Probiotics and Iron Intake in Pregnancy
February 1, 2023
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By Traci Pantuso, ND
Adjunct Faculty, Research Investigator, Bastyr University, Seattle
SYNOPSIS: In a randomized, controlled trial, a significantly smaller decrease in serum ferritin was observed in pregnant women with the intake of a Lactiplantibacillus plantarum 299v supplement containing a low dose of iron, folic acid, and ascorbic acid than in the placebo group.
SOURCE: Axling U, Onning G, Niskanen TM, et al. The effect of Lactiplantibacillus plantarum 299v together with a low dose of iron on iron status in healthy pregnant women: A randomized clinical trial. Acta Obstet Gynecol Scand 2021;100:1602-1610.
Pregnant women are at an increased risk of iron deficiency anemia, which increases the risk of preterm birth, low birthweight, perinatal and neonatal mortality, and neurodevelopmental disorders.1 Iron requirements increase drastically in pregnancy, from 0.8 mg/day in early pregnancy to 7.5 mg/day in the third trimester.2 Because of the increased requirements for iron during pregnancy, many women do not have sufficient dietary intake and/or body stores. Iron supplementation is common during pregnancy to both treat and prevent iron deficiency anemia.
However, not all researchers and guidelines are in agreement, and there is some discrepancy regarding serum ferritin levels, with < 15 mcg/L or < 12 mcg/L being indicative of iron deficiency.3 Meanwhile, some guidelines advise that a serum ferritin of < 30 mcg/L in pregnancy is an indicator for recommending supplemental iron.3 Unfortunately, high-dose iron supplements are not well absorbed in the gastrointestinal tract, leading to gastrointestinal side effects and decreased compliance with treatment. However, the probiotic Lactiplantibacillus plantarum 299v has been found to significantly increase iron absorption from different food matrices.4 The World Health Organization defines probiotics as living organisms that confer a health benefit to the host when administered in adequate amounts.5 Lactiplantibacillus plantarum 299v, formerly known as Lactobacillus plantarum 299v, is a gram-positive lactic acid bacteria species commonly found in traditionally fermented foods, such as sauerkraut, brined olives, sourdough, and wine.6
Lactiplantibacillus plantarum is highly versatile and competent at colonizing and inhabiting the human gastrointestinal system.6 In fact, Lactiplantibacillus plantarum 299v was first discovered through isolation from healthy human gut mucosa.4 This study was funded by the corporate sponsor Probi AB. Probi AB is a research and probiotics company that provided the study product, employs four of the authors of this study, and has published previously on Lactiplantibacillus plantarum 299v.4
The authors sought to further evaluate the effects of Lactiplantibacillus plantarum 299v in combination with a low amount of iron, ascorbic acid, and folic acid (LP) on iron status in healthy pregnancy. Because there is a reduction in iron stores during pregnancy, and many women require supplemental iron later in pregnancy, the authors elected to measure serum ferritin at gestational week 28 as their primary endpoint. The authors recruited 340 pregnant women at five different study sites in Sweden between September 2016 and March 2018. The women were enrolled between gestational weeks 10-12, if eligible. Eligibility criteria included being between the ages of 18-42 years, having a body mass index between 18 kg/m2 and 30 kg/m2, being pregnant with a singleton, and not being currently anemic (hemoglobin ≥ 110 g/L, serum ferritin ≥ 20 mcg/L).
Exclusion criteria included chronic gestational diseases, such as hyperemesis gravidarum; having any anemia associated with chronic disease; or having a known diagnosis of thalassemia. The authors also determined that women were not eligible if they had donated blood products 12 weeks prior to the baseline visit, had used antibiotics within a month prior to the baseline visit, or were using any nicotine products. Also, women were excluded if they had a history of alcohol abuse. Once enrolled, the participants were instructed to avoid taking any additional iron or probiotic products unless iron therapy was recommended by a midwife. The participants were instructed to discontinue use of the study product if the midwife recommended iron therapy, but they remained in the study.
The study consisted of a baseline visit and four additional visits to the midwifery clinic at the gestational weeks 25, 28, and 35 with a follow-up visit eight weeks after delivery. At all of the visits, blood samples were collected to assess iron status in participants. The following lab tests were conducted: serum ferritin, hemoglobin (Hb), soluble transferrin receptor (sTfR), total iron binding capacity (TIBC), plasma iron, transferrin saturation, mean corpuscular volume (MCV), and C-reactive protein. Participants were randomized at a 1:1 ratio to receive LP or the placebo. Participants were instructed to consume the study product twice daily with their main meals until delivery or until the need to start iron therapy. No difference in reported side effects between groups was reported. A phone call at week 15 was performed to check in with the participants and remind them about study procedures and to assess adverse events.
The study product capsule contained 1010 colony-forming units of freeze-dried Lactiplantibacillus plantarum 299v, 4.2 mg of iron (ferrous fumarate), 12 mg of ascorbic acid, and 30 mcg of folic acid per capsule. The study authors included the 4.2 mg of iron, which is 30% of the recommended daily intake in Sweden, in the LP capsule to ensure that there was a baseline iron intake. Meanwhile, the 12 mg of ascorbic acid is 15% of daily intake and the 30 mcg of folic acid is 7.5% of the recommended daily intake in Sweden. The placebo capsules contained maize starch and magnesium stearate and were identical in appearance, taste, and texture to the LP study product.
A total of 88 women in the LP group and 90 women in the placebo group completed the study with a compliance of 80%, meaning that there were no major protocol deviations and no supplemental iron intake. Potential major protocol deviations included violation of inclusion and exclusion criteria, visit window deviations, deviations related to the study product, or deviation related to study assessments. The adverse events that were reported in the study were comparable between groups.
A total of 131 participants completed the study without iron therapy (70 in the LP group and 61 in the placebo group). In all, 28% of the women in the LP group and 39% in the placebo group required iron supplementation at delivery. The primary endpoint was the change in serum ferritin at gestational week 28 between the LP and placebo groups. The decrease was -44 mcg/L for the LP group and -49 mcg/L for the placebo group (P = 0.0003). This smaller decrease in serum ferritin from baseline in the LP group compared to the placebo group also was apparent at gestational week 25 (P = 0.015) and week 35 (P < 0.001). The LP group resulted in a ferritin level of 49.4 mcg/L compared with the placebo, which was 40.2 mcg/L at the week 8 follow-up visit (-14 mcg/L vs. -25 mcg/L, P = 0.034). Only at week 35 was the percentage of women with iron deficiency significantly lower in the LP group (59%) than in the placebo group (78%, P = 0.017). Further analysis of covariate effects demonstrated that baseline log serum ferritin had a significant covariate effect (P = 0.005) at 28 weeks.
Hb levels were significantly decreased from baseline at week 25, with the LP group having less of a decrease compared to placebo (P = 0.030), and again at week 35 (P = 0.002). However, at week 28, there was no statistical significance. At the follow-up visit, Hb levels were close to baseline levels for both groups. The incidence of anemia was significantly lower in the LP group than in the placebo group at week 28 (14% vs. 26%, P = 0.050) and at week 35 (7.4% vs. 21%, P = 0.023). At week 35, the prevalence of iron deficiency anemia was significantly lower in the LP group than in the placebo group (7.4% vs. 21%, P = 0.023). The sTfR increased in both groups and was significantly lower than placebo at week 28 (P = 0.011) and week 35 (P = 0.011). A decrease in total body iron was significantly smaller in the LP group than in the placebo group at week 25 (P = 0.041), week 28 (P = 0.002), and week 35 (P < 0.001). The authors also evaluated if differences in dietary habits could have influenced iron status by food intake questionnaires that were filled out at baseline, week 28, and week 35. No significant correlations were detected between changes in ferritin and Hb levels and dietary habits.
The strengths of this study include the measurement of various markers of iron status and that the study was powered to detect small changes in iron status. Although 28 weeks was considered the primary endpoint, the authors collected blood samples, tested at a number of different points in time, and included an eight-week follow-up visit.
There are a number of limitations to this study, including the relatively low number of women who developed iron deficiency anemia when compared with the global prevalence of 40%. Also, the number of women requiring iron therapy according to standard guidelines was relatively low, with 31 women in the LP group and 45 women in the placebo group receiving a recommendation for iron therapy prior to delivery.
There are two other drawbacks to this study. One is that the placebo did not contain the corresponding amount of iron, folic acid, and ascorbic acid as the intervention product. The authors explain this issue by stating that they were low amounts of iron, folic, and ascorbic acid that were unlikely to make a big difference. Another issue is that the baseline iron status was found to be a significant factor in the iron status of the participants at week 28. Much more research needs to be performed to understand whether this particular product increases iron absorption in pregnant women and should be prescribed. However, research into the importance of probiotics and how individual probiotics affect the human gut microbiome and their importance in human health is in its infancy. Fermented foods have been documented for their health benefits and medicinal use since the time of Hippocrates.7 More research is both required and ongoing to better understand fermented foods and their role in human health.
In this study, the iron level for pregnant women was significantly positively correlated to their iron levels at the baseline visit, indicating that iron-rich foods should be recommended to all women, with a specific emphasis on those of childbearing age. Bottom line: Recommending that pregnant and non-pregnant people include iron-rich foods in addition to fermented foods in their diet is a healthy suggestion. Pregnant people should be counseled to avoid unpasteurized products because of the risk of Listeria monocytogenes contamination. However, informing patients that fermented foods, such as yogurt, miso, sauerkraut, pickles, and sourdough, can be enjoyed safely also should be part of the recommendation.
- World Health Organization. The Global Prevalence of Anaemia in 2011. Geneva;2011.
- Milman N. Iron and pregnancy — a delicate balance. Ann Hematol 2006;85:559-565.
- Daru J, Allotey J, Peña-Rosas JP, Khan KS. Serum ferritin thresholds for the diagnosis of iron deficiency in pregnancy: A systematic review. Transfus Med 2017;27:167-174.
- Nordström EA, Teixeira C, Montelius C, et al. Lactiplantibacillus plantarum 299v (LP299V®): Three decades of research. Benef Microbes 2021;12:441-465.
- Food and Agriculture Organization, World Health Organization. Evaluation of Health and Nutritional Properties of Probiotics in Food Including Powder Milk with Live Lactic Acid Bacteria. Córdoba, Argentina;2001.
- Fidanza M, Panigrahi P, Kollmann TR. Lactiplantibacillus plantarum-nomad and ideal probiotic. Front Microbiol 2021;12:712236.
- Ali Z, Wang Z, Amir RM, et al. Potential uses of vinegar as a medicine and related in vivo mechanisms. Int J Vitam Nutr Res 2016;86:127-151.
In a randomized controlled trial, a significantly smaller decrease in serum ferritin was observed in pregnant women with the intake of a Lactiplantibacillus plantarum 299v supplement containing a low dose of iron, folic acid, and ascorbic acid than in the placebo group.
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