Recent evidence of endogenous erythritol synthesis in human blood (Hootman et al., 2017), and in A549 lung cancer cells by the reductases ADH and SORD (Schlicker et al., 2019), casts doubt on the view that polyols are not endogenously produced in humans (Hiele et al., 1993). The gene discussed is AVP; the disease is lung carcinoma.