Acute absorption of folic acid from a fortified low-fat spread.

OBJECTIVE: To explore the feasibility of low-fat spreads as vehicles for folic acid (FA) fortification by determining the acute absorption of FA from a fortified spread. DESIGN: Double blind, crossover study to test each of the following treatments administered at 1-weekly intervals: (A) 20 g low-fat (40%) spread fortified with 200 microg FA and a placebo tablet; (B) 20 g low-fat placebo spread and a 200 microg FA tablet; (C) 20 g low-fat placebo spread and a placebo tablet. SUBJECTS: A total of 13 male volunteers, aged 31.8+/-13.2 y. MAIN OUTCOME MEASURES: Plasma total folate concentrations, measured before and up to 10 h after each treatment (n=10 samples per treatment). RESULTS: Plasma folate concentrations were significantly increased compared with baseline values 1 h after administration of the FA tablet, and 1.5 h after the FA spread, and remained significantly higher than the baseline values for up to 7 h after both treatments. The maximum plasma folate response (R(max)), corrected for baseline values and 'placebo response', was established between 1 and 3 h postprandially in response to both FA spread and FA tablet, and no significant difference in R(max) was found between the two treatments (13.4 vs 14.4 nmol/l, P=0.9). The acute absorption of FA from fortified spread relative to that from the tablet, calculated on the basis of area under the plasma folate response curve, was 67% (P=0.04). CONCLUSION: The absorption of FA from fortified low-fat spread, although lower than from a tablet, is effective. These results suggest that low-fat spreads, typically associated with fat-soluble vitamin fortification, may also be considered feasible as vehicles for FA fortification.

Conjugated linoleic acid isomers have differential effects on triglyceride secretion in Hep G2 cells.

The effect of different conjugated linoleic acid (CLA) isomers (trans-10,cis-12 (t10,c12)-CLA and cis-9,trans-11 (c9,t11)-CLA), compared with oleic acid (OA) and linoleic acid (LA), on hepatic lipid synthesis and secretion were investigated in Hep G2 cells. The cells were incubated in a medium containing 1 mmol/l fatty acid-bovine serum albumin (BSA) complex for 5 h, with BSA alone as control. [(3)H]Glycerol and [(14)C]acetate were used to monitor lipid synthesis and secretion. The results show that cellular uptake rates of these fatty acids were similar. Incubation with OA, t10,c12-CLA, c9,t11-CLA and LA resulted in 6-, 4-, 2- and 1.8-fold increases in intracellular [(3)H]triglyceride ([(3)H]TG) compared with incubation with BSA alone. OA, LA and c9,t11-CLA increased [(3)H]TG secretion 3.6-, 2.5- and 1.2-fold above the control, whereas t10,c12-CLA markedly suppressed the secretion of [(3)H]TG. Hepatic secretion of TG mass increased 3.5-, 3.3-, 2.7- and 1.5-fold in the cells incubated with OA, LA, c9,t11-CLA and t10,c12-CLA, respectively. Since the secreted TG is mainly contained in very low density lipoproteins (VLDL), the decreased ([(3)H])TG secretion by t10,c12-CLA reflects a diminished secretion of VLDL. With respect to cholesterol synthesis OA was more effective in stimulating the incorporation of [(14)C]acetate into cellular total cholesterol followed in descending order by LA, c9,t11-CLA and t10,c12-CLA. In conclusion, the biological properties of 18-carbon fatty acids are clearly influenced by both the number and (geometric) positions of their double bonds. Furthermore t10,c12-CLA is more effective than c9,t11-CLA on suppressing hepatic TG secretion in vitro.

Possible beneficial effect of fish and fish n-3 polyunsaturated fatty acids in breast and colorectal cancer.

Breast and colorectal cancer are main causes of death in industrialized countries. In these cancers dietary factors appear to play beneficial or adverse roles. One of the possible beneficial factors may be fish intake or the n-3 polyunsaturated fatty acids from fish, as found in epidemiological and clinical studies. In population studies, high intake of fish during many years is associated with reduced risks of breast and colorectal cancer. Prospective and case-control studies either do not show an association between fish intake and cancer risks or show reduced risks at high fish intakes. In these studies, fish consumption may have been too low or may not reflect fish consumption over a longer period. In population, case-control, and prospective studies, fish and fish n-3 polyunsaturated fatty acids were not found to increase cancer risks. Clinical studies on markers of colorectal cancer indicate that fish n-3 polyunsaturated fatty acids may reduce cancer risk. In several studies in which the effect of fish consumption on cancer risk was investigated, meat and meat products were positively related to cancer risk, suggesting that cancer risks might be reduced more effectively when meat and meat products in meals are replaced by fish. In conclusion, the existing knowledge suggests that an increase in the consumption of fish and fish n-3 polyunsaturated fatty acids in industrialized countries may contribute to lower breast and colorectal cancer risks.

Effects of conjugated linoleic acid (CLA) isomers on lipid levels and peroxisome proliferation in the hamster.

Effects of the conjugated linoleic acid (CLA) isomers cis-9, trans-11 (c9,t11 CLA) and trans-10, cis-12 (t10,c12 CLA) on lipid metabolism and markers of peroxisome proliferation were investigated in hamsters fed on purified diets containing 30% energy as fat and 0.1 g cholesterol/kg for 8 weeks. Four groups (n 32 each) received diets without CLA (control), with a mixture of equal amounts of c9,t11 and t10,c12 CLA (CLA mix), with c9,t11 CLA, and with t10,c12 CLA. The total amount of CLA isomers was 1.5% energy of 6.6g/ kg diet. CLA was incorporated into glycerides and exchanged for linoleic acid in the diet. Compared with the control, the CLA mix and t10,c12 CLA decreased fasting values of LDL- (21 and 18% respectively) and HDL-cholesterol (8 and 11%), increased VLDL-triacylglycerol (80 and 61%, and decreased epididymal fat pad weights (9 and 16%), whereas c9,t11 CLA had no significant effects. All CLA preparations increased liver weight, but not liver lipids. However, the increase in liver weight was much less in the c9,t11 CLA group (8%) than in the other two groups (25%) and might have been caused by the small amount of t10,c12 CLA present in the c9,t11 CLA preparation. Liver histology revealed that increased weight was due to hypertrophy. Markers of peroxisome proliferation, such as cyanide-insensitive palmitoyl CoA oxidase (EC 1.3.3.6) and carnitine acetyl transferase (EC 2.3.1.7) activities, were not increased by CLA. Both c9,t11 CLA and t10,c12 CLA were incorporated into phospholipids and triacylglycerols, but t10,c12 CLA only about half as much as c9,t11 CLA. In addition, linoleic acid and linolenic acid concentrations were lower in lipids of the t10,c12 CLA group compared with the c9,t11 CLA group. These data suggest that t10,c12 CLA stimulated the oxidation of all C18 polyunsaturated fatty acids. The results indicate that the t10,c12 CLA isomer, and not the so-called natural CLA isomer (c9,t11), is the active isomer affecting lipid levels in hamsters.

Health aspects of fish and n-3 polyunsaturated fatty acids from plant and marine origin.

An expert workshop reviewed the health effects of n-3 polyunsaturated fatty acids (PUFA), and came to the following conclusions. 1. Consumption of fish may reduce the risk of coronary heart disease (CHD). People at risk for CHD are therefore advised to eat fish once a week. The n-3 PUFA in fish are probably the active agents. People who do not eat fish should consider obtaining 200 mg of very long chain n-3 PUFA daily from other sources. 2. Marine n-3 PUFA somewhat alleviate the symptoms of rheumatoid arthritis. 3. There is incomplete but growing evidence that consumption of the plant n-3 PUFA, alpha-linolenic acid, reduces the risk of CHD. An intake of 2 g/d or 1% of energy of alpha-linolenic acid appears prudent. 4. The ratio of total n-3 over n-6 PUFA (linoleic acid) is not useful for characterising foods or diets because plant and marine n-3 PUFA show different effects, and because a decrease in n-6 PUFA intake does not produce the same effects as an increase in n-3 PUFA intake. Separate recommendations for alpha-linolenic acid, marine n-3 PUFA and linoleic acid are preferred.

Influence of dietary retrograded starch on the metabolism of neutral steroids and bile acids in rats.

Diets enriched in retrograded amylose (RS3) have been shown to lower serum cholesterol concentrations in rats. The possibility was tested that this hypocholesterolaemic effect of RS3 is caused by an increase in excretion of neutral steroids and/or bile acids. Six groups of ten rats were fed on purified diets containing either 12 or 140 g RS3/kg solid ingredients with and without added cholesterol (5g/kg). Low-RS3 diets, with and without added cholesterol, to which the bile-acid-binding resin cholestyramine (20 g/kg) was added, were used as reference. The high-RS3 diets v. the low-RS3 diets tended to reduce the increase in the total serum cholesterol concentration during the course of the experiment (P = 0.067), decreased serum triacylglycerol concentrations, raised total neutral steroids and total bile acids in caecal contents and faecal excretion of total bile acids, but lowered faecal excretion of neutral steroids. In addition, the serum concentration of total 3 alpha-bile acids was markedly raised by the high-RS3 diets. The high-RS3 diets raised the faecal excretion of lithocholic and muricholic acids, but lowered that of hyodeoxycholic acid, and increased the caecal amounts of lithocholic, ursodeoxycholic, beta-muricholic and omega-muricholic acids. Apart from the stimulation of faecal bile acids excretion, the effects of cholestyramine on bile acid metabolism differed at various points from those of RS3. Cholesterol feeding had predictable effects on cholesterol metabolism and led to greater elevating effects of RS3 on the faecal and caecal amounts of muricholic acids. The results suggest that the serum-cholesterol-lowering effect of high-RS3 diets may be explained by an increased influx of neutral steroids and bile acids into the caecum, and increased faecal excretion of bile acids, and/or by an altered intestinal bile acid profile.

Both raw and retrograded starch decrease serum triacylglycerol concentration and fat accretion in the rat.

Male Wistar rats were meal-fed on diets containing various amounts of resistant starch in the form of raw starch (either amylomaize starch, potato starch or modified high-amylose starch) or retrograded starch (prepared from each of the starches) for 6 weeks. Two diets containing normal maize starch were fed as diets poor in resistant starch. Energy absorption (energy consumption minus faecal energy loss), growth, weight of the epididymal fat pads, serum total cholesterol and triacylglycerol concentrations and a number of intestinal and faecal variables were determined. The resistant starches affected all the variables determined except the serum total cholesterol concentration. Relationships were found between energy absorption and both growth and the weight of the fat pads, and between the weight of the fat pads and both the serum triacylglycerol concentration and the serum total cholesterol concentration. No clear differences between the effects of the two types of resistant starch (raw starch v. retrograded starch) were found except that raw potato starch hardly stimulated H2 excretion and led to lower amounts of propionic and butyric acids in the caecal contents than the other starches. The results suggest that dietary resistant starch reduces energy absorption leading to less abdominal depot fat and lower serum triacylglycerol concentrations.

Resistant starch decreases serum total cholesterol and triacylglycerol concentrations in rats.

Rats were meal-fed semipurified diets containing a low (0.8 g/MJ) and a high (9.6 g/MJ) amount of resistant starch (RS) or various amounts of RS (0.8 to 9.6 g/MJ) and guar gum (0 to 8.8 g/MJ). In one experiment, rats were fed the low and high RS diets in three dietary regimens (ad libitum consuming, 12 h ad libitum/12 h food deprived, and meal fed). Effects of RS and guar gum on serum postprandial and postabsorptive concentrations of total cholesterol (TC) and triacylglycerol (TAG), growth, hydrogen excretion, tissue weights and contents of small intestine and cecum, and pH of cecal contents were investigated. In addition, effects of RS on food intake, de novo hepatic synthesis of fatty acids and neutral sterols, and on lipoprotein lipase activity and weight of epididymal fat pads were investigated. Compared with feeding the low RS diet, the high RS diet reduced the serum TC and TAG concentrations, with these effects observed after 1 and 2 wk of feeding, respectively. The dietary regimen did not influence the effect of RS on the serum TC and TAG concentrations, but it did affect the serum TAG concentration. Resistant starch had no effect on the hepatic synthesis of fatty acids and neutral sterols or on the lipoprotein lipase activity in epididymal fat pads. Guar gum also reduced the serum TC concentration, but it had no effect on serum TAG concentration. The tissue weights and contents of small intestine and cecum as well as hydrogen excretion increased with increasing amounts of dietary RS and guar gum, whereas the pH of cecal contents decreased. No effects of RS on food intake and total body weight gain were found, whereas guar gum decreased weight gain. Feeding the high RS diet also led to a lower weight of the epididymal fat pads. We conclude that dietary RS can reduce serum TC and TAG concentrations and fat accretion.

Hepatic de novo fatty acid synthesis in the rat.

Generally, the rate of hepatic de novo fatty acid (FA) synthesis (lipogenesis) in vivo is determined by measuring the amount of newly synthesized FA present in the liver 1 h or less after injection of label (3H2O) for FA synthesis (1-hour value of labelled FA). Since this value may well be affected by momentary conditions, our objective was to investigate whether the amount of labelled FA present in the liver 24 h after injection of 3H2O can be used as a parameter of lipogenesis (24-hour value of labelled FA). To this end, effects of the amounts of dietary fat, sucrose and linoleic acid and the effect of meal feeding versus d libitum feeding on this 24-hour value were investigated. The 24-hour value decreased with the dietary fat level and was higher in rats fed a diet in which starch was partly replaced by sucrose [20% of metabolizable energy (E%)]. This is in accordance with literature data on the 1-hour value of labelled FA. No effect of meal feeding versus ad libitum feeding on the 24-hour value of labelled FA was found. Furthermore, no significant effect of the dietary linoleic acid level (1-10 E%) on the 24-hour value of labelled FA was found, although when lipogenesis was stimulated by feeding a diet containing 20 E% sucrose, the 24-hour value tended to be higher at 1 E% linoleic acid than at 2.5 E% linoleic acid or higher.

Effects of type and amount of dietary fat on rabbit and rat lymphocyte proliferation in vitro.

To investigate whether dietary linoleic acid inhibits lymphocyte proliferation, rabbits were fed diets containing 35% of the digestible energy (35 en%) as sunflower seed oil (25 en% linoleic acid) or palm oil (3.5 en% linoleic acid). No differences in the mitogen-induced proliferation of peripheral blood lymphocytes (PBL) or splenocytes or in the effect of sera on PBL proliferation were observed. To investigate whether the amount of dietary fat affects lymphocyte proliferation, rats were fed diets containing 10 or 35 en% as fat. No difference in the mitogen-induced proliferation of splenocytes was obtained. However, serum from fed rats but not from fasted rats of the 35 en% fat group inhibited splenocyte proliferation, in comparison with serum from rats of the 10 en% fat group. Removing chylomicrons from the sera did not affect proliferation. The very low density lipoprotein + chylomicron fraction of the plasma inhibited proliferation. The inhibition was stronger for the 35 en% fat group than for the 10 en% fat group and was increased by fasting. No systematic differences in the effects on proliferation were obtained with the low or high density lipoprotein fractions of both groups. Diets containing a high amount of linoleic acid do not inhibit lymphocyte proliferation. The amount of dietary fat might affect lymphocyte proliferation through one or more factors in the plasma.

Dietary manipulation of prostaglandin and thromboxane synthesis in heart, aorta and blood platelets of the rat.

We conclude that dietary changes can have a profound influence on prostaglandin and thromboxane synthesis of organ systems. A better insight into underlying mechanisms is necessary before more definite advice with respect to feeding a linolenic acid and very long-chain polyunsaturated fatty acids as found in fish oils can be given.

PGF2 alpha stimulates release of PGE2 and PGI2 in the isolated perfused rat heart.

The effect of prostaglandin F2 alpha on the release of PGI2 and PGE2 was investigated in isolated perfused rat heart. PGF2 alpha at concentrations of 1.7 nmoles liter-1 or higher increased the release of PGI2 and PGE2 alpha. The release of PGI2 was highest after 3 to 4 min of perfusion with PGF2 alpha. This phenomenon may be of physiological significance and might explain the observed variable effects of PGF2 alpha on vascular resistance.

Influences of dietary fats on coronary flow rate and left ventricular work of the isolated rat heart: sunflower seed oil versus lard.

The influences of dietary sunflower seed oil and lard on coronary flow rate and external left ventricular work were studied in the isolated Langendorff-perfused and working rat heart. For 1, 4 or 6 weeks, rats were fed diets containing 25--50% of the total digestible energy as fat, 23% as casein an 52--27% as starch. The coronary flow rate and the maximum left ventricular work of hearts of rats fed sunflower seed oil were higher than those of hearts of rats fed lard (about 15 and 10%, respectively). The maximum left ventricular work was achieved at a left ventricular filling pressure of 10--12 mm Hg: this value was not affected by the type of dietary fat. The effect of dietary fat on coronary flow rare is already seen after 1 week of feeding, and on left ventricular work after 4 weeks of feeding. Analysis of variance shows a positive relationship between the maximum left ventricular work and the amount of sunflower seed oil. It is concluded that dietary fats affect coronary flow rate and left ventricular work in the isolated rat heart. The increase in left ventricular work may be caused by an increase in contractility.

Effects of prostaglandins on coronary flow rate and left ventricular work in isolated rat heart.

In isolated rat hearts PGD2, PGE1, PGE2, PGF2 alpha and PGI2 increased coronary flow rate at concentrations of about 23, 1.4, 0.4, 2.5 and 0.6 nmol per l respectively. PGD2, PGE2, and PGI2 did not affect left ventricular work (W 1v). PGE1 (14 nmol/l) lowered W 1v (12% and PGF2 alpha (9 nmol/l) increased W 1v (10%). It is concluded that endogenously released PGI2 can probably affect coronary flow rate.