OLIVE OILS AND HEALTH 110 8.2. Dietary fat, biological membranes, and oxidative stress The role of nutrition on healthy ageing and its associated diseases is well known. Several studies have demonstrated that caloric restriction (partially reducing food ingestion) promotes healthy ageing and longevity, and that the ingestion of antioxidants and the right dietary fat play a key role on the issue. The effect of dietary fat on ageing characteristics has been demonstrated. The function of dietary fat is mainly related to differences in its capacity to generate oxidative stress. Oxidative stress is an imbalance between free radical/ reactive oxygen species generation and the body’s antioxidant reserves. When the former prevails, it leads to an oxidative stress situation. Concerning fats and oxidative stress, it is well-known that the number of double bonds in the fatty acids conditions their susceptibility to oxidation. The more double bonds a fatty acid has (more unsaturated) the more oxidizable it becomes. There is a body of scientific evidence, both in physiological and pathological conditions, concerning the benefits of olive oil (slightly unsaturated) consumption on preventing oxidation versus seed oils (highly unsaturated). It has also been shown that when a human or animal eats a type of fat their cell membranes reflect the composition of the ingested fat. Therefore, in a monounsaturated fatty acid-rich diet (olive oil), biological membranes will have this type of fatty acid, and, in a similar manner, after a polyunsaturated fatty acid-rich diet the biological membranes will have a more oxidizable type of fat. Oxidation is related to ageing. One principal hypothesis (oxidative stress and mitochondria) is that individuals age due to the oxidation of their cell membranes, particularly the mitochondrial ones. A diet rich in monounsaturated fats, less oxidizable, thus promotes a slow and healthy ageing. 8.3.Experimental Evidence of the Benefits of Virgin Olive Oil for Ageing and Longevity How can we modulate ageing and ageing-related diseases through nutrition? Based on what was explained in the previous section, various studies have shown that biological membranes formed from different sources of fat modulate ageing and longevity. A number of studies have been performed in rats fed throughout their lives with three types of oil with differing lipid profiles: virgin olive oil, rich in oleic acid; sunflower oil, rich in linoleic acid; and fish oil, rich in linolenic acid derivatives, and the effects on some of rat organs were evaluated.
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