Olive oil and rapeseed oil differ in their effect on plasma low-density lipoprotein metabolism in the guinea-pig.

The effects of olive oil and rapeseed oil, two different high-oleic-acid oils, on plasma LDL and hepatic cholesterol metabolism were compared in guinea-pigs. Animals were fed on semipurified diet containing 150 g fat/kg as either olive oil (OL), rapeseed oil plus 100 g palm oil/kg (C-P) or olive oil plus 350 g safflowerseed oil/kg (OL-S). Olive oil was enriched with safflowerseed oil (OL-S diet) to increase linoleic acid and to decrease palmitic acid concentrations, in order to evaluate whether differences in plasma LDL concentrations were due to intrinsic effects of the specific oil (rapeseed or olive oil) or to differences in the content of specific fatty acids. No differences due to dietary fat source were found in plasma total and HDL-cholesterol levels or in LDL composition. Plasma LDL-cholesterol levels were lower on the C-P diet than the OL diet (P < 0.05) while plasma LDL-cholesterol levels in animals fed on the OL-S diet were not significantly different from either dietary group (P > 0.05). The number of hepatic apo B/E (LDL) receptors was on average 25% higher in animals fed on the C-P diet compared with those fed on diets containing olive oil. Likewise, cardiac muscle lipoprotein lipase (EC 3.1.1.34) activity was significantly higher in the C-P group than in the OL and OL-S dietary groups. Dietary fat source had no effect on hepatic cholesterol levels or 3-hydroxy-3-methylglutaryl (HMG) CoA reductase (EC 1.1.1.34) activity. The results indicate that olive oil and rapeseed oil, both rich sources of monounsaturated fatty acids, differ in their effect on LDL metabolism in the guinea-pig.

Effect of dietary alpha-linolenic acid and its ratio to linoleic acid on platelet and plasma fatty acids and thrombogenesis.

The effect of dietary alpha-linolenic acid (18:3n-3) and its ratio to linoleic acid (18:2n-6) on platelet and plasma phospholipid (PL) fatty acid patterns and prostanoid production were studied in normolipidemic men. The study consisted of two 42-d phases. Each was divided into a 6-d pre-experimental period, during which a mixed fat diet was fed, and two-18 d experimental periods, during which a mixture of sunflower and olive oil [low 18:3n-3 content, high 18:2/18:3 ratio (LO-HI diet)], soybean oil (intermediate 18:3n-3 content, intermediate 18:2/18:3 ratio), canola oil (intermediate 18:3n-3 content, low 18:2/18:3 ratio) and a mixture of sunflower, olive and flax oil [high 18:3n-3 content, low 18:2/18:3 ratio (HI-LO diet)] provided 77% of the fat (26% of the energy) in the diet. The 18:3n-3 content and the 18:2/18:3 ratio of the experimental diets were: 0.8%, 27.4; 6.5%, 6.9; 6.6%, 3.0; and 13.4%, 2.7, respectively. There were appreciable differences in the fatty acid composition of platelet and plasma PLs. Nevertheless, 18:1n-9, 18:2n-6 and 18:3n-3 levels in PL reflected the fatty acid composition of the diets, although very little 18:3n-3 was incorporated into PL. Both the level of 18:3n-3 in the diet and the 18:2/18:3 ratio were important in influencing the levels of longer chain n-3 fatty acid, especially 20:5n-3, in platelet and plasma PL. Production of 6-keto-PGF1 alpha was significantly (P < 0.05) higher following the HI-LO diet than the LO-HI diet although dietary fat source had no effect on bleeding time or thromboxane B2 production.(ABSTRACT TRUNCATED AT 250 WORDS)

From the Canadian Dietetic Association. Concept of dietetic practice and framework for undergraduate education for the 21st century.

Rapid change and marked diversity are expected to characterize the 21st century. If dietitians are to serve as change facilitators in this environment they will have to demonstrate greater flexibility and creativity, practise critical analysis and problem solving and employ creative thinking. Although provision of quality nutrition care will remain the unique contribution of dietitians, practitioners in the future will require a greater understanding of the impact of social, economic and political systems on food availability and food consumption and, in turn, health and well-being. Critical to the future practice of dietetics will be a greater understanding of research methodology, computer technology, quality improvement processes and risk management, principles governing learning and behaviour, personnel management and organizational behaviour, family and group dynamics, interpersonal communication and their application to dietetic practice. The Canadian Dietetic Association recently adopted a framework for the development of baccalaureate programs in dietetics designed to enable the dietetic practitioner to continue to make a unique contribution in the 21st century. The framework allows individual institutions the freedom and flexibility to plan programs that are compatible with their philosophy and organizational structure. In addition, it is predicted on the principle that a career in dietetics entails a lifetime commitment to education, of which the baccalaureate program is only the beginning.

Dietary alpha-linolenic acid is as effective as oleic acid and linoleic acid in lowering blood cholesterol in normolipidemic men.

The effect of dietary oleic acid (OA), linoleic acid (LA), and linolenic acid (LNA) on plasma lipid metabolism was studied in eight normolipidemic men. A mixed-fat diet composed of conventional foods was fed during 6-d pre- and post-experimental periods. The same basic diet but with 75% of the fat (26% of total energy) provided by sunflower and olive; canola; soybean; and sunflower, olive, and flax oils was fed during four 18-d experimental periods. Mean plasma total cholesterol (-18%), low-density-lipoprotein-cholesterol, (-22%) and very-low-density-lipoprotein-cholesterol (-41%) concentrations were significantly (P less than 0.004) lower after the experimental diets than after the mixed-fat diet. Mean serum apolipoprotein B (-19%) and apolipoprotein A-I (-9%) concentrations were also significantly (P less than 0.0007) lower after the experimental diets. The experimental diets were equally effective in lowering total and lipoprotein cholesterol and apolipoprotein concentrations in plasma, indicating that dietary OA, LA, and LNA were equally hypocholesterolemic.

Reducing Cholesterol Intake: Are the recommendations valid?

The authors question dietary recommendations for the general public calling for reduced cholesterol intake. Metabolic studies have shown that dietary cholesterol normally induces only small increases in blood cholesterol level. There is evidence that only a portion of the population responds to a change in cholesterol intake; hence lowering dietary cholesterol will be effective for only some.

Accumulation of eicosapentaenoic acid in plasma phospholipids of subjects fed canola oil.

The metabolism of alpha-linolenic acid from canola oil was studied in eight normolipidemic men. The 42-day study was divided into three periods: a 6-day pre-experimental and two 18-day experimental. Approximately 75% of the dietary fat (28% of total energy) was provided by a mixture of fats during the pre-experimental period and either canola oil (CO) or sunflower oil (SO) during the experimental periods. The CO and SO diets were fed in a cross-over design. The ratios of linoleic to linolenic acid were 2.6:1 and 73.9:1 in the CO and SO diets, respectively. Dietary fat source had an effect on plasma phospholipid fatty acids: 18:1n-9, 18:3n-3 and 20:5n-3 were higher (p less than 0.05), and 18:2n-6 was lower in the phosphatidylcholine fraction; 18:1n-9 was higher and 20:4n-6 lower in the phosphatidyl-ethanolamine fraction; and 18:1n-9 and 20:5n-3 were higher and 20:4n-6 and 22:6n-3 were lower in the alkenylacyl ethanolamine phospholipid fraction on the CO diet as compared to the SO diet. Consumption of the canola oil diet resulted in higher n-3 fatty acid levels and lower n-6 fatty acid levels in plasma phospholipids than consumption of the sunflower oil diet.

Dietary canola oil: effect on the accumulation of eicosapentaenoic acid in the alkenylacyl fraction of human platelet ethanolamine phosphoglyceride.

Volunteers consumed a mixed-fat diet for 6 d (Pre-exp) and then either a canola-oil-based diet (CAN) containing linolenic acid (18:3n-3) or a sunflower-oil-based diet (SUN) rich in linoleic acid (18:2n-6) for 18 d, followed by the alternative diet in a crossover design. Platelet phospholipids were analyzed for changes in fatty acid composition. Eicosapentaenoic acid (EPA) (20:5n-3) was significantly higher in alkenylacyl ethanolamine phosphoglyceride (PPE) and in total phosphatidylcholine (PC) after CAN compared with SUN and Pre-exp. The 22:5n-3 was increased in PPE after CAN above concentrations found after both SUN and Pre-exp. Lower concentrations of 20:4n-6 and 22:4n-6 were observed with CAN in PC and lower concentrations of 22:4n-6 in PPE. These results indicate that the consumption of canola oil moderately increases EPA concentrations and alters the concentrations of other n-6 and n-3 fatty acids in human platelet phospholipids.

Serum paraoxonase and its influence on paraoxon and chlorpyrifos-oxon toxicity in rats.

Paraoxon and chlorpyrifos-oxon, the active metabolites of the organophosphorus insecticides parathion and chlorpyrifos, respectively, are hydrolyzed by an "A"-esterase, paraoxonase, which is present in the sera of several mammalian species. In this study, we investigated whether levels of serum paraoxonase activity in laboratory animals can influence the in vivo toxicity of paraoxon and chlorpyrifos-oxon. Paraoxonase was found to be 7-fold higher in rabbit serum than in rat serum. The dose of paraoxon required to produce similar signs of toxicity and similar degrees of cholinesterase inhibition in rats and rabbits (0.5 and 2.0 mg/kg, respectively) differed by 4-fold. Paraoxonase was then purified from rabbit serum and 8.35 units was injected in the tail veins of rats, increasing the peak hydrolytic activity of rat serum by 9-fold toward paraoxon and by 50-fold toward chlorpyrifos-oxon. The increase in serum paraoxonase/chlorpyrifos-oxonase activity was long-lasting, with a 2- and 10-fold increase, respectively, still present after 24 hr. Thirty minutes following enzyme injection, rats were challenged with an acute dose of paraoxon or chlorpyrifos-oxon given by the intravenous, intraperitoneal, dermal, or oral route. Cholinesterase activities were measured in plasma, red blood cells, brain, and diaphragm after 4 hr. Rats pretreated with paraoxonase exhibited less inhibition of cholinesterase than vehicle-treated controls following identical doses of paraoxon, particularly when the organophosphate was given iv or dermally. A very high degree of protection, particularly toward brain and diaphragm cholinesterase, was provided by paraoxonase pretreatment in animals challenged with chlorpyrifos-oxon by all routes. These results indicate that levels of serum paraoxonase activity can affect the toxicity of paraoxon and chlorpyrifos-oxon.

Comparison of the effect of canola oil and sunflower oil on plasma lipids and lipoproteins and on in vivo thromboxane A2 and prostacyclin production in healthy young men.

The effect of dietary fatty acid composition on plasma lipids and eicosanoid production was studied in normolipidemic men. Approximately 75% of the fat in the diet was provided by a mixture of fats (MF) during the 6-d pre and postperiods and either canola oil (CO) or sunflower oil (SO) during the two 18-d experimental periods. Saturated, monounsaturated, and polyunsaturated fatty acids provided 14%, 15%, and 7%; 5%, 20%, and 10%; and 7%, 7%, and 22%, respectively, of total dietary energy in the MF, CO, and SO diets, respectively. The CO and SO diets produced similar decreases in plasma total (20% and 15%, respectively) and low-density lipoprotein (25% and 21%, respectively) cholesterol. Plasma high-density lipoprotein cholesterol and triglyceride concentrations were not altered by either fat source. Bleeding time was longer and in vivo 1-keto-PGF1 alpha production was greater (p less than 0.05) when on the CO diet than when on the MF diet. The hypocholesterolemic and antithrombotic effects of the CO diet were equivalent to those of the SO diet.

Food safety and health effects of canola oil.

Canola oil is a newly marketed vegetable oil for use in salads and for cooking that contains 55% of the monounsaturated fatty acid; oleic acid, 25% linoleic acid and 10% alpha-linolenate [polyunsaturated fatty acid (PUFA)], and only 4% of the saturated fatty acids (SFAs) that have been implicated as factors in hypercholesterolemia. It is expressed from a cultivar of rapeseed that was selectively bred from old varieties in Canada to be very low in erucic acid--a fatty acid suspected to have pathogenic potential in diets high in the original rapeseed oil in experimental animals. Canola oil is free of those problems. It is the most widely consumed food oil in Canada, and has been approved for Generally Recognized as Safe (GRAS) status by the Food and Drug Administration (FDA) of the United States Department of Health and Human Services. The fatty acid composition of canola oil is consistent with its use as a substitute for SFAs, in meeting the dietary goals recommended by many health associations: an average diet containing about 30% of calories as fat made up of less than 10% SFAs, 8-10% PUFAs in a ratio of linoleic to linolenic acids between 4:1 and 10:1, the remainder being monounsaturated fatty acids. No single oil meets these current recommendations for ratios of PUFA/monounsaturated/polyunsaturated fatty acid ratios as the sole source of cooking and salad oil.

Diet and coronary heart disease: does beef fit in?

Changes in the fat and cholesterol content of retail cuts of Canadian beef over the past 16 years indicate that it is not necessary to limit beef in diets designed to meet the guidelines recommended at the recent Canadian Consensus Conference on Cholesterol. Recent studies have shown that the retail cuts of beef available in Canada today contain 20% to 60% less fat than previously reported in the Canadian nutrient data file. Cuts from the loin and hip region of the carcass (e.g., sirloin steak, round steak, and rump roast) that are trimmed of all visible fat are similar in fat, energy, and cholesterol content to chicken and fish.

Spatial memory impairment and central muscarinic receptor loss following prolonged treatment with organophosphates.

Memory impairment is one of the recurrent complaints of agricultural workers repeatedly exposed to organophosphorus insecticides. In an effort to establish an animal model for such behavioral effects, which would allow studying its underlying biochemical mechanism(s), in this study we evaluated spatial memory in animals following repeated organophosphate exposure. Male Long-Evans rats were given daily i.p. injections of either diisopropylfluorophosphate (DFP; 1 mg/kg/day) or disulfoton (O,O-diethyl S-[2-(ethylthio)ethyl] phosphorodithioate; 2 mg/kg/day) for 14 days. Acetylcholinesterase activity was inhibited 71-77% in the cortex, hippocampus, and striatum of rats treated with DFP, and 73-74% in those treated with disulfoton. Binding of [3H]quinuclidinyl benzilate ([3H]QNB) to cholinergic muscarinic receptors in the same brain areas was reduced 16-28% in organophosphate-treated rats. This decrease was due to a reduction in muscarinic receptor density (Bmax) with no changes in receptor affinity. At the end of the treatment rats were tested for spatial memory using the spontaneous alternation task in a T-maze. Rates of true spontaneous alternation were 64.4, 45.0, and 44.8% in animals which received corn oil, DFP, or disulfoton, respectively (P less than 0.05). These results indicate that prolonged inhibition of acetylcholinesterase caused by repeated organophosphate exposure alters spatial memory functions in rats, as well as causing a loss of muscarinic receptors. Considering the role of the cholinergic system in cognitive processes, these biochemical alterations could be related to the observed behavioral changes and may offer a potential explanation of the memory impairment reported by workers chronically exposed to organophosphates.

A comparison of the effect of diets containing beef protein and plant proteins on blood lipids of healthy young men.

The effect of plant and animal protein on blood lipid levels was investigated in eight healthy normolipidemic men aged 18 to 27 yr. All subjects were fed both plant and animal protein diets in a cross-over design. Each diet was consumed for a 21-day period. Proteins from commonly used plant sources made up the plant protein diet. Beef protein was substituted for 55% of the plant proteins in the animal protein diet. Fasting venous blood samples were collected at the beginning of the study and at 7-day intervals throughout the 42-day study. Serum was analyzed for total cholesterol and triglycerides. Plasma low-density and high-density lipoprotein cholesterol were determined. There were not any statistically significant differences in mean serum total cholesterol or mean plasma low-density lipoprotein cholesterol when subjects consumed the diets. Mean plasma high-density lipoprotein cholesterol levels were significantly (p less than 0.05) elevated at the end of the 21-day period when the animal protein diet was consumed (48 +/- 3 mg/dl) compared to the period when the plant protein diet was fed (42 +/- 2 mg/dl). Mean serum triglyceride values were significantly (p less than 0.05) increased at day 7 of the plant protein diet period (136 +/- 19 mg/dl) compared to the same time period when the animal protein diet was consumed (84 +/- 12 mg/dl). The results of the study indicated that the ingestion of a diet in which 55% of the protein was supplied by beef protein was not associated with a hypercholesterolemic effect in healthy normolipidemic young men.

Solar oblateness and fluid spin-down.

An experiment performed on a differentially rotating, density-stratified fluid shows that "spin-down" need not occur under the condition of stratification. Inasmuch as density stratification occurs in the interior of the sun, spin-down probably does not exist in the solar interior, and the observed solar oblateness may indicate that the sun contains a rapidly spinning core.