Trans fatty acids in human milk lipids: influence of maternal diet and weight loss

Geometric and positional isomers of octadecanoic acid in milk expressed during the first 9 weeks of lactation were determined for mothers delivering prematurely (PT) and at term (FT). Total C18:1 concentration was lower in PT than FT milk. C18:1 trans (elaidic acid) content was higher in PT and FT colostrum compared with subsequent milk samples. No relationship was observed between C18:1 trans level in milk and oleic acid, linoleic acid, total fatty acid levels, or volume of milk expressed. While gestational age and lactational stage appeared to affect the trans fatty acid pattern, the overriding influence was rate of maternal postpartum weight loss. Effect of weight loss on milk trans fatty acid levels was independent of maternal diet. Trans fatty acid content of milk as a function of recent maternal fat intake was also demonstrated. This study indicates that infants receiving human milk ingest levels of trans fatty acids reflecting short and long term maternal diet.     

trans Fatty acids in human milk are inversely associated with concentrations of essential all-cis n-6 and n-3 fatty acids and determine trans, but not n-6 and n-3, fatty acids in plasma lipids of breast-fed infants.

BACKGROUND: Human milk fatty acids vary with maternal dietary fat composition. Hydrogenated dietary oils with trans fatty acids may displace cis n-6 and n-3 unsaturated fatty acids or have adverse effects on their metabolism. The effects of milk trans, n-6, and n-3 fatty acids in breast-fed infants are unclear, although n-6 and n-3 fatty acids are important in infant growth and development. OBJECTIVE: We sought to determine the relations between trans and cis unsaturated fatty acids in milk and plasma phospholipids and triacylglycerols of breast-fed infants, and to identify the major maternal dietary sources of trans fatty acids. DESIGN: We collected milk from 103 mothers with exclusively breast-fed 2-mo-old infants, blood from 62 infants, and 3-d dietary records from 21 mothers. RESULTS: Mean (+/-SEM) percentages of trans fatty acids were as follows: milk, 7.1 +/- 0.32%; infants' triacylglycerols, 6.5 +/- 0. 33%; and infants' phospholipids, 3.7 +/- 0.16%. Milk trans fatty acids, alpha-linolenic acid (18:3n-3), arachidonic acid (20:4n-6), docosahexaenoic acid (22:6n-3) (P < 0.001), and linoleic acid (18:2n-6) (P = 0.007) were each related to the same fatty acid in infant plasma phospholipids. Milk trans fatty acids were inversely related to milk 18:2n-6 and 18:3n-3, but not to milk or infant plasma 20:4n-6 or 22:6n-3. trans Fatty acids represented 7.7% of maternal total fat intake (2.5% of total energy); the major dietary sources were bakery products and breads (32%), snacks (14%), fast foods (11%), and margarines and shortenings (11%). CONCLUSIONS: There were comparable concentrations of trans fatty acids in the maternal diet, breast milk, and plasma triacylglycerols of breast-fed infants. Prepared foods were the major dietary source of trans fatty acids.     

Fatty acid composition of human milk from South African black mothers consuming a traditional maize diet

Fatty acid composition of mature human milk of rural and urban black South African mothers was determined by gas-liquid chromatography. Rural mothers consumed traditional diets low in animal protein and fat, and high in carbohydrate and fibre. Urban mothers consumed more varied, partially westernized diets, and two-thirds were overweight. Plasma cholesterol concentrations were significantly lower in the rural group (3.64 vs 4.75 mmol/l, P less than 0.01). Milk of rural mothers contained significantly higher percentages of C10:0, C12:0, and total saturated fatty acids. Fatty acids C8:0-C14:0 synthesized de novo in the mammary gland were substantially higher in the milk of the rural mothers (24.7 vs 15.9 per cent). Conversely, the milk of the urban group contained higher percentages of monounsaturated fatty acids, 18:3 omega 3 and 20:2 omega 6. The ratio of polyunsaturated to saturated fatty acids in rural samples was 0.36 +/- 0.13 compared to 0.41 +/- 0.15 in urban samples (P greater than 0.1). It is concluded that maternal dietary intake significantly affects milk composition, as demonstrated by the high percentages of fatty acids synthesized de novo in the mammary gland of rural mothers habituated to low-fat, high-carbohydrate intakes.     

Hepatic fatty acid metabolism in rats fed diets with different contents of C18:0, C18:1 cis and C18:1 trans isomers

In the present study the effects of some C18 fatty acids on hepatic fatty acid metabolism have been compared. Male rats were fed cholesterol-free diets containing either C18:0, C18:1 cis or C18:1 trans isomers as the variables. In accordance with previous work, oleic acid in the diet caused an increase in cholesterol concentration in the liver and in the lipoprotein fraction of density (d; kg/l) < 1.006. Oleic acid also reduced the triacylglycerol:cholesterol value in this fraction. Surprisingly, the C18:1 trans isomers diet induced a decrease in the amount of cholesterol in total plasma as well as in the 1.019 < d < 1.063 lipoprotein fraction. Both oleic acid and C18:1 trans isomers increased the concentration of triacylglycerols in the liver. The two C18:1 fatty acids differently influenced the hepatic activities of carnitine palmitoyltransferase-I and 3-hydroxy-acyl-CoA dehydrogenase; both enzymes were inhibited by C18:1 trans isomers, while no change was induced by oleic acid. The activity of the citrate carrier was lower in the oleic acid- and C18:1 trans isomers-fed rats, when compared with the rats fed stearic acid. No diet effects were seen for the activities of acetyl-CoA carboxylase, fatty acid synthase, diacylglycerol acyltransferase, citrate synthase and phosphofructokinase. The results are interpreted in that oleic acid raised liver triacylglycerol by reducing the secretion of it with the d < 1.006 lipoprotein fraction whereas the C18:1 trans isomers enhanced liver triacylglycerol by lowering the hepatic oxidation of fatty acids.     

Intensification of essential fatty acid deficiency in the rat by dietary trans fatty acids

Two studies were conducted using male rats to assess the effect of trans fatty acids upon essential fatty acid (EFA) deficiency. In the first study 5% corn oil (CO), hydrogenated coconut oil (HCNO) or margarine stock (MS, partially hydrogenated soybean oil) were fed, and the levels of trans fatty acids in tissue lipids were measured. The trans fatty acids present in MS were found to intensify EFA deficiency and to be retained in tissue lipids to a high degree, especially in heart phospholipids (PL). In the second study, as the level of trans fatty acids increased in the diet, increasingly higher levels of trans fatty acids were deposited in the heart PL. As dietary trans acid increased, a decrease in total omega 6 fatty acids, and a decrease in the sum of 18:2 omega 6 + 20:4 omega 6 - 20:3 omega 9 fatty acids in heart PL occurred, both criteria indicating a shift toward an increasing EFA deficiency state. Studies of delta 5 desaturase activity of liver microsomes in selected groups showed an increase in the conversion of 20:3 omega 6 to 20:4 omega 6 as the trans fatty acid level in the diet increased.     

北京市城乡乳母的营养状况、乳成分和婴儿摄入母乳量及生长发育的关系——Ⅲ母乳的脂质分析

本文报导了1983～1984年北京市城区(宣武区),近郊区(西红门)和远郊区(大皮营)母乳脂质成分的测定结果,并结合乳母营养状况给予评价。 共测定了207例母乳比重,平均范围在1.018～1.023之间;测定了216例母乳的脂肪含量(g/100g乳),城区平均值为3.78,近郊区为3.31,远郊区为3.08,城区的显著较高;测定了194例母乳胆固醇含量,初乳的最高(23.4mg/100g乳),以后逐渐减低,到第三个月后达稳定水平(约10mg/100g乳),三个调查点的情况相同,测定了221例母乳的脂肪酸组成,其主要成分为油酸(29～37％),棕榈酸(17～25％)和亚油酸(12～25％),远郊区母乳中所含的必需脂肪酸显著较高。 统计分析证明三个地区的乳脂含量(％)与乳胆固醇含量(mg/100g乳)间有显著性相关(P<0.01);188例乳母的膳食脂肪摄入量(g/日或％kcal)与乳脂含量间也有显著性相关(P<0.05),此结果表明,北京城乡母乳的乳脂含量可能受膳食脂质与量的影响,其脂肪酸组成的特点是亚油酸含量高,反映了我国人民以素食为主的饮食习惯。乳中的必需脂肪酸供给量可满足婴儿所需,胆固醇供给量为70～85mg/d,可作为同龄婴儿自母乳摄入量的参考。     

Effect of maternal dietary linoleic acid and trans-octadecenoic acid on the fatty acid composition and prostaglandin content of rat milk

The effects of seven levels of dietary linoleic acid (18:2), with and without trans-octadecenoic acid (18:1t), on the fatty acid composition and prostaglandin content of milk were investigated in lactating rat dams. At parturition, 14 groups of 4 rats each were fed diets containing 20% fat, with mixtures of coconut and safflower oils providing seven concentrations of 18:2 ranging from 3.6 +/- 0.5 to 44.5 + 2.3% of total fatty acids. Hydrogenated soybean oil was added such that 18:1t comprised 10.3 +/- 0.3% of total fatty acids. Milk samples were collected on day 12 postpartum for prostaglandin analyses and on day 16 for fatty acid analyses. The relationship of dietary 18:2 to milk 18:2 was linear (r = 0.98; P = 0.0001), with milk 18:2 ranging from 2.6 +/- 0.1% of total fatty acids at the lowest level of dietary 18:2 to 27.9 +/- 1.6% at the highest. Milk 18:1t was highly correlated (r = 0.99; P = 0.0001) with the amount of dietary 18:1t. In rats fed hydrogenated fat, milk 18:1t averaged 7.0 +/- 0.2% of total fatty acids. Transfer from diet to milk was 46.4 +/- 4.2% for 18:2 and 37.5 +/- 1.7% for 18:1t. Mean concentrations of prostaglandin F2 alpha and E in rat milk were 269 +/- 16 pg/mL and 477 +/- 24 pg/mL respectively. There were no significant differences in the concentrations of either prostaglandin relative to 18:1t consumption at any level of 18:2.     

Trans fatty acids in human milk in Canada declined with the introduction of trans fat food labeling

Trans fatty acids in human milk have raised concerns because of possible adverse effects on infant growth and development. Analyses of human milk in the late 1990s in Canada showed high amounts of trans fatty acids from partially hydrogenated oils. Canada introduced labeling of trans fatty acids on retail foods in 2003. We analyzed trans and cis unsaturated and saturated fatty acids in human milk collected from 87 women in 2004-2006 and compared the levels to those in milk collected from 103 women in 1998 and analyzed using similar methods. The total trans fatty acids (mean +/- SEM, g/100 g fatty acids) in human milk in Canada decreased significantly, from 7.1 +/- 0.32 in 1998 to 6.2 +/- 0.48, 5.3 +/- 0.49, and 4.6 +/- 0.32 over 3 consecutive 5-mo periods from November 2004 to January 2006. The milk total trans fatty acids were significantly and inversely related to 16:0, 18:2(n-6), 18:3(n-3), 20:4(n-6), 22:4(n-6), and 22:5(n-6) and positively related to 18:0 and conjugated linolenic acids (P < 0.05, n = 190). The estimated exposures of exclusively breast-fed infants to trans fatty acids decreased from a mean and 95th percentile intake of 2.0 and 4.4 g x infant(-1) x d(-1) in 1998 to 1.33 and 2.41 g x infant(-1) x d(-1), respectively, in late 2005. The estimated intake of the mothers was 4.0 (range 0.51-12.3) and 2.2 (0.56-7.65) g x person(-1) x d(-1) in 1998 and late 2005, respectively. Our studies show trans fatty acids have decreased in human milk in Canada, which suggests a concomitant decrease in trans fatty acid intake among lactating women and breast-fed infants.     

Time-course effects of protein malnutrition on hepatic fatty acids delta 6 and delta 5 desaturation in the growing rat

1. In growing rats, the time-course effects of giving a normal-protein diet (200 g casein/kg; NP) for 52 d, a low-protein diet (20 g casein/kg; LP) for 52 d and a LP diet for 26 d followed by balanced refeeding (200 g casein/kg; BR) for 26 d, on the fatty acid composition of liver total lipids and microsomal phospholipids were investigated together with delta 6- and delta 5-microsomal desaturase activities. 2. The oleic acid content (mg/g tissue) of liver total lipids increased progressively with the LP diet, while linoleic acid was increased only at days 7 and 52. 20:3 omega 6, 20:4 omega 6, 22:5 omega 6 and 22:6 omega 3 fatty acids decreased during the period on the LP diet. BR for 7 d was sufficient to restore the fatty acid composition of total lipids to control values. Changes in the fatty acid composition of liver microsomal L-alpha-phosphatidylcholines were observed only after 52 d on the LP diet; the proportions (% w/w total fatty acids) of 18:0, 20:3 omega 6 and 20:4 omega 6 fatty acids decreased while oleic acid increased. The fatty acid composition of L-alpha-phosphatidylethanolamines was less affected. 3. delta 6- and delta 5-desaturase activities decreased to 20-30% of their original values after 2 d on the LP diet; a smaller deficit prevailed after 14 d but disappeared after 25 d, to appear again after 52 d. As early as day 2 of BR, desaturase activities were greatly recovered and returned to control values at day 13. 4. The present work shows that modifications in microsomal delta 6- and delta 5-desaturase activities are not strictly paralleled by the changes in the composition of fatty acids of liver total lipids and microsomal phospholipids.     

Will dietary omega-3 fatty acids change the composition of human milk?

The most abundant long-chain polyunsaturated fatty acid in brain and retinal lipids is docosahexaenoic acid (DHA, C22:6 omega 3). It becomes incorporated into nerve tissues mostly in utero and during the 1st yr of life. DHA is derived in humans either performed in the diet or by hepatic synthesis from dietary linolenic acid (C18:3 omega 3). Since human milk contains DHA, this study was designed to see if increased dietary DHA would be reflected in a higher DHA content in human milk. Eight lactating women were given supplements of a fish oil concentrate rich in omega-3 fatty acids, including DHA (11% of fatty acids). Six women took 5 g/day of fish oil for 28 days; five women consumed 10 g/day for 14 days; and one woman consumed 47 g/day for 8 days. Each intake level of fish oil produced significant dose-dependent increases in the DHA content of milk and plasma. Base-line DHA levels in milk were 0.1 +/- 0.06% of total fatty acids. Five g/day of fish oil raised the levels to 0.5 +/- 0.1% (p less than 0.001); 10 g/day raised DHA levels to 0.8 +/- 0.1% (p less than 0.001); and 47 g/day produced DHA levels of 4.8%. The results of this study indicated that relatively low intakes of dietary DHA significantly elevated milk DHA content. This would clearly elevate the infant's DHA intake and might have implications for brain and retinal development.     

Fatty acid profiles in response to soybean oil lipid emulsion infusions in essential fatty acid-deficient miniature swine

The ability of soybean oil lipid emulsions to affect essential fatty acid deficiency (EFAD) and plasma fatty acid distribution was studied in neonatal pigs. The test animals were maintained on a fat-free diet prior to administration of lipid emulsion. Plasma and red blood cell (RBC) membrane levels of essential [linoleic (C-18:2 omega 6) and arachidonic (C-20:4 omega 6)] and nonessential [palmitic (C-16, palmitoleic (C-16:1 omega 7), stearic (C-18), and oleic (C-18:1 omega 9)] fatty acids and the triene:tetraene ratio [5,8,11-eicosatrienoic acid (C-20:3 omega 9):arachidonic acid (C-20:4 omega 6)] were monitored to ascertain the establishment of EFAD and its correction. Nonessential fatty acids were studied, as these components of lipid therapy have received little attention. Results indicate that soybean oil emulsions are effective in reversing fatty acid profiles found in EFAD, and both essential and nonessential fatty acids are under strict metabolic control.     

trans Octadecenoic acid and trans octadecadienoic acid are inversely related to long-chain polyunsaturates in human milk: results of a large birth cohort study

BACKGROUND: Several observational studies indicate that trans isomeric fatty acids may interfere with the metabolism of essential fatty acids in the human organism. OBJECTIVE: The objective was to investigate the relation between trans fatty acids and long-chain polyunsaturates in mature human milk. DESIGN: Human milk samples (n=769) were obtained at the 6th week of lactation from mothers participating in a birth cohort study in Germany. The fatty acid composition of the milk samples was measured by high-resolution capillary gas-liquid chromatography. RESULTS: trans Octadecenoic and trans octadecadienoic acids were inversely correlated with linoleic acid (r=-0.32 and -0.33, P<0.0001 for both), alpha-linolenic acid (r=-0.35 and -0.27, P<0.0001), arachidonic acid (r=-0.60 and -0.47, P<0.0001), and docosahexaenoic acid (r=-0.51 and -0.33, P<0.0001). In contrast, no inverse correlations were observed between trans hexadecenoic acid and polyunsaturated fatty acids. CONCLUSIONS: The data obtained in the present study suggest that the availability of 18-carbon trans isomeric fatty acids may be inversely related to the availability of long-chain polyunsaturated fatty acids in mature human milk.     

Comparison of the mean-term physiological effects of cis or trans docosenoic acids in the rat. I. Digestibility of fatty acids. Effects on growth, organ weights and heart histology

The mean-term physiological effects of brassidic acid (n-9, trans docosenoic acid) and of erucic acid (n-9, cis docosenoic acid) have been compared to those of their C 18 homologues, elaidic and oleic acid, in a 2(3) factorial experiment; the 3 tested factors are: 1) the chain length of the dietary monoenes (C 22:1 vs. C 18:1), 2) the geometrical configuration of their double bond (trans vs. cis) and 3) the dietary level of linoleic acid (30% vs. 1,7% of dietary fatty acids). Wistar weanling rats have been fed for 16 weeks semi-synthetic diets containing 15% of lipids by weight, in which the fatty acids under study (brassidic, erucic elaidic) ranged to 40%. Although caution has been taken to optimize the digestibility of brassidic acid (interesterification of the lipid mixture, reduced level of calcium in the diet, addition of monoglycerides), it remains lower that of erucic acid. However, because of different levels of food consumption, the absorbed amounts of the two isomers are about the same. With a high dietary supply of linoleic acid, the dietary monoenes (C 22:1 or C 18:1), cis or trans) do not induce great changes in the weight gain of the rats, when adjusted to food consumption; linoleic acid subdeficiency lowers this adjusted weight gain, except when the diet contains oleic acid as the only monoene. These effects do not parallel those observed on the absolute growth of the rats. The trans monoenes, and to a lesser extent, erucic acid, induce an increase of liver weight (adjusted to body weight). The light microscopic histological study of the heart does not reveal any difference between the brassidic acid fed-rats and those fed the C 18:1 monoenes (elaidic, oleic). In contrast, erucic acid induces definite lesions of the myocardium. The dietary level of linoleic acid has little influence on the incidence and the severity of the lesions. The effects of these dietary fatty acids on the lipid contents and fatty acid compositions of different organs will be reported in a second paper.     

Fatty acids and retinyl esters of rat milk: effects of diet and duration of lactation

This study was initiated to explore the quantitative and qualitative differences in milk total fatty acids and milk retinyl esters when either hydrogenated or nonhydrogenated fat is fed during pregnancy and lactation. Rats were fed diets containing 10% by weight of corn oil or partially hydrogenated corn oil. Milk was collected on d 1, 8 and 14 of lactation and analyzed for protein, total fatty acids, fatty acid pattern, and retinyl ester pattern. Whereas diet produced no quantitative differences in milk protein or total fatty acids, the pattern of milk fatty acids varied significantly. Rats fed corn oil produced milk having more medium-chain saturated fatty acids, less long-chain monoenoic fatty acids, and more polyunsaturated fatty acids compared to those fed hydrogenated corn oil. Rats fed hydrogenated corn oil produced milk fat having 21-26% of the trans fatty acid, elaidic acid. Significant differences were also observed with duration of lactation: medium-chain fatty acids increased three to fourfold between d 1 and 8, where cis-monoenes and polyunsaturated fatty acids declined. The pattern of milk retinyl esters strongly reflected, but was not identical to, that of total milk fat. Comparing d 14 milk from rats fed corn oil with that from rats fed hydrogenated corn oil, medium-chain esters of retinol constituted 24 and 11% of total retinyl esters, whereas saturated long-chain fatty acid esters constituted 52 and 44%, respectively. trans Fatty acid esters of retinol comprised 24% of vitamin A esters in milk of rats fed hydrogenated fat. These data provide evidence that the composition of milk retinyl esters, as well as that of total milk fat, is determined both by the type of fatty acids from diet and from diet-related differences in de novo synthesis of fatty acids within the mammary gland and other tissues.     

Maternal dietary PUFAs intake and human milk content relationships during the first month of lactation

Maternal dietary fatty acids (FFAs) intake and corresponding human milk composition relationships have been assessed throughout the first month of lactation in 34 lactating women consecutively enrolled. All mothers were on their habitual diet. Food records (95 items) were administered to the mothers, six-times during the first month of lactation (1 day after delivery, 4, 7, 14, 21, and 28 days after colostrum appearance) and referred to maternal dietary intake of the day before. Milk collected on day 1 was considered as colostrum, day 4 and 7 samples as transitional milk, and day 14, 21 and 28 samples as mature milk. Five gas chromatographic analyses were performed on each sample. Statistics were made using Friedman's and Pearson's test. Maternal dietary saturated fatty acids (SFAs) and monounsaturated fatty acids (MUFAs) were significantly related to the corresponding milk pattern in the phase of transitional milk (P<0.01), while total polyunsaturated (PUFAs) content was significantly related only to the mature milk (P<0.01); in this phase about 42% of the variations occurring in PUFAs milk content can be related to variation of maternal PUFAs dietary intake. The results in the present study provide evidence of the relationships between maternal diet and milk composition. The degree of correlation between maternal diet and PUFAs milk content increases throughout milk maturational process and reaches significance only in mature milk. This would imply that advancing lactation, milk PUFAs provision sources gradually shift from adipose tissue catabolism to maternal diet.     

Suppression of arachidonic acid in lipids of rat tissues by dietary mixed isomeric cis and trans octadecenoates

The influence of dietary isomeric cis and trans octadecenoic fatty acids (ICTO) on the metabolism of polyunsaturated fatty acids in rat tissues was studied by feeding a defined diet rich in partially hydrogenated soybean oil. Experimental and control animals received equal and more than adequate amounts of linoleic and linolenic acids. The total phospholipid (PL) fatty acids of liver, heart, testis, brain and sciatic nerve, and the fatty acids of liver triacylglyceride, cholesteryl ester and individual PL classes were analyzed by capillary gas chromatography. The content of arachidonic acid in the total fatty acids of liver lipids of ICTO-fed rats was found to be lower than those from control rats by the following amounts (in percent): total PL, 35; phosphatidylcholine, 50; phosphatidylinositol, 35; phosphatidylserine 26; phosphatidylethanolamine, 12; cholesteryl ester, 55; and tryglyceride 75. PL 18:2 omega 6 and 20:3 omega 6 levels were elevated, suggesting inhibition of the desaturase-elongase enzymes involved in synthesis of arachidonic acid. Synthesis of 20:5 omega 3 and 20:3 omega 9 was accentuated by the ICTO diet, suggesting an omega 6 series-specific inhibition. A nearly perfect negative correlation between cis 12-18:1 and arachidonic acid was found in liver PL.     

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.     

Composition of phospholipid fatty acids in red blood cell membranes of patients in intensive care units: effects of different intakes of soybean oil, medium-chain triglycerides, and black-currant seed oil.

Fatty acid composition of phospholipids in red blood cell membranes was studied in 32 severely head-injured or cerebral stroke patients receiving enteral nutrition for 3 weeks. During this study the effects of three diets differing only by their lipid composition were investigated. The daily energy intake of each patient amounted to 2950 kilocalories, of which the lipid fraction represented 45.7%. Diet A contained only soybean oil, diet B consisted of a 50% soybean oil and 50% medium-chain triglycerides mixture, and diet C was an emulsion of 50% soybean oil, 42.5% medium-chain triglycerides, and 7.5% black-currant seed oil. Our results showed no biochemical signs of fatty acid deficiency in red blood cell membranes for the patients at the beginning of the study, after a comparison with a control group of 20 healthy adults. Inhibition of delta 6-desaturase activity on linoleic acid (C18:2 omega 6) after diet A was suggested by an increase of linoleic acid without a corresponding increase of dihomo-gamma-linolenic acid (C20:3 omega 6). Replacing 50% of soybean oil by with medium-chain triglycerides (diet B) prevented this enzyme inhibition. Supply of black-currant seed oil rich in gamma-linolenic (C18:3 omega 6) and stearidonic (C18:4 omega 3) acids (diet C) induced significant increases of dihomo-gamma-linolenic and eicosapentaenoic (C20:5 omega 3) acids, without influencing arachidonic acid (C20:4 omega 6) levels. This balance was evaluated through the ratio (C20:3 omega 6 + C20:5 omega 3)/C20:4 omega 6.     

Fatty acid and sn-2 fatty acid composition in human milk from Granada (Spain) and in infant formulas

OBJECTIVE: To investigate differences in fatty acid and sn-2 fatty acid composition in colostrum, transitional and mature human milk, and in term infant formulas. SETTING: Departament de Nutrició i Bromatologia, University of Barcelona, Spain and University Hospital of Granada, Spain. SUBJECTS: One-hundred and twenty mothers and 11 available types of infant formulas for term infants. DESIGN: We analysed the fatty acid composition of colostrum (n=40), transitional milk (n=40), mature milk (n=40) and 11 infant formulas. We also analysed the fatty acid composition at sn-2 position in colostrum (n=12), transitional milk (n=12), mature milk (n=12), and the 11 infant formulas. RESULTS: Human milk in Spain had low saturated fatty acids, high monounsaturated fatty acids and high linolenic acid. Infant formulas and mature human milk had similar fatty acid composition. In mature milk, palmitic acid was preferentially esterified at the sn-2 position (86.25%), and oleic and linoleic acids were predominantly esterified at the sn-1,3 positions (12.22 and 22.27%, respectively, in the sn-2 position). In infant formulas, palmitic acid was preferentially esterified at the sn-1,3 positions and oleic and linoleic acids had higher percentages at the sn-2 position than they do in human milk. CONCLUSION: Fatty acid composition of human milk in Spain seems to reflect the Mediterranean dietary habits of mothers. Infant formulas resemble the fatty acid profile of human milk, but the distribution of fatty acids at the sn-2 position is markedly different.