Solid lipid nanoparticles (SLN) can be used as vehicles for oral administration of phenolic compounds (PC). Hence, SLN loaded with rosmarinic acid (RA), sage and savoury extracts were evaluated for their impact on the intestinal microbiota composition and metabolic products. The fermentations in anaerobic batch culture were monitored by generation of short chain fatty acids (SCFA) and lactate, changes in the dynamic bacterial populations by PCR-real time, and quantification of phenolic compounds and fatty acids (FA) by analytical methods. The herbal extracts PC that were released by the SLN showed to have a beneficial effect on the growth of the GM, and were used as a substrate for growth in contrast with RA. SLN release PC at non-inhibitory and bifidogenic concentrations. The presence of PC induces the metabolic activity of PUFA and trans FA, and production of SFA and potential beneficial conjugated linoleic acid isomers. Acetate, formiate, lactate and butyrate are produced in higher concentrations.