Nutrition is a well-known factor in the growth, health and development of children. It is also acknowledged that worldwide many people have dietary imbalances resulting in over- or undernutrition. In 2009, the multinational food company FrieslandCampina initiated the South East Asian Nutrition Survey (SEANUTS), a combination of surveys carried out in Indonesia, Malaysia, Thailand and Vietnam, to get a better insight into these imbalances. The present study describes the general study design and methodology, as well as some problems and pitfalls encountered. In each of these countries, participants in the age range of 0·5–12 years were recruited according to a multistage cluster randomised or stratified random sampling methodology. Field teams took care of recruitment and data collection. For the health status of children, growth and body composition, physical activity, bone density, and development and cognition were measured. For nutrition, food intake and food habits were assessed by questionnaires, whereas in subpopulations blood and urine samples were collected to measure the biochemical status parameters of Fe, vitamins A and D, and DHA. In Thailand, the researchers additionally studied the lipid profile in blood, whereas in Indonesia iodine excretion in urine was analysed. Biochemical data were analysed in certified laboratories. Study protocols and methodology were aligned where practically possible. In December 2011, data collection was finalised. In total, 16 744 children participated in the present study. Information that will be very relevant for formulating nutritional health policies, as well as for designing innovative food and nutrition research and development programmes, has become available.

Indonesia is currently facing the double burden of malnutrition. While undernutrition is still a major public health problem, the prevalence of overnutrition is increasing. The objective of the South East Asian Nutrition Survey (SEANUTS) was to provide up-to-date data on nutritional status, food consumption and biochemical parameters related to nutrition for children aged 0·5–12 years. The SEANUTS study in Indonesia was conducted in a nationwide representative sample of 7·211 children using multistage cluster sampling based on probability proportional to size, stratified for geographical location, in forty-eight out of 440 districts/cities. The results show that the growth (weight for age, height for age, weight for height and BMI for age) of Indonesian pre-school- and school-aged children is below the WHO standards. The older the children, the more the deviation from the WHO standard curves. Underweight was more prevalent in rural areas (28·9 v. 19·2 %) and overweight/obesity was observed to be more widespread in urban areas (5·6 v. 3·2 %). The prevalence varied with age groups and sexes. The overall prevalence of stunting was 25·2 and 39·2 % in urban and rural areas, respectively. The prevalence of anaemia was nearly 55 % in children aged 0·5–1·9 years and ranged from 10·6 to 15·5 % in children aged 2–12 years. Fe deficiency was observed in 4·1–8·8 % of the children. The percentage of children with dietary intakes of energy, protein, and vitamins A and C below the Indonesian RDA was high and differed across urban and rural areas and age groups.

The dual burden of malnutrition reportedly coexists in Malaysia; however, existing data are scarce and do not adequately represent the nutritional status of Malaysian children. The Nutrition Survey of Malaysian Children was carried out with the aim of assessing the nutritional status in a sample of nationally representative population of children aged 6 months to 12 years. A total of 3542 children were recruited using a stratified random sampling method. Anthropometric measurements included weight, height, mid-upper arm circumference, and waist and hip circumferences. Blood biochemical assessment involved analyses of Hb, serum ferritin, and vitamins A and D. Dietary intake was assessed using semi-quantitative FFQ, and nutrient intakes were compared with the Malaysian Recommended Nutrient Intakes (RNI). The prevalence of overweight (9·8 %) and obesity (11·8 %) was higher than that of thinness (5·4 %) and stunting (8·4 %). Only a small proportion of children had low levels of Hb (6·6 %), serum ferritin (4·4 %) and vitamin A (4·4 %), but almost half the children (47·5 %) had vitamin D insufficiency. Dietary intake of the children was not compatible with the recommendations, where more than one-third did not achieve the Malaysian RNI for energy, Ca and vitamin D. The present study revealed that overnutrition was more prevalent than undernutrition. The presence of high prevalence of vitamin D insufficiency and the inadequate intake of Ca and vitamin D are of concern. Hence, strategies for improving the nutritional status of Malaysian children need to consider both sides of malnutrition and also put emphasis on approaches for the prevention of overweight and obesity as well as vitamin D insufficiency.

In the present study, we investigated nutritional status and health-related factors in a multistage cluster sample of 3119 Thai urban and rural children aged 0·5–12·9 years. In a subsample, blood samples were collected for the measurement of Hb, transferrin receptor, vitamin A and vitamin D concentrations. The prevalence of stunting and underweight was higher in rural children than in urban children, whereas the wasting rate was similar in both rural and urban areas. Among children aged 3·0–5·9 years, the prevalence of overweight was significantly higher in urban areas than in rural areas and so was the obesity rate in children aged 6·0–12·9 years. Protein intakes of all age groups were relatively high in both the areas. Intakes of Ca, Fe, Zn and vitamin C were significantly higher in urban areas than in rural areas. The prevalence of anaemia in rural areas was twice as high as that in urban areas, particularly in infants and young children. However, the prevalence of Fe-deficiency anaemia was similar in both urban and rural areas. While the prevalence of vitamin A deficiency (by serum retinol cut-off < 0·7 μmol/l) seemed to be very low, vitamin A insufficiency (by serum retinol cut-off < 1·05 μmol/l) was more prevalent (29·4–31·7 %) in both the areas. The prevalence of vitamin D insufficiency ranged between 27·7 and 45·6 % among the children. The present study indicates that the double burden of malnutrition is still a major public health problem in Thailand. Further studies need to explore the associated risk factors for these nutrient deficiencies. Effective strategies and actions are needed to tackle the nutritional problems in Thai children.

The Vietnamese South East Asian Nutrition Survey (SEANUTS), a cross-sectional study, was undertaken to assess the nutritional status in a nationally representative sample of children aged 0·5–11·9 years. A multi-stage cluster-randomised sampling method was used to recruit 2872 children. Anthropometric measurements included weight, height, mid-upper arm circumference, and waist and hip circumferences. Blood biochemistry involved analyses of Hb, serum ferritin, and vitamins A and D. Dietary intake was assessed using a 24 h recall questionnaire, and nutrient intakes were compared with the Vietnamese RDA. In children aged < 5 years, approximately 14 % were stunted, 8·6 % underweight and 4·4 % thin. A higher prevalence of stunting (15·6 %) and underweight (22·2 %) was observed in school-aged children. Undernutrition was more prevalent in rural areas than in urban areas. In contrast, almost 29 % of the urban children were either overweight or obese when compared with 4 % of the overweight children and 1·6 % of the obese children in rural areas. A higher percentage of children in the age group 0·5–1·9 years and residing in rural areas had low Hb levels than those in the age group 2·0–5·9 years and residing in urban areas. In children aged 6–11 years, a small percentage had low Hb (11–14 %) and vitamin A (5–10 %) levels, but almost half the children (48–53 %) had vitamin D insufficiency. Food consumption data indicated that the children did not meet the RDA for energy, protein, Fe, vitamin A, vitamin B1 and vitamin C. Results from the SEANUTS highlight the double burden of malnutrition in Vietnam. Information from the SEANUTS can serve as an input for targeted policy development, planning and development of nutrition programmes.

Nutrition is an important factor in mental development and, as a consequence, in cognitive performance. Malnutrition is reflected in children's weight, height and BMI curves. The present cross-sectional study aimed to evaluate the association between anthropometric indices and cognitive performance in 6746 school-aged children (aged 6–12 years) of four Southeast Asian countries: Indonesia; Malaysia; Thailand; Vietnam. Cognitive performance (non-verbal intelligence quotient (IQ)) was measured using Raven's Progressive Matrices test or Test of Non-Verbal Intelligence, third edition (TONI-3). Height-for-age z-scores (HAZ), weight-for-age z-scores (WAZ) and BMI-for-age z-scores (BAZ) were used as anthropometric nutritional status indices. Data were weighted using age, sex and urban/rural weight factors to resemble the total primary school-aged population per country. Overall, 21 % of the children in the four countries were underweight and 19 % were stunted. Children with low WAZ were 3·5 times more likely to have a non-verbal IQ < 89 (OR 3·53 and 95 % CI 3·52, 3·54). The chance of having a non-verbal IQ < 89 was also doubled with low BAZ and HAZ. In contrast, except for severe obesity, the relationship between high BAZ and IQ was less clear and differed per country. The odds of having non-verbal IQ levels < 89 also increased with severe obesity. In conclusion, undernourishment and non-verbal IQ are significantly associated in 6–12-year-old children. Effective strategies to improve nutrition in preschoolers and school-aged children can have a pronounced effect on cognition and, in the longer term, help in positively contributing to individual and national development.