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Canada now allows a health claim on the labels of products with flax seeds, saying that we know with sufficient certainty that flax seeds do indeed help lower cholesterol levels. The products have to contain two tablespoons, and have to be relatively healthy in the first place. So, they can’t boast about the cholesterol-lowering effects of flax seed-enriched meatballs or something.

Such claims are based on studies like this “double-blind, randomized, placebo-controlled trial.” Wait, how can you come up with placebo food? I mean, there are sugar pills for drugs, but how can you slip spoonfuls of flax past someone? The researchers made all these special products, snack bars, muffins, and bagels so the research subjects would unknowingly be getting tablespoons of ground flax seeds, or just tablespoons of the control: whole wheat. And they did this for a year! No one knew who got which muffins until the code was broken at the end. And…the dietary flax seed group saw a 15 percent reduction in LDL cholesterol as early as one month into the trial, but only fell significantly lower than the whole wheat group in those on cholesterol-lowering drugs. In those off drugs, the whole wheat group’s cholesterol went down too, diminishing the efficacy of the flax in comparison. That’s why food placebos are so hard.

Like in this study. The reason they give for doing a so-called “open label” study where the study group is aware they’re eating flax seeds is because they couldn’t come up with an “inert placebo” for flax seed. I mean, whole wheat flour is a whole grain, and could be beneficial in its own right, and white flour could make the control group look even worse. So, what they did in this study was that overweight patients were randomly assigned to receive either lifestyle advice and daily ground flax seeds, or just the lifestyle advice alone, as the control group. And, not surprisingly: “Body weight, waist circumference, and body mass index decreased significantly in both groups.” Even without the lifestyle advice, just enrolling people in a study where you know they’re going to keep weighing you can get people to lose weight, though there was a significantly greater reduction in the flax seed group, and not just by a little. The control group that just got lifestyle advice over a 12-week period lost nearly seven pounds, and about an inch off their waist. But the group that got the same advice plus spoonfuls of flax a day? So, in effect given more food to eat, lost over 20 pounds on average over the same period and cut nearly four inches off their waist. Those are extraordinary numbers for an intervention that added, rather than actively removed, calories from the diet. Was that just some crazy fluke?

How about flax seed supplementation for non-alcoholic fatty liver disease? Thanks to the obesity epidemic, that’s now “the most common liver disease.[,]..recognized as a major public health problem around the world. A “high-fat diet is the most common cause,” but flax seed fat may be better, compared to lard. Well, that’s not very helpful; so, let’s put it to the test.

Same as last time, lifestyle modification advice with or without flax seeds. They were told to just mix it with water and juice, and drink it down after breakfast. And…body weight went down, along with liver inflammation, and scarring and fat inside the liver in both groups, but better in the flax seed group. And again, that extraordinary 20-pound weight loss, telling people to add something to their diet. So, maybe that first study wasn’t a fluke. Or, maybe, they both were.

There have been dozens of randomized, controlled trials of flax seeds and weight loss, and as you can see most were more equivocal. Here are those two recent 20-pound weight loss studies, which appear to be the outliers. But still, put all the studies together, and you do see a significant reduction in body weight, BMI, and waistlines following flax seed supplementation in randomized, controlled trials—though one should expect more like two pounds of weight lost rather than 20.

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