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Palm oil lowers the total blood cholesterol and ‘bad’ LDL cholesterol and increases the ‘good’ HDL cholesterol. Palm oil should be classified as both a “saturated fat” and an “unsaturated fat”. It contains equal proportions of saturated fatty acids and unsaturated fatty acids. The saturated fatty acids are made up of 44% palmitic acid and 5% stearic acid. The unsaturated fatty acids consist of 39% oleic acid (monounsaturates) and 10% linoleic acid (polyunsaturates). The fatty acid composition is entirely different from the so-called “saturated fats” such as coconut oil and palm kernel oil. A number of pre-1990 human feeding studies reported that palm oil diets showed a reduction of blood cholesterol values ranging from 7% to 38% (Ahrens et al., 1957; Anderson et al., 1976; Baudet et al., 1984; Mattson and Grundy, 1985; Bonanome and Grundy, 1988) Recent studies, specifically designed to evaluate palm oil, confirm that palm oil’s impact on blood cholesterol and lipoprotein profiles are beneficial. The following are the salient studies: · A comparative study in young Australian adults showed that the total blood cholesterol, triglycerides and HDL-cholesterol levels of those fed on palm oil (palm olein) and olive oil were lower than those fed on the usual Australian diet (Choudhury, Tan and Truswell, 1995). They showed that young Australian adults fed on palm oil diets had the same total blood cholesterol, triglycerides and ‘good’ HDL-cholesterol levels as those fed on olive oil. · A double-blind cross-over study (Sundram 1997) showed that palm olein-rich diet is identical to oleic-acid rich diet. Trans fatty acid rich diet performed the worst by elevated total cholesterol, ‘bad’ LDL-cholesterol, lipoprotein (a) and depressed ‘good’ HDL-cholesterol relative to oleic acid, stearic acid, lauric and myristic acids rich diets. · A study on fifty-one Pakistani adults showed that those given palm oil rich diets performed better than sunflower oil. Palm oil increased HDL-cholesterol and Apo A-1 levels. Hydrogenated cottonseed oil behaved the worst by raising serum triglycerides and lipoprotein levels. (Farooq et al., 1996) · A study by a group of researchers from the Institute of Nutrition and Food Hygiene, Beijing, China compared the effects of palm oil, soybean oil, peanut oil and lard (Zhang et al., 1997a; Zhang et al., 1997b; Zhang et al., 1995). They showed that palm oil has the effect of decreasing total blood cholesterol and ‘bad’ LDL-cholesterol and increasing the level of ‘good’ HDL-cholesterol. Soya bean oil and peanut oil had no effect on the blood cholesterol but lard increased the cholesterol levels. Among those hypercholesterolemic subjects, palm oil diets lower the cholesterol levels. · Study conducted on healthy Indian subjects (Ghafoorunissa et al., 1995) showed that palm olein and groundnut oil have comparable effects. Both of the oil do not induce hypercholesterolemia. · Sundram et al., (1992) performed a dietary intervention study on a free-living Dutch population which normally consumes diets high in fats. Using a double blind cross-over study design consisting of two periods of six weeks of feeding, the normal fat intake of a group of 40 male volunteers was replaced with 70% of palm oil. The palm oil diet did not raise serum total cholesterol and ‘bad’ LDL-cholesterol, and caused a significant increase in the ‘good’ HDL-cholesterol and a significant reduction in ‘bad’ LDL-triglycerides. · The effect of palm olein and of canola oil on plasma lipids was examined in double blind experiments in healthy Australian adults. Palm oil performed better than canola oil in raising the ‘good’ HDL-cholesterol (Truswell et al., 1992). · A cross-over feeding study showed that the blood cholesterol, triglycerides, HDL-cholesterol and LDL-cholesterol levels of palm olein and olive oil diets were comparable (Ng et al., 1992). · A Malaysian study (Ng et al., 1991) was conducted to compare the effects of diets containing palm oil (olein), corn oil and coconut oil on serum cholesterol. Coconut oil raised serum total cholesterol by >10% whereas both corn and palm oil diet reduced the total cholesterol; corn oil diet reduced the total cholesterol by 36% and palm oil diet by 19%. · A similar cholesterol-lowering effect of palm oil was observed in 110 students in a study conducted in Malaysia (Marzuki et al., 1991). The study compared the effect of palm oil with that of soybean oil. Volunteers fed on palm oil (olein) and soy oil for five weeks, with a six-week wash-out period, had comparable blood cholesterol levels. However, the blood triglycerides were increased by 28% on the soybean oil diet. Thus the impact of palm oil on serum lipids is more like that of a mono-unsaturated rather than a saturated oil. There appear to be several explanations:- 1. Palm oil is made up of 50% unsaturated fats. It is not totally saturated and the saturated fatty acids present are palmitic (90%) and stearic (10%). Stearic acid does not elevate blood cholesterol, and palmitic acid does not raise blood cholesterol level in people whose blood cholesterol level is in normal range (Hayes, 1993; Hayes et al., 1995; Hayes et al., 1991; Khosla and Hayes, 1994; Khosla and Hayes, 1992). 2. The vitamin E, particularly the tocotrienols present in palm oil can suppress the synthesis of cholesterol in the liver (Qureshi et al., 1986). As a consequence, tocotrienols lower blood cholesterol levels (Qureshi et al., 1995; Qureshi et al., 1991a; Qureshi et al., 1991b; Qureshi et al., 1980; McIntosh et al., 1991). 3. The position of the saturated and unsaturated fatty acid chains in a triglyceride backbone of the fat molecule determines whether the fat will elevate cholesterol level in the blood (Kritchevsky, 1996; Kritchevsky, 1995; Kritchevsky, 1988 and Innis et al., 1993). In palm oil, 75% of the unsaturated fatty acid chains are found in position 2 of the carbon atom of the triglyceride backbone molecule (Padley et al., 1986; Ng, 1985; Berger, 1983). This could explain why palm oil is not cholesterol-elevating. Blood clotting can be induced by injury to the blood vessel wall and the alteration in the aggregating properties of blood platelets. Hornstra (1988) in the Netherlands first demonstrated the palm oil has anti-clotting effect, and is as anti-thrombotic as the highly unsaturated sunflower seed oil. A human study (Kooyenga et al., 1997 and Tomeo et al., 1995) showed that tocotrienols (from palm oil) supplementation can reduce restenosis of patients with carotid atherosclerosis. Holub et al. (1989) reported that the vitamin E in palm oil inhibits human platelets from “sticking” to each other. Other supporting evidence showed that a palm oil diet either increases the production of a hormone that prevents blood-clotting (prostacyclin) or decreases the formation of a blood-clotting hormone (thromboxane) (Sugano and Imaizumi, 1991; Sundram et al., 1990; Rand et al. 1988; Abeywardena et al., 1989; Charnock et al. 1989; Ng et al., 1992). Thus scientific evidence indicates that the palm oil diet is as anti-thrombotic as one based on polyunsaturated oil. It does not promote the formation of plaques in the arteries Atherosclerosis is the thickening and hardening of the walls of the arteries. Fatty deposits or plaques are made up of mainly fats and cholesterol. Atherosclerosis results in the narrowing of the lumen of the arteries, thus inhibiting the flow of blood. By feeding diets high in cholesterol along with certain saturated fats such milk fat, tallow and coconut oil, atherosclerosis can be produced in animals such as rabbits, quail, pigs and monkeys. A Netherlands study was conducted on rabbits to test the effect of palm oil on atherosclerosis (Hornstra, 1988). After feeding the rabbits for 11/2 years, palm oil and sunflower oil diets caused the lowest degree of atherosclerosis in comparison with fish oil, linseed oil and olive oil. Similarly Kurfeld et al. (1990) in
the United States, also using the rabbit model, compared the effects of palm oil
with hydrogenated coconut oil, cottonseed oil, hydrogenated cottonseed oil, and
an American fat blend containing a mixture of butterfat, tallow, lard,
shortening, salad oil, peanut oil and corn oil. At the end of the 14-month
feeding period, coconut oil fed rabbits had the most atherosclerotic lesions,
while in palm oil-fed rabbits the number of lesions was no different from that
with the other oils. PALM OIL HAS ANTI-CANCER EFFECTS Vitamin E of Palm Oil Palm oil is the richest known source of tocotrienols (Slover, 1971). No other common edible oil (except rice bran oil) contains this form of Vitamin E in significant amount. Tocotrienols of palm oil exhibit anti-cancer properties (Komiyama et al., 1989; Guthrie et al., 1993; Goh et al., 1994 Nesaretnam et al., 1992). Tocotrienols have greater physiological efficiency in inhibiting the growth of human and mouse tumour cells than tocopherols (Kato et al., 1985; Komiyama et al., 1989; Sundram et al., 1989). Prof. K.K. Carroll (1997) and Guthrie (1997a; 1997b) from University of Western Ontario, Canada showed that tocotrienols inhibit proliferation & growth of both estrogen receptor-negative MDA-MB-435 and –positive MCF-7 human breast cells in culture. Gamma tocotrienol is 3 times more potent in stopping the growth of human breast cancer cultured-cells than Tamoxifen (a drug widely used in the treatment of breast cancer). When used together with Tamoxifen, the combination was found to be 45 times as potent. In comparison, tocopherols have been found to have no effect on the growth of breast cancer cells. Recently a study conducted at University of Readings (Nasarethnam et al., 1998) also showed similar results. Prof. K.K. Carroll of the Centre for Human Nutrition at the University of Western Ontario and Prof. David Kritchevsky of the Wistar Institute recently concluded that evidence from animal and in vitro studies indicate that the tocotrienols of palm oil are effective anti-cancer agents, and that there is adequate justification for clinical trials in human cancer patients. Carotenoids of Palm Oil Crude palm oil is one of the richest natural plant sources of carotenoids with concentration of 500-700 ppm. It has 15 times more retinol-equivalent than carrots and 300 times more than tomatoes. No other vegetable oil contains carotenoids in significant quantities. Analysis shows that alpha and beta carotenes constitute approximately 90% of the total carotenoid content. Carotenoids impart a rich orange-red colour to the raw oil. More than 80% of the carotenoids are still retained in the specially-refined product called the “red palm oil”. The beneficial effects of carotenes on cancer and other chronic diseases have been demonstrated in population studies and human clinical trials (Krinsky, 1993; Bendich, 1990; Garewal, 1993; Ziegler et al., 1993; Greenberg, 1993; Zhang et al., 1992; Wolf, 1993; Greenberg et al., 1990; Blot et al., 1993). If future studies further confirm the anti-cancer effects of carotenoids, palm oil will play a vital role in the prevention of cancer. Vitamin A content
Palm oil has been shown to be stable and versatile even without hydrogenation. Margarines and shortenings made from palm oil do not require hydrogenation. On the other hand, margarines and shortenings made from polyunsaturated oils require hydrogenation. In the process of converting liquid oils to solid fats, hydrogenation of oils produces saturated fatty acids as well as trans-fatty acids and modified cis-fatty acids. Until the last seven years, little scientific attention was devoted to trans fatty acids. Evidence now gives every reason to be concerned about them, and in particular their negative effect upon serum lipid profiles. Professor Scott Grundy (1990) commented that there is “convincing evidence that trans fatty acids definitely raise LDL-cholesterol levels, in a manner similar to that of the cholesterol-raising saturated fatty acid”. A Dutch human study (Mensinsk and Katan, 1990) concluded, “the effect of trans-fatty acids; it increases the ‘bad’ LDL-cholesterol level and lowers the HDL-cholesterol level”. Professor Grundy (National Academy of Sciences, 1993) commented that: “It has been estimated that the average intake of trans-monounsaturates in the American diet is six to eight grams a day. This intake will produce a five to seven milligram per dl increase in cholesterol levels. You might think that’s not very much, but when you consider that for every milligram of increase in cholesterol level there’s about a one percent increase in risk for coronary heart disease, then we could attribute five to seven percent of all coronary heart disease to trans fatty acids in the diet”. In May 1994, Prof. Walter C. Willett and Dr. Albert Ascherio (1994), members of the Harvard University Department of Nutrition and Epidemiology, reviewed the growing science on trans fatty acids and heart disease, and concluded: “Although the percentage of coronary heart disease deaths in the United States attributable to intake of trans fatty acids is uncertain, even the lower estimates from the effects on blood lipids would suggest that more than 30,000 deaths per year may be due to consumption of partially hydrogenated vegetable fat. Further, the number of attributable cases of non-fatal coronary heart disease will be even larger”. They also recommended “a regulated phase out or strict limitation of partially hydrogenated fat in the US diet”. Other studies also confirmed that trans fatty acids are worse than butter by raising the ‘bad’ LDL-cholesterol, lowering the ‘good’ HDL-cholesterol and increasing the Lp(a), a very powerful risk factor for ischaemic heart disease (Mensink and Katan, 1990; Nestle et al., 1992; Zock and Katan, 1992; Mensink et al., 1992; Wood et al., 1993; Judd, et al., 1994; Aro et al., 1997). There are findings showing that trans fatty acids may be related with human fetal development. Two European studies showed significant associations between low birth weights and the content of trans-fatty acids in the blood (Koletzko, 1992a; 1992b; Jendryczko et al., 1993). The uptake of essential fatty acids (EFA) by the fetus may be impaired by trans-fatty acids. Trans-fatty acids may also affect the metabolism of EFA of the fetus which could result in poor development of the fetal organs and tissues. A recent five-center Euramic study (Kohlmejer et al., 1997) suggested that trans-fatty acids were associated with increasing breast cancer risk in post-menopausal women. A high trans content was found to be associated with a 40% increase in breast cancer risk. CONCLUSION Palm oil has the advantages of the polyunsaturates without their disadvantages, has the advantages of the saturates without their disadvantages, and Palm oil can be even better than olive oil and canola oil. Why
Palm Oil?
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