Oxidised oils and fats are damaging to the health because when ingested, they are absorbed and interact with tissues causing the initiation free radical chain reactions. This creates oxidative stress in the cells and tissues of the body and in time, chronic exposure to sources of oxidative stress, such as oxidised fats, can lead to Western lifestyle diseases such as cardiovascular disease and cancer. The effects of free radical damage of the initiation of disease has been postulated since the late 1950’s when Denham Harman published his free radical theory of ageing. As this theory has been explored scientifically, a number of mechanisms have been uncovered which explain the link between free radicals, the generation of oxidative stress and disease. One such avenue of scientific investigation has lead to the uncovering of the molecular mechanisms by which free radicals are able to induce insulin resistance and thus can contribute to the development of weight gain and obesity.
Research suggests that oxidative stress can negatively affect the function of the insulin system. When the hormone insulin attaches to its receptor on the outside of the cell, the signal is transduced to the interior of the cell using a second messenger system. Second messengers are systems of enzymes and molecules that detect the hormone receptor interaction on the surface of the cell, and then relay this signal to the interior of the cell to enact the hormone’s designated molecule effects. Cells have many second messenger systems for this purpose because many hormones are water soluble and therefore cannot penetrate through the lipid membrane that surrounds all cells. In the case of insulin, the molecule second messenger system is not fully described and there are still areas of this cellular pathway that are not understood. However, it is known that oxidative stress is able to interfere with the insulin second messenger system and thus prevent the signal from the insulin hormone reaching the interior of the cell.
The idea that oxidative stress can induce insulin resistance through interference with the insulin signal cascade is supported by studies showing beneficial effects for antioxidants on insulin sensitivity. A number of antioxidants including alpha lipoic acid, vitamin E, as well as phytochemicals from plants such as cinnamon and olive appear to have beneficial effects on insulin sensitivity and improve fasting blood glucose levels. The molecular mechanisms by which these chemicals can reverse insulin resistance appears to be via reduction of the oxidative stress that interferes with the insulin signal cascade. Reducing the oxidative stress that cells are exposed to is therefore pivotal if insulin sensitivity is to be maintained and insulin resistance is to be avoided. Eliminating oxidised fats and oils from the diet is a pivotal step in this strategy because these modified fats contribute a significant amount to the overall oxidative stress from consumption of the typical Western diet.
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