Correction of the malabsorption of the preterm infant with a medium-chain triglyceride formula

Feeding medium-chain fatty acid-rich formula causes liver steatosis and alters hepatic metabolism in neonatal pigs

Medium-chain fatty acids (MCFA) and long-chain fatty acids (LCFAs) are often added to enhance the caloric value of infant formulas. Evidence suggests that MCFAs promote growth and are preferred over LCFAs due to greater digestibility and ease of absorption. Our hypothesis was that MCFA supplementation would enhance neonatal pig growth to a greater extent than LCFAs. Neonatal pigs (n = 4) were fed a low-energy control (CONT) or two isocaloric high-energy formulas containing fat either from LCFAs, or MCFAs for 20 days. Pigs fed the LCFAs had greater body weight compared with CONT- and MCFA-fed pigs (P < 0.05). In addition, pigs fed the LCFAs and MCFAs had more body fat than those in the CONT group. Liver and kidney weights as a percentage of body weight were greater (P ≤ 0.05) for pigs fed the MCFAs than those fed the CONT formula, and in those fed LCFAs, liver and kidney weights as a percentage of body weight were intermediate (P ≤ 0.05). Pigs in the CONT and LCFA groups had less liver fat (12%) compared with those in the MCFA (26%) group (P ≤ 0.05). Isolated hepatocytes from these pigs were incubated in media containing [13C]tracers of alanine, glucose, glutamate, and propionate. Our data suggest alanine contribution to pyruvate is less in hepatocytes from LCFA and MCFA pigs than those in the CONT group (P < 0.05). These data suggest that a formula rich in MCFAs caused steatosis compared with an isocaloric LCFA formula. In addition, MCFA feeding can alter hepatocyte metabolism and increase total body fat without increasing lean deposition.NEW & NOTEWORTHY Our data suggest that feeding high-energy MCFA formula resulted in hepatic steatosis compared with isoenergetic LCFA or low-energy formulas. Steatosis coincided with greater laurate, myristate, and palmitate accumulation, suggesting elongation of dietary laurate. Data also suggest that hepatocytes metabolized alanine and glucose to pyruvate, but neither entered the tricarboxylic acid (TCA) cycle. In addition, the contribution of alanine and glucose was greater for the low-energy formulas compared with the high-energy formulas.

Role Medium-Chain Fatty Acids in the Lipid Metabolism of Infants

Human breastmilk, the ideal food for healthy infants, naturally contains a high concentration of medium-chain fatty acids (MCFAs, about 15% of total fatty acids). MCFAs are an important energy source for infants due to their unique digestive and metabolic properties. MCFA-enriched oils are widely used in an infant formula, especially the formula produced for preterm infants. Recently, there has been a growing interest in the triglyceride structure of MCFAs in human milk, their metabolism, and their effects on infant health. This study summarized the MCFA composition and structure in both human milk and infant formula. Recent studies on the nutritional effects of MCFAs on infant gut microbiota have been reviewed. Special attention was given to the MCFAs digestion and metabolism in the infants. This paper aims to provide insights into the optimization of formulations to fulfill infant nutritional requirements.

High versus low medium chain triglyceride content of formula for promoting short-term growth of preterm infants

BACKGROUND

In-hospital growth of preterm infants remains a challenge in clinical practice. The high nutrient demands of preterm infants often lead to growth faltering. For preterm infants who cannot be fed maternal or donor breast milk or may require supplementation, preterm formulas with fat in the form of medium chain triglycerides (MCTs) or long chain triglycerides (LCTs) may be chosen to support nutrient utilization and to improve growth. MCTs are easily accessible to the preterm infant with an immature digestive system, and LCTs are beneficial for central nervous system development and visual function. Both have been incorporated into preterm formulas in varying amounts, but their effects on the preterm infant's short-term growth remain unclear. This is an update of a review originally published in 2002, then in 2007.

OBJECTIVES

To determine the effects of formula containing high as opposed to low MCTs on early growth in preterm infants fed a diet consisting primarily of formula.  SEARCH METHODS: We used the standard search strategy of Cochrane Neonatal to search Cochrane Central Register of Controlled Trials (CENTRAL; 2020, Issue 8), in the Cochrane Library; Ovid MEDLINE Epub Ahead of Print, In-Process & Other Non-Indexed Citations, Ovid MEDLINE(R) Daily, and Ovid MEDLINE(R); MEDLINE via PubMed for the previous year; and Cumulative Index to Nursing and Allied Health Literature (CINAHL), on 16 September 2020. We also searched clinical trials databases and the reference lists of retrieved articles for randomized controlled trials (RCTs) and quasi-RCTs.

SELECTION CRITERIA

We included all randomized and quasi-randomized trials comparing the effects of feeding high versus low MCT formula (for a minimum of five days) on the short-term growth of preterm (< 37 weeks' gestation) infants. We defined high MCT formula as 30% or more by weight, and low MCT formula as less than 30% by weight. The infants must be on full enteral diets, and the allocated formula must be the predominant source of nutrition.

DATA COLLECTION AND ANALYSIS

The review authors assessed each study's quality and extracted data on growth parameters as well as adverse effects from included studies. All data used in analysis were continuous; therefore, mean differences with 95% confidence intervals were reported. We used the GRADE approach to assess the certainty of evidence.

MAIN RESULTS

We identified 10 eligible trials (253 infants) and extracted relevant growth data from 7 of these trials (136 infants). These studies were found to provide evidence of very low to low certainty. Risk of bias was noted, as few studies described specific methods for random sequence generation, allocation concealment, or blinding. We found no evidence of differences in short-term growth parameters when high and low MCT formulas were compared. As compared to low MCT formula, preterm infants fed high MCT formula showed little to no difference in weight gain velocity (g/kg/d) during the intervention, with a typical mean difference (MD) of -0.21 g/kg/d (95% confidence interval (CI) -1.24 to 0.83; 6 studies, 118 infants; low-certainty evidence). The analysis for weight gain (g/d) did not show evidence of differences, with an MD of 0.00 g/d (95% CI -5.93 to 5.93; 1 study, 18 infants; very low-certainty evidence), finding an average weight gain of 20 ± 5.9 versus 20 ± 6.9 g/d for high and low MCT groups, respectively. We found that length gain showed no difference between low and high MCT formulas, with a typical MD of 0.10 cm/week (95% CI -0.09 to 0.29; 3 studies, 61 infants; very low-certainty evidence). Head circumference gain also showed little to no difference during the intervention period, with an MD of -0.04 cm/week (95% CI -0.17 to 0.09; 3 studies, 61 infants; low-certainty evidence). Two studies reported skinfold thickness with different measurement definitions, and evidence was insufficient to determine if there was a difference (2 studies, 32 infants; very low-certainty evidence). There are conflicting data (5 studies) as to formula tolerance, with 4 studies reporting narrative results of no observed clinical difference and 1 study reporting higher incidence of signs of gastrointestinal intolerance in high MCT formula groups. There is no evidence of effect on the incidence of necrotizing enterocolitis (NEC), based on small numbers in two trials. Review authors found no studies addressing long-term growth parameters or neurodevelopmental outcomes.

AUTHORS' CONCLUSIONS

We found evidence of very low to low certainty suggesting no differences among short-term growth data for infants fed low versus high MCT formulas. Due to lack of evidence and uncertainty, neither formula type could be concluded to improve short-term growth outcomes or have fewer adverse effects. Further studies are necessary because the results from included studies are imprecise due to small numbers and do not address important long-term outcomes. Additional research should aim to clarify effects on formula tolerance and on long-term growth and neurodevelopmental outcomes, and should include larger study populations to better evaluate effect on NEC incidence.

Medium chain triglyceride and medium-and long chain triglyceride: metabolism, production, health impacts and its applications - a review

Structured lipid is a type of modified form of lipid that is "fabricated" with the purpose to improve the nutritional and functional properties of conventional fats and oils derived from animal and plant sources. Such healthier choice of lipid received escalating attention from the public for its capability to manage the rising prevalence of metabolic syndrome. Of which, medium-chain triacylglycerol (MCT) and medium-and long-chain triacylglycerol (MLCT) are the few examples of the "new generation" custom-made healthful lipids which are mainly composed of medium chain fatty acid (MCFA). MCT is made up exclusively of MCFA whereas MLCT contains a mixture of MCFA and long chain fatty acid (LCFA), respectively. Attributed by the unique metabolism of MCFA which is rapidly metabolized by the body, MCFA and MCT showed to acquire multiple physiological and functional properties in managing and reversing certain health disorders. Several chemically or enzymatically oils and fats modification processes catalyzed by a biological or chemical catalyst such as acidolysis, interesterification and esterification are adopted to synthesis MCT and MLCT. With their purported health benefits, MCT and MLCT are widely being used as nutraceutical in food and pharmaceutical sectors. This article aims to provide a comprehensive review on MCT and MLCT, with an emphasis on the basic understanding of its structures, properties, unique metabolism; the current status of the touted health benefits; latest routes of production; its up-to-date applications in the different food systems; relevant patents filed and its drawbacks.

Lipid Intake Enhances Muscle Growth But Does Not Influence Glucose Kinetics in 3-Week-Old Low-Birth-Weight Neonatal Pigs

BACKGROUND

Low-birth-weight (LBWT) neonates grow at a slower rate than their normal-birth-weight (NBWT) counterparts and may develop hypoglycemia postnatally.

OBJECTIVE

We investigated whether dietary lipid supplementation would enhance growth and improve glucose production in LBWT neonatal pigs.

METHODS

Twelve 3-d-old NBWT (1.606 kg) crossbred pigs were matched to 12 LBWT (1.260 kg) same-sex littermates. At 6 d of age, 6 pigs in each group were fed a low-energy (LE) or a high-energy (HE) isonitrogenous formula containing 5.2% and 7.3% fat, respectively. Body composition was assessed using dual-energy X-ray absorptiometry; plasma glucose and glycerol kinetics were assessed using stable isotope tracers. After killing, weights of skeletal muscles and visceral organs were measured. Data were analyzed by ANOVA for a 2 × 2 factorial design; temporal effects were investigated using repeated-measures analysis.

RESULTS

Lipid supplementation did not affect body weight of LBWT or NBWT pigs. However, liver and longissimus dorsi weights as a percentage of body weight were greater for pigs fed an HE diet than for those fed an LE diet (4.3% compared with 3.4% and 1.5% compared with 1.2%, respectively) but remained less for LBWT than for NBWT pigs (3.8% compared with 3.9% and 1.3% compared with 1.5%, respectively) (P < 0.05). In addition, hepatic fat content increased (7.9 compared with 2.6 g) in pigs fed the HE compared with those fed the LE formula (P < 0.05). Lipid supplementation did not influence plasma glucose concentration which remained lower in the LBWT than in the NBWT group (4.1 compared with 4.5 mmol/L) (P < 0.05).

CONCLUSIONS

Our data suggest that lipid supplementation modestly improved growth of skeletal muscle and the liver but did not affect glucose homeostasis in all groups, and glucose concentration remained lower in LBWT than in NBWT pigs. These data suggest that the previously reported hyperglycemic effect of lipid supplementation may depend on the route of administration or age of the neonatal pig.

Intestinal absorption of lipid emulsion in premature infants: a pilot study

BACKGROUND

Adequate nutritional intake is essential in the very-low-birth-weight infant, but difficult to achieve in the first few postnatal days. Can lipids be given enterally in the first few days of life in sick preterm infants?

OBJECTIVE

To determine tolerance and absorption of lipid emulsion when fed enterally to very-low-birth-weight infants.

DESIGN/METHODS

Infants had a birth weight <1,500 g, an appropriate weight for gestational age, and were receiving parenteral nutrition. We performed a progressive series of studies, enrolling 5 infants in each group. Group 1 infants were fed enteral lipid emulsion at 1 g/kg/day for 4 days, starting when 60 ml/kg/day of breast milk was tolerated enterally. Simultaneously, a matched control group which received no oral lipid emulsion was enrolled. We then enrolled group 2 infants who were fed 3 g/kg/day with the same protocol as group 1. Group 3 infants were fed enteral lipid emulsion starting in the first 72 h of life. The infants were fed 1, 2 and 3 g/kg/day subsequently for 48 h each. Fat absorption was measured.

RESULTS

Gestational age was 24.6-30.8 weeks and birth weight was 620-1,400 g. One infant (group 1) developed necrotizing enterocolitis 1 week after the study. There were no other adverse clinical findings. On average, enteral lipid emulsion was started on day 8 of life in groups 1 and 2, and on day 2 in group 3. The intestinal lipid absorption was 93.6% (min. = 76%). There was no difference in fat absorption between the 4 groups (p > 0.05).

CONCLUSIONS

Lipid emulsions are an isotonic high-calorie source which can be given safely enterally instead of intravenously in the immediate neonatal period of very-low-birth-weight infants without clinical adverse effects and with almost complete absorption. There are potential advantages to oral administration of a lipid emulsion starting in early life which require further investigation.

New lipids in enteral feeding

PURPOSE OF REVIEW

Lipid sources for enteral nutrition continue to be an exciting area of investigation. It is timely to review recent developments which have largely contributed to thrust enteral feeding into a new era.

RECENT FINDINGS

Although much more research needs to be done, there is a better understanding of the competitive relationships between n-6/n-3 fatty acids in conditions of metabolic and immune stress as well as in autoimmune and degenerative diseases. Although structured lipids are more completely absorbed and cleared, other more important clinical benefits need to be documented before they can be considered cost-effective. Immune enhancing formulas are the subject of controversy and some have been shown to be more effective than others. Enteral formulations with short-chain fatty acids are promising but more experimental work on the normal, and the sick colon is needed. Finally, there are a few isolated studies suggesting that enteral feeding with liposomes and with lipolytic products may have advantages when the digestive phase needs to be circumvented. The era of nutrigenomics, in which the effect of specific lipids on genes and proteins is being explored, is with us. We can look forward to nutrigenetics when the effect of genetic variation on the interaction between diet and disease will guide our practice.

SUMMARY

Clinicians already have access to lipid sources and formulations which allow them to individualize enteral feeding programs. More clinical and technological research needs to be carried out, however, before products can be tailored to produce optimal effects in specific conditions.

High versus low medium chain triglyceride content of formula for promoting short term growth of preterm infants

BACKGROUND

In-hospital growth of most very low birth weight infants remains below the 10th percentile of reference intrauterine growth curves (Ehrenkranz 1999). To improve growth, fat is added to preterm formula in the form of medium chain triglycerides (MCT) or long chain triglycerides (LCT). MCT are easily accessible to the preterm infant with an immature digestive system while LCT are important in the development of the retina and visual acuity. Both have been incorporated into preterm formulas in varying amounts, but their effect on the preterm infant's short term growth is unclear.

OBJECTIVES

To determine among preterm, formula fed infants, does high MCT as opposed to low MCT (high LCT) formula promote higher short term growth rates.

SEARCH STRATEGY

MEDLINE (1966-2002), CINAHL (1982-2002), Cochrane Controlled Trials Register (The Cochrane Library, Issue 4, 2001), conference proceedings, and reference lists of articles were searched.

SELECTION CRITERIA

All randomized trials comparing the effects of exclusive feeding of high versus low MCT formula (for a minimum of one week) on the short term growth of healthy, preterm infants.

DATA COLLECTION AND ANALYSIS

Two reviewers assessed each study's quality and extracted data on growth parameters as well as adverse effects from included studies. All data used in analysis were continuous, and therefore weighted mean differences with 95% confidence intervals were reported.

MAIN RESULTS

Eight randomized trials studying a total of 182 infants were included. There was no evidence of difference in short term growth parameters when high and low MCT formulas were compared. The meta-analysis of weight gain based on five studies yielded a WMD of -0.35 g/kg/d (95% CI -1.44, 0.74). Similarly, meta-analysis of weight gain in g/d based on two studies showed no evidence of difference (WMD 2.09 g/d, 95% CI -1.46, 5.64). Length gain, based on five studies, showed a non-significant WMD of 0.14 cm/wk (95% CI -0.04, 0.31). Head circumference gain, based on data from five studies, showed a non-significant WMD -0.03 cm/wk (95% CI -0.15, 0.08). Only one study reported skin fold thickness gain, with a mean difference -0.15 mm/wk (95% CI -0.41, 0.11), again not significant. Subgroup analyses according to % MCT in the high MCT formula, by 10% intervals, showed no evidence of effect of high MCT on short term weight gain within any subgroup. There are conflicting data (two studies) as to formula tolerance. There is no evidence of effect on incidence of necrotizing enterocolitis (NEC), based on small numbers in two trials. No studies were located addressing long term growth parameters or neurodevelopmental outcomes.

REVIEWER'S CONCLUSIONS

There is no evidence of difference between MCT and LCT on short term growth, gastrointestinal intolerance, or necrotizing enterocolitis. Therefore, neither formula type could be concluded to improve short term growth or have less adverse effects. Further studies are necessary because the results from the included eight studies are imprecise due to small numbers and do not address important long term outcomes. Additional research should aim to clarify effects on formula tolerance and on long term growth and neurodevelopmental outcomes, and include larger study populations to better evaluate effect on NEC incidence.

Feeding behavior in neonates whose diet contained medium-chain triacylglycerols: short-term effects on thermoregulation and sleep

BACKGROUND

Feeding formulas for premature infants often contain medium-chain triacylglycerols (MCTs). However, previous studies in animals and adults showed that MCTs may decrease food intake.

OBJECTIVES

The objectives were to determine in hospitalized premature infants whether food intake is modified by dietary MCT supply and to assess the effects on thermoregulation and sleep, which are involved in the regulation of energy metabolism and in the optimal physiologic development of the neonates.

DESIGN

Food intake, body mass, and nutritional efficiency during 3 consecutive days were compared in 2 groups of neonates according to the fat composition of their feeding formula [MCT group: 37% MCT, 63% long-chain triacylglycerols (LCTs); LCT group: 100% LCT]. On the third day, sleep and metabolic rate were recorded in the morning during an interval between meals.

RESULTS

Regardless of day, energy intake was greater in the MCT group than in the LCT group (x difference: 67.3 kJ x kg(-1) x d(-1); P = 0.007). Metabolic rate (1.8 mL x min(-1) x kg(-1); P < 0.001), cheek skin temperature (0.31 degrees C; P = 0.04), and total sleep time (52 min; P = 0.01) were also higher in the MCT group.

CONCLUSION

The ratio of MCTs to LCTs in neonates' feeding formulas can modify physiologic functions involved in energy-balance regulation.

Medium-chain fatty acids but not L-carnitine accelerate the kinetics of [14C]triacylglycerol utilization by colostrum-deprived newborn pigs

The effect of L-carnitine on in vivo fatty acid utilization was determined using colostrum-deprived newborn piglets fed emulsified triglycerides (TG) composed of [1-14C]octanoate (tri-8:0) or [1-14C]octadecanoate (tri-18:1). A soy protein-based liquid diet devoid of L-carnitine was fed piglets for 1 d to allow development of fatty acid-metabolizing enzymes and intestinal fat digestion and absorption before assessment of in vivo fat utilization. The radiolabeled TG were fed in isoenergetic amounts (97.7 kJ/kg(0.75)), with or without L-carnitine (1 mmol/kg(0.75)) as 30% (v/v) emulsions, using polyoxyethylene sorbitan monooleate as an emulsifier. Expired CO(2) was quantified and specific radioactivity (Bq/micromol) was determined at 20-min intervals over 24 h. The rate (mmol ATP.kg(-0.75).min(-1)) and extent (mol ATP/kg(0.75)) of TG oxidative utilization (i.e., composite of digestion, absorption and oxidation) were calculated from the kinetics of 14CO(2) expiration. The maximal rate and extent of tri-8:0 oxidation were three and fourfold greater than those of tri-18:1, respectively (P < 0.001), and tri-18:1 delayed the time to reach 10 and 50% of maximal oxidation rate by 1.2 and 1.9 h (P < 0.01, respectively), regardless of supplemental carnitine. Collectively, these findings quantify the accelerated oxidation of medium-chain vs. long-chain triglycerides, but fail to support a need for supplemental carnitine to maximize fat oxidation in colostrum-deprived piglets.

Medium-chain triglyceride absorption in patients with pancreatic insufficiency

BACKGROUND

The role of medium-chain triglycerides (MCTs) in the management of patients with pancreatic insufficiency is controversial. The aim of the study was to evaluate the absorption of MCTs in the presence of pancreatic insufficiency and the effect of pancreatic extracts on MCT absorption so as to clarify whether the replacement of usual dietary fats with MCTs is cost-effective.

METHODS

Six patients with severe pancreatic steatorrhea were for 5 days fed a low-fat diet to which butter (long-chain triglycerides (LCTs)) or MCT oil was added, with and without pancreatic extracts, in a crossover design.

RESULTS

Fecal weight and nitrogen losses were the same during MCT and LCT intake. Steatorrhea was substantial during both periods but was significantly lower during MCT than LCT intake. Fecal weight and nitrogen and fat losses were reduced by pancreatic extracts in both diets. Steatorrhea was the same when MCTs and LCTs were consumed together with pancreatic extracts.

CONCLUSIONS

MCTs are absorbed better than LCTs in the presence of pancreatic insufficiency but require pancreatic extracts for optimal absorption. No advantage is to be expected from replacing usual dietary fats with MCTs if pancreatic supplements are used.

Conversion of octanoic acid into long-chain saturated fatty acids in premature infants fed a formula containing medium-chain triglycerides

A large number of very-low-birth weight infants are fed formulas containing medium-chain triglycerides (MCT) to enhance fat and calcium absorption. Studies are available on the intestinal absorption of MCT, which is nearly complete, but uncertainties exist on the metabolic fate of octanoic acid, the major component of MCT. Oxidation accounts for approximately 50% of the dietary intake, and losses as dicarboxylic acids in the urine are negligible. Since storage in adipose tissue is limited, conversion into long-chain fatty acids (LCFA) is likely to be an important route. To study the nonoxidative metabolism of MCT, six preterm infants fed a standard premature formula containing 38 weight% (wt%) MCT (54 mol% medium-chain fatty acids (MCFA), of which 35 mol% is octanoic acid) were studied at 4 weeks of age, when on full oral intake and receiving on average 130 kcal/kg/d. The study consisted of an oral primed constant-rate infusion of [13C]-octanoate and the measurement of the 13C enrichment of individual fatty acids in plasma triglycerides (TG) by a highly sensitive on-line combustion method using gas chromatography-isotope ratio mass spectrometry (GC-IRMS). We observed a significant incorporation of the dietary [13C]-octanoic acid in plasma TG (10.0% +/- 4.5% of the enrichment of the diet). A noticeable incorporation of the label was detected in myristic and palmitic acids (4.6% +/- 2.5% and 7.8% +/- 4.1% of the octanoic enrichment of the diet). The absolute amount of the fatty acids was studied with conventional GC, and the plasma TG fatty acid profile differed markedly from the diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Controversies in the composition of infant formulas

Available infant formulas contain a vast assortment of carbohydrate, protein, and fat sources in an effort to emulate the composition of human milk. Although infants receiving commercial formulas thrive, physicians should be cognizant of differences in formula composition and the research that has resulted in the differences. Such awareness permits rational and scientific recommendations both in prescription of formulas and in direction of research on the optimal formula composition for infants.

Influence of dietary medium- and long-chain triglycerides on fat deposition and lipogenic enzyme activities in rats

The present study investigates fat deposition, variances of fatty acid (FA) composition, and lipogenic enzyme activities through dietary medium- and long-chain triglyceride (MCT and LCT) supplementation in growing rats. Eighteen male Wistar rats were divided into three groups and fed isocalorically for 4 weeks with control (based on AIN 76), MCT (C8:0 26%), or LCT (corn oil 25%) diets. Compared to the control group with 0.28 +/- 0.01, feed efficiency was lower in the MCT rats and greater in the LCT rats (0.24 +/- 0.01 and 0.33 +/- 0.01, respectively). Weights of perirenal and epididymal adipose tissue pads of the MCT rats were similar to those of the control group, but were significantly lower than those of the LCT group. Whole-body carcass components data of MCT rats showed the decrease in moisture and protein contents compared to those of control and LCT rats. Fat content of LCT rats was 25-30% higher than those of the MCT and control group. Glucose-6-phosphate dehydrogenase, citrate cleavage enzyme, and malic enzyme activities of liver and epididymal adipose tissue were markedly low in LCT rats. In the MCT group, however, lipogenic enzyme activities were not suppressed, and malic enzyme activity was drastically increased. FA composition of whole-body triglycerides and epididymal adipose tissue in MCT rats showed that C16:0 and C16:1 levels were higher than those of the LCT rats. In contrast, FA composition of the LCT group presented high C18:2 content.(ABSTRACT TRUNCATED AT 250 WORDS)

Two different low birth weight formulae compared

The performance of two different, commercially available, low birth weight formulae feeds was compared in preterm infants. The aim of the study was to determine the effect of compositional differences on tolerance, stool frequency and consistency, fat balance and weight gain. Inborn infants with birth weight less than 1500 g were randomised at birth to receive Prematil or Osterprem. Thirty infants received more than 900 ml/kg per week of designated formula alone during a total of 70 weeks of study. Three day fat balance was performed on 23 infants. Osterprem contains 40% more fat than Prematil. The composition of this fat is different in that Osterprem contains no medium chain triglycerides (MCT) compared to 30% in Prematil. Clinical evaluation demonstrated that Osterprem is associated with a significantly higher mean energy intake compared to Prematil (3442 and 3127 kJ/kg per week) but mean weight gain is not significantly different (123 and 112 g/kg per week). Mean stool frequency is higher on Osterprem (20.5 and 14.5 stool/week) and the consistency of stools firmer. This is attributable to a higher mean fat output (2.3 and 0.9 g/kg per day) secondary to the higher fat content of the feed and lower mean absorption (71.6 and 83.5%). Both feeds are well tolerated. The study also confirms that absorption of unsaturated fatty acids is inversely proportional to chain length.

Fat absorption in premature infants: the effect of lard and antibiotics

Fat absorption of an adapted cow's milk formula was studied in a randomized controlled trial involving two groups of 18 premature infants (mean gestational age +/- SD: 33.0 +/- 2.9 weeks, range 26.5-37.5 weeks). The triglyceride configuration was modified by the use of lard. This modification did not improve the absorption of fat or energy. Also no difference in serum concentrations of cholesterol and triglycerides was found. Growth velocity during the study was similar in both groups. Detailed analysis of the data revealed that in infants who received (parenterally) antibiotics (mainly ampicillin and netilmicin) a higher coefficient of fat absorption (+20%, P less than 0.01) and of energy absorption (+8%, P = 0.03) was found. Based on these results, we find no support for the use of lard in adapted cow's milk infant formulas to improve fat absorption. In studies of fat and energy absorption the effects of antibiotics have to be taken into account.

Lipid tolerance in the very low birth weight infant on intravenous and enteral feedings

Nutrition is of critical importance to very low birth weight (VLBW) survival. Intravenous (iv) lipid tolerance has been studied using a soybean or safflower-based lipid emulsion. We studied lipid levels in a group of VLBW infants on both intravenous lipids (soybean-safflower emulsion) and on enteral feedings (24 cal/oz premature formula). Levels were obtained on 1, 2, and 3 g/kg/day of iv lipid and after 3 and 10 days of feeding. Triglyceride (TG) and free fatty acid (FFA) proved the most sensitive indicator of both iv and enteral tolerance. The higher the lipid dose, the more likely there would be elevated lipid levels, especially FFA. Mean lipid levels for the group of enteral-fed infants were normal. Comparison of lipid levels on iv to those on enteral feedings showed significant differences in trough iv levels of TG compared to preprandial TG. FFAs tended to be significantly higher on iv feedings. Monitoring lipid levels on iv and enteral feedings is appropriate to document tolerance.

Feeding the premature and compromised infant: gastrointestinal considerations

We have presented the current concepts of gastrointestinal ontogeny--the various factors governing the ontogeny of the gastrointestinal tract and the interaction and intricate relationship between different determinants. It is only through a better understanding of the development of the gut and the various factors affecting it that pediatric gastroenterologists are able to design nutritional support strategies for managing very young and compromised neonates.

Energy and nitrogen balances in very low birthweight infants

Energy and nitrogen balances were performed in 12 very low birthweight infants fed on either human milk or on a preterm formula. Energy and nitrogen retention were significantly higher in those given the formula feed (p less than 0.05). Highly significant correlations were found between nitrogen intake and nitrogen retention and between energy retention and nitrogen retention (p less than 0.001). Multiple regression analysis failed to show any effect of energy retention on the correlation between nitrogen intake and nitrogen retention in babies fed on human milk. Protein deficiency seems to be the most likely explanation of poor growth in infants fed on human milk.

Medium chain triglycerides and structured lipids

Lipids are an essential component of our body composition and necessary in our daily food intake. Conventional fats and oils are composed of glycerides of long chain fatty acids and are designated as long chain triglycerides (LCT). Body fat as well as the fats and oils in our daily intake fall into this category. In enteral and parenteral hyperalimentation, we can identify such LCT fats and oils. Soy, corn, safflower and sunflowerseed oils are typical of the LCT oils. In the search for alternative noncarbohydrate fuels, medium chain triglycerides (MCT) are unique and have established themselves in the areas of malabsorption syndrome cases and infant care and as a high energy, rapidly available fuel. Structure lipids with a MCT backbone and linoleic acid built into the triglyceride molecule have been developed to optimize the triglyceride structure that is best for patients, particularly the critically ill. Structured lipids with built-in essential fatty acid components or other polyunsaturated fatty acids promise greater flexibility in patient care and nitrogen support.

Fat absorption in preterm infants fed a taurine-enriched formula

An adapted cow's milk infant formula without or with extra taurine (350 mumol/l) was fed to four and five infants, respectively. The infants, born after 28-32 weeks gestation, and initially fed with a starting formula for preterms, were switched to one of the two above-mentioned formulae at approximately the 16th day of life. Each infant was studied during 4 consecutive weeks. The faecal excretion of fat, energy and total bile acids was determined from 3-day stool collections each week. The addition of taurine to the infant formula neither improved the uptake of fat and energy nor changed the faecal bile acid excretion. Growth velocity was similar in both groups of infants. Based on these results there is no rationale for adding taurine to adapted cow's milk infant formula to obtain a better fat absorption.

The impact of development of the gut on infant nutrition

We have described the developmental pattern of the GI tract, constituent tissues of which do not develop simultaneously, either functionally or morphologically. Dietary modifications to suit the stage of development have been described, and possible changes resulting from these modifications are also discussed. It is important to note that the newborn period is a time in which rapid development is taking place while the GI system is still not fully mature, hence the macro- and micronutrients given during this period should be adjusted both quantitatively and qualitatively to suit the needs of the infant, particularly so if he is premature or compromised.

Energy balance in low birth weight infants fed formula of high or low medium-chain triglyceride content

We tested the effect on energy balance of the partial substitution of medium-chain for long-chain triglycerides in the diet of growing low birth weight infants. Fifteen infants were studied in a randomized double-blind crossover clinical trial in which each infant was fed each of two formulas, which were of equal gross energy and protein content but differed in fat composition. The high medium-chain triglyceride (MCT) formula contained medium- and long-chain triglycerides in a weight/weight ratio of 46:54; in the low MCT formula the ratio was 4:96. The hypothesis tested was that under conditions of equal gross energy intake the two diets would differ in their digestible and metabolizable energy contents and would produce differences in the infants' rates of energy expenditure and energy storage. Gross energy intakes averaged 562 and 555 kJ/kg/day (134 and 133 kcal/kg/day) with the high and low MCT formulas, respectively. With each diet, coefficients of energy digestibility (0.93) and metabolizability (0.91) were identical; the rates of energy expenditure were 262 (high MCT) and 265 (low MCT) kJ/kg/day (63 kcal/kg/day for both diets), and of energy storage were 246 (high MCT) and 239 (low MCT) kJ/kg/day (59 and 57 kcal/day). These differences were not significant. There were also no significant differences between the two diets in coefficients of nitrogen retention (mean 0.70) or in rate of weight gain (mean 21.5 gm/kg/day). The use of high MCT content in infant formula neither provided a nutritional advantage in energy digestibility or metabolizability nor resulted in an increased rate of energy expenditure or of energy storage.

Fatty acid balance studies in premature infants fed human milk or formula: effect of calcium supplementation

During the first 4 neonatal weeks, serial total fatty acid and individual fatty acid balance studies were completed in 35 healthy premature infants with appropriate weight for gestational age. Infants weighed less than 1500 gm at birth, were descriptively similar, and were receiving similar volumes of either preterm mothers' milk (PTM) or formula (S-M-A 20). Total fatty acid and major fatty acid contents of the two feeding regimens were similar. Total fecal output and total fatty acid excretion were higher, whereas subsequent total fat absorption and coefficient of absorption were significantly lower, in the group fed S-M-A 20 (P less than 0.001). Administration of oral calcium supplements fed as calcium lactate (1.5 to 2.0 mmol/kg/day) decreased total fatty acid absorption in both the PTM (P less than 0.01) and S-M-A 20 (P less than 0.001) groups. Furthermore, the effect of feeding (P less than 0.0001) and oral calcium (P less than 0.001) independently influenced coefficients of absorption for major fatty acids fed (C12:0, C14:0, C16:0, C18:0, and C18:1). Although the main indices for growth were similar in both feeding groups, infants with inefficient rates of total fatty acid absorption attained slower rates of weight gain and increased skinfold thickness. We conclude that oral calcium supplements significantly alter the efficiency of lipid absorption in enterally fed preterm infants.

Evaluation of a special low birth weight formula, with and without the use of medium chain triacylglycerols

A special low birth weight formula containing 1.8 g/100 ml of medium chain triacylglycerols (Nenatal) was compared with 'modified' Nenatal (medium chain triacylglycerols (MCT) replaced by long chain triacylglycerols (LCT)) and standard modified baby milk (Cow and Gate Premium). 22 infants of birth weight less than 1500 g and gestational age less than 33 weeks were studied for three weeks when enteral feeds were well tolerated. Nenatal was given to all infants for the first and third weeks, during the middle week 11 infants received Premium and 11 infants received modified Nenatal. On Nenatal there was a significant elevation of serum beta-hydroxybutyrate and small amounts of medium chain fatty acids were detected in the serum. Glucose and long chain triacylglycerol levels were similar on all feeds. Incremental weight gain and energetic efficiency of weight gain was significantly greater on Nenatal than on Premium, but there was no difference in this respect between Nenatal and modified Nenatal. We conclude that the use of a special low birth weight formula is associated with increased weight gain, but this is not dependent on the presence of MCT in the feed. Therefore although feeds containing MCT are well tolerated, there seems little advantage in including MCT in the formulation of low birth weight feeds.

Effect of fat and carbohydrate composition on the gastric emptying of isocaloric feedings in premature infants

The gastric emptying of six infant feedings (20 kcal/oz; whey to casein ratio, 60:40) with varying fat and carbohydrate composition was studied. Feedings contained either predominantly long-chain triglycerides (94%) or predominantly medium-chain triglycerides (94%) as the fat and lactose, glucose, or glucose polymers (Polycose) as the carbohydrate. Eleven premature infants were fed 22 ml/kg body wt of all six feedings over a 3-4-day period, and the volume of gastric contents was measured every 20 min using polyethylene glycol 4000 as the marker. Analysis of variance demonstrated that the use of medium-chain triglycerides resulted in faster gastric emptying than long-chain triglycerides (p less than 0.001). Analysis of variance and Tukey's test showed that use of glucose polymers instead of glucose resulted in less volume of gastric contents at 40 min (p less than 0.05). Use of glucose polymers instead of lactose resulted in less volume of gastric contents at 60 and 80 min (p less than 0.05). Gastric emptying can be altered by changes in nutrient composition. The difference between medium-chain and long-chain triglycerides was more pronounced than the differences between the carbohydrates studied. Feedings with medium-chain triglycerides may be more suitable than long-chain triglycerides in patients with delayed gastric emptying.

Fortified mothers' milk for very low birth weight infants: results of growth and nutrient balance studies

Mothers' milk, fortified daily with skim and cream components derived from mature donor human milk, was fed fresh during the first 2 postnatal months to 18 (group FMM) healthy, very low birth weight (VLBW) infants. Following the same feeding protocol, 16 additional VLBW infants were fed commercial formula that had a similar range of energy and nitrogen. Infants were evaluated for growth, metabolizable energy, balances of nitrogen and fat, and biochemical markers of nutritional status. Growth measurements from birth to 1800 gm were similar in the two groups. Nutritional balance was performed at approximately 2.5 (first study period) and 6 (second study period) weeks. Metabolizable energy (average 109 kcal/kg/day) was similar in both groups and met theoretical needs of the growing VLBW infant. Apparent nitrogen retention was similar and equivalent to estimates of intrauterine nitrogen accretion (approximately 325 mg/kg/day). Fat absorption increased from the first (70% of intake) to the second study (80% of intake) and was similar in both groups. Serum values for albumin, total protein, prealbumin, hemoglobin, and creatinine were also similar, and declined with increases in postnatal age. Significant differences were observed between feeding groups for serum phosphorus and calcium. These results indicate that healthy VLBW infants maintain adequate growth and macronutrient balance for the first 2 months postnatally when fed mothers' milk fortified with additional skim and cream components.

Nutrient balance, energy utilization, and composition of weight gain in very-low-birth-weight infants fed pooled human milk or a preterm formula

Growth, protein, and energy balances were studied in two groups of very-low-birth-weight premature infants fed pooled pasteurized human milk (HM) or a preterm formula (PF). Each infant was studied at 33 and 36 weeks gestational age with a combined technique of nutrient balance and indirect calorimetry measurement. Weight and length gains were higher with PF than with HM, but head circumference growth was similar with both milks. Although the volume of milk given was lower, energy intake was higher with PF than with HM in both studies (126 to 130 vs 103 to 109 kcal/kg/day). Percentage of energy absorbed was better with PF than with HM (94% vs 84%) at 33 weeks, and similar (95%) with both milks at 36 weeks. Energy expenditure, which had increased from 33 weeks to 36 weeks, was higher with PF than with HM (57 to 63 vs 46 to 52 kcal/kg/day) during both studies. Energy retention accounted for about 50% of energy absorbed with both milks, but was higher with PF than with HM (60 vs 40 to 50 kcal/kg/day) in both studies, and resulted in fat accretion well above that seen during intrauterine growth for both milks in both studies. Protein intake was higher with PF than with HM (3.1 vs 2.4 gm/kg/day) in both studies, giving a protein accretion similar to the intrauterine accretion with PF (2.2 gm/kg/day), but lower with HM. Our results suggest that the nutritional value of pooled pasteurized human milk for VLBW infants should be reconsidered, especially because of its low protein content, and that energy density of preterm formulas must be questioned in view of elevated fat deposition.

Growth and metabolic response of healthy low birth-weight newborns fed a semi-elemental diet

Twelve normal low birth-weight newborns weighing between 110 and 1765 grams (means +/- SD, 1614 +/- 191) were fed by continuous intragastric drip a semi-elemental diet, providing per kilogram and per day 120 kilocalories, 2.9 grams of proteins, 17.5 grams of carbohydrates, 4.2 grams of fat and 2.4 milliequivalents of sodium. The diet contained a lactalbumin hydrolysate, dextrin maltose, and medium and long chain triglycerides. The newborns regained their birthweight between 6 and 16 days (mean +/- SD, 10.4 +/- 3.1) and gained 14 to 37 grams/day (mean +/- SD, 25.4 +/- 6.8) during the first month of life. The diet proved to be safe and clinically well-tolerated in low birth-weight infants and induced a weight gain similar to the intrauterine growth, once the birthweight had been regained.

Impact of development of the gastrointestinal tract on infant feeding

We have described the developmental pattern of the gastrointestinal tract under optimal conditions (i.e., low risk pregnancy and normal labor and delivery at term). The tissues do not develop simultaneously, and morphologic and functional development are not concurrent. An important consideration is the effect of suboptimal or even adverse conditions on the developmental sequence and attainment of maturity. Malnutrition during both the prenatal and postnatal periods may restrict the morphologic and biochemical development of the gastrointestinal tract. Dietary modifications have been shown to alter the developmental pattern of intestinal and pancreatic enzymes in animal models. Drugs and hormonal therapy given during pregnancy and early infancy have been known to cause developmental defects, but the specific effects on the gastrointestinal tract have not been evaluated. For further understanding of digestibility of nutrients and absorption in the perinatal period, these departures from the normal development of the gastrointestinal tract and the mechanisms by which these potential effects occur remain to be described. In view of these undetermined factors, in the case of intolerance or unavailability of milk from the natural mother, feedings should be individualized, with attention to direct measurement of enzyme concentrations, balance studies, or both, especially in the case of extreme prematurity or unusual requirements.

Effect of oral lipid administration on glucose homeostasis in small-for-gestational-age infants

The metabolic effect of feeding with 1.3 g/kg bw lipids (67% medium chain triglycerides) was studied in 15 small-for-gestational age (SGA) term infants. It was compared to a control group of 7 SGA term infants, to 7 term infants with an appropriate birth weight (AGA) and to 7 AGA preterm infants. Plasma glucose concentration rose from (M +/- SE) 3.6 +/- 0.2 to 4.4 +/- 0.3 mmol/l at 30 min in SGA term infants (p less than 0.01). A similar increase was observed in AGA term and preterm infants. The lipid load produced no change in plasma glucagon concentration but a significant increase in insulin/glucagon molar ratio was observed in AGA term infants only. In term SGA infants, the disappearance rate of glucose in plasma after the lipid load was similar to the control: 1.24% per min. The evolution of blood pyruvate and lactate concentration was not modified by the lipid load. Despite lower concentrations of free fatty acids and ketone bodies (KB) in SGA infants than in AGA term infants, the lipid load induced a 120% increase of ketone bodies in SGA infants and a 40% increase only in AGA infants. These data show that these lipids produce a hyperglycemic response in SGA infants as in AGA infants without any change of the disappearance rate of glucose. They suggest that these lipids can stimulate gluconeogenesis and ketogenesis in SGA infants.

Early postnatal growth of low birthweight infants: what is optimal?

The question as to what is optimal depends on an examination of a number of questions which may be stated as follows: 1) Does physical growth as expressed by height and weight bear any relationship to functional or intellectual development? 2) Should postnatal growth of low birthweight (preterm) infants proceed at their presumed in utero growth rate? 3) Does caloric intake beyond a minimum level influence the growth rate and intellectual development of SGA infants? 4) What is optimal--or do we all need to be the same? These questions imply a projected benefit to nutritional techniques, amounts, and procedures. Against these must be balanced potential hazards which relate to a number of specific factors. These include the effort and expenditure of energies involved in feeding practices. The hazards inherent in gavage, intraluminal, and other forms of forced nutrition. Solute loading and the relationship of solute to free water content. The ommission of specific nutrients from any dietary regimen and the toxicity of other specific contents. A balanced approach combining all of these may best decide what is "optimal".

Fat absorption in low birthweight infants

Studies on the incomplete fat absorption in newborns, particularly preterm ones, are reviewed. In the first week term breastfed newborns have a fat absorption coefficient of 91%. Lyophilization or pasteurigation reduces this figure in term as well as in preterm newborns. Excess Ca++ lowers fat absorption. So far, there is no evidence of immaturity of intracellular fat transport through the enterocyte. In the newborn low pancreatic lipase activity and low intraluminal bile salt concentrations appear to limit fat absorption. The most effective method to improve fat absorption in preterm babies seems to substitute part of the milk fat by medium-chain triglycerides.

History and current status of infant formulas

Formulas that approximate the composition of human milk are widely used as the sole source of nutrients for infants during the first months of life. Such formulas contain milk, soy, or meal proteins, or protein hydrolysates together with those forms of fat carbohydrate, vitamins, and minerals shown to be bioavailable to the infant. Legislation concerning nutrient composition and quality assurance of products labeled as infant formulas has been enacted by Congress. Governmental and industrial standards also help to assure microbiological safety and stability. Problems of nutrient composition and adverse reactions have occurred during the evolution and development of infant formulas. Problems concerning nutrient deficiency are now almost unknown, but adverse reactions of individuals to specific formula ingredients continue. Accurate information on composition and related nutritional properties of infant formulas is essential for their effective use and for the avoidance of undesirable complications.

Effect of oral administration of lipids with 67% medium chain triglycerides on glucose homeostasis in preterm neonates

Since hypoglycemic responses to medium chain triglycerides (MCT) have been reported in adults we studied the effect of an acute oral load of lipids (2,8 g/kg) with 67% MCT on glucose homeostasis in 21 preterm infants in comparison to 14 age-matched control preterm infants. A hyperglycemic response from (mean +/- SEM) 57 +/- 1.1 to 74 +/- 2.5 at 30 min (p less than 0.01) and to 80.5 +/- 2.5 mg/dl at 60 min (p less than 0.01) was observed after administration of the lipids whereas no change in plasma glucose concentration was observed in the control group. After administration of the lipids there was no change in the concentration of insulin and glucagon in plasma. An intravenous glucose tolerance test (1 g/kg) was similar in the control group and 60 min after administration of the lipids. After administration of the lipids free fatty acid concentration remained unchanged while a significant decrease from 304 +/- 56 to 199 +/- 28 muEq/l was observed in 60 min in the control group. At 60 min beta-hydroxybutyrate concentration was higher after lipid administration (630 +/- 86 mumol/l) than in the control group (436 +/- 66 mumol/l) (p less than 0.05). A more rapid decrease in blood lactate concentration was found after lipid administration than in the control group while no change in plasma alanine concentration was observed in either groups. In five additional preterm infants, plasma glucose concentration increased from 56 +/- 0.6 to 75 +/- 0.9 mg/dl (p less than 0.01) 60 minutes after gastric administration of glycerol (0.3 g/kg). These data show that in preterm infants, a lipid load with 67% TCM produces a hyperglycemic response through gluconeogenesis without changing the peripheral rate of glucose disappearance.

Comparative analysis of fecal content of medium and long chain triglycerides using two methods

Accurate assessment of apparent total fat absorption in individuals receiving medium chain triglycerides (MCT) as the predominant source of dietary fat depends upon the method used for fecal fat analysis. Erroneous conclusions may be drawn if the method does not give quantitative recovery of MCT. A simple, previously described, gravimetric technique is shown in this paper to give comparable MCT recoveries to another somewhat more arduous method.

The role of gastric lipolysis on fat absorption and bile acid metabolism in the rat

In vivo studies were carried out in young Sprague-Dawley rats to examine the role of gastric lipolysis on fat absorption and bile acid metabolism. When fed by gastric perfusion 5 times (corn oil, 4 g/day) their usual dietary intake of fat, rats deprived of lingual lipase by the creation of an esophageal fistula had a significant degree of fat and bile acid malabsorption as well as a shortened bile acid half-life when compared to animals with a gastrostomy. The % fat absorption, bile acid loss and bile acid pool were normal in 2 groups of esophageal fistula rats fed the same quantity of corn oil or twice (8 g/day) that amount as a fine emulsion. In view of a negligible gastric lipase activity in animals with an esophageal fistula and of decreased hydrolysis of a triglyceride test meal, these data suggest that gastric lipolysis is of physiological importance in situations where lipolytic mechanisms are stressed by a large fat intkae. Its principal role is to potentiate intestinal lipolysis by facilitating the emulsification of dietary lipids through its formed products and, therefore, the contact of pancreatic lipase with its substrates.

The immature intestine: implications for nutrition of the neonate

The survival and prognosis of the prematurely born human infant are dependent on a successful transition from the intrauterine to the extrauterine environment. This is largely a consequence of the maturation of sufficient gastrointestinal function to provide adequate nutrition. However, the gastrointestinal tract of the premature infant, and to some extent, of the full-term infant, may be unprepared to provide the requisite absorptive function. Data presented in this symposium emphasize the dissociations in the development of human gastrointestinal function. Morphological maturation is completed early in gestation while glucose absorption increases with gestational age. Sucrase and maltase activities appear early; lactase activity begins to increase at 30 weeks and increases steadily to term. The latter pattern is accompanied by increased production of cortisol and thyroid in the fetus. The intraluminal phase of fat digestion is immature even in the full-term neonate. Both pancreatic secretory function and bile salt metabolism mature postnatally. Despite this relative immaturity, breast milk fat is absorbed with great efficiency by the term infant, and breast milk provides other important influences on intestinal development: mitogenic factor, immunological support, control of intestinal flora. The goals of nutrition support of the premature infant have been to maintain intrauterine growth standards; yet premature infants receiving pooled breast milk from mothers at 40 weeks or more may be given too little protein for their needs. Human milk from mothers of premature infants may be a more appropriate nutrient source. Supplements with higher contents of amino acids may lead to amino acid imbalance or hyperammonaemia. Additional stresses and requirements are imposed by illness or congenital anomalies. While we must apply current research findings to clinical care, we must also extend our knowledge of extrauterine human development. The ultimate measure of success in this field will be the physical and neurological capacities of infants followed prospectively.