The breadth of research on the impact of nutrition-specific policies to address child undernutrition is not well documented. This review maps the evidence base and identifies gaps on such policies.

We systematically searched Medline, Embase, PAIS Index for public policy, Scopus and Web of Science databases to identify eligible studies. Key study characteristics, including research design, type of policy, time span of policy before impact assessment, child age at outcome assessment and types of outcomes assessed, were abstracted in duplicate.

Low-, middle- and high-income countries.

Studies were eligible for inclusion if they aimed to assess the impact of population-level nutrition-specific policies on undernutrition among children under 10 years of age.

Of the 5646 abstracts screened, eighty-three studies were included. A range of policies to address child undernutrition were evaluated; the majority were related to micronutrient fortification. Most studies were observational, reported on mandatory regional or sub-national polices, were conducted in high-income countries and evaluated policies within 1 year of implementation. A narrow set of health outcomes were evaluated, most commonly iodine deficiency disorders and neural tube defects.

Nutrition policies were commonly associated with improved child nutritional status and health. However, this evidence is primarily based on limited settings and on a limited number of outcomes. Further research is needed to assess the longer-term impact of a broader range of nutrition policies on child health, particularly in low- and middle-income countries.

To verify the association between changes in socio-economic level (SEL) and nutritional status of Chilean adults over a 10-year period.

Concurrent cohort study.

Individuals born from 1974 to 1978 in the Valparaíso Region of Chile were evaluated between 2000 and 2002 (n 1232) and again between 2010 and 2012 (n 796). SEL was characterized according to the occupation and educational level of the head of household. Nutritional status was based on measurement of BMI and waist circumference (WC).

Between the first and second evaluation there was a 13 % reduction in the number of individuals classified as poor and a 12 % increase in those classified in the medium high SEL. Increases in BMI were found among women who remained in the low SEL (β=2·2, 95 % CI 0·16, 2·87) compared with women who maintained the same SEL (and whose SEL was above low over the 10-year period). Women who remained in the low SEL increased their WC (β=4·10, 95 % CI 0·27, 7·93). There were no associations between nutritional status and SEL among males.

In the period studied, the SEL of the study population improved between the third and fourth decade of life, but BMI and WC also increased among women, with the lowest socio-economic group experiencing the greatest changes. Meanwhile, among males we found no association between anthropometric measurements and changes in SEL.

The present study provides ranges for the magnitude of bias caused by measurement error in stunting rates, a widely used a proxy for long-term nutritional status.

Stunting, which is determined by the number of cases that fall below −2 sd from the mean height-for-age in the population, mechanically increases with higher variance. This variance stems from both natural heterogeneity in the population and measurement error. To isolate the effect of measurement error, we model the true distributions which could give rise to the observed distributions after subtracting a simulated measurement error.

We analyse information from three rounds of the Demographic and Health Survey (DHS) in Egypt (2005, 2008 and 2014). Egypt ranks high among developing countries with low-quality anthropometric data collected in the DHS, currently the main source of anthropometry in the country.

The study relies on re-analysis of existing DHS data, which record height, weight and age data for children under 5 years old.

Under the most conservative assumptions about measurement error, the stunting rate falls by 4 percentage points for the most recent DHS round, while assuming higher levels of measurement error reduces the stunting rate more dramatically.

Researchers should be aware of and adjust for data quality concerns in calculating stunting rates for cross-survey comparisons or in communicating to policy makers.

This study aimed to fill the current gap in the understanding of the knowledge, attitudes and behaviours (KAB) related to dietary Na among adult residents in Singapore.

A cross-sectional online survey was conducted between October and December 2020 on 955 participants selected through random sampling.

The survey was conducted in Singapore.

Participants were recruited from the Singapore Population Health Study Online Panel.

Participants’ mean age was 46·6 ± 14·1 years old and 58 % of them were females. Most of the participants were Chinese (82·1 %), 10·5 % were Indian and 4·5 % were Malay. Findings from the weighted data showed that most participants were aware of the health impact of high Na consumption. However, many participants were unaware of the recommended intake for salt (68%) and Na (83%), had misconceptions, and were unable to correctly use food labels to assess NA content (69%). Findings also alluded to the presence of knowledge gaps in the sources of Na in their diet. While 59 % of the participants reported to be limiting their consumption of Na, many reported facing barriers such as not knowing how to limit their Na intake. Participants also felt that there were limited options for low-Na foods when eating out and were lacking awareness of low-Na products.

Findings highlighted substantial gaps in participants’ knowledge and skills in managing their Na consumption. This suggests the need for more public education and improvements in the food environment.

To develop and evaluate a stand-alone Elementary School-aged Children’s Index of Diet Quality (ES-CIDQ).

In this cross-sectional study, children filled in a food frequency questionnaire (FFQ) with twenty-nine multiple-item questions on the consumption of foods, portion sizes and eating frequency and a 5-d food diary. Nutrient intakes were calculated with nutrient analysis software. FFQ questions best reflecting a health-promoting diet with reference to dietary recommendations were identified by correlations, logistic regression modelling and receiver-operating characteristics curve analysis.

Southwest and Eastern Finland.

Healthy elementary school-aged volunteers [n 266, mean (sd) age 9·7 (1·7) years] were recruited between March 2017 and February 2018.

A set of questions was identified from the FFQ that best depicted the children’s diet quality as defined in the dietary recommendations. These fifteen questions were scored and formulated into a stand-alone index as a continuous index score (range 0–16·5 points) and a two-category score: good and poor diet quality. The cut-off score of six points for a good diet quality had a sensitivity of 0·60 and a specificity of 0·78. Children with a good diet quality (49·8 % of the children) had higher intakes of protein, dietary fibre, and several vitamins and minerals, and lower intakes of sucrose, total fat, SFA and cholesterol compared to children with a poor diet quality.

The developed short stand-alone index depicted diet quality as defined in the dietary recommendations. Thus, ES-CIDQ may be used for assessing diet quality in Finnish elementary school-aged children in school health care and nutrition research.

To quantify associations between four types of social support and measured adiposity among women and men.

The cross-sectional sample from the Canadian Longitudinal Study on Aging (CLSA, 2012–2015). Height, weight and waist circumference (WC) were clinically measured, and perceived availability of informational, tangible, emotional and belonging social supports was self-reported.

Canada.

28 779 adults aged 45–85 years from the CLSA.

All social support types were associated with WC and BMI among women but not among men. Women reporting the lowest informational support had significantly higher mean BMI (28·84 kg/m2 (95 % CI 28·63, 29·05)) and WC (90·81 cm (95 % CI 90·31, 91·30)) compared with women reporting maximum support (respectively, 28·09 kg/m2 (95 % CI 27·88, 28·30) and 88·92 cm (95 % CI 88·43, 89·4)). Women’s abdominal obesity was associated with low levels of informational, emotional and belonging support, and women’s general obesity with informational and emotional support. Notably, informational and emotional support were associated with both obesity outcomes independent of other supports among women. Only a low level of informational support was significantly independently associated with higher odds of obesity among men.

Our study provides novel insights into gender-specific associations between different types of social support and adiposity. Prospective studies are needed to further investigate potential causality of these associations between the specific social supports and future weight status, especially among women.

To quantify PUFA-associated improvement in linear growth among children aged 6–10 years.

Serum fatty acids (FA), including essential FA (EFA) (linoleic acid (LA) and α-linolenic acid (ALA)) were quantified at baseline using GC-MS technology. FA totals by class (n-3, n-6, n-9, PUFA and SFA) and FA ratios were calculated. Height-for-age Z-score (HAZ) relative to WHO population reference values were calculated longitudinally at baseline, 6 and 12 months. Linear regression models estimated PUFA, HIV status and their interaction-associated standardised mean difference (SMD) and 95 % CI in HAZ over 12 months.

Community controls and children connected to community health centre in Kampala, Uganda, were enrolled.

Children perinatally HIV-infected (CPHIV, n 82), or HIV-exposed but uninfected (CHEU, n 76) and community controls (n 78).

Relative to highest FA levels, low SFA (SMD = 0·31, 95 % CI: 0·03, 0·60), low Mead acid (SMD = 0·38, 95 % CI: 0·02, 0·74), low total n-9 (SMD = 0·44, 95 % CI: 0·08, 0·80) and low triene-to-tetraene ratio (SMD = 0·42, 95 % CI: 0·07, 0·77) predicted superior growth over 12 months. Conversely, low LA (SMD = -0·47, 95 % CI: −0·82, −0·12) and low total PUFA (sum of total n-3, total n-6 and Mead acid) (SMD = -0·33 to −0·39, 95 % CI: −0·71, −0·01) predicted growth deficit over 12 months follow-up, regardless of HIV status.

Low n-3 FA (ALA, EPA and n-3 index) predicted growth deficits among community controls. EFA sufficiency may improve stature in school-aged children regardless of HIV status. Evaluating efficacy of diets low in total SFA, sufficient in EFA and enriched in n-3 FA for improving child growth is warranted.

To assess whether parent-reported time and cost for provision of food is associated with consumption of fruits, vegetables and non-core foods in pre-schoolers.

Cross-sectional analysis of baseline data from the Healthy Habits randomised controlled trial. Two subscales of the Children’s Dietary Questionnaire (CDQ) were used to assess fruit and vegetable, and non-core food consumption.

Thirty pre-schools in the Hunter Region of New South Wales, Australia.

Parents (n 396) with a child aged 3–5 years attending a participating pre-school were recruited. Parents needed to reside with that child for at least four days per week and have primary responsibility for providing meals and snacks to their child.

Sixty-three per cent of children had a parent-reported subscale score indicating adherence to dietary guidelines for fruit and vegetable intake, while 64% of children had a subscale score indicating they were exceeding dietary guidelines for non-core foods. Regression models revealed significant positive associations between higher CDQ scores for non-core foods (indicating higher consumption levels) and minutes that parents spent preparing food (P=0·032 and 0·025) and amount spent on purchasing food (P=0·043 and 0·020). The magnitude of the effects was small (estimate=0·003 and 0·001).

Time and cost spent by parents on provision of food was not significantly associated with child fruit and vegetable consumption. Further explorations into time spent on food preparation and cost of food procurement are warranted to help address the increased consumption of non-core foods by pre-school children.

To examine associations between household food insecurity and children’s physical activity and sedentary behaviours.

Secondary analysis was conducted on the Healthy Communities Study, an observational study from 2013 to 2015. Household food insecurity was assessed by two items from the US Department of Agriculture’s 18-item US Household Food Security Survey Module. Physical activity was measured using the 7-d Physical Activity Behaviour Recall instrument. Data were analysed using multilevel statistical modelling.

A total of 130 communities in the USA.

In sum, 5138 US children aged 4–15 years.

No associations were found for the relationship between household food insecurity and child physical activity. A significant interaction between household food insecurity and child sex for sedentary behaviours was observed (P = 0·03).

Additional research capturing a more detailed assessment of children’s experiences of food insecurity in relation to physical activity is warranted. Future studies may consider adopting qualitative study designs or utilising food insecurity measures that specifically target child-level food insecurity. Subsequent research may also seek to further explore sub-group analyses by sex.

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.

A systematic quantitative literature review.

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

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.

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.

To estimate dietary fluoride intake (F) over the course of pregnancy and the overall adjusted difference in dietary F intake by pregnancy stages and levels of compliance with dietary recommendations.

Secondary data analysis from a longitudinal pregnancy cohort study in a population exposed to fluoridated salt. Women were followed during the early, middle and late stages of their pregnancy (n 568). The dietary intake of recommended prenatal nutrients according to Mexican dietary guidelines and F intake (mg/d) was estimated with a validated FFQ. Data were summarised with descriptive statistics. Levels of F intake were compared with the USA’s Institute of Medicine adequate intake (AI) of 3 mg/d for pregnancy. Adjusted differences in F intake by pregnancy stages and levels of compliance with recommendations were estimated using random effects models.

Mexico City.

Women participating in the Early Life Exposures in Mexico to ENvironmental Toxicants (ELEMENT) project, from 2001 to 2003.

Median dietary F intake throughout pregnancy ranged from 0·64 (interquartile range (IQR) 0·38) in the early to 0·70 (IQR 0·42) in the middle, and 0·72 (IQR 0·44) mg/d in the late stage (0·01 mg F/kg per d). Corresponding adjusted intakes of F were 0·72 (95 % CI 0·70, 0·74), 0·76 (95 % CI 0·74, 0·77) and 0·80 (95 % CI 0·78, 0·82) mg/d. Women who were moderately and highly compliant with Mexican dietary recommendations ingested, on average, 0·04 and 0·14 mg F/d more than non-compliant women (P < 0·005).

Dietary F intake was below current AI, was greater with the progression of pregnancy and in women who were moderately and highly compliant with dietary recommendations.