Flaxseed dietary fibers lower cholesterol and increase fecal fat excretion, but magnitude of effect depend on food type.

Key Findings:

The consumption of 5 g of dietary fibers from flaxseeds daily for one week significantly increased fecal excretion of fat and reduced total and LDL-cholesterol. The effect of fiber was less pronounced when incorporated into bread than when administered as a drink.  The 5 g dose of fibers used was relatively low compared to other studies. Fecal energy excretion increased by 129 kJ/d with the flax drink compared to control and would correspond to ~47 MJ excreted per year. A decrease in energy uptake of this magnitude equals a difference in body weight of ~1.6 kg. Viscous flaxseed fibers appear useful for lowering blood cholesterol and may play a role in energy balance..

ABSTRACT:

Background: Dietary fibers have been proposed to play a role in cardiovascular risk as well as body weight management. Flaxseeds are a good source of dietary fibers, and a large proportion of these are water-soluble viscous fibers. Method: Here, we examine the effect of flaxseed dietary fibers in different food matrices on blood lipids and fecal excretion of fat and energy in a double-blind randomized crossover study with 17 subjects. Three different 7-d diets were tested: a low-fiber control diet (Control), a diet with flaxseed fiber drink (3/day) (Flax drink), and a diet with flaxseed fiber bread (3/day) (Flax bread). Total fat and energy excretion was measured in feces, blood samples were collected before and after each period, and appetite sensation registered 3 times daily before main meals. Results: Compared to control, Flax drink lowered fasting total-cholesterol and LDL-cholesterol by 12 and 15%, respectively, (p < 0.01), whereas Flax bread only produced a reduction of 7 and 9%, respectively (p < 0.05). Fecal fat and energy excretion increased by 50 and 23% with Flax drink consumption compared to control (p < 0.05), but only fecal fat excretion was increased with Flax bread compared to control (p < 0.05).

Conclusion: Both Flax drink and Flax bread resulted in decreased plasma total and LDL-cholesterol and increased fat excretion, but the food matrix and/or processing may be of importance. Viscous flaxseed dietary fibers may be a useful tool for lowering blood cholesterol and potentially play a role in energy balance. (Authors abstract)