omega-3 ( n-3 ) fatty acids can be divided into alpha - linolenic acid ( ala ; c18:3n-3 ) from plant origin , and eicosapentaenoic acid ( epa ; c20:5n-3 ) and docosahexaenoic acid ( dha ; c22:6n-3 ) from seafood . because the human body lacks the enzymatic capacity to synthesize ala the estimated average ala intake in the united states and most european countries is 1.3 to 1.7  g / d [ 13 ] . the institute of medicine ( iom ) of the national academies established dietary reference intakes for macronutrients in 2002 . for ala , the adequate intake ( ai ) was set at 1.6  g / d for men and 1.1 the iom noted that intakes of n-3 fatty acids above the ai may confer additional health benefits , especially with respect to cardiovascular health . many advisory boards consider ala intakes greater than 1.5  g / d important for human health . to achieve an adequate ala intake , food sources such as flaxseed and flaxseed oil , walnuts and walnut oil , and canola and soybean oil are recommended . for epa and dha from fish this evidence has been confirmed in randomized controlled trials [ 58 ] . for ala , several large , prospective cohort studies in the united states have shown inverse associations of ala intake with risk of cardiovascular diseases , but other epidemiologic studies have been inconclusive [ 911 ] . a meta - analysis of observational studies showed that increased intake of ala might reduce coronary heart disease ( chd ) mortality by 21% , although this was not statistically significant . in the lyon diet heart study , a randomized controlled trial in coronary patients , consumption of a mediterranean - type diet that included an additional daily intake of roughly 1  g of ala significantly decreased the risk of cardiac death and nonfatal myocardial infarction ( mi ) by more than 60% . this study , however , was not specifically designed to assess the effect of ala supplementation , and many dietary factors differed between the experimental and control group . since then , no randomized controlled trials of ala and cardiovascular events have been published . this article summarizes the current literature ( published after 2008 ) on dietary ala intake , ala tissue levels , and cardiovascular health in humans . several trials have recently been published on the effect of ala supplementation on blood lipids , inflammatory markers , and other indicators of cardiovascular health ( table  1 ) [ 13 , 14 , 1517 , 18 ] . trials were mostly of relatively short duration ( 612  weeks ) and ala doses ranged from 1.2 to 3.6  g / d . there was one long - term trial ( 52  weeks ) in which a high ala dose of 8.8  g / d was given [ 18 ] . increased ala intake was achieved by means of flaxseed oil [ 13 , 15 ] , ala - enriched margarine [ 14 ] , or other ala - enriched foods [ 16 , 17 , 18 ] . table  1overview of randomized controlled trials of increased alpha - linolenic acid intake and cardiovascular risk factors published between january 2008 and june 2010study / yearpopulationdesignoutcome for alakaul et al . /200888 healthy non - smoking canadian men and premenopausal women , aged 33 y12-week , double - blind , parallel randomized controlled trial ; sunflower oil ( placebo ) , flaxseed oil ( 1 g / d ala ) , hempseed oil ( 0.3 g / d ala ) , or fish oil ( 0.6 g / d epa+dha)plasma ala levels increased ( p  <  0.05 ) after 6 wk ; no differences in total cholesterol , ldl - c , hdl - c , tg , ldl oxidation , platelet aggregation , or inflammation markers ( crp , tnf-)egert et al . [ 14]/200979 healthy non - smoking german men and premenopausal women , aged 1945 y6-week , double - blind , parallel randomized controlled trial ; ala ( 3.4 g / d ) , epa ( 2.2 g / d ) , or dha ( 2.3 g / d ) via enriched margarinesldl - ala levels increased ( p  <  0.05 ) ; fasting serum tg decreased ( p  <  0.05 ) ; no differences in total cholesterol , ldl - c , or hdl - cbarcel - coblijn et al . /200862 american men > 40 y of age12-week , parallel randomized controlled trial ; different doses of flax oil , fish oil , and sunflower oil in capsules ; ala doses were 1.2 g / d , 2.4 g / d , and 3.6 g / d2.4 and 3.6 g / d of ala significantly increased erythrocyte ala and epa levels ; no differences in inflammation markers ( crp , tnf- , svcam-1 ) , total cholesterol , tg , or hdl - csioen et al . /200959 healthy belgian male prisoners12-week single - blind study ; diet with 3.2 g / d extra alano effect on waist circumference , weight , bmi , systolic blood pressure ; diastolic blood pressure decreased and hdl - c increased in non - smokersbloedon et al . /200862 men and post - menopausal women from philadelphia , aged 4475 y , with hypercholesterolemia10-week , blind , parallel randomized controlled trial with low - fat diet with extra flaxseed or with wheat bran ( control ) ; ala dose of 3.4 g / dserum ala levels increased ; ldl - c was decreased after 5 wk but not after 10 wk ; lipoprotein(a ) was decreased and insulin sensitivity ( homa index ) improved ; no effect on inflammation ( il-6 , hs - crp ) or oxidative stress ( ox - ldl , urinary isoprostane ) ; hdl - c was reduceddodin et al . [ 18]/2008199 canadian menopausal women , aged 4965 y52-week , blind parallel trial ; 40 g / d flaxseed or wheat germ ; ala dose of 8.8 g / dserum ala levels increased ; modest effects on apolipoproteins a - i and b ; no effects on ldl electrophoretic characteristics or markers of hemostasis and inflammationala alpha - linolenic acid ; bmi body mass index ; dha docosahexaenoic acid ; epa eicosapentaenoic acid ; hdl - c high - density lipoprotein cholesterol ; homa homeostasis model assessment ; hs - crp high - sensitivity c - reactive protein ; il-6 interleukin-6 ; ldl - c low - density lipoprotein cholesterol ; svcam-1 soluble vascular cell adhesion molecule-1 ; tg triglycerides ; tnf tumor necrosis factor overview of randomized controlled trials of increased alpha - linolenic acid intake and cardiovascular risk factors published between january 2008 and june 2010 ala alpha - linolenic acid ; bmi body mass index ; dha docosahexaenoic acid ; epa eicosapentaenoic acid ; hdl - c high - density lipoprotein cholesterol ; homa homeostasis model assessment ; hs - crp high - sensitivity c - reactive protein ; il-6 interleukin-6 ; ldl - c low - density lipoprotein cholesterol ; svcam-1 soluble vascular cell adhesion molecule-1 ; tg triglycerides ; tnf tumor necrosis factor kaul et al .   studied the effects of low - dose supplementation ( 2  g / d , by means of capsules ) of flaxseed oil , fish oil , and hempseed oil in 86 healthy canadian men and women about 34  years of age in a 12-week , randomized , double - blind , placebo - controlled trial . flaxseed oil ( ala dose 1  g / d ) increased plasma ala by 30% to 40% , had a small nonsignificant effect on plasma epa ( 7%8% ) , and no effect on plasma dha . none of the treatments affected serum total , low - density lipoprotein ( ldl ) , or high - density lipoprotein ( hdl ) cholesterol , triglycerides , ldl oxidation , platelet aggregation , or inflammatory markers . in another randomized trial in 62 healthy men approximately 40  years of age in the united states , participants were randomized to flax oil ( ala doses of 1.2 , 2.4 , or 3.6  g / d ) , fish oil ( 0.6 or 1.2  g / d ) , or sunflower oil for 12  weeks . increasing doses of flax oil caused elevation of the ala content in erythrocyte membranes by 40% to 80% , and also of epa ( 20%35% ) , but not of dha . none of the treatments altered plasma inflammatory markers ( c - reactive protein [ crp ] , tumor necrosis factor [ tnf]- , soluble vascular cell adhesion molecule-1 [ svcam-1 ] ) , plasma total or hdl cholesterol , or triglycerides . enrolled 62 american men and post - menopausal women aged 44 to 75  years with hypercholesterolemia . all participants were on a low - fat , low - cholesterol diet and subsequently randomized to flax - based or wheat - based products for 10  weeks . ala intake in the flaxseed group was 3.4  g / d higher than in the control group . flax - based products improved insulin sensitivity and reduced plasma ldl cholesterol by 7% to 13% and lipoprotein(a ) by 14% compared with wheat - based products . in men , there was also a decrease in hdl cholesterol . treatment had no effect on markers of inflammation ( interleukin-6 , high - sensitivity crp ) or oxidative stress ( oxidized ldl , urinary isoprostanes ) . the extent to which the observed effects of the flax - based diet were due to its ala content or other components of flax seeds is not clear . in a single - blind , 12-week field study among 59 healthy male prisoners ( mean age of 42  years ) in belgium , daily ala intake was increased from 2.8 to 4.9  g / d by means of ala - enriched foods without changing the linoleic acid content of the diet . all individuals were first on a regular diet , which was followed by an ala - rich diet , and no randomization was applied . epa and dha , but not ala , were assessed in platelet phospholipids , which showed no significant changes during ala intervention . body weight , waist circumference , and systolic blood pressure did not change , and there were no effects of ala on plasma total and ldl cholesterol , triglycerides , apolipoproteins a - i and b , glucose , and crp . [ 14 ] studied the effects of increased intake of ala , epa , and dha in a 6-week parallel trial in 74 german normolipidemic men and women aged 19 to 43  years . participants were randomly assigned to trial margarines that provided additional ala ( 3.4  g / d ) , epa ( 2.2  g / d ) , or dha ( 2.3  g / d ) . no placebo group was included . in the ala group , the ala content of ldl particles increased by 178% and the epa content increased by 36% , whereas dha remained unchanged . fasting serum triglycerides significantly decreased with epa ( 0.14  mmol / l ) , dha ( 0.30 dha intake significantly increased serum hdl cholesterol , whereas no changes were found with ala or epa intake [ 14 ] . finally , dodin et al . [ 18 ] evaluated the effect of flaxseed on markers of cardiovascular disease risk in 169 healthy menopausal canadian women who were randomly assigned to 40  g / d of flaxseed - based products or wheat - based products for 12  months . in the active - treatment group , flaxseed products increased plasma ala by 85% and plasma epa by 51% after 12  months of intake , which differed significantly from wheat - based intervention ( 12% and 29% , respectively ) . the 12-month intervention with flaxseed had significant effects on body weight ( 0.8  kg ) and serum total cholesterol ( 0.20 ldl cholesterol was reduced by 0.13  mmol / l ( p  =  0.09 ) . apolipoproteins a - i and b increased in both groups , but less during flaxseed - based than wheat - based intervention . treatment had no effect on plasma lipoprotein(a ) , fibrinogen , crp , insulin , glucose , or ldl peak particle size . zatnski et al .   examined trends in chd mortality in 11 eastern european countries and linked these figures to national data on vegetable oil consumption after 1990 . they showed the strongest decline in chd mortality in countries where rapeseed oil ( 9% ala ) rather than sunflower oil ( 0% ala ) was used . although these data are suggestive for a beneficial effect of ala , no definite conclusions can be drawn because the countries also differed in many other aspects that could impact cardiovascular health . cross - country comparisons based on aggregate data can not be adjusted for potential confounders , ( eg , socioeconomic status , lifestyle and other dietary components ) and should be considered for hypothesis generation only . in costa rica , soybean oil has been substituted for palm oil since the 1980s , which has led to an increase in ala intake . [ 19 ] performed a case  control study in 3638 costa rican individuals to examine the association between ala and nonfatal mi ( fig .  1 ) . ala intake was assessed by a 135-item food frequency questionnaire and ranged from 1.1 to 2.4  g / d ( mean , 1.6  g / d ) in this population . dietary ala was inversely associated with nonfatal mi , with odds ratios indicating a 39% reduced risk for approximately a 0.6-g / d difference in intake . the relationship between ala and mi was nonlinear and mainly confined to the lowest levels of intake . dietary ala intake in this study correlated well with ala in adipose tissue , plasma , and erythrocytes , but poorly with biomarkers of epa and dha , suggesting a direct cardioprotective effect of ala rather than via conversion to long - chain n-3 fatty acids [ 19 ] . 1odds ratios and 95% confidence intervals for nonfatal myocardial infarction ( mi ) by deciles of alpha - linolenic acid in adipose tissue ( a ) or intake ( b ) in a case  control study of 3638 men and women in costa rica . data were adjusted for smoking status , physical activity , household income , history of diabetes mellitus , history of hypertension , waist - to - hip ratio , saturated fat intake , and linoleic and trans fatty acids in adipose tissue . [ 19 ] ; with permission ) odds ratios and 95% confidence intervals for nonfatal myocardial infarction ( mi ) by deciles of alpha - linolenic acid in adipose tissue ( a ) or intake ( b ) in a case  control study of 3638 men and women in costa rica . data were adjusted for smoking status , physical activity , household income , history of diabetes mellitus , history of hypertension , waist - to - hip ratio , saturated fat intake , and linoleic and trans fatty acids in adipose tissue . [ 19 ] ; with permission ) an anti - inflammatory action of ala has been proposed as an explanation for the inverse association with cardiovascular diseases found in the case  control study in costa rica [ 19 ] , although negative findings on ala and inflammatory markers have been reported by others . [ 20 ] examined habitual ala intake and plasma concentrations of inflammatory markers , including il-6 and sil-6r , in 353 middle - aged men in the united states who were recruited from a twin registry . ala intake , assessed by the willett questionnaire , ranged from 0.2 to 2  g / d , and was significantly inversely related to plasma sil-6r independent of shared genetic factors and a wide range of potential confounders . a twin with a 1-g higher ala intake ( equivalent to one tablespoon of canola oil ) had 11% lower sil-6r concentrations than his twin with a low intake . despite the robust association with sil-6r , no significant associations were found with plasma il-6 , tnf- , or high - sensitivity crp [ 20 ] . in a study of 511 japanese employees of municipal offices , ala intake was assessed by a diet history questionnaire that had been validated against 16-day weighed food records ( pearson correlation for ala , r  =  0.3 ) . ala comprised 0.8% to 1.0% energy ( > 2  g / d ) and was inversely related to serum crp . data were adjusted for age , body mass index ( bmi ) , lifestyle factors , and physical activity , but not for dietary factors associated with ala , and should therefore be interpreted with caution . [ 22 ] assessed dietary ala intake by the willett questionnaire in 260 post - mi patients and linked these data to 24-hour electrocardiogram recordings that were analyzed for ventricular premature beats . ala intake ( expressed per 1,000  kcal / d ) was associated with a significant reduction in ventricular premature beats after adjustment for age , sex , cardiovascular medication , and co - morbidities . however , lifestyle ( eg , smoking ) and dietary factors were not controlled for and the study had a cross - sectional design , which has inherent methodologic weaknesses . previous analyses in the national heart , lung , and blood institute nhlbi family heart study suggested that ala may protect against atherosclerosis [ 23 , 24 ] . recently , sala - vila et al .   investigated whether serum phosphatidylcholine content of ala and other fatty acids was related to carotid atherosclerosis in a cross - sectional study of 451 asymptomatic spanish individuals ( mean age of 45  years ) with primary dyslipidemia . over half of the participants the habitual mediterranean diet in this population provided a mean ala intake of 0.8  g / d , mainly from olive oil and walnuts , which correlated well with serum ala ( r  =  0.44 ) . the association of serum fatty acids with intima - media thickness ( imt ) of the carotid arteries was assessed , adjusting for age , sex , bmi , smoking , antihypertensive drugs , statins , and other serum fatty acids . significant inverse associations were found between serum ala and internal carotid artery imt , and between serum dha and common carotid artery imt . serum epa was not associated with imt . in a small cross - sectional study of 50 asian men and women ( mean age of 58  years ) who suffered a first nonfatal mi , the mean common carotid imt was inversely associated with ala content of erythrocytes ( p  =  0.09 ) and ala intake ( p  =  0.02 ) . data , however , were only adjusted for age , sex , and total energy ( for dietary ala ) . the average intake of ala was 0.6  g / d , which was similar to that of epa and dha intake . ebbesson et al .   examined whether ala content of erythrocytes was related to heart rate as a risk indicator for ventricular arrhythmias . they performed a cross - sectional study in 707 alaskan eskimos ( mean age of 50  years ) who had a habitual intake of marine n-3 fatty acids of 2.9  g / d . after adjustment for gender , height , bmi , blood pressure , smoking , and heart rate  lowering medications , no association was observed with ala ( p  =  0.98 ) . epa and dha , on the other hand , were significantly inversely associated with heart rate . the delta(6)-desaturase enzyme is the rate - limiting step in the conversion of ala into epa and dha , and genetic variation in the delta(6)-desaturase gene ( fads2 ) may therefore affect the associations of ala with cardiovascular health . truong et al . , in a cross - sectional study , examined the association of ala in adipose tissue with metabolic syndrome , and possible effect modification by fads2 . in a cohort of 1,815 men and women from costa rica , the prevalence of metabolic syndrome ( 656 cases ) was 19% lower in the upper compared with the lower quintile of adipose tissue ala . there was no association between ala and metabolic syndrome among homozygous carriers of the fads2 deletion allele , suggesting that conversion of ala into epa may play a role . it should be noted , however , that the fads2 polymorphism did not influence the inverse association of ala with nonfatal mi in a previous case ala status has been inversely associated with cardiovascular disease events , although data are less consistent than for epa and dha [ 710 ] . an overview of ala biomarker studies is provided in table  2 . in the aforementioned case [ 19 ] , ala was measured in adipose tissue as a biomarker of intake , which correlated well with dietary ala . ala was strongly inversely associated with nonfatal mi , with a 57% reduced risk when comparing the 7th decile with the lowest decile . the relationship between ala and mi was nonlinear and mainly confined to levels below the median ( fig .  1 ) . mozaffarian et al .   suggested that ala may particularly reduce chd risk when intake of marine n-3 fatty acids is low . in the study by campos et al . [ 19 ] , however , concurrent fish intake ( range , 332  g / d ) or epa and dha intake ( range , 130520  mg / d ) did not modify the associations of ala with mi . table  2overview of biomarker studies of alpha - linolenic acid and cardiovascular events published between january 2008 and june 2010study / yearpopulationdesignoutcomecampos et al . [ 19]/2008costa rica : 1,891 cases with first nonfatal mi and 1,891 population - based controls ; matching for age , sex , and area of residencecase  control study : association of ala intake from ffq and ala in adipose tissue with risk of first nonfatal mior ( 95% ci ) for first nonfatal mi was 0.41 ( 0.250.67 ) for top vs lowest decile of ala in adipose tissue , and 0.61 ( 0.420.88 ) for high vs low ala intake ; associations only present at lower ala levelsyamagishi et al . /2008usa , minneapolis : 3,575 white men and women from aric study , ages 4564 yprospective cohort study : association of plasma ala with incident heart failure ; 14.3 y of follow - up195 participants ( 5.5% ) developed heart failure ; ala status ( top vs bottom quintile ) was not associated with incident heart failure ; age- and sex - adjusted hr was 0.99 ( 0.631.53 ) for cholesteryl ester fraction and 0.97 ( 0.611.54 ) for phospholipid fractionwarensj et al . /2008sweden : 2,009 men from ulsam study , aged 50 yprospective cohort study : association of ala in serum cholesteryl esters with cvd mortality ; 30.7 y of follow - upmultivariable - adjusted hr was 1.10 ( 1.001.21 ) per 1-sd increase in serum alapark et al . /2009south korea : 40 cases of ischemic stroke , 40 cases of hemorrhagic stroke and 40 healthy controls ; matching for age and sexcase  control study : association of ala in erythrocytes with risk of ischemic and hemorrhagic strokeerythrocyte ala concentrations ( area% ) in hemorrhagic stroke patients ( 0.71    0.21 ) and ischemic stroke patients ( 0.24    0.03 ) were not significantly different from controls ( 0.44    0.05 ) after adjustment for family history of stroke ; inverse association of ala with ischemic stroke after adjustment for age and systolic blood pressure ( p  =  0.045).virtanen et al . [ 34]/2009finland : 2,174 men from kuopio ischemic heart disease risk factor study , ages 4260 yprospective cohort study : association of serum ala with incident atrial fibrillation ; 17.7 y of follow - up240 men ( 11.0% ) developed atrial fibrillation ; multivariable - adjusted hr for serum ala ( compared to q1 ) was q2 : 1.26 ( 95% ci , 0.841.89 ) , q3 : 0.74 ( 0.461.20 ) , and q4 : 1.14 ( 0.721.79 ; p for trend = 0.98).lemaitre et al . [ 35]/2009usa , seattle : 265 out - of - hospital sudden cardiac arrest patients and 415 community members ; matching for age , sex , and calendar yearcase  control study : association of ala in erythrocytes with risk of sudden cardiac death ; blood collection immediately after the event ( patients ) or during interview ( control)multivariable - adjusted or over quartiles of ala in erythrocytes ( compared to q1 ) : q2 was 1.7 ( 1.03.0 ) , q3 was 1.9 ( 1.13.3 ) , q4 was 2.5 ( 95% ci , 1.34.8 ) ; association independent of erythrocyte levels of epa and dha , linoleic acid , and trans fatty acidsala alpha - linolenic acid ; aric atherosclerosis risk in communities ; cvd cardiovascular diseases ; dha docosahexaenoic acid ; epa eicosapentaenoic acid ; ffq food frequency questionnaire ; hr hazard ratio ; mi myocardial infarction ; or odds ratio ; q quartile ; sd standard deviation ; ulsam uppsala longitudinal study of adult men overview of biomarker studies of alpha - linolenic acid and cardiovascular events published between january 2008 and june 2010 ala alpha - linolenic acid ; aric atherosclerosis risk in communities ; cvd cardiovascular diseases ; dha docosahexaenoic acid ; epa eicosapentaenoic acid ; ffq food frequency questionnaire ; hr hazard ratio ; mi myocardial infarction ; or odds ratio ; q quartile ; sd standard deviation ; ulsam uppsala longitudinal study of adult men yamagishi et al . the data used were from 3,575 white men and women in the united states ( mean age of 54  years ) who participated in the atherosclerosis risk in communities ( aric ) study . during 14  years of follow - up plasma ala was not associated with risk of heart failure ( hazard ratios of 0.99 and 0.97 for upper versus lower quintiles of cholesteryl ester and phospholipid fractions , respectively ; p  =  0.8 ) . data were extensively adjusted for major confounders , including age , sex , bmi , lifestyle factors , and cardiovascular risk factors , but not for potential dietary confounders . conducted a prospective cohort study of ala in serum cholesteryl esters and cardiovascular mortality in more than 2,000 swedish men ( mean age of 50  years ) . the study had 30  years of follow - up and comprised over 60,000 person - years . a 10% higher risk of fatal cardiovascular events was found per standard deviation increase in serum ala , which was borderline statistically significant . data were adjusted for serum cholesterol , bmi , smoking , physical activity , and presence of hypertension . erythrocyte concentrations of n-3 fatty acids were studied in relation to hemorrhagic and ischemic stroke in a case  control study of 120 asian men and women ( mean age of 57  years ) . the average total n-3 fatty acid intake in this population was 1.1  g / d , about half of which was ala . erythrocyte ala concentrations ( area% ) were 0.71    0.21 in hemorrhagic stroke patients and 0.24    0.03 in ischemic stroke patients , which did not differ significantly from controls ( 0.44    0.05 ) after adjustment for family history of stroke . in a logistic regression model , both epa and dha were also inversely related to hemorrhagic stroke , but this was not the case for ala . data , however , were only adjusted for age and systolic blood pressure , so residual confounding may have been present . the risk of atrial fibrillation in relation to serum n-3 fatty acids was examined in a prospective cohort study of 2,174 finnish men ( mean age of 53  years ) [ 34 ] . during 18  years of follow - up hazard ratios in consecutive quartiles of ala were 1.26 ( 95% ci , 0.841.89 ) , 0.74 ( 95% ci , 0.461.20 ) , and 1.14 ( 95% ci , 0.721.79 ) compared with the lowest quartile ( p for trend = 0.98 ) . serum epa did not show an association but dha was inversely related to atrial fibrillation ( hazard ratio of 0.62 for upper vs lower quartile ; p for trend = 0.02 ) [ 34 ] . [ 35 ] investigated in a case  control study whether ala levels in erythrocytes were associated with risk of sudden cardiac death . blood was collected from 265 out - of - hospital sudden cardiac arrest patients in seattle , wa immediately after the event and from 415 randomly selected community members ( mean age of 58  years ) . in contrast to what was expected , higher ala levels were associated with a higher risk of sudden cardiac arrest . after adjustment for age , sex , smoking , diabetes , hypertension , education , physical activity , weight , height , and total fat intake , the risk increased over the quartiles with an odds ratio of 2.5 ( 95% ci , 1.34.8 ) for the highest compared with the lowest quartile . the association was independent of other fatty acids in erythrocyte membranes , including epa and dha [ 35 ] . the trials reviewed here consistently showed an increase in blood ala levels after ala supplementation , starting at low doses ( < 2  g / d ) . ala supplementation also increased blood levels of epa , but not of dha , indicating conversion of ala to epa through elongation and desaturation . short - term trials ( 612  weeks ) in generally healthy individuals mostly showed no or inconsistent effects of ala intake ( 1.23.6  g / d ) on blood lipids , ldl oxidation , lipoprotein(a ) , and apolipoproteins a - i and b. previous studies suggested an anti - inflammatory action of ala [ 5 , 7 , 8 ] , but recent trials showed little effect of ala on crp or other inflammatory markers . there was , however , an interesting inverse association of ala with sil-6r in the twin study by dai et al . the few studies that addressed ala intake in relation to glucose metabolism or blood pressure yielded inconsistent results [ 16 , 17 , 18 ] . there is , however , some observational evidence that a high ala status may be related to a lower risk of metabolic syndrome . long - term treatment with high ala doses had a beneficial effect on body weight and blood ldl cholesterol [ 18 ] , which warrants confirmation in future trials . 23  g / d ) for the primary and secondary prevention of chd . the recently published case  control study by campos et al . [ 19 ] showing strong inverse associations of ala status and intake with nonfatal mi is in line with this recommendation . recent data provide some support that ala could protect against atherosclerosis [ 25 , 26 ] , but it should be noted that this evidence comes from relatively small cross - sectional studies and that conclusions on causality can not be drawn . concerning the hypothesis of an anti - arrhythmic effect of n-3 fatty acids , there was some evidence for protection against ventricular premature beats [ 22 ] , but no evidence for a relation with heart rate   or incidence of atrial fibrillation [ 34 ] . moreover , data from two recent well - conducted epidemiologic studies suggested that high tissue ala is related to an increased rather than decreased risk of fatal cardiovascular events   and sudden death [ 35 ] . performed a meta - analysis of previous studies on tissue fatty acid composition and risk of chd published until 2006 . they showed that ala in adipose tissue or phospholipids was inversely associated with chd , although the association was not statistically significant for fatal events . of 16 studies reviewed , about half were supportive for a beneficial role of ala , whereas other studies were negative or supportive for an adverse effect . in conclusion , there is a need for long - term trials investigating the effect of ala supplementation on cardiovascular risk factors and clinical end points . data are awaited from the alpha omega trial , in which 4,837 post - mi patients ( mean age of 69  years ) were randomized to 2  g / d of ala and/or 400  mg / d of epa and dha and followed for fatal and nonfatal cardiovascular disease events for 40  months . the findings of this study may answer the question of whether a food - based dose of ala affects cardiovascular health in high - risk individuals and , if so , whether this is comparable to the effect of marine n-3 fatty acids .