TF-IUPS160029 271..275 ORIGINAL ARTICLE Dietary habits, nutrient intake and biomarkers for folate, vitamin D, iodine and iron status among women of childbearing age in Sweden Wulf Becker, Anna Karin Lindroos, Cecilia N€als�en, Eva Warensj€o Lemming and Veronica €Ohrvik National Food Agency, P.O. Box, 75126 Uppsala, Sweden ABSTRACT Background: Dietary intake and nutritional status are important for pregnancy and pregnancy out- comes. Dietary advice on folate, targeted to women of childbearing age, aims at preventing neural tube defects in the offspring. Aim: To describe food and nutrient intake and nutritional status among women of childbearing age in Sweden in relation to current nutrition recommendations. Methods: Dietary intake was assessed using a web-based four-day consecutive food record among adults aged 18–80 years—‘Riksmaten 2010–11 adults’. In a subsample, biomarkers of folate, vitamin D, iodine, and iron status were assessed. Results: Women of childbearing age had lower intakes of fruit and vegetables, fish, and whole grains, but higher intakes of soft drinks. Macronutrient composition was generally in line with the Nordic Nutrition Recommendations, except for a lower intake of fibre, a higher intake of saturated fatty acids, and added sugars. Mean intakes of vitamin D, folate, and iron were below recommended intakes (RI). Median urinary iodine concentration (UIC) was 74 lg/L, 20% had insufficient vitamin D status, and 3% low folate concentrations with no age differences. Furthermore, 29% of women 18–44 years of age had depleted iron stores. Conclusions: The dietary pattern among women of childbearing age (18–44 years) was less favourable compared to older women. Intakes of some micronutrients were below RI, but no differences in vitamin D, folate, or iodine status between age groups were observed. However, improvements of folate and iodine status among women of childbearing age are warranted. This can be achieved by following diet- ary guidelines including use of folic acid-containing supplements. ARTICLE HISTORY Received 17 March 2016 Revised 8 June 2016 Accepted 9 June 2016 KEY WORDS Diet; folate; iodine; iron; nutrition status; vitamin D; women Introduction Dietary intake and nutritional status among women affect pregnancy and pregnancy outcomes. Dietary guidelines in Sweden targeted to women of childbearing age include advice on folic acid supplementation (1). Adequate folate sta- tus is important for prevention of neural tube defects (NTD) in the offspring (2). For pregnant women recommended intakes of several micronutrients are increased (3), and suffi- cient status prior to conception is therefore also important. This is the case for e.g. iodine and iron, for which there are valid biomarkers. Iodine and iron deficiencies are still major nutritional problems world-wide (4,5). About 30% of the world’s population is estimated to have insufficient iodine intake, with increased risk of adverse effects on growth and mental development. The prevalence of iron deficiency (with- out anaemia) varies between 5% and 17% in industrialized countries, and young women are especially at risk. Iron defi- ciency precedes anaemia. Anaemia is associated with fatigue, reduced mood and cognitive function, and poor pregnancy outcomes and quality of life (5). In the recent nation-wide dietary survey ‘Riksmaten 2010–11 adults’ biomarkers of these nutrients were collected for the first time. In this paper, data on food consumption, nutrient intake, and status for vitamin D, folate, iodine, and iron among Swedish women are presented with a focus on the childbearing age (18–44 years). Materials and methods Subjects In the Riksmaten adults 2010–11 survey, a representative sample of 5,000 individuals aged 18–80 years and living in Sweden were invited to participate. The data collection took place between May 2010 and July 2011. Food consumption was captured using a web-based food record during four consecutive days (6). A total of 1797 subjects (36%) com- pleted the food record, 1005 women (41%) and 792 men (31%). A subgroup of 1008 individuals, constituting one-fifth of the total sample, were invited to take part in a biomonitor- ing project. Statistics Sweden (SCB) divided the population sample into seven regions according to affiliation to Swedish Occupational and Environmental Medicine Centres (OEMCs). Each region included the regional capital (Link€oping, Lund, Stockholm, Umeå, Uppsala, Gothenburg, and €Orebro) together CONTACT W. Becker Wulf.becker@slv.se National Food Agency, P.O. Box, 75126 Uppsala, Sweden � 2016 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. UPSALA JOURNAL OF MEDICAL SCIENCES, 2016 VOL. 121, NO. 4, 271–275 http://dx.doi.org/10.1080/03009734.2016.1201176 http://creativecommons.org/licenses/by/4.0/ with two randomly selected counties in each region. An equal number of individuals was selected in each region independ- ently of population size. Recruitment took place at four differ- ent occasions during the year to cover different seasons. Twelve individuals per region and occasion were invited to participate. Out of the 1008 individuals that were invited (7 regions, 3 places in each (the capital and 2 counties), 4 occa- sions, and 12 individuals per round), a total of 300 subjects (30%) agreed to participate, with a higher participation rate (33%) among women. See Table 1 for details of number of women in different age groups. Dietary assessment The participants reported everything they ate and drank for four consecutive days, using a web-based food diary devel- oped by the National Food Agency (NFA). Food intake and status in all seasons and all days of the week were captured by carrying out the study from May 2010 to July 2011 and by randomly assigning starting days to participants. The level of education was somewhat higher among participants than among non-participants, and drop-out was also higher among e.g. subjects born outside Sweden. More details on demo- graphic characteristics have been given by Amcoff et al. (6). Nutritional biomarkers Folate. Whole-blood samples for erythrocyte folate status were collected in EDTA tubes and plasma folate samples in PST tubes by nurses at the OEMCs. Erythrocyte folate concen- trations were analysed at the Karolinska University Hospital, Sweden, using an immunoassay kit (Roche Folate III, Roche Diagnostics GmbH, Mannheim, Germany). Plasma folate was analysed at Uppsala University Hospital, Sweden, using a chemiluminescence immunoassay method on an Abbott Architect ci8200 analyser with reference standard (cat. no. 1P74-35, Abbott Laboratories, Abbott Park, IL, USA). Vitamin D. Plasma 25-hydroxy vitamin D (P-25(OH)D) was analysed at Vitas, Oslo, Norway with LC-MS (7). The assay is accredited by the Vitamin D External Quality Assessment Scheme. P-25(OH)D was calculated as 25(OH)D2 þ 25(OH)D3. Iodine. Urinary iodine concentration (UIC) was determined in duplicate by the same laboratory technician at the Sahlgrenska Academy, Department of Internal Medicine and Clinical Nutrition, Gothenburg, Sweden. The method we used was a modified Sandell–Kolthoff method (8), where iodide is used as a catalyst in the reduction of ceric ammonium sul- phate (yellow colour) to the cerous form (colourless) in the presence of arsenious acid. The rate of colour disappearance is directly proportional to iodide concentration. Ferritin. Iron status was measured as the plasma ferritin concentration using a chemiluminescent microparticle immunoassay (CMIA) (ArchitectV R , Abbott Laboratories) at Uppsala University Hospital, Uppsala, Sweden. Assessment of nutrition status Folate. An erythrocyte folate concentration <317 nmol/L and a plasma folate concentration <6.8 nmol/L are considered to indicate insufficient status (3). Vitamin D. Plasma 25(OH)D concentrations <50 nmol/L) are considered to indicate insufficient vitamin D status (3). Iodine. According to the World Health Organization (WHO), a median UIC of 100–200 lg/L indicates sufficient iodine sta- tus in a population (9). Iron. Ferritin concentrations <12 lg/L in children and ado- lescents and <15 lg/L in adults are indicative of depleted iron stores (3,10) in the absence of inflammation. Statistical analyses All statistical analyses were done in STATA (version 11.2 and 12). Shapiro–Wilks tests were used to determine normality. Non-parametric tests Kruskal–Wallis and Wilcoxon rank–sum were used, and ANOVA and t test were used for normally dis- tributed variables. Results There were minor, and non-significant, differences between subjects in the subsample and other participants with regard to weight, height, and BMI. Intake of foods and nutrients The intake of fruit and vegetables, potatoes, fish, and seafood was lower, while intake of juice, soft drinks, and cordials was higher among women of childbearing age (18–44 years) than among older women (45–80 years) (Figure 1). Reported energy intake tended to be higher in the younger age groups. The proportion of macronutrients was relatively 0 50 100 150 200 250 g/ d 18–30 yr 31–44 yr 45–64 yr 65–80 yr Figure 1. Mean intake (g/d) of selected foods among women in Riksmaten 2010–11. Table 1. Number of women completing the food record and for whom analyt- ical data on biomarkers are available. Age group Food record P-folate Ery-folate P-25(OH)D UIC P-ferritin 18–30 years 203 28 26 27 26 28 31–44 years 247 38 35 37 37 38 45–64 years 357 54 53 51 50 54 65–80 years 198 30 27 29 27 30 All 1005 150 141 144 140 150 272 W. BECKER ET AL. similar across age groups. However, intake of added sugars was higher, and intake of dietary fibre and whole grains was lower in the younger age groups (Figure 2; Table 2). Reported daily energy intake among women in the sub- sample was higher than among women not providing blood samples (7.8 versus 7.4 MJ; P¼0.038). There were no differen- ces in gross dietary composition, e.g. per cent energy from protein, fat, carbohydrate, and alcohol, and dietary fibre (g/10 MJ) and sodium (mg/10 MJ). Folate intake and status Women of childbearing age (18–44 years) had a lower folate intake than women aged 45–80 years (P < 0.001) (Table 2). Increasing intake of fruit and vegetables was associated with a higher folate intake. The mean erythrocyte folate concentra- tion was 470 nmol/L (SD 117) (n¼141), and mean plasma fol- ate concentration was 17.5 nmol/L (SD 11.0) (n¼150). Low blood folate concentrations (erythrocyte-folate <317 nmol/L; plasma-folate <6.8 nmol/L) were found in 3% of the women. Despite significantly different folate intakes there were no dif- ferences in folate status between women aged 18–44 and 45–80 years (Figure 3). However, women reporting a fruit and vegetable intake above 500 g/d had a higher folate status (R2¼ 0.26, P ¼ 0.002). Vitamin D intake and status The reported mean intake of vitamin D from the diet among women was 6.4 lg/d lower among the younger age groups (P < 0.001) (Table 2). However, there were no differences in vitamin D status, assessed with plasma 25(OH)D (Figure 4). Insufficient vitamin D status (plasma 25(OH)D <50 nmol/L) was found in 20%. Table 2. Intake of energy, added sugar, whole grains, vitamin D, folate, iron, and heme-iron among women in Riksmaten 2010–11. Mean per day and per 10 MJ. Energy Whole grains Vitamin D Folate Iron Heme-iron Age group n MJ/d g/d g/10 MJ lg/da lg/ 10 MJ lg/da lg/10 MJ mg/d mg/ 10 MJ mg/d mg/10 MJ 18–30 years 202 7.6 35 45 5.2 6.7 223 298 8.9 11.9 0.99 1.38 31–44 years 247 7.6 38 52 6.2 8.3 247 334 9.7 12.9 1.21 1.62 45–64 years 358 7.3 40 56 6.6 9.2 263 365 9.9 13.8 1.19 1.62 65–80 years 198 7.1 43 60 7.6 10.7 275 388 9.4 13.3 1.12 1.62 All 1005 7.4 39 54 6.4 8.8 253 349 9.5 13.1 1.14 1.57 aExcluding supplements. nmol/L nmol/L 0 5 10 15 20 0 100 200 300 400 500 (B) (A) 18-30 y 31-44 y 45-64 y 65-80 y 18-30 y 31-44 y 45-64 y 65-80 y Figure 3. Folate status among women in the subsample. A: mean plasma folate; B: mean erythrocyte folate concentration. 18-30 yr 31-44 yr 45-64 yr 65-80 yr nmol/L 0 10 20 30 40 50 60 70 Figure 4. Means of plasma 25(OH)D (nmol/L) among women in the subsample. 0 5 10 15 20 25 30 35 40 Protein, E% Fat, E% SFA, E% Added sugars E% Fibre, g/10 MJ 18–30 yr 31–44 yr 45–64 yr 65–80 yr Figure 2. Intake of protein, total fat, saturated fatty acids (SFA), added sugars (as E%), and dietary fibre (g/10 MJ) among women in Riksmaten 2010–11. UPSALA JOURNAL OF MEDICAL SCIENCES 273 Iodine status In the subsample of participants in the Riksmaten 2010–11 study the median UIC among women (n ¼ 140) was 74 lg/L. Altogether 66% had a UIC below 100 lg/L. Mean creatinine- adjusted UIC was 102 lg/g. No intakes were calculated due to incomplete values for iodine contents in foods in the NFA food composition database. Iron status Intakes of total and heme-iron (mg per day and mg per 10 MJ and day) were similar among women of childbearing age (18–44 years) and older women (Table 2), and intakes did not differ in the subsample. However, there was a difference between these age groups in mean plasma ferritin concentra- tions, 41 lg/L (SD 34) and 92 lg/L (SD 74), respectively (P < 0.001). Among women of childbearing age, 20% had fer- ritin values �12 lg/L and 29% <15 lg/L, indicative of depleted iron stores. Discussion The low participation rate (41%) in the food consumption sur- vey and in the biomarker subsample (33%) may have influ- enced the results of this survey. However, all age groups were well represented. The level of education was somewhat higher among participants than among non-participants. The reported intake of fruit, berries, vegetables, and whole grains was generally lower compared to dietary guidelines, while the intake of sugary and fatty foods with a high content of saturated fat and salt was high. Women of childbearing age reported lower intakes of fruit and vegetables, fish, and whole grains, and higher intake of soft drinks compared to older women. Folate Reported mean folate intake was generally above the average requirement (200 lg/d), but below recommended intake (300 lg/d), especially for women of childbearing age (400 lg/d). Even adjusting for apparent under-reported intakes, few subjects reached the last-mentioned intake. Sixteen women of childbearing age reported intake of folic acid supplements (4%) regularly or sometimes, and 117 reported intake of multivitamin supplements regularly or sometimes. Among women in the subsample two (3%) reported intake of folic acid supplements and 16 intake of multivitamins. According to data from the Swedish birth register, about 15% of women reported use of folic acid sup- plements during early pregnancy in 2012, compared to about 1% in 1999 (11). In a study of 1098 pregnant women in the south-west of Sweden, carried out in 2013, 30% reported that they used folate-containing supplements during the first tri- mester (12). In an interview study carried out in early 2010 comprising 1000 adults, drawn from a representative sample of Swedish households, 36% of the women reported taking supplements, of which 32% contained folic acid (NFA, unpub- lished). Thus, about one-tenth took folic acid-containing supplements. The study also showed that the knowledge of when a woman should start taking folic acid prior to the planning of pregnancy was low. In Sweden, the prevalence of children born with NTD has decreased since the 1970s. Since 1999, abortions are included in the statistics, and there has been a decrease up to 2013 (11). This is in contrast to data for many European countries, where no clear trend has been observed (13). Data on folate status in the Riksmaten subsample, however, indicate that many women of childbearing age would bene- fit from improved status in order further to reduce the risk of NTD. This can be achieved by adhering to the general dietary guidelines and also using folic acid-containing sup- plements and choosing fortified products. Results from cal- culations based on weekly menus complying with dietary guidelines and including choice of keyhole-labelled food products (14) suggest that such a diet would result in a fol- ate intake of about 400 lg/d for an adult woman (unpub- lished). However, this represents an ideal food pattern, which implies substantial changes in the typical diet of today. Vitamin D Mean vitamin D intake was below recommended intake in all age groups, lowest among the youngest women (18–30 years). Despite this, there were no age differences in plasma 25(OH)D, and levels indicated a sufficient status (�50 nmol/L) for the majority. Under-reporting could be one explanation, also more frequent outdoor activities and thereby contribu- tion from sun exposure. Iodine The median UIC of 74 lg/L in the Riksmaten subsample is below the WHO range of 100–200 lg/L and would thus indi- cate an insufficient status (9). The lower limit of 100 lg/L is based on an average urine volume of 1.5 L/d, which then cor- responds to an intake of about 150 lg/d, equal to the recom- mended intake in the Nordic Nutrition Recommendations (NNR) 2012 (3). However, UIC is dependent on osmolality, and the daily fluid intake may vary considerably. Using a urine volume of 1.5 L the observed UIC of 74 lg/L would corres- pond to 111 lg/24 h, which is above the average requirement (100 lg/d). Alternatively, using data for the creatinine-adjusted UIC (102 lg/g) and mean 24-h creatinine excretion reported for German adults (15), the median 24-h iodine excretion has been estimated to be around 130 lg. This is still below the recommended intake (3). A decreasing trend in iodine con- tent in Swedish milk has been reported, which is in line with data from Swedish Market Basket studies, indicating a decrease in the average iodine supply from food and bever- ages (16). Thus, a general increase in iodine intake is desir- able, especially important for women of childbearing age. Use of iodized salt in home cooking and food products by manu- facturers and increased fish consumption are feasible options. Also, efforts to maintain and possibly restore iodine levels in milk and dairy products are warranted. 274 W. BECKER ET AL. Iron In the Riksmaten subsample there was a non-significant ten- dency for lower dietary intake of total iron and heme-iron in the youngest age group (18–30 years) compared to women aged 45–80 years. Plasma ferritin levels were significantly lower among women of childbearing age, and the proportion with ferritin concentrations <12 lg/L and <15 lg/L was 20% and 29%, respectively. In Sweden sifted flour was fortified with carbonyl-iron until the beginning of 1995. Sj€oberg and Hulth�en (17) compared food habits, iron intake, and status in two cross-sectional studies among 15–16-year-old girls and boys, sampled from schools in Gothenburg, before (1994, n¼1245) and after (2000, n¼1020) discontinuation of the fortification. Among girls the reported intake of both total and heme-iron was lower in the year 2000. Prevalence of iron deficiency, defined as serum ferritin <15 lg/L, was higher (45%) in 2000 than in 1994 (37%). There were, however, no data on mean serum ferritin levels. Reported levels of total and heme-iron intake are, however, lower compared to the Riksmaten sample. In a longitudinal study on Swedish adoles- cents (60 males and 66 females), carried out from 1993 to 1999, changes in iron status were measured from 15 to 21 years of age. In females, median serum ferritin increased sig- nificantly, after a non-significant decrease at 17 years, from 27 lg/L at 15 years to 34 lg/L at 21 years (18). In females, prevalence of iron deficiency, defined as serum ferritin <12 lg/L, was 18%, 26%, and 21% at 15, 17, and 21 years, respectively. In the Riksmaten subsample the median serum ferritin level among women aged 18–30 years was 36.5 lg/L. Thus, it was similar to the value for the 21-year-old women in the study by Samuelson et al. (18). Taken together, the results from these studies indicate that young women would benefit from a diet with a higher iron density and availability. Conclusions Young adults are an important target group for public health work, since food habits are established early in life and women of that age might bear children. In the Riksmaten 2010–11 study, women of childbearing age reported less favourable food habits and lower intakes of some micronutrients com- pared to older women. No or only minor differences in vitamin D, folate, and iodine status between age groups were observed. However, iron status was lower among the younger age groups. The present data indicate that folate, iron, and iod- ine status among women of childbearing age needs improve- ment. This can be achieved by following dietary guidelines including use of folic acid-containing supplements. Acknowledgements We thank Ingalill Gadhasson, National Food Agency for sample handling; Elisabeth Gramatkovski, Sahlgrenska Academy, Department of Internal Medicine and Clinical Nutrition for analysis of iodine and creatinine; and Peter Ridefelt, Department of Medical Sciences, Uppsala University for analysis of serum ferritin, CRP, and plasma folate. Disclosure statement The authors report no conflicts of interest. Funding information Financial support from the Swedish Environmental Protection Agency made the collection of biological samples in the Riksmaten 2010–11 sur- vey possible. References 1. NFA. Advice on folic acid for women. Uppsala: National Food Agency; 2015 [cited 2016 January 18]. 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Sj€oberg A, Hulth�en L. Comparison of food habits, iron intake and iron status in adolescents before and after the withdrawal of the general iron fortification in Sweden. Eur J Clin Nutr. 2015;69:494–500. 18. Samuelson G, L€onnerdal B, Kempe B, Elverby JE, Bratteby LE. Serum ferritin and transferrin receptor concentrations during the transition from adolescence to adulthood in a healthy Swedish population. Acta Paediatr. 2003;92:5–11. UPSALA JOURNAL OF MEDICAL SCIENCES 275 http://www.livsmedelsverket.se/matvanor-halsa–miljo/kostrad-och-matvanor/folsyra-for-kvinnor/ http://www.livsmedelsverket.se/matvanor-halsa–miljo/kostrad-och-matvanor/folsyra-for-kvinnor/ http://www.livsmedelsverket.se/matvanor-halsa–miljo/kostrad-och-matvanor/folsyra-for-kvinnor/ Dietary habits, nutrient intake and biomarkers for folate, vitamin D, iodine and iron status among women of childbearing age in Sweden Introduction Materials and methods Subjects Dietary assessment Nutritional biomarkers Assessment of nutrition status Statistical analyses Results Intake of foods and nutrients Folate intake and status Vitamin D intake and status Iodine status Iron status Discussion Folate Vitamin D Iodine Iron Conclusions Acknowledgements Disclosure statement Funding information References