| BackgroundWith the swiftly developing of economy and social progress, the prevalence of overweight and obesity is increasing rapidly, which has become a serious public health problem. The risks of type two diabetes and cardiovascular diseases and related tumors rise as the Body Mass Index (BMI) increase. All the time, high-energy diets and low physical activity are attributed to the soaring overweight and obesity. In the past few years, some researchers have focused the monosodium glutamate (MSG) in diets. They regard it as an independent risk factor for overweight and obesity. However, epidemiologic studies on the subject are still few in the world, and final conclusion has not been reached.ObjectiveTo find the MSG consumption in Chinese adults, analyze the association of MSG and overweight in different age groups and trace the changes. Finally, assess the effects of MSG on overweight and obesity in Chinese adults and provide theoretical foundation for obesity control.MethodSamples were from China Health and Nutrition Survey in 2000 and 2006. The study includes two parts. The first one was cross sectional analysis of MSG weighing, 24-hour dietary recall, dietary records and physical measurement of 2362 residents aged 20-59 in 2000. Participants were divided into four groups, namely 20-29 year old group (sample size:436),30-39 year old group (sample size:716),40-49 year old group (sample size:750) and 50-59 year old group (sample size:460). Another one was analysis on the 864 traced participants in 2000 and 2006 survey. People who were suffered from hypertension, apoplexy, diabetes, myocardial infarction and sicken in the past four weeks were excluded. The studying targets involved demography, physique, MSG consumption, dietary and physical activities.ANOVA, χ2-test, Pearson correlation, covariance analysis were applied in the analysis of MSG consumption, overweight and obesity distribution and their association. In addition, traced samples were analyzed independently. SAS9.1 was applied in the data analysis.Results1. Cross sectional study:1.1 Basic information of the sample:The sample included 2362 participants, average age was 39.7 years.1095 was male while 1267 were female.1128 were urban residents while 1234 were rural population. During the three days investigation, the participants ate at home for 2.7 days on average.1.2 Overweight and Obesity:The BMI of males and females were normally distributed. The average BMI was 23.01 in females and 22.63 in males. The average BMI was 23.06 in urban residents and 22.52 in rural population. On the whole, the prevalence of overweight and obesity was higher in females and rural population. Among the four groups, the prevalence of overweight and obesity was the highest in 40-49 year old group, which were 29.9% and 8.1% respectively. The prevalence of overweight and obesity of 20-29 year old group was the lowest, which were 13.3% and 4.6% respectively. No statistically significant difference in overweight and obesity was detected between males and females aged 20-29 year old and 30-39 year old. However, the prevalence overweight and obesity among females was significantly higher than males in the last two groups.The average waist circumference was 80.1 cm in females and 76.6 cm in males. The average waist circumference was 78.9 cm in urban residents and 77.6 cm in rural population. As for the prevalence of central obesity, which increased with age, females were higher than males while urban residents were higher than rural population. Among the four groups, the prevalence of central obesity was the highest in 50-59 year old group, males and females were 33.3% and 53.4% respectively. The 20-29 year old group was the lowest, males and females were 14.9% and 17.5% respectively. No statistically significant difference in central obesity was detected between males and females aged 20-29 year old and 30-39 year old. However, central obesity among females was significantly higher than males in the last two groups.1.3 MSG ConsumptionThe MSG consumption of urban residents was significantly higher than rural population, while males ’were a little higher than females’. The average MSG consumption was 2.69g/d in urban residents and 2.18g/d in rural population. While 2.52g/d in males and 2.39g/d in females. No significant difference was detected in the consumptions of the four groups. The average consumption in Heilongjiang, Liaoning, Shandong, and Henan was 2.78g/d, significantly higher than the consumption in Guizhou, Guangxi, Hunan, Hubei and Jiangsu, which was 2.26g/d.1.4 Nutrient Intake and physical activity in the groupsThe average energy intake was always higher in males than in females. The average intake was 2600kcal/d and 2200kcal/d approximately in males and females. No significant difference was detected between urban and rural. Urban residents were likely to consume more protein and fat than rural population, especially animal protein and plant fat. Part of rural population and urban residents did not take adequate some kinds of essential nutrient, such as calcium etc. More than 60 percent males smoked and drank. However, as for females, the percent was only 3 percent and 10 percent respectively.Participants did physical activity for 35-45 hours per week, and rural population did a little longer. Nearly half of physical activity for urban residents was light, while half for rural population was heavy.1.5 The association of overweight with MSG consumptionThe participants were divided into three groups according to their MSG consumption, namely the low consumption group (under than 33.33%), the medium consumption group (between 33.33% and 66.67%) and the high consumption group (over 66.67%). The associations of overweight with MSG consumption were compared with the low consumption group, age, gender, urban and rural, nutrients intake and physical activities were adjusted.No significant association of MSG consumption with overweight was detected in the 20-29 year old group,30-39 year old group and 40-49 year old group. The risk of overweight and central obesity was higher in the 50-59 year old group, the odds risks were 1.73 (1.06-2.83) and 1.90 (1.17-3.08) respectively. However, such association was not detected in the medium consumption group.2. Follow-up study.2.1 Basic information of the sampleThe participants were divided into three groups according to their MSG consumptions in 2000 and 2006, namely the low, the medium and the high group, which included 301,269 and 294 participants respectively, and the MSG consumption were 1.27g/d,2.20g/d and 3.30g/d respectively.The energy, protein and fat intakes did not vary significantly in the two investigations. The intakes of vitamin A, C and E were increased significantly, but the intake of calcium was still inadequate for some participants. No significant difference was detected in most nutrients intake, smoking and physical activity after age, gender and urban or rural were adjusted.2.2 Overweight and obesityThe prevalence of overweight and obesity had been increased from 2000 and 2006. The three groups increased 3.9%,6.3% and 8.5% respectively. While the prevalence of central obesity increased 8.7%,9.3% and 10.9% respectively.2.3 The association of overweight with MSG consumptionIn the covariance analysis of overweight and MSG consumption, age, gender, residency, and BMI in2000 were adjusted. The results demonstrated that the high and the medium consumption groups had a higher risk of overweight and obesity than the low consumption group. The relative risks were 1.74 and 1.56 respectively. As for central obesity, the high consumption group also had a higher risk than the low consumption group. The relative risk was 1.50. But no difference was detected between the low and the medium group.Conclusions1. Average consumption of MSG was 2.45g/d in Chinses people, while 2.69g/d in urban and 2.18g/d in rural.2. Participants who consumed more MSG had a higher risk of overweight and central obesity.3. The positive correlation of MSG consumption and overweight was more significant in the 50-59 year old group. |
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