Earlier this year Canadian researchers said that combining prebiotics and soy protein may lower cholesterol levels and boost heart health.
Consumption of a soy-food-based diet, providing soy protein and isoflavones in combination with 10 g per day of oligofructose-enriched inulin, led to significant reductions in levels of LDL cholesterol, according to results of a small randomized controlled crossover study published in Metabolism Clinical and Experimental.
The LDL reductions were only observed when soy and prebiotics were co-ingested, an observation that suggests “the provision of fermentable substrates may be one means to increase the effectiveness of soy foods as part of a dietary strategy for cardiovascular disease risk reduction,” wrote the researchers led by David Jenkins from the University of Toronto.
The association between soy protein and blood lipid levels led the Food and Drug Administration (FDA) to approve a cardiovascular disease reduction claim for soybean protein in 1999.
Twenty-three people with an average age of 58 and average blood LDL levels of 4.18 millimoles per liter were recruited and randomly assigned to one of three groups: One group received a soy-food-containing diet, providing 30 g per day of soy protein and 61 mg per day of isoflavones, plus maltodextrin (placebo); the second group received the soy food diet, plus prebiotic; the final group received a low-fat dairy diet, plus the prebiotic. Two weeks separated each dietary intervention and 23 people completed all three phases.
The results showed that the joint consumption of soy and prebiotic produced greater reductions in LDL cholesterol of around 0.18 mmol/L and improved the ratio of LDL cholesterol to HDL cholesterol, compared with only the prebiotic phase.
HDL cholesterol levels were also significantly increased following the soy plus prebiotic diet, compared with only the prebiotic.
“These data support the lipid-lowering basis for the current FDA health claim for soy foods. They demonstrate how a non-significant (about three percent) LDL cholesterol reduction seen when soy was consumed alone can be converted to a significant (about five percent) LDL cholesterol reduction when soy was taken with a prebiotic,” wrote the researchers.
“We believe the present study therefore supports the value of soy as one of the few cholesterol-lowering foods, in the five percent reduction range, especially when given with fermentable substrates such as would be naturally present in diets that also contained viscous fibers to lower serum cholesterol,” they added.
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