Dietary antioxidants: do they have a role to play in the ongoing fight against abnormal glucose metabolism?

Overfeeding, an increased intake of saturated fatty acids, and sugary foods are key dietary changes that have occurred in recent decades in addition to the emergence of the obesity epidemic. In addition to an increase in energy storage as fat, these dietary changes are accompanied by an increase in mitochondrial macronutrient oxidation, leading to an excessive free radical production and, hence, oxidative stress. The latter has long been considered a central mechanism linking nutrient overload, insulin resistance, the metabolic syndrome, and diabetes. However, food, through fruit and vegetable consumption, also can be a great source of antioxidants that protect the body against oxidative damage and insulin resistance and thus help cope with the metabolic backlash of the energy-dense Westernized diet. Experimental data are in favor of the beneficial role conveyed by antioxidants in glucose metabolism, but clinical data in humans remain controversial. This review therefore aimed to sort out any underlying discrepancies and provide an overall clear view of the role of antioxidants in the ongoing fight against abnormal glucose metabolism.