Relation between polyunsaturated fatty acids and growth

Although it was discovered in the late 1920s that polyunsaturated fatty acids (PUFA) are essential for proper growth and development in animals, their nutritional importance in humans has not attained general interest until the 1990s, when the role for growth and development has been extensively studied in both humans and animals. It is now known that PUFA regulate various developmental and physiological processes, and that they are of essential importance for early human growth and development. Thus, linoleic acid is the precursor of arachidonic acid, from which hormone-like compounds, such as prostaglandins and leukotrienes, are formed, whereas alpha linolenic acid is the precursor of docosahexaenoic acid, which is an essential compound in cell membranes and occurs in particularly high concentration in the photoreceptors. In this paper the role of PUFA for human growth will be reviewed.     

Relation between polyunsaturated fatty acids and growth

Although it was discovered in the late 1920s that polyunsaturated fatty acids (PUFA) are essential for proper growth and development in animals, their nutritional importance in humans has not attained general interest until the 1990s, when the role for growth and development has been extensively studied in both humans and animals. It is now known that PUFA regulate various developmental and physiological processes, and that they are of essential importance for early human growth and development. Thus, linoleic acid is the precursor of arachidonic acid, from which hormone-like compounds, such as prostaglandins and leukotrienes, are formed, whereas a -linolenic acid is the precursor of docosahexaenoic acid, which is an essential compound in cell membranes and occurs in particularly high concentration in the photoreceptors. In this paper the role of PUFA for human growth will be reviewed.     

Long chain polyunsaturated fatty acids and fetal growth

Long chain polyunsaturated fatty acid composition of plasma choline phosphoglycerides has been measured at birth in 22 preterm infants. Positive correlations were found between both n-6 and n-3 fatty acids and measurements of growth and maturation. 20:4(n-6) and the sum of 20:3(n-6) + 20:4(n-6) correlated most strongly with weight and head circumference, while 22:6(n-3) showed strongest correlation with length of gestation. These findings are of relevance to understanding the role of nutrition in fetal growth and in establishing the group of infants most at risk of postnatal deficiency of essential fatty acids.     

Total parenteral nutrition in the newborn: energy substrates and plasma total fatty acids

Carbohydrate and lipid intakes have both been found to modulate the metabolism of long-chain fatty acids. To define the respective influence of these two energy substrates on plasma fatty acid concentrations, 32 studies were performed in 16 parenterally fed newborn infants (mean +/- SEM, birth wt: 2.15 +/- 0.1 kg, age: 10 +/- 1 d). In a paired cross-over design, the infants received for a given level of energy (60 versus 80 kcal/kg/d) two 6-d isonitrogenous and isocaloric regimens constructed so that the level of fat intake, 1 or 3 g/kg/d varied inversely with that of glucose. Total plasma fatty acid levels did not reflect the composition of the emulsion and varied with energy substrates. Plasma levels of three fatty acids rose inversely to the lipid intake, during the high glucose regimen: 16:1w7, 20:3w9 biologic markers of essential fatty acid deficiency, and 20:3w6 a derivative of 18:2w6. Glucose intake could exert its influence on 20:3w9 and 20:3w6 via insulin, an activator of delta 6 desaturase. Both glucose and fat should be taken into account when evaluating plasma fatty acid profile.     

Trans fatty acids may impair biosynthesis of long-chain polyunsaturates and growth in man

Human diet contains large amounts of trans fatty acids originating primarily from hydrogenated fats. Consumption of trans fatty acids is considered safe for man, but side effects, including impaired biosynthesis of long-chain polyunsaturated fatty acids with 20 and 22 carbon atoms and reduced growth have been observed in animals. We studied whether or not there are indications of untoward effects of trans fatty acids in 29 premature infants (birth weight 1700 +/- 127 g, gestational age 33.6 +/- 1.4 weeks, mean +/- SD). Plasma samples obtained on day 4 of life were analysed for fatty acid composition. Trans octadecenoic acid and total trans fatty acids in plasma lipid fractions (% wt/wt) were not related to the precursor essential fatty acids linoleic and alpha-linolenic acids but correlated inversely to n - 3 and n - 6 long-chain polyunsaturated fatty acids and to the product/substrate ratios of long-chain polyunsaturate biosynthesis. Trans fatty acids were also inversely correlated to birth weight but not to gestational age. These data indicate a potential impairment of essential fatty acid metabolism and early growth by trans isomers in man, and question the safety of high dietary trans isomer intakes during pregnancy and the perinatal period.     

Long-chain polyunsaturated fatty acids in human milk and brain growth during early infancy

Long-chain polyunsaturated fatty acids are essential for growth and development, and their crucial role in the development of the central nervous system and in retinal function has been the subject of many studies. As the balance between n-6 and n-3 fatty acids has to be optimal, their concentrations in the milk given to infants who are exclusively breastfed is of major importance. In this study, the composition of fatty acids in mothers' milk and the growth rate of the infant brain were analysed. Nineteen mother-term infant pairs from Stockholm, Sweden, were studied from birth to 1 mo and 3 mo of age, during which time the infants were breastfed exclusively. The dietary intake of the mothers was calculated and found to concur with the recommended daily dietary allowances of Swedish lactating women as regards energy, protein, fat and carbohydrates. The amounts of linoleic acid and alpha-linolenic acid in the diet were similar to those reported for European and North American women. The ratio between arachidonic acid (AA) and docosahexaenoic acid (DHA) in the milk from Swedish mothers is approximately the same as in the brain of infants, and was found to be positively correlated with the rate of gain of the occipito-frontal head circumference and of the calculated brain weight at 1 mo (p < 0.01) and 3 mo (p < 0.01) of age, respectively. However, further studies are needed to establish the exact requirements of AA and DHA for optimal growth and development during early infancy in exclusively breastfed infants.     

Infant growth charts.

Detection and monitoring childhood growth disorders requires the correct use of growth charts. A check on the accuracy of every point plotted on Gairdner-Pearson growth charts of premature infants in a hospital paediatric department was carried out. Errors beyond set limits were recorded. Of 611 points plotted on the growth charts of 50 premature infants who were at least 1 year of age at the time of the study, there were 173 (28.5%) points plotted in error. Altogether 94.7% of the errors occurred when plotting the age along the horizontal (X) axis of the growth chart, irrespective of whether weight, length, or head circumference was being measured. There was no evidence that the errors caused appreciable changes in clinical management. Potential sources of error identified were failure to adjust for prematurity correctly, inaccuracy in calculating age, and the use of the logarithmic scale. These errors could be serious and it is important that there should be greater vigilance in using growth charts. The use of age calculators or improved chart design is recommended. Assessment of the use of other growth charts in different settings is also suggested.     

Infant growth and income 50 years later

Among 4630 boys, irrespective of the social class into which they were born, those who grew slowly during infancy had poor educational achievements and had lower incomes than those who grew more rapidly. One interpretation of this is that biological processes linked to slow infant growth may lead to lifelong impairment of cognitive function.     

Impact of early dietary intake and blood lipid composition of long-chain polyunsaturated fatty acids on later visual development

BACKGROUND: In contrast to human milk, current infant formulas in the United States do not contain omega3 and omega6 long-chain polyunsaturated fatty acids. This may lead to suboptimal blood lipid fatty acid profiles and to a measurable diminution of visual function in developing term infants. The need for docosahexaenoic acid and arachidonic acid supplementation in the infant diet was evaluated in a double-blind, randomized clinical trial. METHODS: Healthy term infants were randomized to diets of (1) commercial formula, (2) docosahexaenoic acid-enriched formula (0.35% of total fatty acids), or (3) docosahexaenoic acid- (0.36%) and arachidonic acid- (0.72%) enriched formula. Eighty-seven infants completed the 17-week nutritional trial, and 58 were observed until 52 weeks of life. A reference group was exclusively breast fed for at least 17 weeks (n = 29). Outcome measures included electroretinographic responses, visual evoked potentials, and blood fatty acid analysis in infants at birth and at 6, 17, and 52 weeks of age. RESULTS: Commercial formula-fed infants had 30% to 50% lower content of docosahexaenoic acid in total red blood cell lipids during the 17-week feeding trial compared with breastfed infants. Significant differences persisted at the 1-year follow-up. Arachidonic acid content was consistently reduced in the commercial formula group by 15% to 20%. Infants fed long-chain polyunsaturated fatty acid-enriched formulas had docosahexaenoic acid and arachidonic acid blood lipid profiles resembling those of human milk-fed infants. Infants receiving this enriched formula had more mature electroretinographic responses than commercial formula-fed infants at 6 weeks of age. Human milk-fed and docosahexaenoic acid-enriched formula-fed infants had better visual acuity than commercial formula-fed infants at both 17 and 52 weeks of age. Early (17-week) fatty acid profiles in blood lipids were correlated with later (52-week) visual function development in study infants. CONCLUSIONS: Results from this clinical trial demonstrate that long-chain polyunsaturated fatty acid supplementation of formula in term infants produces blood lipid fatty acid profiles that are similar to those observed in breast-fed infants. This supplementation leads to better visual function later in life (i.e., 1 year of age) than that shown by infants fed commercial formula.