Dietary oils

Atkinson, H.A. and Maisey, J., Effects of high levels of dietary oils on autoimmune responses, Biochem Soc Trans, 23, 277S, 1995. 

Burr and Burr reported in 1929 a new deficiency disease produced by the rigid exclusion of fat from the diet. 1 Rodents fed a fat-free diet showed reduced growth and reproductive failure, accompanied by two prominent changes in the skin, that is, increased scaliness and impaired barrier function.1,2 Reversal of the features of deficiency by administration of linoleic acid (LA), led to the concept of essential fatty acids (EFA) that cannot be synthesized by the higher animals.2 Similarities between the clinical features of EFA deficiency and atopic dermatitis led Hansen in 1937 to discover low blood levels of unsaturated fat in atopic children,3 and he later reported that EFA-deficient infants developed an eczematous rash, which responded to LA supplements.4 Several studies had previously examined a range of dietary oil supplements in atopic dermatitis,5-8 with generally reported benefit. 

Li, S.X., Ahn, D.U., Cherian, G., Chung, T.Y., Sim, J.S. 1996. Dietary oils and tocopherol supplementation on cholesterol oxide formation in freeze-dried chicken meat during storage.. / Food Lipids 3, 27 42. 

Medium-chain fatty acids are saturated fatty acids because of the relatively shorter hydrocarbon chain, which does not facilitate unsaturation. The safety of medium-chain triacylglycerol (MCTs) in dietary oil has been debated, and associated effects on cholesterol metabolism remain unclear. Although some studies have shown that... 

These human and animal smdies provide strong evidence that the lipemic effects of the different saturated fatty acids are not equal. 16 0 is hypothesized to behave as a neutral fatty acid (does not raise cholesterol) in normocholesterolemic individuals (<5.2 mmol/L) and when dietary cholesterol intake is low (<300 mg/day). In such simations 14 0 appears to be the unique cholesterohaising fatty acid. The lack of 14 0 in palm oil and the hypothesized neutrality of 16 0 gives credence for the use of palm oil as a dietary oil suitable for the majority of the world s populations. 

Katan, M. B., Zock, p L-, and Mensink, R. P (1995a). Dietary oils, serum lipoproteins, and coronary Iteart disease. Am. /, Ciiri. Nirfr 61,1368S-1373S. 

Scaccini et al [94] gave the first indirect demostration that factors other than the fatty acid composition and the vitamin E content of dietary oils... 

In the 1950s and 1960s, worldwide studies concluded that linoleate-rich dietary oils, such as corn oil and cottonseed oil, lowered the cholesterol level of human plasma, and therefore were advocated as preferred sources of polyunsaturated fatty acids. Hence, in the food industry, polyunsaturated began to mean two double bonds per molecule. More than two double bonds per molecule was associated with rapid unwanted rancidity. In the effort to minimize plasma cholesterol, food oils for humans became richer in linoleic acid (18 2o)6) and lower in linolenic acid (18 3o)3), but were also becoming deficient in essential (o3 polyunsaturates normally found in high levels in brain and nerve lipids. 

The traditional factor used in calcnlating the amount of energy of dietary lipid is 9 kcal/g (32.7 kJ/g), compared to 4 kcal/g (16.7 kJ/g) for carbohydrate and protein. These values were introduced by Atwater, and are based on the amount of energy released when these macronutrients are metabolically oxidized, allowing for incomplete intestinal absorption. Other correction factors are inappropriate for the dietary oils and fats commonly consumed the 9 factor for converting grams of dietary lipid to energy is more suitable and offers consistency. 

Cherian, G., Wolfe, F.H., and Sim, J.S. 1996. Feeding dietary oils with tocopherols effects on internal quahties of eggs during storage, J. Food Set, 61(1), 15. 

Figure 12.3 Tooopherols distribution In commonly used dietary oils. More than 50% of total vitamin E uptake Is derived from dietary oils. Olive and sunflower oils (common to European diet) contain mainly a-tocopherol, corn oils (common to U.S. diet) contain mainly ytocopherol, and soy oils (common to Asian diet) contain mainly Y- and 5-tooopherol. With the exception of palm oil, which has high levels of toootrienols (13% a-tooopherol, 75% tocotrienols), most oils contain only low amounts of toootrienols (not shown). However, the uptake and retention of tocotrienols from the human diet are generally low.

Fig. 2. The concentration of 22 1 in the cardiac triglycerides of rats, pigs, and monkeys is expressed as a ratio to the concentration of 22 1 in the dietary oil fed. Source of data rat (Kramer and Hulan, 1978 Kramer eta/., 1979) pig (Svaar et a/., 1980) and monkey, 1 and 10 weeks cardiac total lipids instead of cardiac triglycerides (Beare-Rogers and Nera, 1972), all other values (Ackman, 1980). Erucic acid was the docosenoic acid in all studies except the data from Ackman (1980) who fed partially hydrogenated fish oil containing mainly cetoleic acid to monkeys for 26 to 130 weeks.

The change in the 22 1 content with time on diet for the three species is shown in Fig. 2. The concentration of 22 1 in the cardiac triglycerides is compared to the concentration of this acid in the dietary oil and expressed as a ratio. As evident from these results, the 22 1 concentration of the rat heart triglycerides is the same as that of the dietary oil during the first week on the experimental diet. The ratio of 22 1 then decreases on continued feeding to a ratio of approximately 0.5 after 16 weeks. In the pig, the ratio was 0.2 throughout the 1 year study. The monkey shows a tendency to accumulate 22 1 in the cardiac triglyceride fraction. Erucic acid (22 1 n-9)... 

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