Vitamin E is an essential nutrient for human health and added tocopherols in foods can help maintain adequate levels. However, supplementation with vitamin E has demonstrated mixed results, with some studies suggesting increased associations with mortality from supplementation while others suggesting neuroprotective benefits or improvements in various biomarkers from supplementation. This may be largely due to differences in populations in which supplementation with dietary antioxidants seems to benefit some and harm others. While tocopherols included in foods may be included at a much lower rate than supplementation, the addition of them in food could cause even higher levels of intake for people who supplement with vitamin E already. Additionally, dl-alpha-tocopherol involves extraction from vegetable oils with high heats and harsh solvents such as hexane, which has shown to have toxic effects in humans. However, the amounts consumed as additives in foods is likely much smaller than the amounts consumed in supplements and may still promote a beneficial antioxidant effect. Synthetic vitamin E does not appear to have the same bioavailability as natural forms.