Analysis of omega-3 fatty acid content of South African fish oil supplements.

INTRODUCTION: Substantial evidence describes the protective effects of marine-derived omega-3 (n-3) polyunsaturated fatty acids (PUFA) on cardiovascular diseases as well as many other conditions. Numerous fatty acid preparations are marketed for supplementing the Western diet, which is low in n-3 fats. Since these preparations may vary in their n-3 PUFA content, we tested 45 commercially available products on the South African market for their fatty acid composition. METHOD: Forty-five commercially available n-3 fatty acid supplements were analysed using gas-liquid chromatography to determine their fatty acid content. RESULTS: More than half of the n-3 supplements available on the South African market contained ≤ 89% of the claimed content of EPA and/or DHA as stated on the product labels. To meet ISSFAL's recommendation of 500 mg EPA + DHA/day can cost consumers between R2 and R5 per person per day (R60 to R150 p/p/month). Regarding rancidity, the majority of capsules contained conjugated diene (CD) levels higher than that of vegetable oil obtained from opened containers (three months) used for domestic cooking purposes, despite the addition of vitamin E as antioxidant. CONCLUSION: Since no formal regulatory structure for dietary supplements currently exists in South Africa, consumers depend on self-regulation within the nutraceutical industry for assurance of product quality, consistency, potency and purity. Our results indicate that more than half of the n-3 fatty acid supplements on the South African market do not contain the claimed EPA and/or DHA contents as stated on product labels, and they contained CD levels higher than that in unused vegetable oils obtained from opened containers used for domestic cooking purposes.

Factors associated with low serum retinol levels in children aged 6-24 months in a rural South African community.

OBJECTIVE: : To identify risk factors for variation in serum retinol levels in children younger than 2 years of age in a rural South African community. DESIGN: : Children (n = 97), 6-24 months of age, were divided into two groups according to their serum retinol levels, using 20 microg dl-1 as the cut-off point. The chi-square test, Fischer exact two-tailed test and analysis of variance were used to identify related variables which were significantly different between the two groups. To evaluate simultaneously the association between several potential risk factors and low serum retinol levels, a multiple regression model for categorical data was developed which included potential risk factors that were statistically significant in the bivariate analysis as the independent variables, and either low or normal vitamin A status as the dependent variable. RESULTS: : There was an association between serum retinol levels and: (i) the place of birth (hospital vs. home deliveries); (ii) the attitude of the care-giver towards family life; and (iii) the health status of the child. Although not included in the multiple variable model because of small numbers, all children who had a previous episode of measles, all underweight children, and all children of widowed care-givers were in the low serum retinol group. CONCLUSIONS: : The care-giver's attitude towards family life was positively associated with the child's vitamin A status, while home deliveries were associated with a low vitamin A status.

Diet can manipulate the metabolism of EPA and GLA in erythrocyte membrane and plasma.

The effect of diet on the metabolism of eicosapentaenoic acid (EPA) and gammalinolenic acid (GLA) was investigated in two groups of African Green Vervet monkeys fed either a Western atherogenic diet (WAD; %E fat 43.5%; P:S 0.3; n=10) or a high carbohydrate diet (HCD; %E fat 20.5%; P:S 3.4; n=10). Vervets within each dietary treatment were supplemented with 300 mg/day with either an EPA concentrate (50% as free fatty acid, n=5) or a GLA concentrate (70% as free fatty acid, n=5) for 24 weeks, increasing the dose every 6 weeks to a maximum of 2400 mg/kg/day. Vervets in the WAD-Group consumed 433.7 mg/kg/day of EPA and those in the HCD-Group 318.2 mg/kg/day of EPA, whereas 421 mg/kg/day of GLA was consumed in the WAD Group and 340 mg/kg/day in the HCD Group during the last 6 weeks (week 18-24) of the supplementation period. The rate of disappearance of EPA and GLA from plasma and erythrocyte memebrane (EMB) phospholipids were estimated for the two diets after supplementation was stopped. The half-lives (t(1/2)) of EPA in EMB phosphatidylcholine (PC) were estimated to be 34.6 days (WAD) and 22.6 days (HCD), compared to 43.5 days (WAD) and 31.3 days (HCD) in EMB phosphatidylethanolamine (PE). In plasma cholesteryl ester (CE) t(1/2) was 23.5 days (WAD) compared to 14.1 days (HCD), and in plasma triacylglycerol (TAG) 17.4 days (WAD) compared to 9.4 days (HCD). Although accurate estimation of the GLA t(1/2) was difficult to assess due to the low tissue levels (probably due to rapid conversion to DGLA), the disappearance rates of GLA from EMB and plasma also suggested a faster metabolic rate in those animals consuming a HCD compared to a WAD. EPA also disappeared faster from EMB PC than from EMB PE. Disappearance of EPA from plasma TAG was also faster than from plasma CE, probably reflecting their relative turnover and metabolic rates. During supplementation, EPA substituted linoleic acid (C18:2 n-6), arachidonic acid (C20:4 n-6), and GLA (C18:3 n-6). This was reversed when supplementation was stopped. Plasma total cholesterol (TC) levels decreased by 17.06 +/- 17.67% in animals consuming the HCD with EPA as supplement, whereas in those consuming the WAD, plasma TC levels increased with 21.78 +/- 28.23% during the supplementation period. The delay of EPA and GLA disappearance from EMB and plasma in animals consuming a WAD, strongly suggests that metabolism of EPA and GLA is modulated by diet. Such a modulation could cause an accumulation of plasma TC levels that could explain the contradictory results reported by previous studies.

Changes in plasma lipoprotein levels during a hiking expedition in South America.

Eleven males participated in a hiking expedition over a period of 6 weeks during which they walked an average of 15 km per day, resting days included. The participants completed a seven-day estimated dietary record before and during the expedition. Their habitual dietary intake before the expedition was typical of a Western diet. During the expedition most animal products, with the exception of canned fish, were excluded from the diet. The dietary intake of fat and carbohydrate changed from 36.9% and 40.6% to 14.0% and 76.4% respectively. Cholesterol intake dropped from 557 mg to 92 mg. Mean plasma total cholesterol (TC) decreased from 190.9 mg/100 ml to 142.0 mg/100 ml. These changes were mainly due to changes in low density lipoprotein cholesterol (LDL-C). Although high density lipoprotein cholesterol (HDL-C) did not change, the ratio of HDL-C to TC increased significantly. It can be concluded that drastic dietary changes, together with increased physical activity and weight loss resulted in major plasma lipoprotein changes. The expected fall in HDL-C due to a high carbohydrate diet was counteracted by the increased physical activity and weight loss.

Dietary intake, anthropometric measurements and plasma lipid levels in throwing field athletes.

Since little descriptive data for field athletes is available, the anthropometric measurement, dietary intake and plasma lipid levels of 22 male and 15 female field athletes (throwers) are reported. Percentage body fat was calculated by using four skinfold thicknesses. Using this measurement as criterion, 53% of the females were obese. Percentage body fat and body mass index showed a positive correlation with total plasma cholesterol and plasma triacyglycerol and a negative correlation with percentage HDL cholesterol for males and females. Five of the males and three of the females were hypercholesterolaemic. The seven day estimated dietary record was used to determine their dietary intake. The males as well as the females consumed a diet that was high in fat and cholesterol content. Their diets were low in carbohydrate. It is recommended that these athletes increase their carbohydrate intake and lower their total fat intake. It is also recommended that the obese subjects should lose weight.

An improved rapid thin-layer chromatographic-gas-liquid chromatographic procedure for the determination of free fatty acids in plasma.

Free fatty acids contained in Dole extracts were separated from other lipid components by either a thin layer chromatographic procedure or by a solvent partitioning system. Subsequent gas-liquid chromatographic analysis of methyl esters prepared from fatty acids purified by these two procedures, showed that when fatty acid standards were subjected to these two procedures, comparable recoveries of fatty acids were obtained. When, however, phospholipids and neutral lipids were present in the extracts, the solvent partitioning system yielded 10 to 46% higher values than recorded with the thin layer chromatographic procedure. Compositional data indicated that the higher values measured by the solvent partitioning procedure were probably derived from hydrolysis of other lipid components during the sodium hydroxide step. Purification of fatty acids by the described thin layer chromatographic procedure eliminates this problem and rapidly yields accurate and reliable results.