Bioavailability of Alpha-Linolenic Acid in Subjects after Ingestion of Three Different Forms of Flaxseed

Background: Dietary flaxseed may have significant health-related benefits due to its high content of the omega-3 fatty acid, alpha-linolenic acid (ALA). However, before extensive work can be undertaken in clinical populations to determine its efficacy, basic information on ALA bioavailability from flaxseed and the physiological effects of its ingestion need to be examined.

Objective: The purpose of this study, therefore, was to determine the bioavailability of ALA when the flaxseed was ingested in the form of whole seed, milled seed or as flaxseed oil.

Design: The flaxseed components (30 g of seed or 6 g of ALA in the oil) were baked into muffins for delivery over a 3 month test period in healthy male and female subjects.

Results: Flaxseed ingestion over a 1 month period resulted in significant (P = 0.005) increases in plasma ALA levels in the flaxseed oil and the milled flaxseed supplemented groups. The former group had significantly (P = 0.004) higher ALA levels than the milled flaxseed group. The subjects supplemented with whole flaxseed did not achieve a significant (P > 0.05) increase in plasma ALA levels. An additional two months of flaxseed ingestion did not achieve significantly higher levels of plasma ALA in any of the groups. However, no significant increase was detected in plasma eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA) levels in any of the flax-fed groups. There were no changes in plasma cholesterol or triglycerides or in platelet aggregation at any time point in any of the groups. Subjects in all of the groups exhibited some symptoms of gastro-intestinal discomfort during the early stages of the study but these disappeared in the oil and milled seed groups. However, compliance was a problem in the whole flaxseed group.

Conclusion: In summary, ingestion of flax oil and milled flaxseed delivered significant levels of ALA to the plasma whereas whole flaxseed did not. Whole seed and oil preparations induced adverse gastrointestinal effects within 4 weeks and these were severe enough to induce the withdrawal of some subjects from these two groups. No one withdrew from the group that ingested milled flaxseed and, therefore, may represent a good form of flaxseed to avoid serious side-effects and still provide significant increases in ALA to the body.     

Effects of Soy-Soluble Fiber and Flaxseed Gum on the Glycemic and Insulinemic Responses to Glucose Solutions and Dairy Products in Healthy Adult Males

Objective: Soy-soluble polysaccharides and flaxseed gum are underutilized dietary fibers of interest to the food industry. However, because the ability of soluble fibers to modulate postprandial glucose and insulin metabolism has been related to their viscous effects, the utility of these and other low-viscosity soluble fibers remains unproven. The objective of this study was to examine the associations between soy-soluble polysaccharides and flaxseed gum concentration, product viscosity, and the postprandial glycemic and insulinemic responses in the context of glucose solutions as well as fluid and gelled dairy products.

Methods: Twelve healthy males participated in a randomized crossover postprandial study in which they visited the laboratory following overnight fasts on 11 occasions to consume one of 11 study treatments, each consisting of 50 g available carbohydrates. The study treatments included a glucose reference (in duplicate), glucose solutions containing soy-soluble polysaccharides (6%), flaxseed gum (0.7%), or guar gum (0.23%), all matched for an apparent viscosity of 61 mPa·s at 50 s^?1, as well as dairy-based beverages and puddings with 0% or 1% soluble fiber added. Blood samples were collected at fasting and up to 2 hours postprandially for determination of glucose and insulin concentrations. Area under the curve (AUC), peak concentration, and time-to-peak values as well as glycemic index (GI) and insulinemic index (II) were calculated.

Results: Fiber fortification of a 50 g glucose solution had no effect on postprandial blood glucose or insulin levels, even at a high concentration (i.e., 6% soy-soluble polysaccharides). Glucose AUC and GI values for the dairy-based beverage (?p < 0.05) and pudding (?p < 0.01) controls were significantly lower than the glucose reference. Glucose AUC and GI values for the soy-soluble polysaccharide-fortified dairy products (?p < 0.01) and flaxseed gum–fortified dairy products (?p < 0.001) were significantly lower than the glucose reference. No significant differences were observed between the fiber-fortified fluid and gelled dairy-based study treatments and no significant differences were observed in terms of the insulin AUC, II, and peak insulin concentration between any of the dairy products.

Conclusions: All dairy products had lower glycemic responses relative to the reference, with no effect of beverage versus pudding matrix observed and minimal impact of 1% flaxseed gum or soy-soluble polysaccharides. Product apparent viscosity, but not fiber concentration, was significantly and inversely correlated with glucose AUC and GI.     

Flaxseed supplementation in non-alcoholic fatty liver disease: a pilot randomized,open labeled,controlled study

A two-arm randomized open labeled controlled clinical trial was conducted on 50 patients with non-alcoholic fatty liver disease (NAFLD). Participants were assigned to take either a lifestyle modification (LM), or LM?+30?g/day brown milled flaxseed for 12 weeks. At the end of the study, body weight, liver enzymes, insulin resistance and hepatic fibrosis and steatosis decreased significantly in both groups (pp?Pp p?p?=?0.013] and steatosis score [?47 compared with ?15.45?dB/m; p =?0.022]. In conclusion, flaxseed supplementation plus lifestyle modification is more effective than lifestyle modification alone for NAFLD management.     

Flaxseed oil increases the plasma concentrations of cardioprotective (n-3) fatty acids in humans

Alpha-linolenic acid (ALA) is a major dietary (n-3) fatty acid. ALA is converted to longer-chain (n-3) PUFA, such as eicosapentaenoic acid (EPA) and possibly docosahexaenoic acid (DHA). EPA and DHA are fish-based (n-3) fatty acids that have proven cardioprotective properties. We studied the effect of daily supplementation with 3 g of ALA on the plasma concentration of long-chain (n-3) fatty acids in a predominantly African-American population with chronic illness. In a randomized, double-blind trial, 56 participants were given 3 g ALA/d from flaxseed oil capsules (n = 31) or olive oil placebo capsules (n = 25). Plasma EPA levels at 12 wk in the flaxseed oil group increased by 60%, from 24.09 +/- 16.71 to 38.56 +/- 28.92 micromol/L (P = 0.004), whereas no change occurred in the olive oil group. Plasma docosapentaenoic acid (DPA) levels in the flaxseed oil group increased by 25% from 19.94 +/- 9.22 to 27.03 +/- 17.17 micromol/L (P = 0.03) with no change in the olive oil group. Plasma DHA levels did not change in either group. This study demonstrates the efficacy of the conversion of ALA to EPA and DPA in a minority population with chronic disease. ALA may be an alternative to fish oil; however, additional clinical trials with ALA are warranted.     

Acute Flaxseed Intake Reduces Postprandial Glycemia in Subjects with Type 2 Diabetes: A Randomized Crossover Clinical Trial

Background: Postprandial glycemic excursions are associated with impairment control of diabetes mellitus. Long-term consumption of flaxseed can lower blood glucose levels; however, its effects on the postprandial glycemic response remain unknown. Therefore, this study aimed to evaluate the acute effects of raw flaxseed consumption on the 2 h postprandial glycemic curve in men with type 2 diabetes mellitus (T2DM). Methods: This was a randomized crossover clinical trial. Nineteen men with T2DM were randomly assigned a standardized breakfast without (control) or with a previous intake of 15 g of ground raw golden flaxseed (flax). Glycemia was measured at fasting and postprandial at 15, 30, 45, 60, 90, and 120 min. Palatability markers (visual appeal, smell, and pleasantness of taste) and taste intensity (sweetness, saltiness, bitterness, sourness, and creaminess) were evaluated. Results: The peak glucose rise and the 2 h AUC glycemic response reduced in the flax group by 17% (p = 0.001) and 24% (p < 0.001), respectively. The glucose peak time, palatability, and taste parameters did not differ between the two groups. Conclusions: Ingestion of 15 g of ground raw golden flaxseed before breakfast decreases the 2 h postprandial glycemic response in men with T2DM.     

Effect of Flaxseed and Wheat Bran on Serum Hormones and Lignan Excretion in Premenopausal Women

Objective: To examine the effects of flaxseed consumption (a lignan-rich plant food) alone and in combination with wheat bran on serum hormones and urinary lignan excretion in premenopausal women.

Methods: Sixteen subjects were studied for four feeding treatments lasting two menstrual cycles each in a randomized, crossover design. During each treatment, subjects consumed their habitual diets supplemented with baked goods containing no flaxseed or wheat bran, 10 g of flaxseed, 28 g of wheat bran, or 10 g of flaxseed plus 28 g of wheat bran/day. Serum samples collected during the mid-luteal phase of the second menstrual cycle of each diet treatment were analyzed for serum hormones and sex hormone binding globulin. Urine samples collected during the same time period were analyzed for urinary lignan excretion.

Results: There were no changes in serum hormone concentrations or sex hormone binding globulin on any of the treatments. Urinary lignan excretion significantly increased on diet treatments that included flaxseed, but inclusion of wheat bran did not significantly alter lignan excretion.

Conclusions: Urinary lignan excretion increased with flaxseed consumption, but serum hormones did not change in this group of premenopausal women. Consumption of wheat bran with flaxseed did not alter urinary lignan excretion associated with flaxseed consumption.     

Flaxseed and cardiovascular risk

Flaxseed has recently gained attention in the area of cardiovascular disease primarily because it is the richest known source of both alpha-linolenic acid (ALA) and the phytoestrogen, lignans, as well as being a good source of soluble fiber. Human studies have shown that flaxseed can modestly reduce serum total and low-density lipoprotein cholesterol concentrations, reduce postprandial glucose absorption, decrease some markers of inflammation, and raise serum levels of the omega-3 fatty acids, ALA and eicosapentaenoic acid. Data on the antiplatelet, antioxidant, and hypotensive effects of flaxseed, however, are inconclusive. More research is needed to define the role of this functional food in reducing cardiovascular risk.     

Supplementing lactating women with flaxseed oil does not increase docosahexaenoic acid in their milk

BACKGROUND: Flaxseed oil is a rich source of 18:3n-3 (alpha-linolenic acid, or ALA), which is ultimately converted to 22:6n-3 (docosahexaenoic acid, or DHA), a fatty acid important for the development of the infant brain and retina. OBJECTIVE: The objective of this study was to determine the effect of flaxseed oil supplementation on the breast-milk, plasma, and erythrocyte contents of DHA and other n-3 fatty acids in lactating women. DESIGN: Seven women took 20 g flaxseed oil (10.7 g ALA) daily for 4 wk. Breast-milk and blood samples were collected weekly before, during, and after supplementation and were analyzed for fatty acid composition. RESULTS: Breast milk, plasma, and erythrocyte ALA increased significantly over time (P < 0.001) and after 2 and 4 wk of supplementation (P < 0.05). Over time, 20:5n-3 (eicosapentaenoic acid, or EPA) increased significantly in breast milk (P = 0.004) and in plasma (P < 0.001). In addition, plasma EPA increased significantly (P < 0.05) after 2 and 4 wk of supplementation. There were significant increases over time in breast-milk 22:5n-3 (docosapentaenoic acid, or DPA) (P < 0.02), plasma DPA (P < 0.001), and erythrocyte DPA (P < 0.01). No significant changes were observed in breast-milk, plasma, or erythrocyte DHA contents after flaxseed oil supplementation. CONCLUSIONS: Dietary flaxseed oil increased the breast-milk, plasma, and erythrocyte contents of the n-3 fatty acids ALA, EPA, and DPA but had no effect on breast-milk, plasma, or erythrocyte DHA contents.     

Effect of Midmorning Puree Snacks on Subjective Appetite,Food Intake,and Glycemic and Insulin Responses in Healthy Adults

ABSTRACT

Objective: Dietary pattern changes, as a part of a healthy lifestyle, may improve weight management. The objective of this study was to examine the effect of midmorning puree snacks varying in macronutrient composition and energy content on subjective appetite, food intake, and glycemic and insulin responses in healthy adults.

Method: In a randomized, repeated measures crossover design, 6 treatments (snack skipping and purees: control [186 kcal], maltodextrin [272 kcal], whey protein [201 kcal], oat [276 kcal], and coconut oil [276 kcal]) were administered to 23 normal weight adults (n = 14 males, n = 9 females). Subjective appetite, blood glucose, and insulin responses were measured at regular intervals for 2 hours immediately followed by an ad libitum pizza lunch. In vitro digestion experiments were conducted to corroborate results of the human trial.

Results: Compared to snack skipping, all snack treatments similarly reduced subjective average appetite (net area under the curve), but only oat (p < 0.032) and coconut oil (p < 0.031) purees significantly decreased test meal food intake. However, caloric compensation did not differ among snack treatments (p < 0.73). Both blood glucose (incremental area under the curve [iAUC]; p < 0.0001) and serum insulin (iAUC; p < 0.0001) were affected by treatment. A positive correlation was found between blood glucose iAUC and in vitro glucose release (r = 0.993, p < 0.0001). The release of free fatty acids (FFAs) was sustained, and oats were difficult to disintegrate during in vitro digestion.

Conclusions: Compared with snack skipping, coconut oil and oat puree snacks suppressed short-term food intake, which was likely due to the sustained release of FFA and slowly digestible oats, respectively. Our in vitro digestion model predicted the relative differences in the glycemic response in vivo.     

Effects of flaxseed oil supplementation on plasma adiponectin levels in dyslipidemic men

Background Dietary alpha-linolenic acid (ALA) has been associated with reduced risk of development of atherosclerosis. Adiponectin is a hormone specifically secreted by adipocytes and considered to have anti-atherogenic properties. Aim of the study We examined the effect of increased dietary intake of ALA on plasma concentration of adiponectin. Methods Thirty-five non-diabetic, dyslipidemic men, 38–71 years old, were randomly allocated to take either 15 ml of flaxseed oil rich in ALA (8.1 g/day; n = 18), or 15 ml of safflower oil per day, containing the equivalent n-6 fatty acid (11.2 g/day linoleic acid, LA; n = 17) (control group). The intervention period lasted for 12 weeks. Results Plasma levels of adiponectin did not change after the increase in dietary intake of ALA in the flaxseed oil supplementation group, compared to the control group. No changes in body mass index, serum lipid concentrations, LDL density, or plasma TNF-α were found in the flaxseed oil versus the control group. Conclusions Dietary ALA has no effect on plasma adiponectin concentration in dyslipidemic men.     

Flaxseed oil and fish-oil capsule consumption alters human red blood cell n-3 fatty acid composition: a multiple-dosing trial comparing 2 sources of n-3 fatty acid

BACKGROUND: An increase in plasma n-3 fatty acid content, particularly eicosapentaenoic acid (20:5n-3; EPA) and docosahexaenoic acid (22:6n-3; DHA), is observed after consumption of fish oil-enriched supplements. Because alpha-linolenic acid (18:3n-3; ALA) is the direct precursor of EPA and DHA, ALA-enriched supplements such as flax may have a similar effect, although this hypothesis has been challenged because of reported low conversion of ALA into DHA. OBJECTIVE: To address this question, we designed a clinical trial in which flax oil, fish-oil, and sunflower oil (placebo group) capsules were given to firefighters (n = 62), a group traditionally exposed to cardiovascular disease risk factors. DESIGN: Firefighters were randomly divided into 6 experimental groups receiving 1.2, 2.4, or 3.6 g flax oil/d; 0.6 or 1.2 g fish oil/d; or 1 g sunflower oil/d for 12 wk. Blood was drawn every 2 wk, and the total phospholipid fatty acid composition of red blood cells was determined. RESULTS: As expected, fish oil produced a rapid increase in erythrocyte DHA and total n-3 fatty acids. The consumption of either 2.4 or 3.6 g flax oil/d (in capsules) was sufficient to significantly increase erythrocyte total phospholipid ALA, EPA, and docosapentaenoic acid (22:5n-3) fatty acid content. There were no differences among groups in plasma inflammatory markers or lipid profile. CONCLUSIONS: The consumption of ALA-enriched supplements for 12 wk was sufficient to elevate erythrocyte EPA and docosapentaenoic acid content, which shows the effectiveness of ALA conversion and accretion into erythrocytes. The amounts of ALA required to obtain these effects are amounts that are easily achieved in the general population by dietary modification.     

The Effect of Meal Frequency on the Fatty Acid Composition of Serum Phospholipids in Patients with Type 2 Diabetes

Objective: Fatty acids are important cellular constituents that can affect many metabolic processes relevant for the development of diabetes and its complications. We previously demonstrated a positive effect of eating just 2 meals a day, breakfast and lunch, compared to 6 small meals. The aim of this secondary analysis was to explore the effect of meal frequency on the fatty acid composition of serum phospholipids in subjects with type 2 diabetes (T2D).

Methods: In a randomized, crossover study, we assigned 54 patients with T2D to follow one of 2 regimens of a hypocaloric diet (?500 kcal/day), each for 12 weeks: 6 meals (A6) or 2 meals a day, breakfast and lunch (B2). The diet in both regimens had the same macronutrient and energy content. The fatty acid composition of serum phospholipids was measured at weeks 0, 12, and 24, using gas liquid chromatography. Insulin sensitivity was derived as an oral glucose insulin sensitivity (OGIS) index.

Results: Saturated fatty acids (mainly myristic and palmitic acids) decreased (p < 0.001) and n6 polyunsaturated fatty acids increased (p < 0.001) in response to both regimens but more with B2 (p < 0.001 for both). Monounsaturated fatty acids decreased (p < 0.05) and n3 polyunsaturated fatty acids increased (p < 0.001) in response to both regimens, with no difference between the regimens. An increase in OGIS correlated positively with changes in the proportion of linoleic acid in B2. This correlation remained significant even after adjustment for changes in body mass index (BMI; r = +0.38; p = 0.012).

Conclusions: We demonstrated that meal frequency affects the fatty acid composition of serum phospholipids. The B2 regimen had more marked positive effects, with saturated fatty acids and the ratio of saturated to unsaturated fatty acids decreasing more. The increase in linoleic acid could partly explain the insulin-sensitizing effect of B2 in T2D.     

Flaxseed oil supplementation does not affect plasma lipoprotein concentration or particle size in human subjects

alpha-Linolenic acid (ALA) is a major dietary (n-3) fatty acid. Some clinical trials with ALA supplementation have shown reduced cardiovascular risk; however the specific cardioprotective mechanism is not known. We studied the effects of daily supplementation with ALA derived from flaxseed oil on concentrations of plasma LDL cholesterol, HDL cholesterol, intermediate density lipoprotein cholesterol, and lipid particle sizes. In a randomized double-blind trial, 56 participants were given 3 g/d of ALA from flaxseed oil in capsules (n = 31) or olive oil containing placebo capsules (n = 25) for 26 wk. Changes in plasma HDL cholesterol, LDL cholesterol, and triglyceride concentrations did not differ between the 2 groups at 26 wk. The adjusted plasma total cholesterol concentration at 26 wk was 0.45 mmol/L higher in the flaxseed oil group (5.43 +/- 0.03 mmol/L) compared with the olive oil group (5.17 +/- 0.07 mmol/L) (P = 0.026). ALA did not affect LDL, HDL, or IDL particle size; however, the concentrations of the large, less atherogenic LDL1 (P = 0.058) and LDL2 (P = 0.083) subfractions tended to be greater in the ALA group. In conclusion, ALA does not decrease CVD risk by altering lipoprotein particle size or plasma lipoprotein concentrations.     

Repeated versus single measurement of plasma omega-3 fatty acids and risk of heart failure

Purpose

Studies have previously examined the relation between a single measure of plasma fatty acids and risk of heart failure. However, it is unclear whether the use of repeated measures of fatty acids over time is required for the assessment of omega-3 fatty acids heart failure relation.

Methods

Using a nested case–control design, this ancillary study used 421 cases and 421 matched controls from the Physicians’ Health Study to assess the variability of plasma phospholipid fatty acids over time and compare the results of omega-3 fatty acids heart failure associations using a single versus repeated measurements of plasma phospholipid fatty acids. Plasma omega-3 fatty acids were measured at baseline (1982) and approximately 15 years later using gas chromatography.

Results

Spearman’s correlation coefficients between baseline and follow-up measures of α-linolenic acid (ALA), EPA, DPA, and DHA were 0.20, 0.45, 0.28, and 0.50, respectively, in the control series. Multivariable adjusted odds ratios for heart failure per standard deviation higher plasma ALA were 0.98 (95 % CI 0.85–1.13) when using baseline ALA and 0.86 (95 % CI 0.74–1.01) when using the average of baseline and follow-up ALA measurements. Corresponding odds ratios for total long chain omega-3 FAs (EPA + DHA + DPA) were 0.87 (0.73–1.03) and 0.88 (0.75–1.04).

Conclusions

Our data demonstrate modest correlation between measurements of plasma phospholipid fatty acids spaced by 15 years. A single measurement of plasma phospholipid fatty acids appears reasonable to estimate the risk of heart failure over long-term follow-up.     

Influence of Flaxseed Lignan Supplementation to Older Adults on Biochemical and Functional Outcome Measures of Inflammation

Evidence from the literature suggests that dietary flaxseed lignans have the ability to modulate inflammation, which is recognized as the underlying basis of multiple chronic human diseases in older adults. Our objective was to determine the effects of oral lignan supplementation on biochemical and functional indicators of inflammation as well as safety and tolerability in older healthy adults. We designed a randomized, double-blind, placebo-controlled clinical trial in older healthy adults (60–80 years) to assess flaxseed lignan–enriched complex (～38% secoisolariciresinol diglucoside [SDG]; 600 mg SDG dose) oral supplementation effects on biochemical and functional indicators of inflammation and safety and tolerability in older healthy adults after 6 months of once-daily oral administration. The clinical trial confirmed that plasma concentration of total flaxseed lignans (free and conjugated forms) secoisolariciresinol (SECO), enterodiol (ED), and enterolactone (ENL) were significantly associated with daily oral supplementation of flaxseed lignan–enriched complex (p < 0.05). A significant decrease in systolic blood pressure (SBP; from a mean of 155 ± 13 mm Hg at baseline to 140 ± 11 mm Hg at 24 weeks) was observed in lignan-supplemented participants stratified into an SBP ≥140 mm Hg subcategory (p = 0.04). No differences were found between treatment or placebo groups in terms of cognition, pain, activity, physical measurements (calf, waist, and upper arm circumstances), and grip strength. With respect to blood inflammatory markers, lipid profiles, and biochemical parameters, no significant differences were found between treatment and placebo groups at the end of the 6-month supplementation. No adverse effects were reported during supplementation. These data further support the safety and tolerability of long-term flaxseed lignan–enriched complex supplementation in older adults and identify an ability to favorably modulate SBP, an important risk factor in cardiovascular disease.     

Weight Changes and Metabolic Outcomes in Calorie-Restricted Obese Mice Fed High-Fat Diets Containing Corn or Flaxseed Oil: Physiological Role of Sugar Replacement with Polyphenol-Rich Grape

Objective: Because diet components are important during dieting in obesity treatment, we examined possible beneficial effects of substituting corn oil and sugar with flaxseed oil and grape in calorie-restricted high-fat diets on weight changes as well as improvement in some metabolic markers and related gene expression.

Methods: Seventy-five C57BL/6J male mice were given free access to a high-fat (36% of energy from fat) diet containing corn oil plus sugar (CO + S). After 11 weeks, 15 mice were sacrificed and another 60 were divided among 4 high-fat diet groups with 30% calorie restriction (CR) for the next 12 weeks. The diets contained corn oil (CO) or flaxseed oil (FO) with sugar (S) or grape (G).

Results: Despite CR, a weight loss trend was observed only during the first 4 weeks in all groups. CR did not significantly increase SIRT1 gene expression. Higher liver weight was observed in mice consuming FO (p < 0.05). Proliferator-activated receptor gamma (PPARγ) expression decreased in FO + G-CR significantly and even with a reduction of adiposity and higher adiponectin levels, fasting blood sugar (FBS) was significantly higher than in CO + G-CR. Grape intake increased Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) expression and decreased insulin resistance in CO + G-CR.

Conclusions: Sugar replacement with polyphenol-rich grape along with CR improved glucose homeostasis, and substituting corn oil with flaxseed oil in obese mice reduced fat mass, but even with no change in adiponectin levels it could not decrease insulin resistance. However, none of the food item combinations facilitated weight reduction in the long-term CR. Therefore, regardless of the total calorie intake, different diet components and fat contents may have unexpected effects on metabolic regulation.     

Implications of dietary α-linolenic acid in bone health

Recent evidence implies the benefit of ω-3 polyunsaturated fatty acids in bone health. Although eicosapentaenoic acid and docosahexaenoic acid, present in fish oil, have been extensively researched, much less is known about the influence of α-linolenic acid (ALA; present in flaxseeds), a metabolic precursor of eicosapentaenoic acid and docosahexaenoic acid, on bone. Our objective was to evaluate the published literature and distinguish between the individual effects of flaxseed oil and flax lignans on bone to elucidate the exact role of ALA in skeletal biology. The search was conducted in several databases resulting in 129 articles of which 30 were eligible for inclusion in this review. The studies showed that consumption of whole flaxseeds did not lead to a marked improvement of osteoporotic bones in humans and animals. However, when combined with estrogen therapy, flaxseed supplementation offered an extra benefit to bone in animal models. Similar results were found in studies conducted with flaxseed oil (predominantly ALA), but the favorable role of flaxseed oil was more obvious in various pathologic conditions (kidney disease, obesity with insulin resistance), resulting in improved bone properties. In contrast, despite a marginal estrogenic effect, the consumption of flax lignans resulted in little benefit to bone and the effect was limited to early life of females only in animal models. Based on the available studies, it could be concluded that supplementation with flaxseeds may contribute to some improvement in osteoporotic bone properties but the bone-protective effect may be attributed to ALA, not to the lignan fraction of flaxseeds.     

Effects of perilla oil on plasma concentrations of cardioprotective (n-3) fatty acids and lipid profiles in mice

The aim of this study was to examine the effects of perilla oil as well as several vegetable oils, including flaxseed oil, canola oil, and rice bran oil on plasma levels of cardioprotective (n-3) polyunsaturated fatty acids in mice by feeding each vegetable oil for a period of eight weeks. Concentrations of docosapentaenoic acid (DHA) and eicosapentaenoic acid (EPA), fish-based (n-3) polyunsaturated fatty acids, showed an increase in the plasma of mice fed perilla and flaxseed oils compared to those of mice in the control group (P < 0.05), whereas rice bran and canola oils did not alter plasma DPA and EPA concentrations. Arachidonic acid concentration was increased by feeding rice bran oil (P < 0.05), but not canola, flaxseed, or perilla oil. In addition, oleic acid, linoleic acid, and docosahexaenoic acid concentrations were altered by feeding dietary rice bran, canola, perilla, and flaxseed oils. Findings of this study showed that perilla oil, similar to flaxseed oil, is cardioprotective and could be used as an alternative to fish oil or even flaxseed oil in animal models.     

Erythrocyte polyunsaturated fatty acid composition is associated with depression and FADS genotype in Caucasians

Background: Polyunsaturated fatty acids (PUFAs) play an important role in the pathophysiology of major depressive disorder (MDD), related, in part, to their role in inflammatory systems. The enzymes δ-5 and δ-6 desaturase are the rate-limiting steps in the metabolism of PUFAs and are encoded in the genes fatty acid desaturase (FADS) 1 and 2, respectively. Single nucleotide polymorphisms (SNPs) and haplotypes within the FADS gene cluster have been shown to influence PUFA composition.

Aim: The objective of this study was to determine whether key omega-3 (n-3) and omega-6 (n-6) fatty acids may be associated with depression, and to explore the role of FADS genotype in PUFA variation.

Methods: Four erythrocyte long chain (LC) fatty acids (linoleic acid [LA], α-linolenic acid [ALA], arachidonic acid [AA] and Eicosapentaenoic acid [EPA]), as well as six SNPs (rs174537, rs174547, rs174570, rs174575, rs498793 and rs3834458) within the FADS gene cluster were measured in a sample of 207 participants (154 with MDD versus 53 non-depressed controls).

Results: The precursor LC-PUFAs LA and ALA appeared to be negatively associated with depression (P?P?0.01, respectively), while AA:LA (surrogate measure of desaturase activity) was positively associated with depression (P?0.01). No significant differences were noted in erythrocyte EPA, AA or AA:EPA between groups. Minor alleles of each SNP (excluding rs498793) were associated with variation in desaturase activity and LA. Both rs174537 and rs174547 were associated with ALA. No genotype was associated with EPA or AA. Minor alleles of rs174537 and rs174547 were significantly associated with lower odds of MDD (although significance was lost after correction for multiple comparisons).

Conclusion: Precursor LC-PUFAs, LA and ALA, appear to be associated with MDD and potentially modulated by genetic variation in the FADS gene cluster. These results provide support for the consideration of PUFA composition, diet and FADS genetic variation in the pathophysiology of MDD.