A Study of Snack Consumption, Night-Eating Habits, and Nutrient Intake in Gestational Diabetes Mellitus

Gestational diabetes mellitus (GDM) is defined as a state of glucose intolerance developed during pregnancy [1]. The prevalence of GDM is approximately 2% to 3% of Koreans, which is similar to that of other countries [2]. However, according to updated diagnostic criteria, the prevalence of GDM reaches 4% of Koreans [3]. GDM is a common complication during pregnancy, and is associated with maternal, prenatal morbidities, and higher incidence of diabetes afterward [4]. GDM can cause preeclampsia, hypertension, and caesarean section on mother and macrosomia, birth trauma, hypoglycemia, jaundice, hypocalcaemia, and hyperbillirubinemia on fetus [4]. Furthermore, GDM may increase the risk for future glucose intolerance and recurrence in the next pregnancy [5]. GDM uncovers a preexisting metabolic abnormality and return to normal glucose level after delivery, but may precede the development of overt diabetes mellitus later in life [6].

Major risk factors for GDM are older age in pregnancy, race or ethnicity, a family history of diabetes, physical activity, excess adiposity, and diet [7, 8]. Appropriate nutritional management during GDM to maintain blood glucose within normal ranges throughout pregnancy can improve maternal, fetal, and neonatal adverse outcomes [9]. Nutrients associated with GDM risk include refined carbohydrates, animal fat, and heme iron [8, 10]. Balanced three meals and snack consumptions are recommended to maintain normal body weight and to prevent ketone body production during pregnancy. Most of the diabetes mellitus patients consumed more snack than normal [11]. Therefore, inappropriate snack consumption may increase the risk of GDM. In addition, fruits provide vitamin C that increases iron absorption and prevent iron deficient anemia which happens frequently during pregnancy [12].

Night-eating is defined as eating at late time, a light meal as a meal substitution or food intake [13]. Frequent night-eating can cause a high calorie intake and because of this, side effects can be increased, including nutritional imbalance and excess intake of the sodium, obesity, and gastrointestinal disorder [14]. Stunkard [15] has reported that there was more food consumption in the subjects who had night-eating snack than the subjects who did not. Furthermore, night-eating subjects gained 5.2 kg of body weight compared to 0.9 kg body weight gain in non-night-eating subjects 6 years later [16]. Most night-eating snacks contain high concentration of fat and carbohydrate, which can increase calorie and fat intakes. It has been reported that intake of high carbohydrate may increase the risk of GDM [17]. And pre-pregnancy and pregnancy adherence to healthful dietary habit may be associated with lower risk of GDM [17, 18]. There are very few studies observing dietary behaviors, including snack consumptions and particularly night-eating snacks in GDM. Since GDM increases the progression of type 2 diabetes mellitus and cardiovascular disease after delivery, it is important to control dietary behavior, including snack consumption for the prevention and treatment of GDM.

This study was performed to identify characteristics of dietary behavior, including snack intake and nutrient intakes in GDM and normal glucose tolerance (NGT) subjects and to evaluate their association with the blood glucose in pregnant women, which contribute to the prevention of GDM and its complications.

In the present study, the snack consumption, night-eating, and nutrient intakes of 219 NGT subjects and 44 GDM patients who visited an endocrine clinic at a general hospital in Seoul were analyzed to investigate the association between the development of GDM and the mothers' dietary behavior and nutrient intakes.

The mean age of GDM group was statistically higher than that of NGT, the result of which was consistent with the previous study that reported age was an important risk factor of GDM [20]. It has been previously reported that fetal chromosomal abnormality, frequency of cesarean section, and the risk of premature amnion rupture among various prenatal complications are increased by aging [21].

OGTT of GDM patients was statistically higher than that of NGT subjects as reported in previous studies [22-24]. The diagnosis of GDM is typically based on the results of OGTT and there was a significant association between adverse maternal and prenatal outcomes and increasing fasting and 1 h and 2 h OGTT glucose values [25]. It has been reported that there was significant association between increasing maternal blood glucose and 1 h and 2 h OGTT glucose values with adverse pregnancy outcomes, including preterm delivery, gestational hypertension, and large-for-gestational-age infant [25, 26]. These results of previous studies were consistent in our present study. It was previously reported that self management program such as improvement of eating pattern encouraged by clinical dietitians had positive effects on controlling glucose in diabetes mellitus patients [27]. GDM's delivery weight was significantly higher than that of NGT, which was consistent with several previous studies which reported that weight gain during pregnancy is associated with various prenatal complications and fetal growth retardation [28, 29].

Frequency and types of coffee were significantly different between the two groups during pregnancy. Most of NGT subjects more consumed black coffee whereas the majority of GDM subjects drank instant coffee mix containing both sugar and cream. Since the coffee mix contains food additives and cream that is mainly composed of fat, drinking instant coffee mix may have adverse effects on the GDM mothers' health. Although 88.2% of Korean pregnant women replied that they continued to drink coffee in spite of their pregnancy in a previous survey, several studies reported that caffeine intake (above 300 mg per day) can increase the risk of newborn mortality [30]. It can be suggested that the Korean mothers nowadays are well aware of the negative aspects of coffee intake as shown by the reduced frequencies of coffee intake of both NGT and GDM mothers in the present study.

There was a difference between the NGT subjects and GDM subjects during their pregnancy regarding the type of snack menu. Dairy products were the most frequently consumed snack among NGT subjects, whereas the GDM group reported to have eaten fruits. Such difference may have affected nutrient density of calcium between NGT and GDM in this study. Nutrient density of calcium in NGT subjects was statistically higher than that of GDM in spite of no significant differences in terms of daily calcium intake. Several recent studies have reported that calcium intake is related to glucose level. Choi et al. [31] reported that high calcium intake was correlated with lower HbA1c levels, and Villegas et al. [32] showed that calcium intake had negative correlation with type 2 diabetes mellitus. It can be suggested that higher calcium intake of NGT compared to GDM in this study may not affect insulin secretion itself but it may have attenuated insulin resistance, thus having positively affected the NGT subjects' health status by lowering the risk of GDM. In contrast to NGT, the majority of GDM in the present study replied that they ate fruits for snack. Both daily intakes and nutrient density of vitamin C in NGT subjects were significantly higher than those in GDM. However, there is limitation to investigate the correlation between the amount of fruit intake was surveyed and GDM occurrence since the frequency of fruit intake was surveyed but the total amount was not. Furthermore, the sugar content may vary because of it highly depends on the kinds of fruit which the subjects had taken. Therefore, further investigations are needed taking into account kinds and amount of fruit consumed.

Frequency and type of night-eating menu were also significantly different between the NGT and GDM subjects. There were no significant differences of frequency and type of night-eating menu between the two groups during prepregnancy. For frequency of night-eating consumption, most of NGT subjects answered "rarely" whereas most of GDM subjects consumed night-eating snacks more than once a week during pregnancy. Due to excessive night-eating snack, high-calorie consumption can be a causative factor for the obesity and gastrointestinal disorder [14]. In case of NGT group, the lower frequency of night-eating snack from 'more than once a week' to 'rarely' may decrease the risk of GDM.

Despite of its inherent limitations of reflecting only subjective opinions, taste preference investigations showed that the proportion of GDM subjects who answered "same" and "like" was much higher than that of NGT subjects and mean daily sodium intake was significantly higher in GDM group than in NGT group, which was consistent with the previous study [33]. It has been reported that salty foods are consumed significantly more in the third trimester and this may be associated with a higher threshold for saltiness. Pregnant women in the third trimester rated less salty than other stages of pregnancy. This salty taste alteration may change salt consumption and cause fluid retention and hypertension [34]. In fact, the values of SBP and DBP in GDM group were significantly higher than those in NGT group. It has been reported that there is association between GDM and gestational hypertension [35]. The rates of both gestational hypertension is increased in women with GDM [36, 37] and the rate of preeclampsia, a category of gestational hypertension, is affected by the severity of GDM [38]. Hypertension in GDM was associated with physiologic abnormal characteristics, including insulin resistance and over expression of innate immune response, which is related with inflammation and oxidative stress, and vascular abnormality [35].

Furthermore, more GDM subjects replied that they prefer 'greasy' taste compared to NGT subjects during pregnancy. This taste preference difference may affect the mean daily intakes of fat, cholesterol, and SFA in GDM which were significantly higher than those in NGT group. It has been reported that cholesterol intake was positively correlated with the risk of stress and mental stress during pregnancy and can affect the fetus in negative ways such as fetal growth retardation and low fetal weight [39]. High levels of cholesterol during pregnancy can change fetal aorta and increase the susceptibility to cardiac disorders such as coronary arteriosclerosis or fat formation [40]. In the present study, a positive correlation between fat intake and the level of blood fasting glucose was observed. Therefore, reducing fat intake may help GDM patients to prevent complications of GDM and reduce negative effects on their fetus.

The strength of our study lies in the fact that we investigated dietary behaviors of not only daily snack, but also night-eating snack in GDM. However, this study has limitations, including small number of GDM subjects and usage of FFQ that is not semi-quantified. Further studies incorporating large number of subjects and more accurate measurement of intake amounts may be able to analyze the correlations between the dietary behavior and the occurrence of GDM as well as its relative risk.

In conclusion, the present study reported that the significant differences in snack intake, night-eating habits, and nutrient intakes between NGT and GDM subjects. We recommend healthy snacks and appropriate dietary behaviors as two important lifestyle factors that can help reduce the risk of GDM and its complications. Particularly, it would be beneficial to consume plenty of vegetables, reduce night-eating snacks consumption, choose less salty and fatty foods, drink black-coffee rather than instant coffee mix with cream and sugar, and consume dairy products to prevent GDM.