Previous studies indicate that diabetes mellitus might be accompanied by a certain erosion of brain function such as cognitive impairment. Vitamin E is an important antioxidant that primarily protects cells from damage associated with oxidative stress caused by free radicals. The brain is highly susceptible to oxidative stress, which increases during ageing and is considered a major contributor to neurodegeneration. High plasma vitamin E levels were repeatedly associated with better cognitive performance. There is evidence of a positive association between reduced levels of vitamin E and risk factors of type 2 diabetes mellitus (T2DM) including insulin resistance and hyperglycemia. It has been proposed that vitamin E inhibits glucose oxidation which is a necessary step for protein glycosylation and producing hemoglobin A1c (HbA1c). Additionally, a prior meta-analysis of prospective cohort studies showed that a higher intake of foods rich in vitamin E (nuts, seeds, liquid oil, and raisin) was associated with a reduced risk of hyperglycemia and diabetes. There is also further evidence indicating the beneficial effects of adherence to vitamin-E-rich diets on glycemic control in diabetic patients. Several clinical trials have examined the efficacy of Vitamin E supplementation in improving cognitive function in diabetic patients. Results have been mixed, with some studies showing beneficial effects while others reporting no significant improvements. This inconsistency may be attributed to variations in study design, participant characteristics (age, disease duration, severity), dosage of Vitamin E, and the duration of supplementation. Larger, well-designed clinical trials with standardized protocols are needed to clarify these findings.