Flaxseed and flaxseed oil

Flaxseed/Drug Interactions:

  • GeneralGeneral: Consumption of flaxseed (not flaxseed oil) may decrease the absorption of co-administered oral medications, vitamins, or minerals. Oral drugs should be taken one hour before or two hours after flaxseed to prevent decreased absorption.
  • Anticoagulants and antiplateletsAnticoagulants and antiplatelets: There is a lack of available literature reporting a flaxseed-warfarin or flaxseed oil-warfarin interaction or flaxseed- or flaxseed oil-related bleeding. However, considering the suspected ability of omega-3 fatty acids to inhibit platelet aggregation, there is at least a theoretical potential for flaxseed (and other sources of omega-3 fatty acids) to affect bleeding. Some studies have reported decreased platelet aggregation (37; 39) and increased bleeding time (38), but this is in contrast with a study in healthy men noting a lack of effect on coagulation status using dietary alpha-linolenic acid (ALA) (83).
  • Antidiabetic agentsAntidiabetic agents: In human research, flaxseed reduced blood glucose levels and hemoglobin A1C (33; 34; 35; 79); theoretically, concurrent use may increase the risk of hypoglycemia.
  • AntihypertensivesAntihypertensives: Preliminary human evidence suggests that higher levels of linolenic acid in human adipose tissue may correlate with lower blood pressure (157) and that two weeks of flaxseed supplementation lowered blood pressure (78). In men, a decrease in diastolic blood pressure was reported after six months of supplementation (91). In patients with dyslipidemia, a decrease in systolic, diastolic, and mean arterial pressure was reported (113). Flaxseed-supplemented diets have had mixed effects on blood pressure in rats (76; 77).
  • Anti-inflammatoriesAnti-inflammatories: In vitro, flaxseed decreased the permeability of ketoprofen (80).
  • AntilipemicsAntilipemics: In humans, consumption of flaxseed or flaxseed oil decreased total cholesterol levels (107; 39; 34; 158; 69; 116; 78; 85) and lowered LDL cholesterol levels (107; 39; 34; 158; 78; 85) and triglycerides (39; 78; 159), although conflicting data exist (73; 160; 161; 109; 106; 90). Flaxseed and flaxseed oil possessed lipid-lowering properties in vitro and in animals (162; 159; 84).
  • AntineoplasticsAntineoplastics: Numerous epidemiologic, animal, in vitro, and in vivo studies support the hypothesis that mammalian lignans have cancer protective effects (2; 3; 4; 5; 6; 7; 8; 9; 10; 11; 12; 13; 14; 15; 16; 17; 18; 19; 20). In animal research, flaxseed enhanced the tumor inhibitory effects of tamoxifen via modulation of estrogen receptors and signal transduction pathways (5; 6; 163; 164; 165).
  • Antiobesity agentsAntiobesity agents: There is limited research on the effects of flaxseed flour and ALA (derived from flax) in obese patients. In humans, flax supplementation caused weight gain or weight loss in different patient populations (121; 140).
  • Diuretics, loopDiuretics, loop: In vitro, flaxseed decreased the permeability of furosemide (80).
  • EstrogensEstrogens: Flaxseed (not flaxseed oil) contains lignans, which may possess estrogen receptor agonist or antagonist properties (22), with unclear interactions with hormonal agents. In humans, supplementation with flaxseed reduced 17-beta-estradiol and estrone sulfate levels, increased prolactin levels (21), improved the 2-hydroxyestrogen:6-alpha-hydroxyestrone ratio (75; 74; 94), and increased the excretion of enterodiol, enterolactone, and matairesinol (compared to baseline values) (96).
  • LaxativesLaxatives: Laxatives and stool softeners may theoretically increase or enhance the laxative effects of flaxseed (29).

    • Flaxseed/Herb/Supplement Interactions:

  • GeneralGeneral: Consumption of flaxseed (not flaxseed oil) may decrease the absorption of co-administered oral medications, vitamins, or minerals. Oral agents should be taken one hour before or two hours after flaxseed to prevent decreased absorption.
  • Anticoagulants and antiplateletsAnticoagulants and antiplatelets: There is a lack of available literature reporting a flaxseed-warfarin or flaxseed oil-warfarin interaction or flaxseed- or flaxseed oil-related bleeding. However, considering the suspected ability of omega-3 fatty acids to inhibit platelet aggregation, there is at least a theoretical potential for flaxseed (and other sources of omega-3 fatty acids) to affect bleeding. Some studies have reported decreased platelet aggregation (37; 39) and increased bleeding time (38), but this is in contrast with a study in healthy men noting a lack of effect on coagulation status using dietary alpha-linolenic acid (ALA) (83).
  • AntihypertensivesAntihypertensives: Preliminary human evidence suggests that higher levels of linolenic acid in human adipose tissue may correlate with lower blood pressure (157) and that two weeks of flaxseed supplementation lowered blood pressure (78). In men, a decrease in diastolic blood pressure was reported after six months of supplementation (91). In patients with dyslipidemia, a decrease in systolic, diastolic, and mean arterial pressure was reported (113). Flaxseed-supplemented diets have had mixed effects on blood pressure in rats (76; 77).
  • Anti-inflammatoriesAnti-inflammatories: In vitro, flaxseed decreased the permeability of ketoprofen (80).
  • AntilipemicsAntilipemics: In humans, consumption of flaxseed or flaxseed oil decreased total cholesterol levels (107; 39; 34; 158; 69; 116; 78; 85) and lowered LDL cholesterol levels (107; 39; 34; 158; 78; 85) and triglycerides (39; 78; 159), although conflicting data exist (73; 160; 161; 109; 106; 90). Flaxseed and flaxseed oil possessed lipid-lowering properties in vitro and in animals (162; 159; 84).
  • AntineoplasticsAntineoplastics: Numerous epidemiologic, animal, in vitro, and in vivo studies support the hypothesis that mammalian lignans have cancer protective effects (2; 3; 4; 5; 6; 7; 8; 9; 10; 11; 12; 13; 14; 15; 16; 17; 18; 19; 20).
  • Antiobesity agentsAntiobesity agents: There is limited research on the effects of flaxseed flour and alpha-linolenic acid (derived from flax) in obese patients. Flax supplementation may cause weight gain or weight loss in different patient populations (121; 140).
  • AntioxidantsAntioxidants: Lignans acted as platelet-activating factor-receptor antagonists and inhibited the production of oxygen free radicals by neutrophils (159; 84). Secoisolariciresinol diglycoside (SDG), a plant lignan found in flaxseed, has been found to possess antioxidant properties (84). Cardiac cellular damage was attenuated when dogs were given an endotoxin with flaxseed vs. endotoxin alone (166). Theoretically, flaxseed (not flaxseed oil) may increase lipid peroxidation and thus may increase oxidative injury (85). Diets supplemented with defatted flaxseed have been associated with a decrease in protein thiol groups, suggesting an increase in oxidative stress (85).
  • DiureticsDiuretics: In vitro, flaxseed altered the effects of some types of diuretics (80).
  • HypoglycemicsHypoglycemics: In human research, flaxseed reduced blood glucose levels and hemoglobin A1C (33; 34; 35; 79); theoretically, concurrent use may increase the risk of hypoglycemia.
  • HypotensivesHypotensives:Preliminary human evidence suggests that higher levels of linolenic acid in human adipose tissue may correlate with lower blood pressure (157) and that two weeks of flaxseed supplementation lowered blood pressure (78). In men, a decrease in diastolic blood pressure was reported after six months of supplementation (91). In patients with dyslipidemia, a decrease in systolic, diastolic, and mean arterial pressure was reported (113). Flaxseed-supplemented diets have had mixed effects on blood pressure in rats (76; 77).
  • LaxativesLaxatives: Flaxseed may possess laxative properties, which may act additively with other laxative agents (29).
  • PhytoestrogensPhytoestrogens: Flaxseed (not flaxseed oil) contains lignans, which may possess estrogen receptor agonist or antagonist properties (22), with unclear interactions with hormonal agents. In humans, supplementation with flaxseed reduced 17-beta-estradiol and estrone sulfate levels, increased prolactin levels (21), improved the 2-hydroxyestrogen:16-alpha-hydroxyestrone ratio (75; 74; 94; 96) and increased the excretion of enterodiol, enterolactone, and matairesinol (compared to baseline values) (39).
  • PsylliumPsyllium: In theory, concomitant use of flaxseed (but not flaxseed oil) and psyllium may reduce the absorption of oral medications.
  • SoySoy: It has been suggested that flaxseed has more potent effects on estrogen metabolism than soy (94). Theoretically, flax and soy or its constituents may have synergistic effects.
  • Vitamin EVitamin E: In animals, consumption of flaxseed (but not flaxseed oil) resulted in increased liver vitamin E levels (73).

    • Flaxseed/Food Interactions:

  • Processing/cookingProcessing/cooking: Processing and cooking may alter the lipid content and stability of ALA in spaghetti containing ground flaxseed (167).
  • SoySoy: It has been suggested that flaxseed has more potent effects on estrogen metabolism than soy (94). Theoretically, flax and soy or its constituents may have synergistic effects.

    • Flaxseed/Lab Interactions:

  • ALA levels:ALA levels: In humans, flaxseed oil or flaxseed ingestion resulted in increases in plasma ALA levels (168; 104; 169; 100; 170). In lactating women, flaxseed oil supplementation increased plasma ALA levels (66). Obese subjects reported a significant increase in ALA when a diet fortified with linseed was consumed compared to control (53).
  • Alkaline phosphatase (ALP)Alkaline phosphatase (ALP): In animals, the use of flaxseed (not flaxseed oil) decreased alkaline phosphatase levels (73).
  • Blood glucoseBlood glucose: In humans, flaxseed decreased blood glucose levels (33; 34; 35).
  • Blood pressureBlood pressure: Preliminary human evidence suggests that higher levels of linolenic acid in human adipose tissue correlated with lower blood pressure (157) and that two weeks of flaxseed supplementation lowered blood pressure (78). Flaxseed-supplemented diets have had mixed effects on blood pressure in rats (76; 77). In adult men, four weeks use of flaxseed had a lack of an effect on lowering blood pressure (160). However, a decrease in diastolic blood pressure was reported after six months of supplementation in men (91); in patients with dyslipidemia, a decrease in systolic, diastolic, and mean arterial pressure was reported (113).
  • Body weightBody weight: In humans, flax supplementation caused weight gain or weight loss in different patient populations (121; 140).
  • Coagulation panelCoagulation panel: In humans, flaxseed or flaxseed oil increased bleeding time (38).
  • Docosahexaenoic acid (DHA) levelsDocosahexaenoic acid (DHA) levels: In children with attention deficit hyperactivity disorder (ADHD), DHA levels were reported to increase with flaxseed oil administration (129). Obese subjects reported a significant increase in DHA when a diet fortified with linseed was consumed compared to control (53). It has been shown that eating four eggs daily from chickens fed flaxseed resulted in elevated serum levels of docosahexaenoic acid (DHA) (54).
  • Docosapentaenoic acid (DPA) levelsDocosapentaenoic acid (DPA) levels: In lactating women, flaxseed oil supplementation increased plasma DPA levels (66). In patients with diabetes, flaxseed supplementation increased DPA levels(100).
  • EstrogensEstrogens: Flaxseed (not flaxseed oil) contains lignans, which may possess estrogen receptor agonist or antagonist properties (22), with unclear interactions with herbs and supplements purported to possess estrogenic properties. In humans, supplementation with flaxseed reduced 17-beta-estradiol and estrone sulfate levels, increased prolactin levels (21), improved the 2-hydroxyestrogen:16-alpha-hydroxyestrone ratio (75; 74; 94), and increased the excretion of enterodiol, enterolactone, and matairesinol (compared to baseline values) (96).
  • Eicosapentaenoic acid (EPA) levelsEicosapentaenoic acid (EPA) levels: In humans, administration of ALA caused an increase in plasma EPA (171; 169; 172; 100). In children with ADHD, EPA levels were reported to increase with flaxseed oil administration (129). In lactating women, flaxseed oil supplementation increased plasma EPA levels (66). However, one study reported that there could be a 55% decrease to a 967% increase depending on certain variables (172). Obese subjects reported a significant increase in EPA when a diet fortified with linseed was consumed compared to control (53). Healthy human subjects fed 160g of chicken that had been fed rapeseed- and linseed-rich chicken feed reported an increase in EPA in serum phospholipids and a decrease in the arachidonic acid:EPA ratio (52).
  • Hemoglobin A1CHemoglobin A1C: In humans, flaxseed lignan administration resulted in an significant decrease in hemoglovin A1C (79).
  • Luteinizing hormone (LH) levelsLuteinizing hormone (LH) levels: In theory, the use of flaxseed (not flaxseed oil) may increase serum levels of LH (148).
  • Lipid profileLipid profile: In humans, consumption of flaxseed or flaxseed oil decreased total cholesterol levels (107; 39; 34; 158; 69; 116; 78; 85; 173) and lowered LDL cholesterol levels (107; 39; 34; 158; 78; 85) and triglycerides (39; 78; 159), although conflicting data exist (73; 160; 161; 160; 109; 106; 90).
  • Prolactin levelsProlactin levels: In humans, supplementation with flaxseed increased prolactin levels (21).
  • Red blood cell countRed blood cell count: In animals, flaxseed (not flaxseed oil) increased total red blood cell counts (73).
  • Testosterone levelsTestosterone levels: In theory, the use of flaxseed (not flaxseed oil) may increase serum levels of testosterone (148).
  • Urine lignan levelsUrine lignan levels: In humans, flaxseed administration results in an increase in various lignans, including enterolactone (ENL), enterodiol (END), secoisolariciresinol diglucoside (SDG), and secoisolariciresinol (SECO) (111; 174; 174; 175; 176; 93; 177).
  • Vitamin E levelsVitamin E levels: In animals, consumption of flaxseed (not flaxseed oil) resulted in increased liver vitamin E levels (73).