Monounsaturated fatty acids dietary sources

The current interest in dietary fat, however, stems primarily from its implication in the origin of several chronic diseases. Interest has centered on both the amount and type of dietary fat in the development of cardiovascular disease, cancer, hypertension, and obesity. As a result, dietary recommendations in many countries call for a reduction in total fat intake, to 30% of energy, and in saturated fat intake, to less than 10% of energy. In addition, some nutrition recommendations specify recommended levels of n-6 and n-3 fatty acids in the diets. Hence, the source of fat in the diet has assumed considerable importance over the past few years. Interest in the nutritional properties of canola oil developed because of its fatty acid composition (Table 2). Canola oil is characterized by a low level of saturated fatty acids, a relatively high level of monounsaturated fatty acids, and an appreciable amount of the n-3 fatty acid ot-linolenic acid (18 3 n-3). 

Organisms such as plants and bacteria can synthesize all the fatty acids they require from acetyl-CoA (Chapter 10). Mammals obtain most of their fatty acids from dietary sources. However, these organisms can synthesize saturated fatty acids and some monounsaturated fatty acids. They can also modify some dietary... 

The United States currently produces over 3.1 billion bushels of soybeans per year (The American Soybean Association, 2007). In 2006, over one-third (1.1 billion bushels) of the crop was exported, while the remainder was sold on the domestic market. Of the edible soybean products in the U.S. market, the consumption of soybean oil (SBO) is greatest U.S. production of SBO has surpassed 20 billion pounds per year (The American Soybean Association, 2007). SBO is the major edible oil in the United States and represented 75% of the total edible oils and fats consumed in 2006. The predominant dietary sources of SBO are salad and cooking oil (48%) and baking and frying fats (34%). SBO has a unique fatty acid profile it is comprised predomi-nandy of unsaturated fatty acids including monounsaturated fatty acids (MU FA) and polyunsaturated fatty acids (PUFA), of which the predominant PUFA is linoleic acid (LA), and to a much lesser extent, a-linolenic acid (ALA). 

The composition of avocado, in tenns of macronutrients, has been widely studied and is compiled in different tables of food composition. According to the United States Department of Agriculture (USDA) National Nutrient Database for Standard Reference [83], 100 g of avocado are an important source of energy (160 kcal) and contain 73.23 g of water, 2 g of proteins, 14.66 g of total fat (67% monounsaturated, 12% polyunsaturated, and 14% saturated fatty acids), and 8.53 g of carbohydrates, of which 6.70 g are total dietary fiber and 0.66 g are sugars. As it can be seen, one of the main components of avocado is the fat, and thus it is not surprising that it is also known as butter fruit. Besides, some of the principal health benefits of avocado have been attributed to its high monounsaturated fatty acid content. These facts make lipids one of the most studied families of compounds in avocado. 

Jerusalem artichoke tubers contain little or no starch, virtually no fat, and have a relatively low calorific value. Of the small amount of fat present, trace amounts of monounsaturated and polyunsaturated fatty acids have been reported, but no saturated fatty acids (Whitney and Rolfes, 1999). The polyunsaturated fatty acids linoleic (18 2 cis, cis n-6) and a-linoleic acid (18 3 n-3) have been recorded as present at 24 mg and 36 mg-100 g 1 of raw tuber, respectively (Fineli, 2004). The tubers are a good source of dietary fiber, because of the presence of inulin. 

One common feature of the mediterranean dietary habit is the use of olive oil as fat source in place of animal fat typical of Northern European and USA diets. As compared to other vegetable oils, olive oil is charaeterized by the peculiar composition of the tryglieeride fraction and by the phenolic and volatile constituents which affect the organolectic properties. Olive oil is rich in monounsaturated fat (56-84% of oleic acid), contains 3-21% of the essential linoleic aeid [3], is low in tocopherols [4,5] and therefore the presence of phenols is important to mantain the anti-oxidative stability. Several articles [1,2,6] reviewed the reasons why olive oil should be preferable to other dietary fat, paying particular attention to the fatty acid composition. Oleic acid is antithrombotic compared to saturated fatty acids [7]. Monounsaturated and polyunsaturated fats reduced low density lipoproteins (LDL) levels. 

Fish oils contain a wide range of fatty acids from C14 to C26 in chain length with 0-6 double bonds. The major acids include saturated (14 0, 16 0, and 18 0), monounsaturated (16 1, 18 1, 20 1, and 22 1) and n-3 polyene members (18 4,20 5,22 5, and 22 6). Fish oils are easily oxidized and are commonly used in fat spreads only after partial hydrogenation. However, they are the most readily available sources of n-3 polyene acids, especially, EPA and DHA, and with appropriate refining procedures and antioxidant addition these acids can be conserved and made available for use in food. The long-chain polyene acids are valuable dietary materials and there is a growing demand for high quality oil rich in EPA and DHA. °... 

Figure 7.13 shows the average and desirable proportions of energy coming from saturated, monounsaturated and polyunsaturated fatty acids in the dietary fat. As a general rule, animal foods (meat, eggs and milk products) are rich sources of saturated fats, whereas oily fish and vegetables are rich sources of unsaturated fats. 

Rice bran has little use as a source of dietary fiber unless the fat is ranoved with hexane. Rice bran is approximately 20% oil rich in monounsaturated and polyunsaturated fatty acids (Table 7.3). These unsaturated fatty acids are prone to oxidative rancidity. In Asia and other rice-producing regions, rice oil is frequently obtained from rice bran. 

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