The majority of unsaturated fat molecules are in the cis configuration thus having the carbons on the same side of the double bond. Most unsaturated fats are cis except for some naturally occurring trans in meats and milk. However when hydrogenation, taking a liquid fat and making into a solid fat by the addition of hydrogens, is performed trans fats are created. Trans fats have the carbons on the opposite side of the double bond. Hydrogenation is used to remove the unsaturation of fatty acids in order to increase the oxidative stability of oils and to raise their melting points, which allows for the modification of their physical properties allowing for a broader range of usage in the food industry. Hydrogenated oils are often used in processed foods due to their stability. Trans fats have not been required on the food label, but will be as of 2006. A product contains trans fatty acids if a hydrogenated oil is listed under the 'ingredient' section of the food label. Research within the last decade has shown a detrimental effect of trans fat on cholesterol (see 'Which is better trans fats or saturated fats').

5. What are the uses of Palm oil?

Palm oil may be used in a variety of ways. Trans free uses of palm oil are shortenings, margarine, puff pastry margarine, frying, and vanspati.

There are also a variety of non-food uses of palm oil and palm kernel oil such as soaps, candles, rubber processing, cosmetic products, fuel for cars with modified engines, and as a substitute for diesel oil for drilling mud.

6. How do the physiological effects of trans fat compare to saturated fats?

Extensive research on trans fats (see 'What are trans fats?') has occurred in the past decade. Numerous studies have suggested that trans fat consumption elevates LDL cholesterol (the 'bad' cholesterol) 1,2,3,4,5 and decreases the ratio of HDL cholesterol (the 'good' cholesterol) to LDL cholesterol resulting in a less desirablecholesterol profile.6 In 1999, a meta-analysis of comparative effects of trans fats versus saturated fats on cholesterol was performed. This study found that as the fat intake increased the LDL: HDL cholesterol ratio (a low value is desired) also increased in a dose-dependent manner, and that trans fat consumption increased this ratio by more thatn saturated fat consumption.

• Aro A., Jauhianen M., Partanen R., Salminen I., Mutanen M. (1997) Stearic acid, trans fatty acids, and dairy fat: Effects on serum and lipoprotein lipids, apolipoproteins, lipoprotein(a), and lipid transfer proteins in healthy subjects. Am. J. Clin. Nutr. 65:1419-1426.

• Judd J.T., Clevidence B.A., Muesing R.A., Wittes J., Sunkin M.E., Podczasy J.J. (1994) Dietary trans fatty acids: Effects on plasma lipids and lipoproteins of healthy men and women. Am. J. Clin. Nutr. 59:861-868.

• Judd J.T., Baer D.J., Clevidence B.A., Muesing R.A., Chen S.C., Weststrate J.A., Meijer G.W., Wittes J., Lichtenstein A.H., Vilella-Bach M., Schaefer E.J. (1998) Effects of margarine compared with those of butter on blood lipid profiles related to cardiovascular disease risk factors in normolipemic adults fed controlled diets. Am. J. Clin. Nutr. 68:768-777.

• Louheranta A.M., Turpeinen A.K., Vidgren H.M, Schwab U.S., Uusitupa M.I.J. (1999) A high-trans fatty acid diet and insulin sensitivity in young healthy women. Metabolism. 48:870-875.

• Müeller H., Jordal O., Seljeflot I., Kierulf P., Kirkhus B., Ledsaak O., Pedersen J.I. (1998) Effect on plasma lipids and lipoproteins of replacing partially hydrogenated fish oil with vegetable fat in margarine. Br. J. Nutr. 80:243-251.

• Sundram K., Ismail A., Hayes K.C., Jeyamalar R., Pathmanathan R. (1997) Trans (elaidic) fatty acids adversely affect the lipoprotein profile relative to specific saturated fatty acids in humans. J. Nutr. 127:514S-520S.

• Mensink R.P. & Katan M.B. (1990) Effect of dietary trans fatty acids on high-density and low-density lipoprotein cholesterol levels in healthy subjects. N. Engl. J., Med. 323:439-445.

• Ascherio A., Katan M.B., Zock P.L., Stampfer M.J., Willett W.C. (1999) Trans fatty acids and coronary heart disease. N. Eng. J. Med. 340:1994-1998.

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