Harmless? Mixed perception and awareness of vitamin and mineral supplements

Effect of micronutrient supplements on low-risk pregnancies in high-income countries: a systematic quantitative literature review

OBJECTIVE

To assess the quantity and focus of recent empirical research regarding the effect of micronutrient supplementation on live birth outcomes in low-risk pregnancies from high-income countries.

DESIGN

A systematic quantitative literature review.

SETTING

Low-risk pregnancies in World Bank-classified high-income countries, 2019.

RESULTS

Using carefully selected search criteria, a total of 2475 publications were identified, of which seventeen papers met the inclusion criteria for this review. Data contributing to nine of the studies were sourced from four cohorts; research originated from ten countries. These cohorts exhibited a large number of participants, stable data and a low probability of bias. The most recent empirical data offered by these studies was 2011; the most historical was 1980. In total, fifty-five categorical outcome/supplement combinations were examined; 67·3 % reported no evidence of micronutrient supplementation influencing selected outcomes.

CONCLUSIONS

A coordinated, cohesive and uniform empirical approach to future studies is required to determine what constitutes appropriate, effective and safe micronutrient supplementation in contemporary cohorts from high-income countries, and how this might influence pregnancy outcomes.

Use of micronutrient supplements in pregnant women of south-east Queensland

BACKGROUND

Multiple micronutrient supplement use in the Australian pregnant population is rising, despite little evidence of benefit in low-risk women. While some supplement recommendations are grounded in high-quality evidence, others warrant further investigation. This highlights a research gap regarding appropriate use of supplements during pregnancy in the Australian population.

AIMS

To describe micronutrient supplement use during pregnancy in the context of current evidence and national recommendations in a population of south-east Queensland women.

MATERIAL AND METHODS

A cross-sectional observational design was used to examine data gathered from pregnant women aged 16-44 years residing in south-east Queensland, Australia. Women were recruited to the study between 23 May 2016 and 30 September 2017.

RESULTS

Pregnancy multivitamin use was declared by 42% of the cohort, with 26.8% declaring multivitamins in combination with individual micronutrients and 9.8% declaring specific micronutrient supplement use. Nulliparous women were more likely to declare use of supplements than their multiparous peers (adjusted odds ratio (aOR) 1.938, 95% CI 1.053-3.571, P = 0.034); smoking (aOR 2.717, 95% CI 1.011-7.302, P = 0.047) and low socio-economic status were associated with no supplement use (aOR 2.451, 95% CI 1.010-5.949, P = 0.048).

CONCLUSIONS

Current recommendations regarding micronutrient supplements throughout pregnancy are based on varying degrees of evidence, resulting in supplement advice of poor cohesion and consistency. Adherence to micronutrient supplement recommendations in the peri-conception period in this population was poor; second and third trimester supplement use was high. Contemporary empirical research is required to determine what constitutes appropriate supplementation in high-income regions and the populations they will benefit most.

Essential Mineral Intake During Pregnancy and Its Association With Maternal Health and Birth Outcomes in South East Queensland, Australia

Micronutrient supplements are often recommended during pregnancy, yet their role and necessity remain poorly understood in the Australian population. This study aimed to determine the essential mineral intake of a population of pregnant women in South East Queensland and investigate the effects of supplements on their micronutrient status and birth outcomes. Women completing the Oral Glucose Tolerance Test at two South East Queensland hospitals between 180 and 210 days gestation provided fasting blood samples and dietary data using the Maternal Outcomes and Nutrition Tool (n = 127). Birth outcomes were sourced from medical records. Serum elemental profiles were determined by inductively coupled plasma mass spectrometry (ICP-MS) analysis. Intake of 8 essential minerals was compared with Australian dietary recommendations; matched serum mineral levels were compared with the current Queensland pregnancy reference ranges. Data were examined using cross-sectional cohort design and independent sample t-tests. Supplement use had no significant influence on serum values of trace elements or the incidence of hypertensive disorders, gestational diabetes, preterm birth or infant birthweight. Dietary selenium, zinc and iodine were significantly higher in women birthing beyond 41 completed weeks; selenium (P = .026) and zinc (P = .034) both made unique contributions to the regression models when controlling for confounders. Women exhibited adequate to excessive serum micronutrient levels compared with pregnancy reference ranges, a finding consistent with dietary intake calculations. Data suggest that excessive essential mineral intake contributed to prolonged pregnancy in this cohort, supporting previous studies in this population. Further research is required to determine individual needs and eliminate the potential for harm before recommending pregnancy supplements.