Essiac four-herb blend (burdock root, sheep sorrel, slippery elm, Indian rhubarb)

Strengthens or boosts the immune system, thereby fighting, controlling, or curing cancer.

No controlled human clinical data demonstrate an anticancer effect (NCI PDQ). A controlled in vivo animal study found only a modest gastric-protective effect and no significant hepatoprotective, hypoglycemic, or immunomodulatory activity (Leonard et al. 2006). A separate in vitro study found antioxidant and immune-cell-activating signals alongside inhibition of CYP450 drug-metabolizing enzymes and clot fibrinolysis; the authors said the clinical significance remained undetermined (Seely et al. 2007). These are laboratory-only surrogate signals, not a demonstrated clinical benefit. Memorial Sloan Kettering's current monograph notes that in laboratory studies rhubarb, one of the four herbs, actually suppressed part of the immune system, directly contradicting the immune-boosting claim. Most strikingly, a controlled laboratory study found that 1%-8% concentrations of Essiac and the distinct eight-herb Flor-Essence product stimulated human breast cancer cell growth in vitro; in MCF-7 cells, 16% Flor-Essence did not differ significantly from controls and 32% was cytotoxic, and the authors said human target-cell concentrations were unknown (Kulp et al. 2006).