer diet to 42 WOA for egg production and bone quality assessments. There was no (P > 0.05) interaction between strains and diets and the main effect of diets on egg production, egg mass, and eggshell quality. There was an interaction (P = 0.008) between strain and diet on egg weight (EW); however, the strain effect on EW (P < 0.001) was such that ISA brown had heavier eggs than Shaver white. Shaver white had higher (P < 0.001) eggshell %, eggshell, and tibia breaking strength (BS), as well as tibia ash concentration compared with ISA brown hens. In contrast, ISA brown hens exhibited heavier (P < 0.05) tibia and keel bones. Feeding breeders DMA and pullets both sources of n-3 FA increased tibia medullary ash concentration compared with other diets (P < 0.001). Shaver white hens showed greater decline in tibia BS (83.7 vs. 96.3%) and ash content (84.1 vs. 94.3%) than ISA brown hens from 18 to 42 WOA (P < 0.05). Strain and diets exhibited independent effects on eggshell, tibia, and keel attributes. Provision of α-linolenic acid and docosahexaenoic acid to breeders and offspring improved tibia medullary ash concentration at 42 WOA.

Impact of feeding microalgae (Aurantiochytrium limacinum) and co-extruded mixture of full-fat flaxseed as sources of n-3 fatty acids to ISA brown and Shaver white breeders and progeny on pullet skeletal attributes at hatch through to 18 weeks of age

Impact of feeding n-3 fatty acids (FA) to ISA brown and Shaver white breeders and their progeny on bone development in pullets was investigated. Breeders were fed Control (CON); CON + 1% microalgae (DMA: Aurantiochytrium limacinum) as the source of docosahexaenoic acid; and CON + 2.6% of a co-extruded mixture of full-fat flaxseed (FFF) and pulses mixture as source of α-linolenic acid. Test diets (DMA and FFF) were balanced for total n-3 FA and n-6: n-3 FA ratio. Samples of day-old progeny were euthanized for bone mineral content (BMC) and tibia collagen type II. The remaining pullets were fed posthatch treatments as follows: from breeder CON: CON (CON-CON), DMA (CON-DMA), and FFF (CON-FFF), from breeder DMA: CON (DMA-CON) and DMA (DMA-DMA) and from breeder FFF: CON (FFF-CON) and FFF (FFF-FFF). A total of 60 pullets per posthatch diets were reared in cages (12 pullets/cage, n = 5) with free access to feed and water, bled at 6, 12, and 18 wk of age (WOA) for bone turnover markers and necropsied at 18 WOA for tibia and femur samples. Day-old pullets from breeder fed CON had greater BMC (P < 0.001) relative to those from breeders fed other diets. There was strain and diet interaction (P ≤ 0.024) on tibia breaking strength (TBS) and tibia cortical ash concentration at 18 WOA such that diet responses were only observed in Shaver white pullets. In this context, TBS of DMA-DMA and FFF-FFF was greater than for pullets originating from CON breeder, and the cortical ash weight of DMA-DMA and FFF-FFF pullets was 23.8 and 20.2%, respectively, higher than for CON-CON pullets. In conclusions, the strain effects were strong on tibia attributes on 18-week-old pullets. Breeder feeding of n-3 FA was more effective when concomitant with posthatch feeding of n-3 FA in supporting the skeletal strength and cortical bone development in Shaver white pullets. Further investigations are warranted to establish the impact these strategies on skeletal health during laying cycle.

Effect of hydroalcoholic extract of flaxseed on bone mineral density in Wistar rats using digital radiography

Background:

Given that the world's population is aging, the problems associated with osteoporosis and related fractures are increasing. The aim of the study was to evaluate the effect of flaxseed extract on bone mineral density (BMD) in Wistar rats using digital radiography.

Methods:

In this experimental study, 25 male and 25 female Wistar rats were randomly divided into 5 groups: 1. Control, 2. Calcium and vitamin D (Ca/VitD), 3. 100 mg/kg flaxseed, 4. 200 mg/kg flaxseed, and 5. 400 mg/kg flaxseed. Then, the animals were kept for thirty days. Maxillary and mandibular BMD as well as serum levels of calcium, vitamin D and phosphorus were measured at baseline and after 30 days of keeping the rats.

Results:

The results showed that serum levels of calcium and phosphorus were not significantly different in all five groups before and after 30 days. Serum levels of vitamin D were significantly higher in the group receiving Ca/vit D (with a mean of 61.6±15.8 in the male group and 85±12.9 in the female group) as compared with other groups (P<0.001). The highest level of change in maxillary and mandibular bone density was in 200 mg/kg flaxseed group with a mean difference of 24.5±6.1 and 26.5±3.1, respectively, which was significant in comparison with the control and Ca/vit D groups (p<0.001) .

Conclusion:

Flaxseed extract is more effective in increasing bone density than the group receiving Ca/vit D. The mandibular and maxillary BMD was higher in the group receiving 200 mg/kg flaxseed compared to the group receiving Ca/vit D (p<0.001).

Flaxseed oil ameliorated high-fat-diet-induced bone loss in rats by promoting osteoblastic function in rat primary osteoblasts

Background

α-Linolenic acid (ALA) is a plant-derived omega-3 unsaturated fatty acid that is rich in flaxseed oil (FO). The effect of FO on bone health is controversial. This study aims to evaluate the effect of FO on bone damage induced by a high-fat diet (HFD) and to explore the possible mechanism.

Methods

Male Sprague-Dawley rats were fed a normal control diet (NC, 10% fat), FO diet (NY, 10% fat), HFD (60% fat), or HFD containing 10% FO (HY, 60% fat) for 22 weeks. Micro CT and three-point bending tests were conducted to evaluate bone microstructure and biomechanics. Serum was collected for the detection of ALP, P1NP, and CTX-1. Rat primary osteoblasts (OBs) were treated with different concentrations of ALA with or without palmitic acid (PA) treatment. The ALP activity, osteogenic-related gene and protein expression were measured.

Results

Rats in the HFD group displayed decreased biomechanical properties, such as maximum load, maximum fracture load, ultimate tensile strength, stiffness, energy absorption, and elastic modulus, compared with the NC group (p < 0.05). However, HY attenuated the HFD-induced decreases in bone biomechanical properties, including maximum load, maximum fracture load, and ultimate tensile strength (p < 0.05). Trabecular bone markers such as trabecular volume bone mineral density (Tb. vBMD), trabecular bone volume/total volume (Tb. BV/TV), trabecular number (Tb. N), trabecular thickness (Tb. Th) were decreased, trabecular separation (Tb. Sp) and the structure model index (SMI) were increased in the HFD group compared with the NC group, and all parameters were remarkably improved in the HY group compared to the HFD group (p < 0.05). However, cortical bone markers such as cortical volume bone mineral density (Ct. vBMD), cortical bone volume/total volume (Ct. BV/TV) and cortical bone thickness (Ct. Th) were not significantly different among all groups. Moreover, the serum bone formation markers ALP and P1NP were higher and the bone resorption marker CTX-1 was lower in the HY group compared with levels in the HFD group. Compared with the NC group, the NY group had no difference in the above indicators. In rat primary OBs, PA treatment significantly decreased ALP activity and osteogenic gene and protein (β-catenin, RUNX2, and osterix) expression, and ALA dose-dependently restored the inhibition induced by PA.

Conclusions

FO might be a potential therapeutic agent for HFD-induced bone loss, most likely by promoting osteogenesis.

Pros and cons of fatty acids in bone biology

Despite the growing interest in deciphering the causes and consequences of obesity-related disorders, the mechanisms linking fat intake to bone behaviour remain unclear. Since bone fractures are widely associated with increased morbidity and mortality, most notably in elderly and obese people, bone health has become a major social and economic issue. Consistently, public health system guidelines have encouraged low-fat diets in order to reduce associated complications. However, from a bone point of view, mechanisms linking fat intake to bone alteration remain quite controversial. Thus, after more than a decade of dedicated studies, this timely review offers a comprehensive overview of the relationships between bone and fatty acids. Using clinical evidences as a starting-point to more complex molecular elucidation, this work highlights the complexity of the system and reveals that bone alteration that cannot be solved simply by taking ω-3 pills. Fatty acid effects on bone metabolism can be both direct and indirect and require integrated investigations. Furthermore, even at the level of a single cell, one fatty acid is able to trigger several different independent pathways (receptors, metabolites…) which may all have a say in the final cellular metabolic response.

Investigating the role of polyunsaturated fatty acids in bone development using animal models

Incorporating n-3 polyunsaturated fatty acids (PUFA) in the diet may promote the development of a healthy skeleton and thereby reduce the risk of developing osteoporosis in later life. Studies using developing animal models suggest lowering dietary n-6 PUFA and increasing n-3 PUFA intakes, especially long chain n-3 PUFA, may be beneficial for achieving higher bone mineral content, density and stronger bones. To date, the evidence regarding the effects of α-linolenic acid (ALA) remain equivocal, in contrast to evidence from the longer chain products, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). This review reports the results of investigations into n-3 PUFA supplementation on bone fatty acid composition, strength and mineral content in developing animal models as well as the mechanistic relationships of PUFA and bone, and identifies critical areas for future research. Overall, this review supports a probable role for essential (ALA) and long chain (EPA and DHA) n-3 PUFA for bone health. Understanding the role of PUFA in optimizing bone health may lead to dietary strategies that promote bone development and maintenance of a healthy skeleton.

The effect of fatty acid positioning in dietary triacylglycerols and intake of long-chain n-3 polyunsaturated fatty acids on bone mineral accretion in growing piglets

Long-chain n-3 PUFA (LCPUFA) and palmitate (16:0) positioning in the triacylglycerol (TAG) of infant formula may affect calcium-uptake which could affect bone health. We investigated if a human milk fat substitute (HMFS) with a modified TAG structure holding 16:0 predominantly in the sn-2-position compared with a control (CONT) and if increasing n-3LCPUFA intake giving fish oil (FO) compared with sunflower oil (SO) would affect bone parameters in piglets in two sets of controlled 14d-interventions (n=12/group). We assessed this by dual-energy x-ray absorptiometry, and ex vivo peripheral quantitative computed tomography and mechanical strength. Bone mineral content (BMC) was higher in the FO compared to the SO-group (p=0.03). Despite similar weight gain in HMFS- and CONT-groups, body fat accumulation was higher with HMFS (p<0.001), and BMC, bone area (BA) and cortical BA in femur were lower (p=0.002, p=0.005, and p=0.02, respectively), indicating importance of both n-3LCPUFA and 16:0 TAG-positioning in infant formulas.

The effects of n-3 long-chain polyunsaturated fatty acids on bone formation and growth factors in adolescent boys

INTRODUCTION

Animal studies indicate that n-3 long-chain polyunsaturated fatty acids (LCPUFAs) increase bone formation. To our knowledge, no studies have examined this in growing humans. This study investigated whether bone mass and markers of bone formation and growth were (i) associated with docosahexaenoic acid (DHA) status and (ii) affected by fish oil supplementation, in adolescent boys.

METHODS

Seventy-eight healthy, slightly overweight 13- to 15-y-old boys were randomly assigned to breads with DHA-rich fish oil (1.1 g/d n-3 LCPUFA) or control for 16 wk. Whole-body bone mineral content (BMC), bone area (BA), bone mineral density (BMD), plasma osteocalcin, and growth factors were measured at wk 0 and wk 16, as well as diet, physical activity, and n-3 LCPUFA status in erythrocytes.

RESULTS

Fish oil strongly increased DHA status (P = 0.0001). No associations were found between DHA status and BMC, BA, BMD, or the markers of bone formation and growth at baseline. Furthermore, the fish oil intervention did not affect any of the outcomes as compared with control. However, dose-response analyses revealed a positive association between changes in DHA status and plasma insulin-like growth factor-1 (IGF-1) during intervention (β = 0.24, P = 0.03, n = 78).

DISCUSSION

DHA status and fish oil supplementation were not associated with bone mass or markers of bone formation in adolescent boys, but IGF-1 increased with increasing DHA status.

High-fat diets affect energy and bone metabolism in growing rats

BACKGROUND

High-fat diets are usually associated with greater weight (W) gain and body fat (BF). However, it is still unclear whether the type and amount of fat consumed influence BF. Additionally, dietary fat intake may also have consequences on skeletal health.

OBJECTIVE

To evaluate in healthy growing rats the effects of high-fat diets and type of dietary fat intake (saturated or vegetable oils) on energy and bone metabolism.

METHODS

At weaning, male Wistar rats (n = 50) were fed either a control diet (C; fat = 7% w/w) or a high-fat diet (20% w/w) containing either: soybean oil, corn oil (CO), linseed oil (LO), or beef tallow (BT) for 8 weeks. Zoometric parameters, BF, food intake and digestibility, and total and bone alkaline phosphatase (b-AP) were assessed. Total skeleton bone mineral density (BMD) and content (BMC), BMC/W, spine BMD, and bone volume (static-histomorphometry) were measured.

RESULTS

Animals fed BT diet achieved lower W versus C. Rats fed high-fat vegetable oil diets showed similar effects on the zoometric parameters but differed in BF. BT showed the lowest lipid digestibility and BMC. In contrast, high vegetable oil diets produced no significant differences in BMC, BMC/W, BMD, spine BMD, and bone volume. Marked differences were observed for LO and BT groups in b-AP and CO and BT groups in bone volume.

CONCLUSION

BT diet rich in saturated fatty acids had decreased digestibility and adversely affected energy and bone metabolisms, in growing healthy male rats. There were no changes in zoometric and bone parameters among rats fed high vegetable oil diets.

A linhaça (Linum usitatissimum) como fonte de ácido α-linolênico na formação da bainha de mielina

A linhaça (Linum usitatissimum) é uma semente oleaginosa que tem sido estudada por seus efeitos benéficos à saúde. É considerada um alimento funcional, pelo fato de ser uma fonte natural de fitoquímicos, e por conter o ácido graxo α-linolênico (C18:3 n-3), que pode ser metabolicamente convertido nos ácidos docosaexahenóico (C22:6 n-3) e eicosapentaenóico (C20:5 n-3), sendo o primeiro essencial para o desenvolvimento do sistema nervoso central. Durante o crescimento do cérebro, há uma grande incorporação do ácido docosaexahenóico, que tem papel importante na formação de suas membranas celulares. Diante disto, esta comunicação visa a abordar os prováveis mecanismos pelos quais o ácido docosaexahenóico, proveniente do ácido α-linolênico presente abundantemente na semente de linhaça, interfere na formação da bainha de mielina, assim como relatar a técnica mais adequada para visualização desta bainha.

Are all n-3 polyunsaturated fatty acids created equal?

N-3 Polyunsaturated fatty acids have been shown to have potential beneficial effects for chronic diseases including cancer, insulin resistance and cardiovascular disease. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in particular have been studied extensively, whereas substantive evidence for a biological role for the precursor, alpha-linolenic acid (ALA), is lacking. It is not enough to assume that ALA exerts effects through conversion to EPA and DHA, as the process is highly inefficient in humans. Thus, clarification of ALA's involvement in health and disease is essential, as it is the principle n-3 polyunsaturated fatty acid consumed in the North American diet and intakes of EPA and DHA are typically very low. There is evidence suggesting that ALA, EPA and DHA have specific and potentially independent effects on chronic disease. Therefore, this review will assess our current understanding of the differential effects of ALA, EPA and DHA on cancer, insulin resistance, and cardiovascular disease. Potential mechanisms of action will also be reviewed. Overall, a better understanding of the individual role for ALA, EPA and DHA is needed in order to make appropriate dietary recommendations regarding n-3 polyunsaturated fatty acid consumption.

Vertebrae of Developing Fat-1 Mice Have Greater Strength and Lower N-6/N-3 Fatty Acid Ratio

Incorporation of dietary n-3 polyunsaturated fatty acids (PUFA) into bone may optimize bone development. The study objective was to use the fat-1 mouse, a transgenic model that synthesizes n-3 PUFA from n-6 PUFA, to determine if bone mineral density (BMD) and biomechanical bone strength were favourably modulated by lowering the n-6/n-3 PUFA ratio in vertebrae. Male and female wild-type and fat-1 mice were fed an AIN93-G diet containing 10% safflower oil from weaning through 12 weeks of age. Vertebrae BMD was determined by dual energy x-ray absorptiometry and peak load, a surrogate measure of fracture risk, was measured by a materials testing system. Vertebrae fatty acid composition was measured by gas liquid chromatography. At 12 weeks of age, vertebrae peak load was higher in fat-1 mice compared to wild-type ( P = 0.026). Fat-1 mice also had lower n-6/n-3 PUFA ratio in vertebrae than wild-type ( P < 0.001) and this ratio was negatively correlated with BMD and peak load ( P = 0.005). Moreover, n-3 PUFA including α-linolenic acid, eicosapentaenoic acid and docosahexaenoic acid were positively correlated ( P < 0.05) with BMD and peak load. Therefore, a lower vertebrae n-6/n-3 PUFA ratio is associated with stronger vertebrae and suggests a positive role for n-3 PUFA in bone development.

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.

Long-chain polyunsaturated fatty acids and the regulation of bone metabolism

The role of prostaglandin E2 (PGE2) in the regulation of bone remodeling is well established. There is increasing evidence that various long-chain polyunsaturated fatty acids (LCPUFAs), as well as nonprostanoid LCPUFA metabolites, also have critical roles in regulating bone metabolism and may have therapeutic potential in the management of postmenopausal osteoporosis. Although only the 18-carbon precursors for the n-3 and n-6 LCPUFAs are deemed "dietary essential," the ability of the body to convert these precursor fatty acids into the more highly unsaturated 20- and 22-carbon LCPUFAs decreases with aging, menopause, and various lifestyle factors (e.g., smoking). Increasing dietary LCPUFA intake increases tissue and blood LCPUFA concentrations, as well as the concentrations of their metabolites. Modification of dietary LCPUFA content, particularly increasing the intake of n-3 LCPUFAs, has been shown to minimize the decline in bone mass caused by menopause in women and ovariectomy in animal models. This review summarizes findings from both in vivo and in vitro studies and outlines the effects of LCPUFAs and their metabolites on calcium balance, osteoblastogenesis, osteoclastogenesis, and osteoblast and osteoclast function.

Flaxseed and soy protein isolate, alone and in combination, differ in their effect on bone mass, biomechanical strength, and uterus in ovariectomized nude mice with MCF-7 human breast tumor xenografts

In our previous study, flaxseed (FS) reduced while soy protein isolate (SPI) stimulated MCF-7 breast tumor growth in ovariectomized mice. In addition, combining SPI and FS resulted in a negation of SPI-induced tumor growth. In this study, the effects of SPI, FS, and their combination were further examined on mouse bone and uterus to further ensure overall safety of the breast cancer treatments. Ovariectomized mice with established MCF-7 xenografts were fed either a basal diet (control), or a basal diet supplemented with 10% FS, 20% SPI, or SPI + FS for 25 wk. Mouse bones were analyzed for mineral and biomechanical strength properties, and uterus weight was measured. The SPI group had a higher femur bone mineral density and biomechanical strength parameters (yield load, stiffness, and peak load) compared to control, while the FS group significantly increased femur stiffness and peak load. The SPI + FS group did not affect femur mineral, but significantly reduced whole femur area and length and increased femur yield load, stiffness, and peak load. Uterus weight was significantly increased by the SPI + FS group, while SPI alone induced an intermediate effect. In conclusion, all dietary treatments induced beneficial effects on bone in a preclinical mouse model of postmenopausal breast cancer. Although the SPI + FS and SPI groups exerted stimulatory effects on uterus weight, other histological parameters need to be measured to determine the overall safety of these breast cancer treatments on the uterus.

Effects of dietary supplementation with flax during prepuberty on fatty acid profile, mammogenesis, and bone resorption in gilts1,2

The possible role of dietary flax on pre-pubertal development of mammary glands and bone resorption was investigated in gilts. Fifty-seven gilts were fed 1 of 4 diets from 88 d of age until slaughter (d 212 +/- 1). Diets were control without flax (n = 14); 10% flaxseed supplementation (n = 13); 6.5% flaxseed meal supplementation (n = 15); and 3.5% flaxseed oil supplementation (n = 15). All diets were isonitrogenous and isocaloric. Jugular blood samples were obtained on d 78 and 210 to establish the fatty acid profile and to determine the concentrations of prolactin, estradiol, and cross-linked N-telopeptides of type I collagen. At slaughter, the mammary glands were excised, parenchymal and extraparenchymal tissues were dissected, and the composition of the parenchymal tissue (protein, fat, DM, and DNA) was determined. Histochemical analyses of the mammary parenchyma were performed, and fatty acid profiles in the extraparenchymal tissue were evaluated. Dietary flax increased (P < or = 0.001) the concentrations of PUFA and decreased those of SFA (P < 0.01) and MUFA (P < or = 0.001) in plasma and extraparenchymal tissues, which was largely due to the inclusion of 10% flaxseed or 3.5% flaxseed oil (P < or = 0.01) but not 6.5% flaxseed meal. Circulating concentrations of prolactin and estradiol were unaltered by treatments (P > 0.1), but concentrations of cross-linked N-telopeptides of type I collagen tended to be greater (P < 0.1) in flax-supplemented gilts. The DM content of parenchymal tissue was the only mammary compositional value affected, showing an increase with flax addition (P < 0.05). No change (P > or = 0.1) in the bromodeoxyuridine labeling index or estrogen receptor localization was observed with treatments. Dietary supplementation with flax as seed, meal, or oil, therefore, brought about the expected changes in the fatty acid profile but had no beneficial effects on mammary development or bone resorption.