We recently had the pleasure of going on a plant walk with our talented herbalist friend jim mcdonald and learned some fascinating information about horsetail (Equisetum sp.). Sometimes called scouring rush, bottle brush, or shavegrass, this botanical ally has been on the planet for more than 350 million years and is rich in minerals, especially silica, which is why you sometimes see it in formulations for healthy skin, hair, nails, and connective tissue. However, horsetail contains thiaminase, which breaks down the necessary thiamin (vitamin B1) levels in the human body and can lead to thiamin deficiency. But did you know ...