Greixos

Greixos, or fats, are a broad category of lipids that are hydrophobic and energy-dense. In nutrition, the term typically refers to dietary fats, primarily triglycerides composed of glycerol esterified with three fatty acids. They provide a concentrated energy source, about 9 kilocalories per gram, and play roles in insulation and cellular structure.

Greixos are classified by fatty acid composition into saturated, monounsaturated, polyunsaturated, and trans fats (trans isomers). Most greixos are solids at room temperature when saturated, whereas unsaturated fats tend to be liquids. Plant- and animal-based sources supply different profiles of fatty acids, influencing taste, texture, and nutritional impact.

Biological roles include serving as long-term energy storage in adipose tissue; constituting components of cell membranes; and acting as precursors to signaling molecules such as steroid hormones. They also aid in the absorption of fat-soluble vitamins A, D, E, and K.

Diet and health guidelines emphasize replacing saturated and trans fats with unsaturated fats, particularly monounsaturated and omega-3/omega-6 polyunsaturated fats, sourced from foods like fatty fish, nuts, seeds, and olive oil. It is advisable to monitor total fat intake as part of a balanced diet, as excessive consumption of certain fats can be associated with health risks.

Processing and storage practices include hydrogenation and refining, which can alter fat properties and, in some cases, increase trans fat content. Fats are susceptible to oxidation and rancidity, so proper storage in cool, dark places helps maintain quality. In cuisine, greixos influence flavor, texture, and cooking properties and are essential for emulsions such as mayonnaise.