Tocopherols in cancer: An update

Tocopherols exist in four forms designated as alpha, beta, delta, and gamma. Due to their strong antioxidant properties, tocopherols have been suggested to reduce the risk of cancer. Cancer prevention studies with tocopherols have mostly utilized ci-tocopherol. Large-scale clinical trials with alpha-tocopherol provided inconsistent results regarding the cancer -preventive activities of tocopherols. This review summarizes our current understanding of the anticancer activities of different forms of tocopherols based on follow-up of the clinical trials, recent epidemiological evidences, and experimental studies using in vitro and in vivo models. The experimental data provide strong evidence in support of the anticancer activities of delta-tocopherol, gamma-tocopherol, and the natural tocopherol mixture rich in gamma-tocopherol, gamma-TmT, over ci-tocopherol. Such outcomes emphasize the need for detailed investigation into the cancer -preventive activities of different forms of tocopherols to provide a strong rationale for intervention studies in the future.