Tropical oils: Nutritional and scientific issues

Effects of sodium saccharin and linoleic acid on mRNA levels of Her2/neu and p53 in a human breast epithelial cell line

The effects of two food-related chemicals (sodium saccharin and linoleic acid) on the levels of Her2/neu and p53 mRNA in a non-cancerous human breast epithelial cell line (HBL-100) were tested in comparison with the effects of the known tumor promoter phorbol 12-myristate 13-acetate (TPA). Treatments were made both with and without prior treatment with two well-known tumor initiators, N-nitroso-N-methylurea (NMU) or 7,12-dimethylbenz[a]anthracene (DMBA). The effects in general were small, the greatest being increases of 46-67% in Her2/neu mRNA levels in response to treatments with TPA or sodium saccharin following NMU treatments. These results demonstrate that sodium saccharin following NMU treatments might be involved in transcriptional regulation of Her2/neu in HBL-100 cells and suggest that its effects may not be limited to urinary bladder.

Characteristics of fats in Japanese diets and current recommendations

Although there is no firm evidence to support the "ideal" or even "appropriate" healthy level of dietary fat, the habitual fat consumption pattern in Japan seems to be a criterion for the recommended allowance both in the quantitative and qualitative points of view as judged from the life expectancy and the incidence of degenerative diseases. The new recommended dietary allowance of Japan, fifth revision effective for five years starting in 1995, adopted dietary fat levels of 20-25 energy percent, the ratio of saturated, monounsaturated, and polyunsaturated fatty acids at 1:1.5:1 and the ratio of n-6/n-3 at 4. The recommended fat level is similar to that previously consumed in Japan, and is even lower than that in diets used to treat hyperlipidemia in Western countries, current recommendations in those countries being 30 energy percent fat. Convincing data for the beneficial effects of n-3 polyunsaturated fatty acids on human health, in particular for healthy people, have been presented in only a few reports. However, the recommended n-6/n-3 ratio of 4 seems reasonable compared with the ratio of around 10 in other developed countries. In this context, it is more important to fully understand the nutritional and physiological roles of fat in healthy people rather than in those with chronic disease. At present, the low-fat dietary pattern in Japan appears to be a healthy way of eating.

Coupling the cholesterol- and tumor-suppressive actions of palm oil to the impact of its minor constituents on 3-hydroxy-3-methylglutaryl coenzyme A reductase activity

The impact of palm oil on cardiovascular disease and cancer may be explained by the mevalonate-suppressive action of constituent isoprenoid end products of plant secondary metabolism. Assorted monoterpenes, sesquiterpenes, carotenoids and tocotrienols down regulate, post-transcriptionally, 3-hydroxy-3-methylglutaryl coenzyme A reductase activity thereby modestly decreasing cholesterol synthesis and concomitantly decreasing LDL cholesterol. The reductase activity in tumor tissues differs from that of liver in being resistant to sterol feedback regulation. Tumor reductase activity retains sensitivity to the post-transcriptional regulation. As a consequence, the isoprenoid-mediated suppression of mevalonate synthesis depletes tumor tissues of two intermediate products, farnesyl pyrophosphate and geranylgeranyl pyrophosphate, which are incorporated post-translationally into growth control-associated proteins.

Utilization of crude and refined palm and palm kernel oils in broiler diets

Four experiments were conducted to evaluate the use of crude and refined palm (PAO) and palm kernel oil (PKO) in diets for broiler chickens. In Experiment 1, refined PAO and PKO were compared with corn oil (CO) and poultry oil (PO) at levels up to 10%. In Experiment 2, refined PAO and PKO were compared with PO at levels up to 8%. In Experiments 3 and 4, crude PAO and PKO were compared with PO at levels up to 8%. Diets were formulated based on the energy level assigned to PAO; other oils were added in amounts calculated to be isocaloric with an inert filler as required. Live production variables were measured. Samples of birds were processed to determine carcass characteristics, and fatty acid composition of adipose tissue was determined. In all studies, broilers fed crude or refined sources of PAO and PKO grew as well and utilized their feed as efficiently as those fed diets with isocaloric amounts of CO or PO. There were minimal interactions of source and dietary level of oil in any of the studies. Dressing percentage and quantity of abdominal fat were not influenced by source of supplemental oil; however, the fatty acid profile of adipose tissue was altered by the source of supplemental oil. There were only minor differences in fatty acid content of adipose tissue of broilers fed PAO (either crude or refined) versus those fed PO. However, increasing levels of PKO resulted in increased deposition of saturated fatty acids, especially lauric and myristic acid, and decreased concentrations of both monoenoic and polyunsaturated fatty acids. The resulting change in hardness of adipose tissue may prove to be advantageous in marketing.

Effect of red palm oil on some hepatic drug-metabolizing enzymes in rats

Red palm oil (RPO) from Elaeis guineensis is being considered for use as an edible oil in India as it is one of the richest natural sources of carotenoids. The effect of RPO on the host detoxification system, which is a vital mechanism in cancer prevention, was studied in three separate batches of Wistar/NIN inbred albino rats, and compared with controls, groundnut oil (GNO) and refined bleached deodorized palmolein oil (RBDPO). The first batch of 36 rats (12 from each group) comprised the adult males (26 wk old) of the third generation (F2b) from a multigeneration reproduction study in which three groups were fed 10% GNO or RPO or RBDPO for three generations continuously. Phase II glutathione-S-transferase (GSH-T) activity was measured in the liver cytosol of these rats after they had twice completed the process of mating, gestation, lactation and weaning, because GSH-T is one of the principal detoxifying enzymes involved in conjugating reactions of phase II metabolism. The fourth generation (F3b) weanling rats of the three groups, receiving GNO, RPO or RBDPO, were continued on the 10% oil diet for 9 wk, after which cytosolic GSH-T activity was measured. In the second experiment, eight male weanling Wistar/NIN inbred albino rats, 5 wk old, weighing 100-120 g, were fed 10% GNO, RPO or RBDPO for 4 wk in a 20% protein synthetic diet. Liver cytosolic GSH-T, reduced glutathione, microsomal total cytochrome P-450, aminopyrine N-demethylase and ethoxyresorufin-O-deethylase activity were measured to elucidate the effect of RPO on some phase I and phase II reactions. Significantly higher levels of GSH-T were observed in F2b and F3b rats given RPO than in those given GNO or RBDPO. In the second experiment, GSH-T induction was also noted, together with increased levels of reduced GSH. Phase I enzymes and total cytochrome P-450 levels were comparable between groups, indicating that no induction attributable to RPO had occurred. Thus, enhancement of one of the detoxifying phase II enzymes, in conjunction with the lack of induction of those activating phase I enzymes that are known to metabolize phenobarbitone and polycyclic aromatic hydrocarbons, suggests that RPO affords protection against chemical carcinogens, probably because of its carotenoid content.