ABSTRACT
Background
Dietary DHA intake among US toddlers is low. Healthy physical growth is an important objective for the clinical care of children born preterm.
Objectives
The aim of the trial was to examine the effects of supplementing toddlers born preterm with DHA and arachidonic acid (AA) for 180 d on growth and adiposity.
Methods
Omega Tots, a randomized placebo-controlled trial, was conducted between April 2012 and March 2017. Children born at <35 wk gestation who were 10–16 mo in corrected age were assigned to receive daily oral supplements of DHA and AA (200 mg each, “DHA + AA”) or corn oil (placebo) for 180 d. Prespecified secondary outcomes included weight, length, head circumference, mid-upper arm circumference, triceps and subscapular skinfolds, BMI, and their respective z scores, and body fat percentage, which were measured at baseline and trial completion. Mixed-effects regression was used to compare the change in outcomes between the DHA + AA and placebo groups, controlling for baseline values.
Results
Among 377 children included in the analysis (median corrected age = 15.7 mo, 48.3% female), 348 (92.3%) had growth or adiposity data at baseline and trial end. No statistically significant differences between the DHA + AA and placebo groups in growth or adiposity outcomes were observed. For instance, the change in weight-for-age z scores was 0.1 for the DHA + AA group and 0.0 for the placebo group (effect size = 0.01, P = 0.99). However, post-hoc subgroup analyses revealed a statistically significant interaction between treatment group and sex, suggesting somewhat slower linear growth for females assigned to the DHA + AA group compared with the placebo group.
Conclusions
Among toddlers born preterm, daily supplementation with DHA + AA for 180 d resulted in no short-term differences in growth or adiposity compared with placebo. If DHA supplementation is implemented after the first year of life, it can be expected to have no effect on short-term growth or adiposity. This trial is registered with clinicaltrials.gov as NCT02199808.
Keywords: omega fatty acids, preterm birth, docosahexaenoic acid, growth, adiposity, infant, toddler
Introduction
Inadequate nutrition and poor growth in infancy have adverse effects on the long-term development of children born preterm (1). Postnatal growth failure at neonatal intensive care unit (NICU) discharge is common among premature infants and is associated with an increased risk for high blood pressure, glucose intolerance, and abnormal adipose tissue distribution later in life (2–5). Evidence suggests that the growth trajectory of preterm infants lags behind that of term infants (6). On average, premature infants fail to achieve the same catch-up growth as their peers within the first year of life, resulting in growth failure that persists into toddlerhood (7). For instance, poor weight gain during infancy has been associated with weight, length, and head circumference measurements below the 10th percentile at 18–22 mo corrected age (7, 8).
DHA (22:6n–3) (ω-3) and arachidonic acid (20:4n–6) (AA) supplementation have been associated with at least short-term improvements in neurologic development, visual maturation, and growth among preterm infants (9–13). Observational studies have also correlated neonatal DHA concentrations with a lower risk of obesity and adiposity during early childhood (14). DHA accumulation occurs most rapidly during the last trimester and into the early postnatal period (11, 15, 16). As a result of decreased time in utero, infants born prematurely are deprived of intrauterine DHA, resulting in potential deficiency (11).
To date, most clinical trials have focused on DHA supplementation during infancy. However, toddlerhood can be a period of poor growth and also DHA deficiency due to weaning from breastmilk or formula to a low n–3 fatty acid diet (7, 8, 17, 18). Despite the absence of rigorous evidence from large trials supporting supplementation for children born preterm during the second year of life, numerous DHA-supplemented foods and formula products are marketed for toddlers. This trial tested the effect of DHA supplementation on the growth and adiposity of toddlers born preterm.
Methods
Trial design and setting
The study methods were previously reported (19). The trial was a single-site, double-masked, randomized controlled trial that took place at the Nationwide Children's Hospital (NCH) in Columbus, OH, from April 2012 to March 2017 (registered with clinicaltrials.gov as NCT01576783). Trial procedures were approved by the Institutional Review Board at NCH, and written informed consent was obtained from each participant's caregiver.
Participants and trial procedures
Families of children 10–16 mo old (adjusted for prematurity) born at <35 wk gestation who received care at a NICU affiliated with NCH or were referred to the NCH Neonatology Clinic for clinical follow-up were contacted to confirm eligibility and invited to participate in the study. Neonatal data were abstracted from electronic medical records. Eligible children weighed between the 5th and 95th percentiles adjusted for prematurity according to WHO growth standards (20) to ensure that children did not have any weight-related issues that would require dietary modification and affect the ability to detect a treatment effect from the supplement on their growth or adiposity. Furthermore, the children had to have discontinued intake of breastmilk and formula and had English as the family's primary language. Exclusion criteria included: consumption of fatty acid supplements, fatty fish, or nutritional supplements with DHA more than twice weekly; fish, corn or soy allergy; plans to move away; or pre-existing disease or malformation likely to affect study participation.
The baseline visit (day 0) included a caregiver questionnaire about demographics, infant feeding, and health care. Caregivers could select ≥1 race and ethnicity categories for their child to enable comparison with the US preterm population. Caregivers completed a brief DHA and eicosapentaenoic acid (20:5n–3) (EPA) FFQ to estimate children's usual intakes (21).
Anthropometric measurements were collected by trained research staff during the initial study visit and the final visit (180 ± 20 d post-randomization). Children were weighed to the nearest 0.001 g wearing only a clean diaper with the use of a SECA Infant Scale 727 (SECA GmbH & Co KG), and head circumference measurements were collected to the nearest 0.1 cm with the use of head circumference measuring tape (SECA GmbH & Co KG). Recumbent length measurements were collected to the nearest 0.1 cm while the child was fully clothed without shoes and socks with the use of an infantometer (Accurate Technologies Inc.). Upper arm length and mid-upper arm circumference measurements were collected to the nearest 0.1 cm with the use of a Graham-Field Tape Measure (GF Health Products). Subscapular and triceps skinfolds were measured to the nearest 0.1 mm with the use of a skinfold caliper (Holtain Instruments Ltd). Weight, length, head circumference, upper arm length, and mid-upper arm circumference measurements were collected to assess growth. Triceps and subscapular skinfolds were collected and BMI was calculated to assess adiposity. All measurements were recorded 3 times and averaged for analysis. Research staff were trained and recertified annually/biannually to ensure that the estimates for inter- and intra-examiner reliability were in a skillful range (22).
The DHA + AA group was assigned to receive 180 d of daily oral supplementation in the form of dissolvable microencapsulated DHA from Schizochytrium sp. algal oil (200 mg) and AA from fungal Mortierella alpina oil (200 mg) powder (Martek Biosciences Corporation/DSM). The placebo group was assigned to receive 400 mg daily microencapsulated corn oil powder. The 180-d duration was selected to ensure both significant incorporation of DHA into neuronal cell membranes and to maximize study participation. Compliance was calculated as the packets consumed out of those dispensed based on caregiver-completed diaries.
Statistical analysis
A sample size of 488 was projected to detect a statistically significant difference in the trial's primary outcome, the Bayley Scales of Infant and Toddler Development (3rd ed.) Cognitive Composite at trial completion (19). The manufacturer of the investigational product discontinued production after 377 participants were enrolled in the study, thereby capping enrollment, but this limit had a negligible effect on power (377 provided 80% power to detect a 0.29-SD difference in Bayley Scales score). The trial was not specifically powered for the secondary outcomes of the trial. However, our sample size is larger than previous studies that were powered to detect a significant difference in growth and adiposity outcomes (sample sizes of prior studies ranged from 57 to 238) (23–26).
Data analyses were performed with SAS Enterprise Guide version 7.1. All analyses were performed on an intent-to-treat basis according to the treatment group assigned at randomization, regardless of withdrawal from treatment or deviation from the protocol (27). Chi-square test, t test, and Wilcoxon rank sum tests were used to check for balance between the treatment and placebo groups. P values < 0.05 were considered statistically significant. In keeping with current epidemiologic practice (28), correction for multiple comparisons was not made.
Anthropometric measurements were converted to z scores for corrected age based on Child Growth Standards from the WHO (20) with the use of WHO Anthro software (29). Z scores were used in addition to raw scores to minimize the potential effect of age and body size on growth outcomes. BMI was calculated as measured weight in kilograms divided by the square of measured length in meters. Body fat percentage was calculated from body weight and triceps skinfold thicknesses with the use of gender- and race-specific equations from Dezenberg et al. (30) Body fat percentages for males who identified as non-white and non-black and all females were calculated with the use of the equations for white children because of a lack of valid equations for this group. Measuring skinfold thickness is a reliable and noninvasive method for assessing fat distribution in infants and young children and is highly correlated with gold-standard methods such as dual-energy X-ray absorptiometry (31, 32).
Differences in the change in anthropometric measures (raw values and z scores) among treatment groups were analyzed, controlling for baseline scores, with the use of a linear mixed model that uses maximum likelihood estimation and repeated measures to include children with missing outcome data and to accommodate multiple time points, respectively (33, 34). The analysis of growth and adiposity measures included treatment group and time point as terms in the model. A random effect for family was included within the mixed model to account for the statistical dependence caused by including multiples.
Some studies, including the largest DHA trial involving preterm neonates, reported treatment effects on growth specific to some sex and birth weight subgroups (24, 35). Thus, post-hoc subgroup analyses were explored by child sex and birth weight strata (<1500 g compared with ≥1500 g) moderators. Interactions were tested by 3-way interaction terms including time, treatment group, and the moderator for sex or birth weight.
Results
Baseline characteristics
A total of 377 children were enrolled in the trial, with 189 randomly assigned to the DHA + AA group and 188 randomly assigned to the placebo group (Figure 1). The demographics and clinical characteristics of the children and their families were comparable between treatment groups at baseline (Table 1, Supplemental Table 1). Growth and adiposity measures were considered secondary outcomes of the Omega Tots trial, and were available for 92.3% of the children at baseline and the end of the trial. For some children who did not attend the last study visit, growth data were abstracted from a clinical appointment at NCH that was within the eligible window for the last study visit. The median corrected age at baseline was 15.7 mo, 48.3% of the children were female, and there were 55 sets of twins or triplets.
FIGURE 1.
Participant CONSORT flow diagram, Omega Tots trial (n = 377), 2012–2017. AA, arachidonic acid; FCCS, Franklin County Children Services.
TABLE 1.
Participant characteristics at baseline, 10- to 16-mo-old children born preterm (<35 wk gestation) randomly assigned to receive either 180 d of DHA + AA (treatment) or corn oil (placebo), Omega Tots trial (n = 377), 2012–20171
| Characteristics | DHA + AA (n = 189) | Placebo (n = 188) | Total (n = 377) | P |
|---|---|---|---|---|
| Sex | 0.14 | |||
| Male | 105 (55.6) | 90 (47.9) | 195 (51.7) | |
| Female | 84 (44.4) | 98 (52.1) | 182 (48.3) | |
| Child's race | 0.38 | |||
| White/Caucasian | 114 (60.3) | 122 (64.9) | 236 (62.6) | |
| Black/African-American | 52 (27.5) | 53 (28.2) | 105 (27.8) | |
| Asian/Pacific Islander | 2 (1.1) | 1 (0.5) | 3 (0.8) | |
| Other or multiple | 21 (11.1) | 12 (6.4) | 33 (8.8) | |
| Child's ethnicity | 0.45 | |||
| Hispanic | 7 (3.7) | 10 (5.3) | 17 (4.5) | |
| Non-Hispanic | 182 (96.3) | 178 (94.7) | 360 (95.5) | |
| Child age,2 mo | 17.3 [15.7, 18.3] | 17.4 [15.3, 18.4] | 17.3 [15.6, 18.4] | 0.80 |
| Child age,3 mo | 15.7 [13.8, 16.5] | 15.6 [13.1, 16.5] | 15.7 [13.6, 16.5] | 0.66 |
| Gestational age at delivery, completed weeks | 32.0 [30.0, 34.0] | 32.0 [30.0, 34.0] | 32.0 [30.0, 34.0] | 0.79 |
| Small for gestational age | 32 (16.9) | 32 (17.0) | 64 (17.0) | 1.00 |
| Birth weight, g | 1705.4 ± 534.3 | 1749.5 ± 570.4 | 1727.4 ± 552.3 | 0.44 |
| Dietary DHA + EPA intake before randomization, mg/d | 44.3 [29.8, 83.5] | 55.3 [26.0, 95.0] | 48.0 [26.8, 90.8] | 0.55 |
| Received human milk | 168 (88.9) | 163 (86.7) | 331 (87.8) | 0.52 |
| Human milk feeding duration, d | 117 [44.0, 269.0] | 101 [40.5, 209.0] | 113.0 [44.0, 239.0] | 0.30 |
| Maternal age, y | 30.6 ± 6.1 | 30.7 ± 7.1 | 30.7 ± 6.6 | 0.86 |
| Maternal education | 0.45 | |||
| High school/GED or less | 46 (24.3) | 56 (29.8) | 102 (27.1) | |
| Some college/associate's degree | 73 (38.6) | 59 (31.4) | 132 (35.0) | |
| Bachelor's degree or higher | 68 (36.0) | 69 (36.7) | 137 (36.3) | |
| Spouse/partner education | 0.51 | |||
| High school/GED or less | 36 (28.6) | 25 (22.1) | 61 (25.5) | |
| Some college/associate's degree | 48 (38.1) | 45 (39.8) | 93 (38.9) | |
| Bachelor's degree or higher | 42 (33.3) | 43 (38.1) | 85 (35.6) | |
| Maternal marital status | 0.86 | |||
| Married or living with partner | 126 (66.7) | 115 (61.1) | 241 (63.9) | |
| Separated or divorced | 7 (3.7) | 8 (4.2) | 15 (3.9) | |
| Single never married or not living with partner | 52 (27.5) | 52 (27.7) | 104 (27.6) | |
| Household size, members | 4.0 [3.0, 5.0] | 4.0 [3.0, 5.0] | 4.0 [3.0, 5.0] | 0.78 |
| Public or no health insurance | 96 (50.8) | 91 (48.4) | 187 (49.6) | 0.76 |
| Annual household income <$35,000 | 85 (45.0) | 89 (47.3) | 174 (46.2) | 0.88 |
| Have a medical home | 58 (55.2) | 49 (49.0) | 107 (52.2) | 0.37 |
| Sets of twins or triplets | 29 (15.3) | 26 (13.8) | 55 (14.6) | 0.46 |
| Attended neonatology follow-up clinic | 102 (54.0) | 107 (56.9) | 209 (55.4) | 0.56 |
Values are n (%), medians [IQRs], or means ± SDs. No differences between groups at baseline based on chi-square, t test, or Wilcoxon rank sum test P < 0.05. Children with missing data included: 1 for birth weight and small for gestational age, 1 for DHA + EPA intake, 4 for human milk feeding duration (among those who were fed human milk), 5 for maternal age, 6 for maternal education, 2 for partner's education, 17 for marital status, 5 for health insurance, 5 for annual income, 9 for medical home (among those who were surveyed), and 2 for household members. GED, General Education Development.
Age is unadjusted for prematurity.
Age is adjusted for prematurity.
Adherence and adverse events
Children consumed 80.6% of the packets (80.6% in the DHA + AA group, 80.7% in the placebo group, of children with adherence data). No complaints about products’ sensory characteristics were reported. Two hundred fifty-six children experienced ≥1 adverse event, totaling 683 adverse events, mainly minor gastrointestinal illness and respiratory infections. Adverse events by organ system were not significantly different between children randomized to the treatment and placebo groups: ears, nose, and throat (DHA + AA, 29 of 189 compared with placebo, 33 of 188; P = 0.56), gastrointestinal (DHA + AA, 69 of 189 compared with placebo, 63 of 188; P = 0.54), respiratory (DHA + AA, 23 of 189 compared with placebo, 22 of 188; P = 0.88), skin/limb (DHA + AA, 12 of 189 compared with placebo 18 of 188, P = 0.25), behavioral (DHA + AA, 22 of 189 compared with placebo, 19 compared with 188; P = 0.63), and miscellaneous (DHA + AA, 35 of 189 compared with placebo, 41 of 188; P = 0.42). All adverse events were reviewed by the study doctor and principal investigator.
Growth and adiposity
There were no statistically significant differences in growth or change in adiposity between the DHA + AA and placebo groups (Table 2). Length- and weight-for-age z scores increased slightly in both groups, whereas skinfold z scores and body fat percentage decreased. The mean change in length-for-age z score was 0.1 for the DHA + AA group and 0.2 for the placebo group (effect size = −0.11, P = 0.27). The change in weight-for-age z scores was 0.1 for the DHA + AA group and 0.0 for the placebo group (effect size = 0.01, P = 0.99); the change for subscapular skinfold-for-age z score was −0.2 for the DHA + AA group and −0.2 for the placebo group (effect size = −0.02, P = 0.82), and the change in body fat percentage was −0.4% for the DHA + AA group and −0.7% for placebo (effect size = 0.08, P = 0.46).
TABLE 2.
Change from baseline to trial completion for growth and adiposity outcome measures in 10- to 16-mo-old (adjusted for prematurity) children born preterm (<35 wk gestation) randomized to receive either 180 d of DHA + AA (treatment) or corn oil (placebo), Omega Tots Trial (n = 377), 2012–20171
| DHA group | Placebo group | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| Growth and adiposity outcomes | Baseline (n = 189) | Day 180 (n = 179) | Mean change | Baseline (n = 188) | Day 180 (n = 169) | Mean change | Difference in change2 | Effect size | P |
| Length, cm | 78.4 ± 3.4 | 84.5 ± 3.6 | 6.1 ± 2.5 | 77.6 ± 3.7 | 84.2 ± 3.6 | 6.6 ± 2.5 | −0.3 (−0.9, 0.2) | −0.14 | 0.20 |
| Length-for-age z score | 0.0 ± 1.2 | 0.1 ± 1.1 | 0.1 ± 0.9 | −0.2 ± 1.1 | 0.1 ± 1.0 | 0.2 ± 0.9 | −0.1 (−0.3, 0.1) | −0.11 | 0.27 |
| Weight, kg | 10.2 ± 1.0 | 11.5 ± 1.3 | 1.3 ± 0.7 | 10.1 ± 1.1 | 11.5 ± 1.3 | 1.3 ± 0.6 | 0.0 (−0.1, 0.2) | 0.03 | 0.80 |
| Weight-for-age z score | 0.1 ± 0.9 | 0.1 ± 0.9 | 0.1 ± 0.4 | 0.2 ± 0.8 | 0.2 ± 0.9 | 0.0 ± 0.4 | 0.0 (−0.1, 0.1) | 0.01 | 0.99 |
| Head circumference, cm | 46.9 ± 1.6 | 48.0 ± 1.6 | 1.0 ± 0.9 | 46.9 ± 1.8 | 48.0 ± 1.9 | 1.0 ± 0.7 | 0.1 (−0.1, 0.2) | 0.06 | 0.59 |
| Head circumference-for-age z score | 0.5 ± 1.0 | 0.5 ± 1.1 | −0.0 ± 0.6 | 0.6 ± 1.2 | 0.6 ± 1.3 | −0.1 ± 0.5 | 0.1 (−0.1, 0.2) | 0.09 | 0.39 |
| Mid-upper arm circumference, cm | 15.4 ± 1.1 | 15.7 ± 1.2 | 0.3 ± 0.9 | 15.4 ± 1.1 | 15.9 ± 1.2 | 0.4 ± 0.9 | −0.1 (−0.3, 0.1) | −0.12 | 0.25 |
| Mid-upper arm circumference z score | 0.7 ± 0.9 | 0.7 ± 0.9 | 0.0 ± 0.8 | 0.7 ± 0.9 | 0.8 ± 0.9 | 0.1 ± 0.7 | −0.1 (−0.3, 0.1) | −0.12 | 0.25 |
| Triceps skinfold, mm | 10.7 ± 1.9 | 10.4 ± 2.0 | −0.2 ± 1.5 | 11.1 ± 2.2 | 10.9 ± 2.3 | −0.3 ± 1.9 | 0.0 (−0.3, 0.4) | 0.02 | 0.86 |
| Triceps skinfold-for-age z score | 1.4 ± 0.8 | 1.4 ± 0.9 | −0.0 ± 0.7 | 1.6 ± 1.0 | 1.5 ± 1.0 | −0.1 ± 0.8 | 0.0 (−0.1, 0.2) | 0.02 | 0.85 |
| Subscapular skinfold, mm | 6.9 ± 1.7 | 6.6 ± 2.1 | −0.2 ± 1.7 | 7.2 ± 1.7 | 6.7 ± 1.6 | −0.5 ± 1.4 | 0.2 (−0.2, 0.5) | 0.10 | 0.34 |
| Subscapular skinfold-for-age z score | 0.3 ± 1.2 | 0.1 ± 1.3 | −0.2 ± 0.8 | 0.5 ± 1.2 | 0.3 ± 1.2 | −0.2 ± 0.9 | −0.0 (−0.2, 0.2) | −0.02 | 0.82 |
| BMI, percentile | 16.6 ± 1.6 | 16.1 ± 1.6 | −0.5 ± 1.3 | 16.8 ± 1.3 | 16.2 ± 1.4 | −0.7 ± 1.1 | 0.1 (−0.2, 0.3) | 0.08 | 0.43 |
| BMI-for-age z score | 0.2 ± 1.1 | 0.2 ± 1.2 | −0.0 ± 0.9 | 0.4 ± 0.9 | 0.3 ± 1.0 | −0.1 ± 0.8 | 0.1 (−0.1, 0.2) | 0.07 | 0.53 |
| Weight-for-length z score | 0.2 ± 1.0 | 0.1 ± 1.1 | 0.0 ± 0.9 | 0.3 ± 0.9 | 0.2 ± 1.0 | −0.1 ± 0.7 | 0.1 (−0.1, 0.2) | 0.10 | 0.36 |
| Body fat percentage | 16.9 ± 2.8 | 16.4 ± 3.0 | −0.4 ± 2.0 | 17.5 ± 3.0 | 16.8 ± 2.9 | −0.7 ± 2.3 | 0.2 (−0.3, 0.6) | 0.08 | 0.46 |
Values are means ± SDs, frequencies, difference in change (95% CIs), Cohen's d effect sizes, and P values.
Difference in change column is based on a mixed-effects model that uses maximum likelihood to account for missing data.
Post-hoc subgroup analyses showed there was a statistically significant interaction between treatment group and sex for length (P = 0.04) and length-for-age z score (P = 0.04) (Table 3). Females in the placebo group showed a greater increase in length than the DHA + AA group did (difference in means for length: −0.9 cm; 95% CI: −1.7, −0.1 cm; effect size = −0.34; P = 0.03; difference in means for length-for-age z score −0.3; 95% CI: −0.5, −0.0; effect size = −0.31; P = 0.03). No other statistically significant differences were observed for other outcome measures for females. In contrast, treatment group assignment was not associated with increase in length among males (difference in means for length: 0.2 cm; 95% CI: −0.4, 0.9; effect size = 0.09, P = 0.53; difference in means for length-for-age z score 0.1; 95% CI: −0.1, 0.3; effect size = 0.12; P = 0.40) (Table 3). No statistically significant interaction was observed between treatment group and birth weight (<1500 g compared with ≥1500 g) for any of the outcomes (Supplemental Table 2).
TABLE 3.
Change from baseline to trial completion for growth and adiposity outcome measures in 10- to 16-mo-old (adjusted for prematurity) children born preterm (<35 wk gestation) randomly assigned to receive either 180 d of DHA + AA (treatment) or corn oil (placebo), stratified by sex, Omega Tots Trial (n = 377), 2012–20171
| DHA group | Placebo group | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| Growth and adiposity outcomes | Baseline | Day 180 | Mean change | Baseline | Day 180 | Mean change | Difference in change2 | Effect size | P |
| Males | (n = 105) | (n = 99) | (n = 90) | (n = 82) | |||||
| Length, cm | 78.7 ± 3.2 | 84.8 ± 3.2 | 6.1 ± 2.5 | 78.5 ± 3.4 | 84.3 ± 3.4 | 6.0 ± 2.1 | 0.2 (−0.4, 0.9) | 0.09 | 0.53 |
| Length-for-age z score | −0.1 ± 1.1 | 0.0 ± 1.1 | 0.2 ± 0.9 | −0.3 ± 1.1 | −0.2 ± 1.0 | 0.1 ± 0.8 | 0.1 (−0.1, 0.3) | 0.12 | 0.40 |
| Weight, kg | 10.4 ± 1.0 | 11.7 ± 1.0 | 1.3 ± 0.7 | 10.5 ± 1.0 | 11.7 ± 1.1 | 1.2 ± 0.5 | 0.1 (−0.1, 0.3) | 0.18 | 0.23 |
| Weight-for-age z score | 0.1 ± 0.8 | 0.1 ± 0.8 | 0.1 ± 0.4 | 0.1 ± 0.8 | 0.1 ± 0.8 | −0.0 ± 0.3 | 0.1 (−0.0, 0.2) | 0.18 | 0.21 |
| Head circumference, cm | 47.4 ± 1.6 | 48.4 ± 1.5 | 1.0 ± 0.9 | 47.6 ± 1.5 | 48.7 ± 1.5 | 1.0 ± 0.7 | −0.1 (−0.3, 0.2) | −0.08 | 0.57 |
| Head circumference-for-age z score | 0.6 ± 1.0 | 0.5 ± 1.1 | −0.1 ± 0.5 | 0.7 ± 1.1 | 0.6 ± 1.1 | −0.1 ± 0.5 | −0.1 (−0.2, 0.1) | −0.10 | 0.49 |
| Mid-upper arm circumference, cm | 15.6 ± 1.0 | 15.9 ± 1.1 | 0.3 ± 0.9 | 15.6 ± 1.1 | 15.9 ± 1.1 | 0.3 ± 0.9 | −0.1 (−0.3, 0.2) | −0.06 | 0.66 |
| Mid-upper arm circumference z score | 0.7 ± 0.8 | 0.7 ± 0.9 | 0.0 ± 0.7 | 0.7 ± 0.9 | 0.7 ± 0.9 | 0.1 ± 0.8 | −0.1 (−0.3, 0.2) | −0.07 | 0.64 |
| Triceps skinfold, mm | 10.5 ± 1.8 | 10.3 ± 2.0 | −0.1 ± 1.4 | 11.1 ± 2.3 | 10.5 ± 2.0 | −0.7 ± 1.8 | 0.4 (−0.1, 0.8) | 0.23 | 0.12 |
| Triceps skinfold-for-age z score | 1.4 ± 0.8 | 1.4 ± 0.9 | 0.0 ± 0.7 | 1.6 ± 1.0 | 1.5 ± 0.9 | −0.2 ± 0.8 | 0.2 (−0.1, 0.4) | 0.20 | 0.18 |
| Subscapular skinfold, mm | 6.8 ± 1.7 | 6.3 ± 1.5 | −0.5 ± 1.0 | 7.4 ± 1.8 | 6.6 ± 1.4 | −0.7 ± 1.5 | 0.0 (−0.3, 0.3) | 0.03 | 0.83 |
| Subscapular skinfold-for-age z score | 0.2 ± 1.3 | 0.0 ± 1.3 | −0.2 ± 0.8 | 0.6 ± 1.2 | 0.3 ± 1.1 | −0.3 ± 0.8 | −0.0 (−0.3, 0.2) | −0.02 | 0.92 |
| BMI, percentile | 16.8 ± 1.6 | 16.3 ± 1.5 | −0.5 ± 1.5 | 17.0 ± 1.3 | 16.4 ± 1.3 | −0.7 ± 1.0 | 0.1 (−0.3, 0.4) | 0.05 | 0.72 |
| BMI-for-age z score | 0.3 ± 1.1 | 0.3 ± 1.2 | −0.0 ± 1.0 | 0.4 ± 0.9 | 0.3 ± 1.0 | −0.1 ± 0.8 | 0.0 (−0.2, 0.3) | 0.01 | 0.93 |
| Weight-for-length z score | 0.2 ± 1.0 | 0.2 ± 1.1 | 0.0 ± 1.0 | 0.3 ± 0.8 | 0.3 ± 0.9 | −0.1 ± 0.6 | 0.1 (−0.2, 0.3) | 0.09 | 0.55 |
| Body fat percentage | 16.8 ± 2.8 | 16.2 ± 2.8 | −0.5 ± 1.8 | 17.8 ± 3.2 | 16.6 ± 2.8 | −1.3 ± 2.4 | 0.4 (−0−0.2, 1.0) | 0.19 | 0.19 |
| Females | (n = 84) | (n = 80) | (n = 98) | (n = 87) | |||||
| Length, cm | 78.0 ± 3.6 | 84.0 ± 4.0 | 6.1 ± 2.5 | 76.8 ± 3.7 | 84.1 ± 3.8 | 7.1 ± 2.8 | −0.9 (−1.7, −0.1) | −0.34 | 0.03 |
| Length-for-age z score | 0.2 ± 1.2 | 0.2 ± 1.2 | 0.0 ± 0.8 | −0.1 ± 1.1 | 0.3 ± 1.0 | 0.3 ± 0.9 | −0.3 (−0.5, −0.0) | −0.31 | 0.03 |
| Weight, kg | 9.9 ± 1.1 | 11.2 ± 1.5 | 1.4 ± 0.7 | 9.8 ± 1.2 | 11.3 ± 1.5 | 1.4 ± 0.7 | −0.1 (−0.3, 0.1) | −0.10 | 0.51 |
| Weight-for-age z score | 0.2 ± 0.9 | 0.2 ± 1.0 | 0.0 ± 0.3 | 0.2 ± 0.9 | 0.3 ± 0.9 | 0.1 ± 0.4 | −0.1 (−0.2, 0.0) | −0.19 | 0.23 |
| Head circumference, cm | 46.2 ± 1.5 | 47.4 ± 1.6 | 1.2 ± 1.0 | 46.3 ± 1.9 | 47.4 ± 2.0 | 1.0 ± 0.7 | 0.2 (−0.1, 0.4) | 0.19 | 0.24 |
| Head circumference-for-age z score | 0.4 ± 1.1 | 0.5 ± 1.2 | 0.1 ± 0.8 | 0.5 ± 1.3 | 0.5 ± 1.4 | −0.1 ± 0.5 | 0.2 (−0.0, 0.4) | 0.30 | 0.07 |
| Mid-upper arm circumference, cm | 15.2 ± 1.2 | 15.5 ± 1.2 | 0.3 ± 1.0 | 15.3 ± 1.1 | 15.8 ± 1.3 | 0.4 ± 0.8 | −0.2 (−0.4, 0.1) | −0.17 | 0.28 |
| Mid-upper arm circumference z score | 0.6 ± 1.0 | 0.6 ± 1.0 | 0.0 ± 0.8 | 0.8 ± 0.9 | 0.9 ± 1.0 | 0.1 ± 0.6 | −0.1 (−0.3, 0.1) | −0.16 | 0.30 |
| Triceps skinfold, mm | 10.8 ± 2.0 | 10.6 ± 2.1 | −0.3 ± 1.5 | 11.1 ± 2.1 | 11.1 ± 2.5 | 0.0 ± 1.8 | −0.3 (−0.9, 0.2) | −0.20 | 0.22 |
| Triceps skinfold-for-age z score | 1.5 ± 0.9 | 1.4 ± 0.9 | −0.1 ± 0.6 | 1.6 ± 0.9 | 1.6 ± 1.0 | 0.0 ± 0.8 | −0.1 (−0.4, 0.1) | −0.20 | 0.22 |
| Subscapular skinfold, mm | 7.0 ± 1.6 | 7.1 ± 2.6 | 0.1 ± 2.3 | 7.1 ± 1.6 | 6.8 ± 1.7 | −0.3 ± 1.2 | 0.4 (−0.2, 0.9) | 0.21 | 0.20 |
| Subscapular skinfold-for-age z score | 0.4 ± 1.2 | 0.2 ± 1.3 | −0.1 ± 0.8 | 0.4 ± 1.2 | 0.3 ± 1.2 | −0.1 ± 0.9 | −0.0 (−0.3, 0.3) | −0.02 | 0.91 |
| BMI, percentile | 16.3 ± 1.5 | 15.8 ± 1.7 | −0.4 ± 1.1 | 16.6 ± 1.3 | 16.0 ± 1.5 | −0.7 ± 1.2 | 0.2 (−0.2, 0.5) | 0.13 | 0.40 |
| BMI-for-age z score | 0.1 ± 1.0 | 0.1 ± 1.2 | 0.0 ± 0.8 | 0.4 ± 0.9 | 0.2 ± 1.1 | −0.2 ± 0.8 | 0.1 (−0.1, 0.4) | 0.15 | 0.33 |
| Weight-for-length z score | 0.1 ± 1.0 | 0.1 ± 1.1 | −0.0 ± 0.7 | 0.3 ± 0.9 | 0.2 ± 1.0 | −0.2 ± 0.7 | 0.1 (−0.1, 0.3) | 0.12 | 0.43 |
| Body fat percentage | 17.0 ± 2.8 | 16.7 ± 3.2 | −0.2 ± 2.3 | 17.3 ± 2.7 | 17.0 ± 3.0 | −0.2 ± 2.0 | 0.0 (−0.7, 0.7) | 0.00 | 1.00 |
Values are means ± SDs, frequencies, difference in change (95% CIs), Cohen's d effect sizes, and P-values. P values for interactions: length, 0.04; length-for-age z score, 0.04; weight, 0.16; weight-for-age z score, 0.06; head circumference-for-age z score, 0.07, triceps skinfold measurement, 0.06; and triceps skinfold-for-age z score, 0.09.
Difference in change column is based on a mixed effects model that uses maximum likelihood to account for missing data.
Discussion
In this randomized controlled trial, daily supplementation with 200 mg DHA and 200 mg AA did not affect the growth or adiposity of toddlers born preterm. Post-hoc subgroup analyses revealed a statistically significant interaction between treatment group and sex, suggesting somewhat slower linear growth for females assigned to the DHA + AA group compared with the placebo group. This effect was mild and could have resulted from chance or because girls and boys may have different nutritional requirements and therefore respond differently to supplementation. No other moderating effects by sex or birth weight were observed.
Although supplementation during toddlerhood has not been the focus of previous trials, several studies have examined the effect of long-chain polyunsaturated fatty acids (LCPUFAs), more specifically DHA and AA, on the growth of infants born preterm. Findings have been inconsistent, resulting in controversy over whether these LCPUFAs are essential nutrients for the physical growth and development of preterm infants (36, 37). Vanderhoof et al. (12) and Lapillonne et al. (38) reported no significant differences in weight, length, or head circumference at 92 wk postconceptional age and 28 d after establishment of oral feeding, respectively. In contrast, Innis et al. (23) and Clandinin et al. (11) found that preterm infants fed supplemented formula containing DHA and AA had significantly higher weight and length measurements than infants randomly assigned to receive the control formula. One trial found no short-term differences in growth outcomes at expected date of delivery and 4 or 12 mo corrected age but did observe a later effect for children born preterm—at 18 mo the higher DHA group had a greater increase in length and length-for-age z score than the standard DHA group (35).
Similar to our findings, several studies reported differences in response to LCPUFA supplementation by sex (16, 24, 25, 39). Fewtrell et al. (25) reported significantly greater weight, weight gain, and linear growth from birth to 9 mo among males randomly assigned to receive a formula supplemented with DHA and γ-linolenic acid. At 18 mo, the interaction between diet and sex for weight and weight gain was no longer present (25). Findings from a 10-y follow-up of these children found that girls who received the DHA + γ-linolenic acid supplement had significantly higher weight and head circumference, height, suprailiac and biceps skinfold thickness, and blood pressure (24). Shared genome- and sex-specific differences in metabolic conversion of α-linolenic acid to EPA and DHA have been cited as potential explanations for the differential response by sex to LCPUFA supplementation (40). However, results from a recent Cochrane review indicate that there have been no consistent sex-specific findings regarding LCPUFA supplementation during infancy for children born preterm (36). Thus, further research is needed to clarify whether there is indeed differential response to LCPUFA supplementation by sex among children born preterm that cannot be explained by methodologic limitations (e.g., small sample size) and if so, what mechanisms contribute to that response (40).
Inconsistent findings from previous randomized controlled trials can be attributed to variation in sample size, inclusion/exclusion criteria, dose and source of LCPUFAs, method of supplementation, and compliance (36). Clandinin et al. (11) and Innis et al. (23) fed participants formula or human milk with similar doses of DHA and AA derived from fungal and algal oil sources, which could possibly explain the significant increase in weight and length found in both studies. In contrast, O'Connor et al. (16) supplemented formula with DHA and AA derived from fish and fungal oil. The varying doses and sources of LCPUFAs could potentially explain the different results found between the trials. Past animal studies have shown that n–3 fatty acids derived from animal sources (e.g., fish oil) may be more beneficial in terms of tissue incorporation and lowering n–3/n–6 fatty acid ratios than those derived from plant sources (e.g., linseed oil) (41, 42). Furthermore, the method of LCPUFA supplementation could also potentially explain the differences in findings between various trials. Some trials provided supplementation to mothers during pregnancy or during lactation, whereas others have supplemented infants during their NICU stay (23, 43, 44). Another explanation for the inconsistent findings could be that some studies recruited participants who were smaller and sicker at birth. For example, Lapillonne et al. (38) enrolled infants with very low birth weights (700–1500 g) and an average gestational age of 28.8 wk. Our study involved a sample of premature children with an average birth weight of 1727.4 ± 552.3 g and a median gestational age of 32 wk, which could explain why we did not observe a statistically significant change in growth or adiposity.
Several factors can influence growth and adiposity outcomes among toddlers born preterm, such as diet and physical activity, current health status, and access to medical care. At baseline, the proportion of children fed human milk, the duration of human milk feeding prior to the trial, estimated dietary intakes of DHA + EPA, macronutrients and total energy, sex, and birth weight were balanced between groups. Furthermore, baseline red blood cell concentrations of DHA and AA were comparable between the intervention (median DHA concentration: 1.0 mol%; IQR: 0.8, 1.1 mol%; median AA concentration: 5.7 mol%; IQR: 4.9, 6.6 mol%) and placebo (median DHA concentration: 0.9 mol%; IQR: 0.8, 1.1 mol%; median AA concentration: 5.6 mol%; IQR: 4.8, 6.4 mol%) groups (19). However, data on physical activity were not collected because there were no valid tools to assess physical activity in 1-y-old children at the time the study was designed. The fact that baseline characteristics were balanced between groups allows us to rule out those factors as alternative explanations for treatment effects. Unbalanced groups based on sociodemographics and lack of data on dietary intake, fatty acid biomarkers, and compliance have recently been cited as a problem in previous fatty acid trials that may have contributed to inconsistencies in results (45).
The strengths of this study include its large, socioeconomically diverse sample, broad inclusion criteria to improve generalizability to the preterm population, masking, and research-trained anthropometrists. As in typical growth studies, we studied a number of outcomes to form a comprehensive understanding of the growth and adiposity of children born preterm. However, the number of analyses required could mean that our findings for females were due to chance.
The study was powered for the primary outcome, not to detect subgroup differences. Some children were lost to follow-up, but our statistical methods leveraged their baseline data in estimating treatment effects through the use of a mixed-effects regression approach that uses maximum likelihood to include children with missing outcome data (33, 34). As a trade-off for our broad inclusion criteria, the median gestational age of children in this study was higher than several of the infant trials. This increased heterogeneity may have made it more difficult to detect treatment effects. Also, our intervention was not adjusted per kilogram of body weight. However, we believe that this did not have any impact on our results, given that there was very little variation in baseline weight among the children in this study (e.g., DHA + AA:10.2 ± 1.0 kg; placebo:10.1 ± 1.1 kg) and the short duration of the trial means that the child's weight increased by only a little more than 1 kg on average. Long-term follow-up of this cohort would help clarify whether supplementation during toddlerhood has detectable effects later.
This trial examined the effect of DHA + AA supplementation on the growth and adiposity of toddlers born preterm. Little is known regarding the optimal dose of DHA required to support optimal growth during toddlerhood. Although we detected no treatment effect on growth and adiposity, our findings are informative. Given the growing number of DHA-supplemented foods and formulas marketed for toddlers, the results from the Omega Tots trial are promising because they show no effect of DHA + AA supplementation on short-term growth or adiposity of children. If DHA supplementation is implemented after the first year of life, no clinically important effect is expected on short-term growth or adiposity.
Supplementary Material
Acknowledgments
We thank Seanceray Bellinger, Holly Blei, Ashlea Braun, Anne Brown, Lautaro Cabrera, Chelsea Dillon, Ava Fabian, Connor Grannis, Rachel Haeuptle, Nathan Hanna, Chenali Jayadeva, Sarah Landry, Julia Less, Cara Lucke, Melissa Kwitowski, Joseph Macklin, Krista McManus, Emily Messick, Yvette Noah, Grace Pelak, Whitney Phillips, Evan Plunkett, John Rissell, Rachel Ronau, Ashley Ronay, Katie Smith, Sarah Snyder, Reena Oza-Frank, Kamma Smith, and Justin Jackson of the NCH for data collection and administrative support. The authors’ responsibilities were as follows—SAK, KMB, MAN, MAK, ANT, and KOY: designed research; SAK, KMB, and MAN: conducted research; RL and JR: analyzed data; TTI: wrote the paper; RL, SAK, KMB, MAK, JR, ANT, KOY, and KWS: revised the manuscript for important intellectual content; SAK: had primary responsibility for the final content; and all authors: read and approved the final version of the manuscript.
Notes
Supported by the US Health Resources and Services Administration (R40MC28316), the March of Dimes (12-FY14-171), the Allen Foundation, Cures Within Reach, the National Center for Advancing Translational Sciences/National Institutes of Health (UL1TR001070), and internal support from the Research Institute at Nationwide Children's Hospital. Martek Biosciences Corporation of DSM provided the investigational products at no cost. Neither the study sponsors nor product providers had a role in the study design; the collection, analysis and interpretation of data; writing of this report; or the decision to submit the manuscript for publication.
Author disclosures: TTI, RL, KM, JR, MAK, ANT, KOY, MAN, KWS, and SAK, no conflicts of interest.
Supplemental Tables 1 and 2 are available from the “Supplementary data” link in the online posting of the article and from the same link in the online table of contents at https://academic.oup.com/jn/.
Abbreviations used: AA, arachidonic acid; LCPUFA, long-chain polyunsaturated fatty acid; NCH, Nationwide Children's Hospital; NICU, neonatal intensive care unit.
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