The effect of smell and taste of milk during tube feeding of preterm infants (the Taste trial): a protocol for a randomised controlled trial

Exposure to the smell and taste of milk to accelerate feeding in preterm infants

BACKGROUND

Preterm infants (born before 37 weeks' gestation) are often unable to co-ordinate sucking, swallowing, and breathing for oral feeding because of their immaturity. In such cases, initial nutrition is provided by orogastric or nasogastric tube feeding. Feeding intolerance is common and can delay attainment of full enteral and sucking feeds, prolonging the need for nutritional support and the hospital stay. Smell and taste play an important role in the activation of physiological pre-absorptive processes that contribute to food digestion and absorption. However, during tube feeding, milk bypasses the nasal and oral cavities, limiting exposure to the smell and taste of milk. Provision of the smell and taste of milk with tube feeds offers a non-invasive and low-cost intervention that, if effective in accelerating the transition to enteral feeds and subsequently to sucking feeds, would bring considerable advantages to infants, their families, and healthcare systems.

OBJECTIVES

To assess whether exposure to the smell or taste (or both) of breastmilk or formula administered with tube feeds can accelerate the transition to full sucking feeds without adverse effects in preterm infants.

SEARCH METHODS

We conducted searches in CENTRAL, MEDLINE, Embase, CINAHL, and Epistemonikos to 26 April 2023. We also searched clinical trial databases and conference proceedings.

SELECTION CRITERIA

We included randomised and quasi-randomised studies that evaluated exposure versus no exposure to the smell or taste of milk (or both) immediately before or at the time of tube feeds.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected studies, assessed risk of bias, and extracted data according to Cochrane Neonatal methodology. We performed meta-analyses using risk ratios (RRs) for dichotomous data and mean differences (MDs) for continuous data, with their respective 95% confidence intervals (CIs). We used GRADE to assess the certainty of evidence.

MAIN RESULTS

We included eight studies (1277 preterm infants). Seven studies (1244 infants) contributed data for meta-analysis. The evidence suggests that exposure to the smell and taste of milk with tube feeds has little to no effect on time taken to reach full sucking feeds (MD -1.07 days, 95% CI -2.63 to 0.50; 3 studies, 662 infants; very low-certainty evidence). Two studies reported no adverse effects related to the intervention. The intervention may have little to no effect on duration of parenteral nutrition (MD 0.23 days, 95% CI -0.24 to 0.71; 3 studies, 977 infants; low-certainty evidence), time to reach full enteral feeds (MD -0.16 days, 95% CI -0.45 to 0.12; 1 study, 736 infants; very low-certainty evidence) or risk of necrotising enterocolitis (RR 0.93, 95% CI 0.47 to 1.84; 2 studies, 435 infants; low-certainty evidence), although the evidence for time to reach full enteral feeds is very uncertain. Exposure to the smell and taste of milk with tube feeds probably has little to no effect on risk of late infection (RR 1.14, 95% CI 0.74 to 1.75; 2 studies, 436 infants; moderate-certainty evidence). There were no data available to assess feeding intolerance. The included studies had small sample sizes and methodological limitations, including unclear or lack of randomisation (four studies), lack of blinding of participants and personnel (five studies), unclear or lack of blinding of the outcome assessor (all eight studies), and different inclusion criteria and methods of administering the interventions.

AUTHORS' CONCLUSIONS

The results of our meta-analyses suggest that exposure to the smell and taste of milk with tube feeds may have little to no effect on time to reach full sucking feeds and time to reach full enteral feeds. We found no clear difference between exposure and no exposure to the smell or taste of milk on safety outcomes (adverse effects, necrotising enterocolitis, and late infection). Results from one ongoing study and two studies awaiting classification may alter the conclusions of this review. Future research should examine the effect of exposing preterm infants to the smell and taste of milk with tube feeds on health outcomes during hospitalisation, such as attainment of feeding skills, safety, feed tolerance, infection, and growth. Future studies should be powered to detect the effect of the intervention in infants of different gestational ages and on each sex separately. It is also important to determine the optimal method, frequency, and duration of exposure.

Effects of human milk odor stimulation on feeding in premature infants: a systematic review and meta-analysis

Previous studies suggested odor stimulation may influence feeding of premature neonates. Therefore, this systematic review and meta-analysis of randomized controlled trials was conducted to assess the effect of human milk odor stimulation on feeding of premature infants. All randomized controlled trials related to human milk odor stimulation on feeding in premature infants published in PubMed, Cochrane, Library, Medline, Embase, Web of science databases and Chinese biomedical literature databases, China National Knowledge Infrastructure, China Science and Technology Journal Database (VIP) and Wanfang Chinese databases were searched, and The Cochrane Handbook 5.1.0 was used to evaluate the quality and authenticity of the literature. Relevant information of the included studies was extracted and summarized, and the evaluation indexes were analyzed using ReviewManager5.3. The retrieval time was from the establishment of the database to July 28, 2022.12 articles were assessed for eligibility, and six randomized controlled studies were eventually included in the meta-analysis (PRISMA). A total of 6 randomized controlled studies with 763 patients were finally included in the study, and the quality evaluation of literatures were all grade B. Human milk odor stimulation reduced the transition time to oral feeding in premature infants [SMD = - 0.48, 95% CI (- 0.69, - 0.27), Z = 4.54, P < 0.00001] and shortened the duration of parenteral nutrition [MD = - 1.01, 95% CI (- 1.70, - 0.32), Z = 2.88, P = 0.004]. However, it did not change the length of hospitalization for premature infants [MD = - 0.03, 95% CI (- 0.41, 0.35), Z = 0.17, P = 0.86]. The implementation of human milk odor stimulation can reduce the transition time to oral feeding and the duration of parenteral nutrition in premature infants, but further studies are needed to determine whether it can reduce the length of hospital stay in premature infants. More high-quality, large-sample studies are needed to investigate the effect of human milk odor stimulation on the feeding process and other outcomes in premature infants.

Smell and taste of milk during tube feeding of preterm infants: neurodevelopmental follow-up of the randomized TASTE trial, study protocol

BACKGROUND

The Taste And Smell To Enhance nutrition (TASTE) trial investigated the effects of smell and taste of milk with tube feeding compared to routine care on the growth of preterm infants. There was no difference between groups in growth (weight, head circumference, length) z-scores at discharge from the hospital. Infants in the intervention group had higher head circumference and length z-scores at 36 weeks postmenstrual age, both secondary outcomes. The objective of this follow-up study is to assess 2-year neurodevelopmental and growth outcomes after exposure of preterm infants to the smell and taste of milk with tube feeding compared to routine care.

METHODS

This is a neurodevelopmental follow-up study of a two-center, placebo-controlled randomized trial. Infants born before 29 weeks postmenstrual age and/or with a birth weight of less than 1250 g were randomized to smell and taste of milk with each tube feed or routine care. The current follow-up assessed the 2-year neurodevelopmental and growth outcomes of participants of the TASTE trial discharged from the hospital (n = 334). The primary outcome is survival free of any major neurodevelopmental impairment comprising any moderate/severe cerebral palsy (Gross Motor Function Classification System score II-V), Bayley Scales of Infant and Toddler Development, Third/Fourth Edition (Bayley-III/Bayley-4) motor, cognitive, or language scores < -2SD, blindness, or deafness at 2 years of age. Other outcomes include death, breastfeeding within the first year, and respiratory support, oral feeding, and anthropometric parameters at 2 years of age. The Human Research Ethics Committees of Mater Misericordiae Limited and the Royal Women's Hospital approved the TASTE trial including the neurodevelopmental follow-up described in this protocol.

DISCUSSION

For patients and their families, the neurodevelopmental outcomes of preterm infants are of utmost importance. Consequently, they should be investigated following any interventional study performed during the newborn period. Furthermore, improved weight gain and head growth in the hospital are associated with better long-term neurodevelopmental outcomes. Smelling and tasting of milk is an uncomplicated and cost-effective intervention that may improve the growth and neurodevelopmental outcomes of preterm infants. Potential limitations affecting this follow-up study, caused by the COVID-19 pandemic, are anticipated and discussed in this protocol.

TRIAL REGISTRATION

Name of the registry: Australian and New Zealand Clinical Trials Registry; Registration number: ACTRN12617000583347 ; Registration date: 26 April 2017.

Effects on Growth of Smell and Taste of Milk During Tube Feeding of Preterm Infants: A Randomized Clinical Trial

IMPORTANCE

Smell and taste of food increase food anticipation, activate gut motility, and stimulate digestion and metabolism. Despite poor growth of many preterm infants in neonatal intensive care units, the smell and taste of milk with tube feeding are not generally considered a regular component of care.

OBJECTIVE

To determine the effect of smell and taste of milk with tube feeding on weight z scores at discharge from the hospital.

DESIGN, SETTING, AND PARTICIPANTS

A randomized, controlled, nonblinded, superiority trial was conducted at 2 perinatal centers between May 9, 2017, and February 1, 2020. Eligible infants (n = 659) were born at less than 29 weeks' postmenstrual age (PMA) and/or with a birth weight of less than 1250 g.

INTERVENTIONS

Infants were randomly assigned to receive either the smell and taste of milk with each tube feeding or routine care without the provision of smell and taste of milk.

MAIN OUTCOMES AND MEASURES

The primary outcome was weight z score at discharge from any hospital. Secondary outcomes included anthropometric measures at predefined time points, time to full enteral feeds, and other health outcomes associated with prematurity.

RESULTS

Of the 658 infants, a total of 396 infants were randomized; some parents had not been approached for consent (n = 144) or declined participation (n = 117), and 1 infant with consent was not randomized. Of the 396 infants, 196 were assigned to the treatment group (51% male; mean [SD] PMA at birth, 27.5 [2.2] weeks) and 200 were assigned to the control group (52% male; mean [SD] PMA at birth, 27.6 (2.3) weeks). Mean weight z scores at discharge were -0.87 (95% CI, -1.02 to -0.72) for the treatment group and -0.97 (95% CI, -1.11 to -0.83) for the control group (P = .40). The mean difference in z scores between the treatment and control groups at 36 weeks' PMA was 0.21 (95% CI, 0.01 to 0.4; P = .04) for head circumference and 0.26 (95% CI, 0.05 to 0.51; P = .04) for length. There were no clinically notable differences between the study groups for any other anthropometric, feeding, or health outcomes.

CONCLUSIONS AND RELEVANCE

In this randomized clinical trial, regular smell and taste of milk included with tube feeding did not improve weight at discharge in preterm infants. Secondary outcomes suggest exposure to smell and taste may improve head circumference and length at 36 weeks' PMA, but not at discharge. Regular exposure to the smell and taste of milk is a simple and inexpensive intervention with potential benefits and no apparent adverse effects.

TRIAL REGISTRATION

anzctr.org.au Identifier: ACTRN12617000583347.

Olfactory Cues in Infant Feeds: Volatile Profiles of Different Milks Fed to Preterm Infants

Background: Smell is determined by odor-active volatile compounds that bind to specific olfactory receptors, allowing us to discriminate different smells. Olfactory stimulation may assist with digestion and metabolism of feeds in the neonate by activation of the cephalic phase response of digestion. Infants' physiological responses to the smell of different milks suggest they can distinguish between breastmilk and infant formula. We aimed to describe the profile of volatile compounds in preterm breastmilk and investigate how this differed from that of other preterm infant feeding options including pasteurized donor breastmilk, breastmilk with bovine milk-based fortifier, human milk-based products and various infant formulas. Methods: Forty-seven milk samples (13 different infant formulas and 34 human milk-based samples) were analyzed. Volatile compounds were extracted using Solid Phase Micro Extraction. Identification and relative quantification were carried out by Gas Chromatography with Mass Spectrometry. Principal Component Analysis (PCA) and one-way Analysis of Variance (ANOVA) with Tukey's HSD (parametric data) or Conover's post-hoc test (non-parametric data) were used as appropriate to explore differences in volatile profiles among milk types. Results: In total, 122 compounds were identified. Breastmilk containing bovine milk-based fortifier presented the highest number of compounds (109) and liquid formula the lowest (70). The profile of volatile compounds varied with 51 compounds significantly different (adjusted p < 0.001) among milk types. PCA explained 47% of variability. Compared to preterm breastmilk, the profile of volatile compounds in breastmilk with added bovine milk-based fortifier was marked by presence of fatty acids and their esters, ketones and aldehydes; infant formulas were characterized by alkyls, aldehydes and furans, and human milk-based products presented high concentrations of aromatic hydrocarbons, terpenoids and specific fatty acids. Conclusions: Sensory-active products of fatty acid oxidation are the major contributors to olfactory cues in infant feeds. Analysis of volatile compounds might be useful for monitoring quality of milk and detection of oxidation products and environmental contaminants. Further research is needed to determine whether these different volatile compounds have biological or physiological effects in nutrition of preterm infants.

Effect of Oropharyngeal Administration of Mother's Milk Prior to Gavage Feeding on Gastrin, Motilin, Secretin, and Cholecystokinin Hormones in Preterm Infants: A Pilot Crossover Study

BACKGROUND

Oropharyngeal administration of milk prior to gavage feeding has been shown to improve feeding tolerance in preterm infants.

OBJECTIVES

The aim is to study the effect of oropharyngeal administration of mother's milk (OPAMM), prior to gavage feeding, on the levels of gastrin, motilin, secretin, and cholecystokinin hormones.

METHODS

Preterm infants (<32 weeks' gestation) were randomized at a corrected gestational age of 33-34 weeks, in a crossover design, to receive 1 of 2 protocols: 24 hours of OPAMM practice (applying 0.2 mL of mother's milk prior to each gavage feeding) followed by 24 hours of regular gavage-feeding practice in the first protocol or vice versa in the second protocol. The levels of gastrin, motilin, secretin, and cholecystokinin hormones were measured at the end of 24 hours of both practices.

RESULTS

The data of 40 preterm infants (20 in each protocol) were analyzed. OPAMM was associated with a significant increase in the levels of motilin (median, 233; interquartile range [IQR], 196-296 vs median, 196; IQR, 128-233; P < .01), secretin (median, 401; IQR, 353-458 vs median, 370; IQR, 331-407; P = .04), and cholecystokinin (median, 21.4; IQR, 16-27.1 vs median, 14.9; IQR, 11-20.5; P <.01) but not gastrin (median, 202; IQR, 125-238 vs median, 175; IQR, 128-227; P = .7), compared with regular gavage-feeding practice.

CONCLUSION

Oro-pharyngeal stimulation by OPAMM, prior to gavage feeding, significantly increased motilin hormone and possibly increased secretin and cholecystokinin hormones.