P.J. Drury

Differential oxidation of saturated and unsaturated fatty acids in vivo in the rat.

The oxidation rates of lauric, myristic, palmitic, stearic, oleic, alpha-linolenic, linoleic, kappa-linolenic, dihomo-gamma-linolenic and arachidonic acids were studied by use of a radioisotope tracer technique in weanling rats at rest in a metabolism chamber over 24 h. Of the saturated fatty acids, lauric acid (12:0) was the most efficient energy substrate: the longer the chain length of the saturated fatty acids, the slower the rate of oxidation. Oleic acid (18:1) was oxidized at a remarkably fast rate, similar to that of lauric acid. Of the omega 6 essential fatty acids studied, linoleic acid (18:2 omega 6) was oxidized at a faster rate than any of its metabolites, with arachidonic acid (20:4 omega 6) being oxidized at the slowest rate. The rate of oxidation of gamma-linolenic acid (18:3 omega 3) was almost as fast as that of lauric and oleic acids.

n-6 and n-3 fatty acids during early human development.

Abstract. The food intakes of pregnant women were analysed from two contrasting socio‐economic areas in London. There were significant differences in mean calorie and EFA intakes. Analysis of maternal and cord blood essential fatty acids (EFAs) in relation to birth weight, placental weight and head circumference were consistent with the dietary data. To assess the EFA tissue status of the low birth weight babies, the umbilical arteries from 14 separate babies of different birth weights were studied. Surprisingly high levels of the Mead acid (20:3 n‐9) were found, with the highest appearing in the artery from the baby with the lowest birth weight. This data may not necessarily imply an EFA deficiency, but at the least it probably indicates a remarkable thirst for long chain n‐6 and n‐3 fatty acids for fetal brain development.

An investigation on the influence of steroidal contraceptives on milk lipid and fatty acids in Hungary and Thailand

A double-blind clinical trial to examine the effects of oral and long-acting injectable contraceptive steroids on milk lipid and its fatty acid content has been done in Szeged, Hungary, and Khon-Kaen, Thailand. In Szeged, a combined and a progestin-only pill did not significantly alter total milk lipid. In Khon-Kaen, treatment with the combined pill was followed by a significant increase in the proportion of milk lipid. In the group treated with the long-acting injectable contraceptive, depot-medroxyprogesterone acetate (DMPA), the milk lipid decreased significantly in the first six weeks in comparison with the control group and the individual pretreatment values. A similar but weaker effect was noticed with the progestin-only pill in Khon-Kaen. Few consistently significant differences were found in the shorter chain fatty acids (myristic, lauric and palmitic acids) during treatment. The percentage proportions were increased during the combined pill treatment in Szeged and Khon-Kaen, and reduced in DMPA and progestin-only treatment in Khon-Kaen milks. The possibility that these reflected a response to a milk volume decrease in the combined pill treatment and a reduction in milk lipid synthesis in association with DMPA and the progestin-only pill is discussed. In Khon-Kaen, linoleic acid (which is not synthesized in the body) was increased by comparison with the controls, as a percentage proportion of the fatty acids in the progestin-only and DMPA groups. Calculation of the amounts of linoleic acid per litre of milk revealed that there had been a significant decrease of linoleic, eicosadienoic, dihommo-gamma-linolenic, arachidonic, docosatetraenoic acids in the w6 family and alpha-linolenic acid in the w3 family in the first two post-treatment visits (3 and 4). This reduction in essential fatty acid output follows the reduction in milk volume. In Khon-Kaen, the combined pill group showed a significant decrease compared with the controls, in the proportions of dihommo-gamma-linolenic acid. The difference in response of the mothers in Khon-Kaen and Szeged is discussed in relation to their different nutritional backgrounds.

Fatty Acid Composition of Milk of Refugee Karen and Urban Korean Mothers. Is the Level of DHA in Breast Milk of Western Women Compromised by High Intake of Saturated Fat and Linoleic Acid

Background: Lower proportions of docosahexaenoic acid (DHA) and total n-3 metabolites have been reported in breast milk of European, Australian and North American women compared with milk of mothers from non-Western countries. This difference is not always explained by intakes of marine products. Objective: We investigated the possibility that the relative composition of DHA and total n-3 metabolites in breast milk of non-Western mothers with low fat intakes is higher than the levels commonly reported in their Western counterparts. Subjects: Mature milk of refugee Karen women from two different camps in Thailand (n = 26 and n = 53), and transition milk from urban Korean mothers (n = 12) in Seoul was collected. In common with their respective community, the mothers have low fat intake, which is predominately of plant origin. Results: The percentage levels of DHA and n-3 metabolites in the milk of the Karen mothers were 0.52 ± 0.14 and 0.85 ± 0.24 (camp 1) and 0.54 ± 0.22 and 0.92 ± 0.42 (camp 2). In the Korean milk, DHA was 0.96 ± 0.21 and total n-3 metabolites 1.51 ± 0.3. Conclusion: We postulate that the levels of DHA and total n-3 metabolites may be compromised in breast milk of mothers on the Western high fat diet. This calls into question the use of DHA composition of such milk as a reference for the formulation of milk designed, for infant feed or, to test the function of DHA in neuro-visual development.

The nutritional contribution to bovine spongiform encephalopathy

Evidence that changes in feeding style alter the membrane fatty acid composition of ruminant tissue is presented here by comparing zoo giraffe with the same species from their natural habitat. The membrane changes seen are similar to those used experimentally to make animals susceptible to basic brain protein and encephalomalacia. Similar membrane responses have been noted in cattle. Use of animal protein and increased nitrogen in cattle feeds would lead to a relative deficiency of essential fatty acids in the cell membranes and hence reduced membrane stability. By analogy with crazy chick disease (nutritional encephalomalacia) and experimental encephalomyelitis in rats, the possibility that the changes in animals feeds would have depleted cattle tissue membranes and made them susceptible to BSE is discussed. The assumption being made is that the principle of a requirement of essential fatty acids for neural integrity and immune system function would apply to cattle as well as to other species.

Food Intakes of Children, the DHSS, and the Prevention of Heart Disease

The DHSS recently reported on school childrens food intakes (1). Although the type of fat eaten is clearly an important issue, the DHSS study did not analyse the fat intake for its saturated and essential fatty acid content. We have explored the intakes of the children for fibre, sugar and saturated fats as well as additional vitamins and trace elements, not reported by the DHSS. The data from the DHSS survey was presented as a summary of the main food types eaten. They aggregated some food groups e.g. meat and meat products, fish and fish products, cakes and biscuits. While this approach might make little difference to protein intakes, it may be expected to make a difference to fat and essential fatty acid intakes. We have re-analyzed the childrens food intakes keeping within the confines of the food groups reported. We had to rely on certain assumptions about the nature of an ‘average’ diet; we therefore explored the possibility that our assumption of an average diet was incorrect and examined a worse and a better situation to define how much the nutrient intake varied. The result of the analyses illustrate an important principle in the context of the present concern for food and health. The only way in which we could satisfy NACNE and COMA recommendations for fat, saturated fat, fibre and sugar, without a radical change in eating habits, was by simply replacing half the ‘junk’ foods by an isocaloric amount of fresh fruit and vegetables. In addition there was a marked improvement in the intakes of beta-carotene, vitamin C, B6 and folic acid. These improvements in diet are of particular importance to children as it is well known that the period most vulnerable to nutritional distortions is during growth and development. No matter which way we looked at the data it is clear that not only are the school childrens diets unsatisfactory from the view point of prevention of cardiovascular disease in later life but they also leave much to be desired from the view point of the wide range of nutrients known to be important for general health, growth and development. If this is true for the mean values obtained, it will be even more true for the ‘high risk groups’.

Fatty acids in human milk and steroidal contraceptives in Hungary and Thailand.

A controlled double-blind clinical trial was carried out in Hungary and Thailand to assess the effects of contraceptive hormones on human breast milk. Subjects were randomly assigned to 1 of 4 treatments: 1) control group--no treatment 2) 75 mcg d-1 norgestrel 3) 150 mcg levonorgestrel and 30 mcg ethinyl estradiol and 4) injectable depot-medroxyprogesterone acetate (DMPA). Milk was collected from study subjects at 3 6 9 12 16 20 and 24 weeks postpartum and fatty acid analysis was performed. At the study center in Hungary no differences were found in the proportion of lipid in the milk of subjects compared with controls. Among study subjects from Thailand however a reduction in the proportion of total milk lipid was found for the DMPA and progestin-only treatment groups. The percentage proportions of the shorter chain fatty acids were increased during the combined hormonal treatment in both centers. There was no evidence of an alteration of the ratio of linoleic acid to arachidonic acid in the milk before or after any of the treatments in Thailand. It is hypothesized that the impact of steroidal preparations on milk lipids in Thailand but not in Hungary reflects differences in nutritional backgrounds in the countries. Fat is the source of 10-15% of the mothers dietary energy in Thailand compared with 38-42% in Hungary. These findings suggest that the effect of contraceptive hormones on breast milk may be greater in developing countries where the intake of dietary fat is generally lower.