Ground flaxseed vs high blood pressure — Book Excerpt

The following expert is from the book How not to die from Dr. Michael Greger.


In chapters 11 and 13, we will see how effective flaxseeds can be against breast and prostate cancers, but you have to be a little skeptical when scientists throw around words like “miraculous” to describe them. (One medical journal published a review titled “Flaxseed: A Miraculous Defense Against Some Critical Maladies.”) 124 But a remarkable intervention trial published in the journal Hypertension suggests that in this case, the term “miraculous” may not be too far off. Rarely does one see a dietary study of this caliber: It was a prospective, doubleblind, placebo-controlled, randomized trial. That’s hard to pull off with food. With a drug trial, a blinded study is easy: Researchers give someone a sugar pill that looks identical to the drug, so that neither the study subject nor the person giving the pill knows which one is which (hence, double-blind). But how do you do that with food? People tend to notice if you try to sneak a quarter cup of ground flaxseed into their lunch.

The researchers tried a clever tactic to overcome this problem. They created a number of recipes for common foods including muffins and pasta in which they could disguise placebo ingredients like bran and molasses to match the texture and color of the flax-laden foods. This way, they could randomize people into two groups and secretly introduce tablespoons of daily ground flaxseeds into the diets of half the participants to see if it made any difference. After six months, those who ate the placebo foods started out hypertensive and stayed hypertensive, despite the fact that many of them were on a variety of blood pressure pills. On average, they started the study at 155/81 and ended it at 158/81. What about the hypertensives who were unknowingly eating flaxseeds every day? Their blood pressure dropped from 158/82 down to 143/75. A seven-point drop in diastolic blood pressure may not sound like a lot, but that would be expected to result in 46 percent fewer strokes and 29 percent less heart disease over time. 125

How does that result compare with taking drugs? The flaxseeds managed to drop subjects’ systolic and diastolic blood pressure by up to fifteen and seven points, respectively. Compare that result to the effect of powerful antihypertensive drugs, such as calcium-channel blockers (for example, Norvasc, Cardizem, Procardia), which have been found to reduce blood pressure by only eight and three points, respectively, or to ACE inhibitors (such as Vasotec, Lotensin, Zestril, Altace), which drop patients’ blood pressure by only five and two points, respectively. 126 Ground flaxseeds may work two to three times better than these medicines, and they have only good side effects. In addition to their anticancer properties, flaxseeds have been demonstrated in clinical studies to help control cholesterol, triglyceride, and blood sugar levels; reduce inflammation, and successfully treat constipation. 127

Karl Niebuhr

Karl Niebuhr

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Karl Niebuhr

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