Dietary Folate Intake Levels in Rural Women Immediately Before Pregnancy in Northern China Qinqin Meng1,2, Le Zhang2, Jufen Liu2, Zhiwen Li2, Lei Jin2, Yali Zhang2, Linlin Wang2, and Aiguo Ren*2
Background: The study aims to assess dietary folate levels and food sources in women immediately before pregnancy in a rural area of northern China associated with a high prevalence of neural tube defects. Methods: Information was collected by face-to-face interviews with women who sought premarital healthcare and planned to become pregnant within the next 12 months from November 2009 through December 2012. Information regarding food consumption was obtained by means of 24-hr dietary recall. Folate values were assigned to foods according to the China Food Composition 2004. Factors associated with dietary folate intake were analyzed by multiple linear regression. Results: Mean (6 standard deviation) and median (interquartile range) daily folate intake levels were 114.3 6 59.7 and 102.8 (69.3–146.8) lg/day, respectively. Over 99% of the subjects had an intake level below 320 lg/day, the estimated average requirement for nonpregnant women. Only 1% and 7% of the women consumed 75% and 50%, respectively, of the recommended daily folate intake of 400 lg for
Introduction Folate is an essential vitamin that cannot be synthesized de novo by the body; therefore, it must be obtained from either food sources or dietary supplements. Folate occurs naturally in staples such as leafy green vegetables, legumes, egg yolks, liver, and citrus fruit, whereas its synthetic form, folic acid, is found in dietary supplements, enriched foods, and pharmaceutical vitamins (Pietrzik et al., 2010; Greenberg et al., 2011). The quantity of dietary folate equivalents (DFEs) occurring naturally in food equals the micrograms of folate as reported, and folic acid from fortified food or supplements are equal to 1.7 times the equivalent amount of naturally-occurring food folate (Suitor and Bailey, 2000). Low blood folate levels during early pregnancy are linked to an increased risk for neural tube defects (NTDs) (Daly et al., 1995). Periconceptional folic acid supplementa-
Additional Supporting Information may be found in the online version of this article. 1 Department of Epidemiology and Biostatistics, School of Public Health, Peking University, Peking, China 2 Institute of Reproductive and Child Health/Ministry of Health Key Laboratory of Reproductive Health, Peking University; and Department of Epidemiology and Biostatistics, School of Public Health, Peking University, Beijing, China
This work was supported in part by the National Natural Science Foundation of China (Grant Numbers: 31371523 and 31071315). *Correspondence to: Aiguo Ren, 38 College Road, Haidian District, Institute of Reproductive and Child Health, Peking University Health Science Center, Beijing 100191, China. E-mail: [email protected] Published online 26 July 2014 in Wiley Online Library (wileyonlinelibrary.com). Doi: 10.1002/bdra.23280
C 2014 Wiley Periodicals, Inc. V
nonpregnant women. Over 80% of total folate consumption came from cereals, vegetables, and tubers, whereas fruit consumption was severely lacking. Underweight women, farmers, women enrolled during the winter, and women with access to fewer food types or daily meals were more likely to exhibit low folate intake levels. Conclusion: Dietary folate intake among study participants was far below the recommended intake level. Folic acid fortification of cereals is advised to raise folate intake in rural Chinese women planning to become pregnant. Birth Defects Research (Part A) 103:27–36, 2015. C 2014 Wiley Periodicals, Inc. V
Key words: folate; food source; dietary survey; 24-hr dietary recall; reproductive-aged women
tion can dramatically reduce the risk. An early randomized trial conducted by the Medical Research Council in the United Kingdom revealed that supplementation with a daily dosage of 4000 lg of folic acid during the periconceptional period substantially reduced the risk of NTDs in women who previously had a NTD-affected pregnancy (Medical Research Council Vitamin Study Research Group, 1991). This was an important finding that was supported by daily supplementation of 400 to 800 lg of folic acid in women who had no history of an NTD-affected pregnancy (Czeizel and Dudas, 1992; Berry et al., 1999). Because neural tube development occurs early in pregnancy (before many women actually become aware of their condition), taking a folic acid-containing supplement and/or consumption of a folic acid-fortified staple in addition to consumption of sufficient amounts of folate from the diet are essential for all women who plan to become pregnant or are at risk of pregnancy. However, 85% to 90% of women of childbearing age in China do not routinely take folic acid supplements (Zhang et al., 2006; Zeng and Zhu, 2010; Liu et al., 2014); thus, naturally occurring food items are the sole source of folate because fortified food is not available. High dietary folate intake stemming from natural sources can also reduce the risk of NTDs (Werler et al., 1993). A population-based case-control study in the southern United States found that women in the upper three quartiles of average daily dietary folate intake during the periconceptional period had lower odds of bearing offspring with NTDs than those in the lowest quartile of average daily folate intake (McMahon et al., 2013). China has one of the highest NTD rates in the world (Moore et al., 1997), with distinct distribution
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characteristics. Higher NTD rates are found in rural versus urban areas, as well as in northern versus southern provinces in China (Dai et al., 2002; Ye et al., 2002; Li et al., 2013). Among the northern provinces, infants born in the Shanxi Province are at the highest risk of NTDs (13.9 per 1000 births in 2003) (Li et al., 2005). Over 50% of pregnant women in the rural areas of Shanxi Province had low blood folate levels, and folic acid supplementation was not prevalent (Zhang et al., 2006; Ren et al., 2007). Accordingly, food is the main source of folate. In rural China, the majority of women become pregnant within the first 12 months of marriage (Tian, 2011). Therefore, ensuring adequate dietary folate intake among these women is crucial to the well-being of their offspring. The present study was conducted to evaluate the dietary folate intake of women immediately before pregnancy from a population with a high prevalence rate of NTDs, and to determine the types of foods that make the greatest contribution to dietary folate intake. We used micrograms of folate that are equivalent to DFEs in the evaluation of the dietary folate intake.
Materials and Methods STUDY POPULATION
The study subjects were women who underwent premarital health check-ups at a maternal and child health care center in a rural county of Shanxi Province, China from November 2009 through December 2012. The premarital check-ups, paid by the local government, were voluntary and free for all couples. In addition to health check-ups, women were advised to take a folic acid supplement. All young men and women who planned to register for marriage were advised to have the check-ups, and participation rate in 2012 was almost 100% (Shouyang County Government, 2013). The inclusion criteria of the present study were as follows: (a) subjects who were not pregnant at the time of check-up; (b) subjects who were planning to become pregnant within the next 12 months; and (c) subjects who agreed on their own accord to participate in the study. A total of 1771 women met these inclusion criteria. Of these, 345 women did not provide dietary information, with the remaining 1426 subjects being included in the current analysis. The study was approved by the Institutional Review Board of Peking University (Beijing, China). All participants gave verbal informed consent before enrolment in the study. We excluded: (a) 65 women whose energy intake was
Background: The study aims to assess dietary folate levels and food sources in women immediately before pregnancy in a rural area of northern China associated with a high prevalence of neural tube defects. Methods: Information was collected by face-to-face interviews with women who sought premarital healthcare and planned to become pregnant within the next 12 months from November 2009 through December 2012. Information regarding food consumption was obtained by means of 24-hr dietary recall. Folate values were assigned to foods according to the China Food Composition 2004. Factors associated with dietary folate intake were analyzed by multiple linear regression. Results: Mean (6 standard deviation) and median (interquartile range) daily folate intake levels were 114.3 6 59.7 and 102.8 (69.3–146.8) lg/day, respectively. Over 99% of the subjects had an intake level below 320 lg/day, the estimated average requirement for nonpregnant women. Only 1% and 7% of the women consumed 75% and 50%, respectively, of the recommended daily folate intake of 400 lg for
Introduction Folate is an essential vitamin that cannot be synthesized de novo by the body; therefore, it must be obtained from either food sources or dietary supplements. Folate occurs naturally in staples such as leafy green vegetables, legumes, egg yolks, liver, and citrus fruit, whereas its synthetic form, folic acid, is found in dietary supplements, enriched foods, and pharmaceutical vitamins (Pietrzik et al., 2010; Greenberg et al., 2011). The quantity of dietary folate equivalents (DFEs) occurring naturally in food equals the micrograms of folate as reported, and folic acid from fortified food or supplements are equal to 1.7 times the equivalent amount of naturally-occurring food folate (Suitor and Bailey, 2000). Low blood folate levels during early pregnancy are linked to an increased risk for neural tube defects (NTDs) (Daly et al., 1995). Periconceptional folic acid supplementa-
Additional Supporting Information may be found in the online version of this article. 1 Department of Epidemiology and Biostatistics, School of Public Health, Peking University, Peking, China 2 Institute of Reproductive and Child Health/Ministry of Health Key Laboratory of Reproductive Health, Peking University; and Department of Epidemiology and Biostatistics, School of Public Health, Peking University, Beijing, China
This work was supported in part by the National Natural Science Foundation of China (Grant Numbers: 31371523 and 31071315). *Correspondence to: Aiguo Ren, 38 College Road, Haidian District, Institute of Reproductive and Child Health, Peking University Health Science Center, Beijing 100191, China. E-mail: [email protected] Published online 26 July 2014 in Wiley Online Library (wileyonlinelibrary.com). Doi: 10.1002/bdra.23280
C 2014 Wiley Periodicals, Inc. V
nonpregnant women. Over 80% of total folate consumption came from cereals, vegetables, and tubers, whereas fruit consumption was severely lacking. Underweight women, farmers, women enrolled during the winter, and women with access to fewer food types or daily meals were more likely to exhibit low folate intake levels. Conclusion: Dietary folate intake among study participants was far below the recommended intake level. Folic acid fortification of cereals is advised to raise folate intake in rural Chinese women planning to become pregnant. Birth Defects Research (Part A) 103:27–36, 2015. C 2014 Wiley Periodicals, Inc. V
Key words: folate; food source; dietary survey; 24-hr dietary recall; reproductive-aged women
tion can dramatically reduce the risk. An early randomized trial conducted by the Medical Research Council in the United Kingdom revealed that supplementation with a daily dosage of 4000 lg of folic acid during the periconceptional period substantially reduced the risk of NTDs in women who previously had a NTD-affected pregnancy (Medical Research Council Vitamin Study Research Group, 1991). This was an important finding that was supported by daily supplementation of 400 to 800 lg of folic acid in women who had no history of an NTD-affected pregnancy (Czeizel and Dudas, 1992; Berry et al., 1999). Because neural tube development occurs early in pregnancy (before many women actually become aware of their condition), taking a folic acid-containing supplement and/or consumption of a folic acid-fortified staple in addition to consumption of sufficient amounts of folate from the diet are essential for all women who plan to become pregnant or are at risk of pregnancy. However, 85% to 90% of women of childbearing age in China do not routinely take folic acid supplements (Zhang et al., 2006; Zeng and Zhu, 2010; Liu et al., 2014); thus, naturally occurring food items are the sole source of folate because fortified food is not available. High dietary folate intake stemming from natural sources can also reduce the risk of NTDs (Werler et al., 1993). A population-based case-control study in the southern United States found that women in the upper three quartiles of average daily dietary folate intake during the periconceptional period had lower odds of bearing offspring with NTDs than those in the lowest quartile of average daily folate intake (McMahon et al., 2013). China has one of the highest NTD rates in the world (Moore et al., 1997), with distinct distribution
28
characteristics. Higher NTD rates are found in rural versus urban areas, as well as in northern versus southern provinces in China (Dai et al., 2002; Ye et al., 2002; Li et al., 2013). Among the northern provinces, infants born in the Shanxi Province are at the highest risk of NTDs (13.9 per 1000 births in 2003) (Li et al., 2005). Over 50% of pregnant women in the rural areas of Shanxi Province had low blood folate levels, and folic acid supplementation was not prevalent (Zhang et al., 2006; Ren et al., 2007). Accordingly, food is the main source of folate. In rural China, the majority of women become pregnant within the first 12 months of marriage (Tian, 2011). Therefore, ensuring adequate dietary folate intake among these women is crucial to the well-being of their offspring. The present study was conducted to evaluate the dietary folate intake of women immediately before pregnancy from a population with a high prevalence rate of NTDs, and to determine the types of foods that make the greatest contribution to dietary folate intake. We used micrograms of folate that are equivalent to DFEs in the evaluation of the dietary folate intake.
Materials and Methods STUDY POPULATION
The study subjects were women who underwent premarital health check-ups at a maternal and child health care center in a rural county of Shanxi Province, China from November 2009 through December 2012. The premarital check-ups, paid by the local government, were voluntary and free for all couples. In addition to health check-ups, women were advised to take a folic acid supplement. All young men and women who planned to register for marriage were advised to have the check-ups, and participation rate in 2012 was almost 100% (Shouyang County Government, 2013). The inclusion criteria of the present study were as follows: (a) subjects who were not pregnant at the time of check-up; (b) subjects who were planning to become pregnant within the next 12 months; and (c) subjects who agreed on their own accord to participate in the study. A total of 1771 women met these inclusion criteria. Of these, 345 women did not provide dietary information, with the remaining 1426 subjects being included in the current analysis. The study was approved by the Institutional Review Board of Peking University (Beijing, China). All participants gave verbal informed consent before enrolment in the study. We excluded: (a) 65 women whose energy intake was
