Supports Healthy Liver Herbal Supplement Approved by Michael Tierra L.Ac, O.M.D Planetary Herbals Full Spectrum Milk Thistle Seed Extract is a highly concentrated extract of milk thistle seeds (Silybum marianum) that modern research has shown to support a healthy liver. This extract matches the constituent profile of extracts used in human research studies. Extra milk thistle seeds are added to ensure the presence of important secondary compounds.