GSTM1 and lung carcinoma: It is thought that there is an interaction between smoking, beta‐carotene and glutathione‐S transferase (GST) genetic variants such that high‐dose beta‐carotene supplementation—potentially leading to supra‐physiological concentrations of beta‐carotene—confers a higher risk of lung cancer mainly in heavy smokers without the GSTM1 variant, thereby having reduced ability to metabolise certain toxins and carcinogens including those derived from tobacco smoke.3