Potent Antihypertensive Action of Dietary Flaxseed in Hypertensive Patients

Flaxseed contains n3 fatty acids, lignans, and fiber that together may provide benefits to patients with cardiovascular disease. Animal work identified that patients with peripheral artery disease may particularly benefit from dietary supplementation with flaxseed. Hypertension is commonly associated with peripheral artery disease. The purpose of the study was to examine the effects of daily ingestion of flaxseed on systolic (SBP) and diastolic blood pressure (DBP)
in peripheral artery disease patients. In this prospective, double-blinded, placebo-controlled, randomized trial, patients (110 in total) ingested a variety of foods that contained 30 g of milled flaxseed or placebo each day over 6 months. Plasma levels of the n3 fatty acid alpha linolenic acid and enterolignans increased 2- to 50-fold in the flaxseed-fed group but did not increase significantly in the placebo group. Patient body weights were not significantly different between the 2 groups at any time. SBP was10 mm Hg lower, and DBP was 7 mm Hg lower in the flaxseed group compared with placebo after 6 months. Patients who entered the trial with a SBP greater than140 mm Hg at baseline obtained a significant reduction of 15 mm Hg in SBP and 7 mm Hg in DBP from flaxseed ingestion. The antihypertensive effect was achieved selectively in hypertensive patients. Circulating alpha linolenic acid levels correlated with SBP and DBP, and lignan levels correlated with changes in DBP. In summary, flaxseed induced one of the most potent antihypertensive effects achieved by a dietary intervention. (Authors abstract)

The purpose of this research was to study flaxseed for its capacity to regulate CVD through its antiatherogenic effects, anti-inflammatory properties,  improvements in vascular contractile function, and antiarrhythmic action during ischemic challenge.   Hypertension is strongly associated with patients who have peripheral artery disease (PAD). Ninety-two percent of PAD patients in the PARTNER trials had high BP.  BP is a strong predictor of PAD.   BP is a major risk factor for both symptomatic and noninvasively determined PAD.  Because of the vascular effects of flaxseed in animal studies, it was thought that a patient population with PAD may be ideal to respond to dietary flaxseed. This double blinded, placebo-controlled, randomized FLAXPAD (FLAX effects in Peripheral Arterial Disease) trial18 has focussed on the effects of dietary flaxseed on SBP and DBP over a 6 month ingestion period. SBP was elevated in many of the patients entering this study despite the presence of a variety of antihypertensive medications. The most important finding from the FLAX-PAD study was the potent antihypertensive effect shown by patients who ingested flaxseed. This represents a major advance in the treatment of hypertension from a number of perspectives. First, it is the first demonstration of the effects of dietary flaxseed on a hypertensive population. It is noteworthy that the present study was done in a placebo controlled, double blinded, randomized manner. In contrast to the flaxseed fed group, patients who fed the placebo food had BP values that were stable or slightly elevated over the course of the study.

Second, the effects were demonstrated even in the presence of the administration of antihypertensive medication to these patients. Thus, flaxseed represents an effective combination of nonpharmacological and pharmacological therapies.  Approximately 80 percent
of patients from both groups maintained the same dose of antihypertensive medication throughout the trial. Approximately 8 percent of those patients who ingested flaxseed decreased their dose of antihypertensive medications versus 3.5 percent in the placebo group.

Third, the magnitude of the effect on BP would be expected to result in a significant decrease in the incidence of cardiovascular events over time. A reduction of 7 mm Hg in DBP would be expected to result in a 46 percent and 29 percent decrease in the incidence of stroke and coronary heart disease, respectively.  A 10 mm Hg decrease in SBP would result in a 36 percent and 27 percent decrease in the incidence of stroke and myocardial infarctions, respectively.

Fourth, severely hypertensive patients will benefit the most from dietary flaxseed. Hypertensive patients with an initial SBP greater than140 mm Hg responded to dietary flaxseed with an average decrease of 15 mm Hg. The magnitude of this decrease in BP demonstrated by dietary flaxseed, therefore, is as good or better than other nutritional intervention and comparable to many drugs.   DBP did not react as strongly to the flaxseed intervention in the present trial, although this may be because it is not as highly elevated at the start of the study as was SBP.
Finally, the use of flaxseed as an antihypertensive therapy appears to be relatively safe. There were no significant differences between the groups in any of the major cardiovascular complications.  The antihypertensive effects of dietary flaxseed are potent, selective to hypertensive patients, and long lasting. The ALA and lignan content of flaxseed provides this antihypertensive effect. A nutritional strategy like flaxseed, which compliments antihypertensive medication and can be delivered in a relatively inexpensive manner, should be particularly appealing in economically disadvantaged populations. (Editors comments)