According to findings published in the American Journal of Clinical Nutrition, Bifidobacterium breve and Lactobacillus casei were associated with protection against necrotizing enterocolitis (NEC), a devastating complication of pre-term birth.
A second and separate study, published in the same journal, also found that consumption milk-based probiotic products by women during pregnancy was associated with an 18 percent reduction in the risk of premature delivery.
Both studies add to a small but compelling body of science supporting the potential benefits of specific probiotic strains for mother and child. In an accompanying editorial, the University of Florida’s Jona Rushing and Josef Neu explain: “Premature birth (before 37 weeks of gestation) can cause severe short- and long-term health problems as well as incur high monetary costs.”
However, Rushing and Neu are critical on the current state of the science and said: “Much more needs to be learned about probiotics before considering routine use in either pregnant women or preterm infants.”
According the FAO/WHO, probiotics are defined as "live microorganisms which when administered in adequate amounts confer a health benefit on the host".
Promise should not dictate policy
The comments of Rushing and Neu echo those of a recent statement from the American Academy of Pediatrics (AAP). Writing in Pediatrics (doi: 10.1542/peds.2010-2548), Dan Thomas, MD, and Frank Greer, MD and the AAP’s Committee on Nutrition; Section on Gastroenterology, Hepatology, and Nutrition report that clinical trials have provided ‘encouraging’ but ‘preliminary’ evidence for a range of benefits, including treatment of childhood Helicobacter pylori gastritis, IBS, and infantile colic.
“Important questions remain in establishing the clinical applications for probiotics, including the optimal duration of probiotic administration as well as preferred microbial dose and species,” wrote the committee.
“The long-term impact on the gut microflora in children is unknown. It also remains to be established whether there is significant biological benefit in the administration of probiotics during pregnancy and lactation, with direct comparison to potential biological benefit derived from probiotic-containing infant formulas,” it added.
For the first study, which focussed on NEC, Brazilian researchers led by Taciana Duque Braga from the Neonatal Intensive Care Unit at the Instituto de Medicina Integral Professor Fernando Figueira in Recife, 231 preterm infants participated in the was a double-blind, randomized trial. Infants were fed either control milk or milk fortified with B. breve and L. casei. Infants were followed for 30 days.
Data showed a positive effect of probiotic use on the risk of NEC, with no infants in the probiotic group developing the condition, but four infants in the control group being diagnosed with NEC. As a result, the study was stopped early.
“The number of studies published that have evaluated the role of Lactobacillus and Bifidobacteria in the prevention of NEC is extremely low,” explained the Brazilian researchers.
“Considering that the effects of probiotics are species specific, it remains to be determined whether there are any probiotic strains more suitable for preventing NEC in preterm infants,” they concluded.
The second study, led by Ronny Myhre from the Norwegian Institute of Public Health, was not an intervention study, but an epidemiologic/observational. Data from 18,888 healthy pregnant women was analysed, and the incidence of premature birth correlated with probiotic consumption.
Women with the highest amounts of probiotic consumption were 18 percent less likely to experience premature delivery, compared with women reporting no probiotic use, report the researchers.
“Our results imply that high intake (in mL) of probiotic food items, which in this study corresponded to a mean intake of 138.4 mL/d, had an effect with a range of 2.85x109 to 2.0x1011 probiotic bacteria/d in the high-intake group,” explained the researchers.
“Further investigation is warranted with the use of randomized controlled trials for evaluation as to whether to view presence of foods containing probiotics as protective and their absence as a risk factor for [spontaneous preterm delivery] and to improve understanding of health complications during pregnancy to further facilitate effective health promotion strategies,” they concluded.
Commenting on the findings of the studies, Rushing and Neu note that, for the Norwegian study, no data was provided for the history of preterm birth for the participating women, an omission they see as a major limitation of the findings.
“Despite pitfalls of this study, the theoretical basis for use of probiotics remains tenable, and this study provides a signal that after appropriate additional study, probiotics may end up as reasonable adjuncts in the prevention of preterm labor,” they add.
Regarding the Brazilian study, Rushing and Neu said that the early termination of the study was “very odd”.
“Although there appear to be benefits in Braga et al’s study, such as improved feeding tolerance, this is very difficult to measure using the techniques in this study, especially because most of the measures were nonsignificant and the differences were small (17.4 compared with 15.2 d in the control and probiotics groups, respectively) to reach full enteral feedings,” they state.
“Whether this has any effect on length of stay or other morbidity is questionable,” they added.
Sources: American Journal of Clinical Nutrition
2011, Volume 93, Pages 81-86
“Efficacy of Bifidobacterium breve and Lactobacillus casei oral supplementation on necrotizing enterocolitis in very-low-birth-weight preterm infants: a double-blind, randomized, controlled trial”
Authors: T.D. Braga, G. Alves Pontes da Silva, P.I. Cabral de Lira, M. de Carvalho Lima
American Journal of Clinical Nutrition
2011, Volume 93, Pages 81-86
“Intake of probiotic food and risk of spontaneous preterm delivery”
Authors: R. Myhre, A.L. Brantsaeter, S. Myking, H.K. Gjessing, V. Sengpiel, H.M. Meltzer, M. Haugen, B. Jacobsson
Editorial: American Journal of Clinical Nutrition
2011, Volume 93, Pages 3-4
“Probiotics for pregnant women and preterm neonates”
Authors: J. Rushing, J. Neu