Were the flaxseed studies showing 20 pounds of weight loss just flukes? 

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

Such claims are based on studies like one that I review in my video Benefits of Flaxseed Meal for Weight Loss: a double-blind, randomized, placebo-controlled trial that supplemented research subjects’ diets with flaxseeds. How do you come up with placebo food? There are placebo sugar pills for drugs, but how can you slip spoonsful of flax past someone? The researchers made special products—snack bars, muffins, bagels, and more—so the study participants would unknowingly be getting tablespoons of either ground flaxseeds or the control, whole wheat. And they did this for a year. No one knew who got which until the code was broken at the end. Their findings? The dietary flaxseed group saw a 15 percent reduction in LDL cholesterol as early as one month into the trial, but it only fell significantly lower than the whole-wheat group in those on cholesterol-lowering drugs. In whole-wheat group participants not on drugs, their cholesterol went down, too, diminishing the efficacy of the flax in comparison. You can see charts at 1:12 in my video. That’s why food placebos are so hard. 

In another trial, the researchers conducted an “open label” study, where the participants were aware they were eating flaxseeds, because they couldn’t come up with an inert placebo for flaxseed. Whole-wheat flour is a whole grain and could be beneficial in its own right, for instance, whereas white flour could make the control group look even worse. So, for this study, the researchers randomly assigned overweight participants to receive either lifestyle advice and daily ground flaxseeds 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 lifestyle advice, simply enrolling people in a study where they know they’re going to keep getting weighed can get them to lose weight.) However, there was “a significantly greater reduction in [the] flaxseed group in comparison with controls.” And not just by a little. As you can see at 2:21 in my video, the control group that just got lifestyle advice lost nearly seven pounds and about an inch off their waist, while the group receiving the same advice plus spoonsful of flax a day—so, in effect, given more food to eat—lost more than 20 pounds on average and cut nearly four inches off their waist over the same period. Those are extraordinary numbers for an intervention that added rather than actively removed calories from the diet. Was it just a fluke? 

How about using flaxseed supplementation for non-alcoholic fatty liver disease? Thanks to the obesity epidemic, “it is the most common liver disease and now recognized as a major public health problem in contemporary society around the world.” The most common cause is a high-fat diet, but flaxseed fat may be better, compared to lard. Lard? Well, that’s not very helpful. Let’s put it to the test. 

As with the last study, participants received lifestyle modification advice with or without flaxseeds. They were told to mix the flaxseeds with water and juice and drink it down after breakfast. And? Their body weight went down, along with liver inflammation, and scarring and fat inside the liver in both groups, but the results were better in the flaxseed group. And again, there was that extraordinary 20-pound weight loss for the subjects told to add something (flaxseeds) to their diet, as you can see at 3:36 in my video. So, maybe that first study wasn’t a fluke—or maybe they both were. 

There have been dozens of randomized, placebo-controlled trials of flaxseeds and weight loss, and, as you can see in the graphic below and at 3.54 in my video, most were more equivocal. Those two recent 20-pound weight-loss studies appear to be the outliers. But still, after putting all of the studies together, you do see a significant reduction in body weight, BMI, and waistlines following flaxseed supplementation in randomized controlled trials, though one should expect more like 2 pounds of weight loss rather than 20 pounds. 

What else can flaxseeds do? So much! Check out the Related Videos below. 

What about the cyanide? Cyanide? See Friday Favorites: How Well Does Cooking Destroy the Cyanide in Flaxseeds and Should We Be Concerned About It?.

For more on weight loss, based on my book How Not to Diet, see the topic page here and the list of videos below.