St. Boniface Research Centre, 2016,

Flaxseed and Hypertension

Dr. Grant Pierce

“Hypertension (high blood pressure), known as the “silent killer”, accounts for approximately half of the nearly 17 million cardiovascular deaths worldwide making it the leading risk factor attributed to death globally”, states Dr. Grant Pierce, Executive Director of Research at St. Boniface Hospital in Winnipeg, Manitoba. “Approximately 40 per cent of adults aged 25 plus years have hypertension worldwide.”

If left uncontrolled, hypertension can lead to heart attacks, strokes, kidney failure, blindness, dementia, and peripheral arterial disease (PAD), which is a serious plaque build-up in the arteries of arms and legs.1 Hypertension cost the Canadian economy over $7B annually. It is thus imperative that new therapies be identified to treat and prevent hypertension. Recent data has assessed flaxseed in both animal models and clinical trials and found powerful anti-hypertensive actions for flaxseed.

Lifestyle factors that may lead to high blood pressure include heavy alcohol consumption, high salt intake, and obesity. In addition, another potential cause is inflammation which can negatively affect the inside lining of blood vessels (the endothelium). Chronic inflammation can cause “endothelial dysfunction”, an imbalance between vasodilating and vasoconstricting substances produced by (or acting on) the endothelium. Enhanced constriction of the vessels can result in hypertension and further, the development of atherosclerosis.2

“Current medications used to control hypertension are costly, can induce unwanted side-effects and they are not always effective in controlling blood pressure in all hypertensive patients. Having a food that will control blood pressure represents a less expensive intervention than drugs”, says Dr. Pierce.

Flaxseed is a rich source of protein, fat, and dietary fibre. Canadian flaxseed contains on average 41% fat, 20% protein, and 28% total dietary fibre. This modest seed has health-promoting qualities due to its content of four health-promoting components: the omega-3 polyunsaturated fatty acid alpha-linolenic acid (ALA, 20% of dry weight), the plant lignan secoisolariciresinol diglucoside (SDG, 1% of dry weight), soluble fibre (6% of dry weight) and protein.3

“We have completed a major double blinded, placebo controlled, randomized trial (the “gold standard” for clinical studies) in Winnipeg in which patients with PAD were supplemented daily for one year with flaxseed in their diet (The FlaxPAD Trial)”, describes Dr. Pierce.

Fifty-eight patients were fed 30 g of milled flaxseed and another fifty-two patients were fed 30 g of whole wheat (placebo group) 4.  Most of the PAD patients were hypertensive and administered anti-hypertensive medication.  Subjects could select from seven different food options which contained the 30 g of flax or whole wheat including bagels, muffins and bars (each in three different flavors), biscuits, buns and pasta. They also could choose baggies of ground flax (or placebo) to sprinkle onto their food of choice.

The ingestion of flaxseed produced a strong and consistent anti-hypertensive effect at all time points examined: 1, 6 and 12 months.  Systolic blood pressure (SBP) was reduced by flaxseed by 10 mmHg and diastolic blood pressure (DBP) was decreased by 7 mmHg at 6 months in comparison to the placebo patients.4 Patients on placebo did not exhibit a significant drop in either SBP or DBP. Even more impressive, patients who entered the trial with systolic hypertension were the most affected by dietary flaxseed and reacted with a 15 mm Hg drop in SBP.

“This represents the largest anti-hypertensive effect ever demonstrated by a dietary intervention and is comparable to most hypertensive medication available. This large decline in SBP and DBP would be expected to lower5 the incidence of heart attacks and strokes by >50%”, stresses Dr. Pierce.

The study also showed that dietary flaxseed in PAD patients resulted in a significant 15% reduction in circulating low-density lipoprotein (LDL, the “bad”) cholesterol as early as 1 month into the study6. A randomized, controlled, double-blinded clinical trial currently underway will investigate if ground flaxseed can lower blood pressure and prevent the need for medication in people newly diagnosed with hypertension.7

Flaxseed has been shown to reduce oxylipins which are highly bioactive molecules produced in the body from polyunsaturated fatty acids such as ALA and that cause the blood vessels to constrict.8 Flaxseed ALA and lignans may contribute to blood pressure reduction through anti-inflammatory actions that improve the health of the endothelium2,7. Dietary flaxseed decreased the percentage of patients with uncontrolled hypertension by 17 per cent9.

“If flaxseed continues to be shown to be effective, it has many advantages as an anti hypertensive treatment option for patients. It provides an alternative or complementary strategy for patients who cannot control their blood pressure with medication, for patients who cannot afford or do not have access to medication, or for patients who prefer a dietary approach”, states Dr. Pierce, “And in patients already taking anti-hypertensive medication, flaxseed can provide additional blood pressure and cholesterol lowering capabilities”.


  1. World Health Organization. A global brief on Hypertension: Silent killer, global public health crisis. WHO/DCO/WHD/2013.2 ed. Geneva, Switzerland: 2013.
  2. Puddu P, et al. Acta Cardiol. 2000; 55: 221-232..
  3. Adolphe JL et al. Br J Nutr. 2010; 103: 929.
  4. Rodriguez-Leyva D et al. Hypertension. 2013; 62(6):1081.
  5. Law MR et al. BMJ. 2003; 326: 1427.
  6. Edel AL et al. J Nutr. 2015; 145(4):749-57.
  7. Caligiuri SP et al. Trials. 2014; 18(15):232.
  8. Caligiuri SP et al. Hypertension. 2014; 64(1):53.
  9. Caligiuri SP et al. Curr Hypertension Rep 2014; 16:499-512.