Jan 2, 2017

Superfood Showdown: Chia vs. Flax

Research
Chia seeds

Chia seeds

These days, it’s hard to find a top-10 health foods list without chia or flax. And with good reason — these nutrient-dense seeds are loaded with protein, fibre and omega-3 fats and minerals, along with antioxidants and phytochemicals that may reduce cancer risk. And unlike whole grains, they contain few or no carbohydrates.

But are chia and flax equally good for you?

Vladimir Vuksan is a professor in the Departments of Nutritional Sciences and Medicine at the University of Toronto. He studies how food and natural health products affect disease risk, and he compared flax and chia seeds directly in a clinical trial published late last year.

Vuksan found that on two key measures — control of blood sugar and appetite — the edge goes to chia. He spoke with Faculty of Medicine writer Jim Oldfield about his study results, why flax and chia may differ and which type of chia may be best.

Why did you compare flax and chia seeds?

Chia and flax seeds have very similar nutritional profiles, and people consume them in similar ways, you know, sprinkled on breakfast foods like yogurt or added to smoothies, soups and salads. You can bake with them too. But we’ve studied the health aspects of chia for a dozen years, and we’ve noticed that people report feeling fuller after eating it. And in the lab we’ve observed that chia has different gelling properties, it’s much more viscous than flax. So we hypothesized that this viscosity may increase satiety and delay the rate of absorption in the gut, and that it may also slow the emptying of the stomach. I have a particular interest in diabetes and cardiovascular disease risk factors, so we set up a trial to compare the two seeds head-to-head on the sensation of satiety (with an eye to weight management) and glycemia (for diabetes).

What did you find?

We found that during a glucose challenge — in our trial, a three-meal consumption of a glucose drink mixed with either seed or the glucose drink alone (as a control) — the peak rise in blood sugar level was significantly lower with chia than flax. Chia also postponed the time to peak by more than 10 minutes, which suggests a slower rate of nutrient absorption. Thirty minutes after consumption, during the drink’s absorptive phase, blood sugar level was about 35 per cent lower with chia than with flax. In addition, feelings of satiety from chia compared to a glucose drink were twice as high as flax (compared to the same drink). Now, I should point out that this was a small, preliminary trial, but it was randomized and controlled. We think the findings are novel and exciting, and that they hold practical merit for consumers.

You used a particular type of chia seed, right?

Yes, we tested single variety called Salba-chia, which is a white-coloured strain, not genetically modified, but developed by selective breeding to minimize compositional variability. Most chia seeds are black and were traditionally consumed as a food and remedy by the Aztecs in Mexico — who called it ‘running food,’ by the way. There are dozens of varieties of chia and flax seeds, so they are prone to large variations in nutritional makeup, dependent on growing locations, farming practices and seed handling. But both seeds are highly nutrient-dense and should be considered healthy additions to our diets.

What about the quantity of seeds in your trial?

We used 25 grams of chia, or just under two tablespoons, which we matched in fibre amount to 31.5 grams of flax. That's a reasonable daily amount to consume. However, in previous studies we found comparable benefits from smaller doses of chia, as little as seven grams per meal, and the benefits don’t change when consumed as a whole seed or ground. Anyway, it's an exciting time to study seeds — chia and flax but also sesame and poppy, given the exploding interest in them. Seeds are cool. They definitely have a future in research and likely deserve a more prominent place on the table.