Flax seed reduces high blood pressure

January 14, 2014

Jacob Schor, ND, FABNO




A study published last December caught many of us by surprise.   


The results suggest that daily consumption of flax seed will reduce elevated blood pressure significantly, more than any other dietary intervention so far tested. This is a big deal.


This study by Rodriguez et al was a prospective, double-blinded, placebo-controlled, randomized trial.  All the patients involved in the study (110 in total) had peripheral artery disease (PAD). This was out of convenience as the researchers rand a clinic for PAD and about 75% of the patients there have hypertension. Baseline characteristics (body weight, waist circumference, and body mass index) were similar between the experimental group (n-58) and placebo group (n=52). About three-quarters of the participants had high blood pressure; 80% were taking antihypertensive medications


The patients in the study were provided with a variety of foods, including bagels, muffins and buns that supplied them with a daily dose of 30 grams of milled flaxseed. The placebo group ate similar foods but without flax seed.


Plasma levels of α-linolenic acid and enterolignans were followed to check for compliance, that is whether the study participants were actually eating the flax enriched foods. These biomarkers increased quickly so that at 1 month, fatty acids had doubled and lignans had increased tenfold in the flaxseed group; these increases persisted through out the study.


Body weights did not differ between the groups at any time. After six months systolic blood pressure was ~ 10 mm Hg lower and diastolic ~7 mm Hg lower in the flax seed group (p=0.04 for SBP and p=0.004 for DBP). The flax eaters who started out with elevated blood pressure (>140 mm Hg) had more pronounced decreases, 15 mm Hg in systolic and 7 mm Hg in diastolic. Levels of circulating α-linolenic acid levels were correlated with decreases in both systolic and diastolic blood pressure while increased lignan levels were only correlated with changes in diastolic blood pressure. In the placebo group systolic blood pressure increased by ~3 mm Hg and diastolic remained the same. [1]


These results come as a pleasant surprise. To quote the lead author, Dr Delfin Rodriguez , "This reduction of SBP and DBP after administration of dietary flaxseed is the largest decrease in BP ever shown by any dietary intervention."


Who knew?


Flax receives so much attention for its role in naturopathic oncology, decreasing breast cancer risk [2], and inhibiting cancer growth and metastasis [3] , that other potential benefits are rarely on our radar.


Recent attention has been on the ability of flax seed to mitigate injury from radiation therapy[4]. Flax seed lignans in particular are often thought to act in a similar manner to tamoxifen against estrogen receptor (ER) positive breast cancers [5] . Evidence also suggests flax may inhibit Her-2 positive [6] and ER-negative tumors [7].


A 2013 review on flax and breast cancer concluded, “Current evidence suggests that flax may be associated with decreased risk of breast cancer. Flax demonstrates antiproliferative effects in breast tissue of women at risk of breast cancer and may protect against primary breast cancer. Mortality risk may also be reduced among those living with breast cancer.” [8]


No one was talking or thinking much about flax seed and blood pressure.


While several earlier animal studies have suggested that flax seed might have an anti-hypertension action, this current paper may be the first human RCT that clearly demonstrates this effect. [9,10]              A 1997 trial of 15 obese individuals had reported that eating a margarine made of flax oil was associated with a “… marked rise in arterial compliance [and] reflected rapid functional improvement in the systemic arterial circulation….”[11] Still, the degree of improvement seen here is surprising.


It is interesting that the anti-hypertensive effect was selective: it only appears to lower blood pressure in hypertensive individuals. Such specificity is welcomed.


We should point out that by 6 months, 13 of the flaxseed patients and 11 of the placebo group had dropped out of the study. This relatively high percentage [22%] of participants dropouts is not that surprising. Thirty grams of milled flax meal is just over an ounce dry weight. Flax seed, at least in constipated mice, can be an effective laxative [12].              Some participants may have found this effect intolerable.


While we await a longer trial to confirm these early improvements and tell us if long-term flax consumption reduces risk of cardiovascular incidents, we already encourage many of our cancer patients to consume flax seed. Our experience suggests that patient compliance improves if we provide specific recipes for foods made with high volumes of flax seeds, in particular cookies, and muffins, similar foods to those these researchers chose. This recent Rodriguez study justifies the use of flax seeds by a far larger proportion of our patients, in particular those with elevated blood pressure.



Rena’s Flaxseed Cookies:


Preheat oven to 350 degrees


In a food processor mix

1 cup ground flax seed [100 grams]

1 cup almonds

Grind to a fine meal.



1 cup flour

¼ tsp salt

½ cup oil [if you use walnuts instead of almond reduce oil by half]

½ cup maple syrup

½ tsp vanilla extract


Process again until dough forms a ball.

Form into 20 small balls and place on a cookie sheet, with your thumb make a dent in the center of each dough ball and add a dollop of jam to fill it. Bake for about 15 minutes until the bottoms of the cookies are brown.


Makes about 20 cookies that each contain almost a tablespoon of flax seed. To achieve the dose of flax used in this Rodriguez study you would need to eat be about half a dozen of these cookies per day. Given the laxative effect, it is surprising how few people actually dropped out of this trial.


[Recipe adapted from “One bite at a time” by Rebecca Katz]





1. Rodriguez-Leyva D, Weighell W, Edel AL, LaVallee R, Dibrov E, Pinneker R, Maddaford TG, Ramjiawan B, Aliani M, Guzman R, Pierce GN. Potent antihypertensive action of dietary flaxseed in hypertensive patients. Hypertension. 2013 Dec;62(6):1081-9.


2. Lowcock EC, Cotterchio M, Boucher BA. Consumption of flaxseed, a rich source of lignans, is associated with reduced breast cancer risk. Cancer Causes Control. 2013 Apr;24(4):813-6. doi: 10.1007/s10552-013-0155-7.


3. Dabrosin C, Chen J, Wang L, Thompson LU. Flaxseed inhibits metastasis and decreases extracellular vascular endothelial growth factor in human breast cancer xenografts. Cancer Lett. 2002 Nov 8;185(1):31-7.


4. Pietrofesa R, Turowski J, Tyagi S, Dukes F, Arguiri E, Busch TM, Gallagher-Colombo SM, et al. Radiation mitigating properties of the lignan component in flaxseed. BMC Cancer. 2013 Apr 4;13:179.


5. Abrahamsson A, Morad V, Saarinen NM, Dabrosin C. Estradiol, tamoxifen, and flaxseed alter IL-1β and IL-1Ra levels in normal human breast tissue in vivo. J Clin Endocrinol Metab. 2012 Nov;97(11):E2044-54. doi: 10.1210/jc.2012-2288.


6. Mason JK, Fu MH, Chen J, Yu Z, Thompson LU. Dietary flaxseed-trastuzumab interactive effects on the growth of HER2-overexpressing human breast tumors (BT-474). Nutr Cancer. 2013;65(3):451-9.


7. Wang L, Chen J, Thompson LU. The inhibitory effect of flaxseed on the growth and metastasis of estrogen receptor negative human breast cancer xenografts is attributed to both its lignan and oil components. Int J Cancer. 2005 Sep 20;116(5):793-8.


8. Flower G, Fritz H, Balneaves LG, Verma S, Skidmore B, Fernandes R, Kennedy D, Cooley K, Wong R, Sagar S, Fergusson D, Seely D. Flax and Breast Cancer: A Systematic Review. Integr Cancer Ther. 2013 Sep 8. [Epub ahead of print]


9. Park JB, Velasquez MT. Potential effects of lignan-enriched flaxseed powder on bodyweight, visceral fat, lipid profile, and blood pressure in rats. Fitoterapia. 2012 Jul;83(5):941-6. doi: 10.1016/j.fitote.2012.04.010. Epub 2012 Apr 19.



10. Prasad K. Flaxseed and cardiovascular health. J Cardiovasc Pharmacol. 2009 Nov;54(5):369-77. doi: 10.1097/FJC.0b013e3181af04e5.


11. Nestel PJ, Pomeroy SE, Sasahara T, Yamashita T, Liang YL, Dart AM, Jennings GL, Abbey M, Cameron JD. Arterial compliance in obese subjects is improved with dietary plant n-3 fatty acid from flaxseed oil despite increased LDL oxidizability. Arterioscler Thromb Vasc Biol. 1997 Jun;17(6):1163-70.


12. Xu J, Zhou X, Chen C, Deng Q, Huang Q, Yang J, Yang N, Huang F. Laxative effects of partially defatted flaxseed meal on normal and experimental constipated mice. BMC Complement Altern Med. 2012 Mar 9;12:14. doi: 10.1186/1472-6882-12-14.