Prebiotics and probiotics are food components that directly target the gut microbiota. This recent human study investigated their effects on gut microbiota and metabolic risk markers in obesity.

In this trial, researchers tested the probiotic Lactobacillus paracasei, which has been associated with a healthy metabolic profile in previous research. They also tested flaxseed — composed of 30% dietary fibres, including soluble viscous fibres (mucilage) — as a possible prebiotic.

In this randomised trial, obese postmenopausal women (n=58) consumed Lactobacillus paracasei F19, flaxseed mucilage, or a placebo daily for six weeks.

The group of women consuming L. paracasei F19 showed no differences in metabolic profile compared to those in the placebo group. Those consuming flaxseed mucilage showed improved insulin sensitivity as well as lower serum C-peptide and insulin release in a glucose tolerance test. Fecal samples identified changes in gut microbiota in the flaxseed-consuming group: the relative abundance of 33 species was altered, yet these changes could not explain how flaxseed mucilage affected insulin sensitivity.


Brahe LK, et al. (2015) Dietary modulation of the gut microbiota – a randomised controlled trial in obese postmenopausal women. British Journal of Nutrition. doi:10.1017/S0007114515001786