Secoisolariciresinol diglucoside (SDG) is an antioxidant[1] phytoestrogen present in flax, sunflower, sesame, and pumpkin seeds.

[4] Secoisolariciresinol diglucoside slows the growth of human breast cancer in mice.

For example, due to 400-500Da size limit for Blood–Brain Barrier permeability, in one assessment of a Grade IV histology group of adult patients diagnosed with malignant glioma, high intake of secoisolariciresinol (for highest tertile compared to lowest tertile, in all cases) was associated with poorer survival.

[6] In rabbits, SDG reduced hypercholesterolemic atherosclerosis and this effect was associated with a decrease in serum cholesterol, LDL-C, and lipid peroxidation product and an increase in HDL-C and antioxidant reserve.

[7] SDG has been shown to counter oxidative stress in human colonic epithelial tissue and protect against mtDNA damage in vitro, by H2O2 exposure, in a dose-dependent manner[citation needed], and counters (in-vitro) oxidative stress on heart cells caused by Iron overload.