Flaxseed and cardiovascular risk factors: results from a double blind, randomized, controlled clinical trial

J Am Coll Nutr. 2008 Feb;27(1):65-74. doi: 10.1080/07315724.2008.10719676.


Objective: Flaxseed is a rich source of alpha linolenic acid (ALA), fiber and lignans, making it a potentially attractive functional food for modulating cardiovascular risk. We studied the effects of flaxseed on markers of cardiovascular risk in hypercholesterolemic adults.

Methods: Sixty-two men and post-menopausal women with pre-study low density lipoprotein cholesterol (LDL-C) between 130 and 200 mg/dl were randomized to 40g/day of ground flaxseed-containing baked products or matching wheat bran products for 10 weeks while following a low fat, low cholesterol diet. Fasting lipoproteins, measures of insulin resistance, inflammation, oxidative stress, and safety were assessed at 0, 5 and 10 weeks.

Results: Flaxseed was well-tolerated, and increased serum levels of ALA (p < 0.001). Compared to wheat, flaxseed significantly reduced LDL-C at 5 weeks (-13%, p < 0.005), but not at 10 weeks (-7%, p = 0.07). Flaxseed reduced lipoprotein a (Lp[a]) by a net of 14% (p = 0.02), and reduced the homeostatic model assessment of insulin resistance (HOMA-IR) index by 23.7% (p = 0.03) compared to wheat at 10 weeks, but did not affect markers of inflammation (IL-6, Hs-CRP) or oxidative stress (ox LDL, urinary isoprostanes) at any time points. In men, flaxseed reduced HDL-C concentrations by a net of 16% (p = 0.03) and 9% (p = 0.05) at 5 and 10 weeks, respectively.

Conclusions: Ground flaxseed has a modest but short lived LDL-C lowering effect, yet reduces Lp(a) and improves insulin sensitivity in hyperlipidemic adults. The HDL-C lowering effect of flaxseed in men warrants additional study.

Publication types

  • Randomized Controlled Trial
  • Research Support, N.I.H., Extramural

MeSH terms

  • Aged
  • Biomarkers
  • Cardiovascular Diseases / blood
  • Cardiovascular Diseases / epidemiology
  • Cardiovascular Diseases / prevention & control
  • Cholesterol, HDL / blood*
  • Cholesterol, LDL / blood*
  • Diet, Fat-Restricted*
  • Double-Blind Method
  • Female
  • Flax*
  • Humans
  • Hypercholesterolemia / blood
  • Hypercholesterolemia / diet therapy*
  • Insulin Resistance
  • Male
  • Middle Aged
  • Oxidative Stress
  • Time Factors
  • Treatment Outcome
  • alpha-Linolenic Acid / administration & dosage
  • alpha-Linolenic Acid / blood


  • Biomarkers
  • Cholesterol, HDL
  • Cholesterol, LDL
  • alpha-Linolenic Acid