I changed medication around the same time as I started to take grape seed extract so I couldn't say for certain what effect GSE has had on me in the past year or so since I started taking it. I do find that the supplements I take improve my overall sense of wellbeing (GSE, Omega 3, Vit D3 and Vit B complex are the main ones I take) but this could be due to the placebo effect.
As GSE isn't causing me any side effects, and it might be the reason for the increase in bacteroidetes percentage, and lowering of firmicutes, I will continue to take it as it is thought to have anti-inflammatory properties.
www.ncbi.nlm.nih.gov/pubmed/23143736GSE may act as a blood thinner so possibly not a good idea for people on anticoagulants (eg warfarin).
umm.edu/health/medical/altmed/herb/grape-seed