280 OLIVE OILS AND HEALTH Finally, a representative example from another family of unsaturated fatty acids, the omega-9 (ω-9) series, is oleic acid, a monounsaturated ω-9 fatty acid. oleic acid (C18H34O2) (C18:1 ω-9) 9 Unlike saturated fatty acids, which have straight chains, the double bonds in unsaturated fatty acids are usually in cis configuration (adjacent carbon atoms -C-oriented to the same side). This causes kinks in the carbon chain, so their structure is not linear (as previously illustrated) but curved at the points where the double bonds are located. The following diagrams show this structural feature. This configuration makes it harder for molecules to pack closely together, which explains why unsaturated fatty acids tend to be liquid at room temperature and have lower melting points than saturated fatty acids, which are usually solid. Moreover, the longer the fatty acid chain and the fewer the double bonds, the lower the water solubility. For example, olive oil, which is rich in oleic acid (a monounsaturated fatty acid), has a melting point of 13.4ºC, whereas its saturated counterpart, stearic acid (C18:0), melts at 69.6ºC. Essential fatty acids (linoleic acid –C18:2 ω-6– and alpha-linolenic acid –C18:3 ω-3–) are both unsaturated. Since the body cannot synthesise them, it is essential to include dietary sources containing these fats, as they are part of living structures and play important biological roles. Unsaturated lipids are found in significant amounts in plant-based foods (seed oils, nuts, etc.) as well as in certain animal sources like oily fish and seafood. These lipids are often referred to as “good fats” because, in general, they have been shown to benefit health when consumed in appropriate amounts. However, some, such as omega-6 (ω-6) fatty acids, may have both benefits and risks. While they may help lower blood cholesterol levels, excessive intake could have negative effects. For instance, they have been associated with the progression of certain types of cancer. In any case, these fats should also be consumed in moderation. It is recommended that 25-30% of total caloric intake come from fats. Of this, 15-20% should be monounsaturated fats, and around 5% polyunsaturated fats (omega-3 and omega-6), with a healthy ratio of 1 part omega-3 to 1–4 parts omega-6. - unsaturation/s Term used to refer to the presence of one or more double bonds between carbon atoms in a molecule. These bonds produce a three-dimensional change in the molecular structure, influencing its biological activity. linoleic acid OH O alpha-linolenic acid OH O H3C oleic acid O OH H H H H H H H H H H H H H H H H 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 .,,.o Hc-c-c-c-c-c-c-c-c=c-c-c-c-c-c-c-c-c 3 1 I I 1 1 1 1 1 1 1 1 1 1 1 'oH H H H H H H H H H H H H H H e e
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