Trends in nutritional status

This case study used the CHNS and NSS data to describe trends in the nutritional status of children and adults in China. Data from CHNS are preferred as they cover five points in time from 1989 to 2000. Unfortunately, CHNS surveyed very few children under two years of age and so cannot be used to provide information about trends in the prevalence of malnutrition for children in that age group. NNS, which provides data for 1992 and 2002, was used to examine changes in prevalence of stunting and underweight among children up to five years of age.

Trends in the nutritional status of children aged two to five years

The analysis results of CHNS showed that dramatic improvements in the nutritional status of Chinese children aged two to five years occurred between 1989 and 2000 (Figure 10). The prevalence of stunting decreased from 33 to 10 percent overall, from 17 to 3 percent in urban areas, and from 30 to 14 percent in rural ones. The height for age Z-score also increased, from -0.72 to 0.54 in urban areas, and from -1.28 to -0.27 in rural ones. There was also a sustained decrease in the prevalence of underweight children, from 16 to 6 percent overall, 11 to 3 percent in urban areas and 15 to 7 percent in rural ones. The weight-for-age Z-score increased from -0.36 to 0.32 in urban areas and from -0.71 to -0.35 in rural ones. Over the same period, the prevalence of overweight children increased from 2.6 to 8.2 percent.

FIGURE 10
Trends in the nutritional status of children aged two to five years, 1989 to 2000

Sample sizes: 1989, 699; 1991, 721; 1993, 651; 1997, 325; 2000, 451.

CHNS growth references: underweight = weight-for-age < -2SD; wasting = weight-for-height < -2SD; stunting = height-for-age < -2SD; overweight = weight-for-height > 2SD.

Source: CHNS.

The results of many investigations have shown that in developing countries, energy intake plays an important role in the long-term development of children (Zhai et al., 2004; Chang et al., 1996). When nutritional status and energy intake improve, the increase in the percentage of energy intake from animal protein becomes a key contributor to child development. The data from CHNS show that the height gain of children is positively correlated with the percentage of energy they derive from animal food (Figure 11).

FIGURE 11
Trends in energy supply from animal foods and mean height-for-age Z scores, 1989 to 2000

Sample sizes: 1989, 699; 1991, 721; 1993, 651; 1997, 325; 2000, 451.
Source: CHNS.

Trends in the nutritional status of children up to five years of age

Tables 8 and 9 show data for stunting and underweight by age and residence. In rural areas, stunting prevalence is 17.3 percent, compared with 4.9 percent in urban ones. The prevalence of underweight is lower than that of stunting, but differences by residence remain. A further disaggregation by economic status and residence (not shown) indicates that the prevalence rates of stunting and underweight in poor rural areas in 2002 were 29.3 and 14.4 percent, respectively. The prevalence of stunting and underweight were lowest among the one-year age group, at 8.0 and 2.6 percent, respectively. The highest prevalence of stunting in 2002 was in the 12 to 23-month age group, after which age prevalence decreased slightly.

TABLE 8
Trends in prevalence of stunting (percentage) by age and residence, 1992 and 2002

Reference: WHO Growth Reference.
Source: NNS.

TABLE 9
Trends in prevalence of underweight (percentage) by age and residence, 1992 and 2002

Reference: WHO Growth Reference.
Source: NNS.

Trends in the nutritional status of adults

CHNS and NNS provided detailed anthropometric data that made it possible to analyse the trends in adult nutritional status. The CHNS data were used to describe the trends in body mass index (BMI) distribution among adults aged 18 to 45 years. The World Health Organization (WHO)-defined cut-offs were used to classify adults as underweight, normal weight or overweight. Underweight was defined as BMI less than 18.5 kg/m². BMI of more than 25 kg/m² was classified as overweight/obese.

Figures 12 and 13 show trends in the BMI distribution of males and females aged 18 to 45 years. The shape of the BMI distribution curves of males and females changed over the 11 years from 1989 to 2000. The main characteristic of the change is a shift to the right for both the male and the female curves. For males, mean BMI increased from 21.3 to 22.4 kg/m²; for females, it increased from 21.8 to 22.5 kg/m². At the same time, the dispersion of BMI distributions widened. For males, the standard deviation increased from 2.3 to 3.1, for females, from 2.7 to 3.2. When the male and female BMI distribution curves from 1989 to 2000 are compared, the mean BMIs for females in 1989 and 1997 are significantly higher than those for males. The difference in BMI distribution between genders disappeared in 2000, because the change was significantly higher in males than in females.

In 2002, the total prevalence of overweight and obesity was 22.7 percent; however, 6.8 percent of adults aged 18 to 45 years were underweight. The prevalence of adult obesity was 7.1 percent. It is estimated that 200 million Chinese adults are overweight, and 60 million obese. The prevalence rates of overweight and obesity among adults in large cities were 30.0 and 12.3 percent, respectively.

FIGURE 12
Trends in under- and overnutrition in adults (18 to 45 years) by residence and gender, 1989 to 2000

Sample sizes: 1989, 4 527; 1991, 7 204; 1993, 7 621; 1997, 7 969; 2000, 7 862.
Source: CHNS.

FIGURE 13
Changes in BMI distribution curves for males and females, 1989 to 2000

Survey population: adult males 18 to 45 years; adult females 20 to 45 years.
Sample sizes: 1989, 4 527; 1991, 7 204; 1993, 7 621; 1997, 7 969; 2000, 7 862.
Source: CHNS.

TABLE 10
Prevalence of overweight and obesity in China (percentages), 2002

Sample size: 209 849.
Reference: WHO reference.
Source: NNS.

Trends in micronutrient deficiencies

Although the prevalence rates of micronutrient deficiencies, including iron and vitamin A, have declined in the past ten years, they are still common problems in China.

Anaemia

The NNS data from 1992 and 2002 were used to analyse changes in the prevalence of anaemia among the Chinese. The WHO and United Nations Children’s Fund (UNICEF) cut-offs of 2001 were used to define the prevalence of anaemia. The results showed that prevalence decreased slightly in the period 1992 to 2002 (Table 11). In adults, the prevalence of anaemia in urban males declined from 15.2 to 12.0 percent, and in urban females it declined from 25.8 to 20.1 percent. The prevalence among rural males remained at 18 percent, and among rural females at 24 to 25 percent. The prevalence rates of anaemia among infants and children under two years of age, people over 60 years of age and child-bearing women were 24.2, 21.5 and 20.6 percent, respectively. Anaemia is still a public health problem in China.

TABLE 11
Changes in the prevalence of anaemia (percentages) by gender and residence, 1992 and 2002

Source: NNS.

Vitamin A deficiency

In 2002, the prevalence of vitamin A deficiency (VAD) (measured as serum retinol < 20 µg/dl) among children aged three to 12 years was 9.3 percent, in urban areas it was 3.0 percent, and in rural ones 11.2 percent. The prevalence of marginal VAD (measured as serum retinol between 20 and 29µg/dl) was 45.1 percent, with a prevalence in urban areas of 29.0 percent and in rural areas of 49.6 percent.

Iodine deficiency

The prevalence of goitre among children eight to ten years of age declined from 20 percent in 1995 to 6 percent in 2002; in 2002 it was less than 5 percent in 12 provinces, between 5 and 10 percent in 14 provinces, and more than 10 percent in five provinces.

Trends in chronic disease risk factors

Hypertension

The 2002 NNS data and the 1991 National Sample Hypertension Survey data were used to study the prevalence of hypertension. Hypertension was defined as a mean systolic blood pressure of 140 mm Hg, mean diastolic blood pressure of ³ 90 mm Hg, or both, when taken at two ambulatory visits five to 14 days apart. The prevalence of hypertension in people over 18 years of age increased from 11.9 percent in 1991 to 18.8 percent in 2002. It is estimated that more than 160 million people in China have hypertension. Compared with 1991, the prevalence of hypertension increased by 31 percent, and there have been more than 70 million new hypertension patients in the past decade. The prevalence of hypertension in rural areas also increased rapidly; there is no significant difference between urban and rural prevalence rates.

TABLE 12
Trends in the prevalence of hypertension in adults, 1991 and 2002

Sources: NNS, 2002; National Hypertension Survey, 1991.

Diabetes

It is estimated that there are more than 20 million diabetic patients in China. In 2002, the prevalence of type-2 diabetes among adults over 18 years of age was 2.6 percent, and among those over 60 years of age living in large cities it was 16.97 percent. The prevalence of diabetes is significantly higher in urban than in rural areas; in 2002, the prevalence in large cities was three times as much as it was in rural areas.

There are insufficient history data on diabetes to allow the change in prevalence of type-2 diabetes in China to be described. However, data from urban areas in the National Diabetes Survey in 1996 and the NNS in 2002 can be compared (Table 13). The prevalence of type-2 diabetes in large cities increased from 4.58 to 6.07 percent during the 1996 to 2002 period.

TABLE 13
Trends in the prevalence of type-2 diabetes among adults in China, 1996 and 2002

Sources: NNS, 2002; National Diabetes Survey, 1996.

Blood lipids

The 2002 NNS was the first survey to provide national information about abnormal blood lipid levels in China. Hypercholesterolaemia was defined as blood cholesterolaemia of ³ 5.72 mmol/l, while blood cholesterolaemia between 5.20 and 5.71 mmol/l was defined as borderline high cholesterol. Low serum HDL cholesterol was defined as serum HDL £ 0.91 mmol/l, and hypertriglyceridaemia as serum triglyceridaemia ³ 1.70 mmol/l. A person who has one of these conditions is regarded as being in the abnormal blood lipids group.

The results show that the problem of abnormal blood lipid levels in China requires close attention. The prevalence of abnormal blood lipid levels among adults over 18 years of age was 18.6 percent - 22.2 percent among males and 15.9 percent among females. In 2002, it was estimated that 160 million people suffered from abnormal blood lipid levels. The prevalence rates of various types of abnormalities were: hypercholesterolaemia, 2.9 percent overall, 2.7 percent in males, and 2.9 percent in females; hypertriglyceridaemia, 11.9 percent overall, 14.5 percent in males, and 9.9 percent in females; and low blood HDL cholesterol, 7.4 percent overall, 9.3 percent in males, and 5.4 percent in females. An additional 3.9 percent of survey subjects had borderline high cholesterol levels. There was no significant difference in the prevalence of abnormal blood lipid levels between middle-aged and elderly subjects, nor any significant difference between urban and rural populations.

Physical activity levels

Large changes in technology at the workplace and in leisure activities are linked to rapid declines in physical activity. Economic activities are shifting towards the service sector, particularly in urban areas.

Data from CHNS for the last decade show a remarkable downward shift for the proportion of adults aged 18 to 45 years whose daily activity profile (based on occupation) would put them into a heavy activity category, compared with those in the light and medium categories.

The ownership of television sets has increased considerably over the past 20 years, especially in rural areas and among lower-income groups. In 2000, more than 90 percent of Chinese households owned a television. Television ownership represents a major potential source of inactivity.

TABLE 14
Trends in physical activity levels among Chinese adults (percentages), 1989 to 2000

Classifications: light physical activity = working in standing position (e.g., office worker, watch repairer, salesperson, laboratory technician, teacher); moderate physical activity (e.g., student, driver, electrician, metal worker); heavy physical activity (e.g., logger, miner, stonecutter, farmer, dancer, steelworker, athlete).

Source: CHNS.

Trends in morbidity and mortality from chronic and infectious disease

In the past 20 years, the prevalence rates of chronic diseases have increased rapidly in China, while mortality from infectious disease has declined (Figure 14 and Table 15). China has shifted from infections and malnutrition to diseases related to hypertension, coronary heart disease (CHD) and cancers. Chronic diseases have become the main cause of death in China. In 2000, the leading cause of death was cancer, followed by cerebral-vascular disease and CHD. Although infectious diseases are no longer the main causes of death, the morbidity levels from hepatitis, tuberculosis and dysentery remain high, and the burden of infectious diseases is still very high.

FIGURE 14
Trends in mortality from chronic disease in urban and rural areas, 1980 to 1999

Source: Ministry of Health of China.

TABLE 15
Trends of morbidity and mortality rates to infectious disease (per 100 000 population), 1990 to 2002

Source: China Disease Surveillance.

Policies and programmes

China is undergoing a remarkably - and undesirably - rapid transition towards a stage of the nutrition transition characterized by high rates of DR-NCDs. Some public sector organizations in China have combined their efforts in the initial stages of systematic attempts to reduce these problems. Such efforts, which focus on both under- and overnutrition, include the new Dietary guidelines for Chinese residents, the Chinese Pagoda and the National Plan of Action for Nutrition in China, which has been issued by the highest body of the government - the State Council. Apart from some activities in the agriculture sector, few systematic efforts are having an impact on behaviour. In the health sector, efforts to reduce hypertension and diabetes are increasing, but limited work is being done in the nutrition sector. There is a need for nutrition education activities and dissemination to promote the principles of the Dietary guidelines for Chinese residents, as well as more guidance on increased physical activity and its benefits (Zhai et al., 2002b).

Conclusion

The nutrition and health status of Chinese people has improved significantly in the past 20 years. China is one of the world’s most rapidly developing countries. Over the past two decades, the annual gross domestic product (GDP) growth rate was more than 8 percent, the highest in recent world history (World Bank, 2002). As a result, the proportion of the absolutely poor population in China decreased sharply from 80 percent in 1978 to less than 12 percent in 1989; the proportion of the extremely poor decreased from 20 to 6 percent over the same period (State Statistical Bureau, 2002). China has achieved remarkable economic progress and high levels of education, and a rapid evolution of the Chinese diet has accompanied these economic shifts and related social changes.

Historically, the Chinese diet has been primarily plant-based. The classic diet includes cereals and vegetables, with few animal foods. Many experts consider such a diet to be very healthy when adequate levels of intake are achieved (Du et al., 2002; Campbell, Parpia and Chen, 1998). The fat intake of the Chinese population remained at a low level for a relatively long time. Since the 1990s, however, there have been noticeable changes in the Chinese dietary pattern resulting from rapid economic development, an adequate food supply and changes in consumption patterns. With income increases, the consumption of animal food - particularly meat and eggs - has grown dramatically, while consumption of cereals and tubers has decreased.

The quality of the average diet in China has improved significantly. Energy and protein intakes among both urban and rural populations have been basically satisfactory, consumption of meat, poultry, eggs and other animal products has increased significantly as has the percentage of good-quality protein in the diet. In general, the changes have improved the quality of the Chinese diet, but there are some alarming trends in the proportional intake of energy from fat, the increased consumption of saturated fat and cholesterol and the decreasing consumption of fruits and vegetables. Many, but not all, of these changes are more pronounced in urban areas (Du et al., 2002; Campbell, Parpia and Chen, 1998; Zhai et al., 2002a; Wang et al., 2003; Popkin and Du, 2003; Popkin, Lu and Zhai, 2002), and dietary patterns among urban residents are not entirely satisfactory. Meat and oil consumption is too high, and cereal consumption is at a relatively low level. Low consumption of dairy products remains a common problem in China.

China is facing simultaneous challenges of malnutrition and overnutrition. The growth of children and teenagers has improved steadily. The prevalence of malnutrition and nutrition deficiencies such as stunting and underweight in children under six years of age, has decreased continuously (UNESCAP, 2004; UNDP, 2004; Du et al., 2002; Campbell Parpia and Chen, 1998; Chang et al., 1996; Zhai et al., 2004; Wang, Monteiro and Popkin, 2002). Deficiencies of micronutrients such as iron and vitamin A are still important public health problems in both urban and rural populations. The prevalence of malnutrition is still high: in 2002, 14.3 percent of preschool children were stunted, while 7.8 percent of preschool children and 6.8 percent of adults were suffering from underweight (NNS, 2005). On the other hand, the prevalence of overweight and obesity has risen at a relatively high degree, and stood at 22.7 percent for the overall population in 2002 (NNS, 2005).

Mortality from infectious diseases such as hepatitis, dysentery and malaria has been controlled in the past 20 years. Meanwhile, however, China is shifting remarkably quickly to a stage of the nutrition transition dominated by high intakes of fat and animal food, and an increasing prevalence of DR-NCDs such as obesity, diabetes mellitus, cardiovascular disease and cancer. The overweight and obesity prevalence and the morbidity to NCDs such as hypertension and type-2 diabetes have increased significantly in the past 20 years (Popkin et al., 2001; Wang et al., 2004). High dietary energy, high dietary fat and reduced physical activity are closely related to the occurrence of overweight, obesity, diabetes and abnormal blood lipid level. High salt intake increases the risks of hypertension. It should be emphasized that those with higher levels of fat intake and lower physical activity are at the highest risk of these chronic diseases (Popkin, 2001). Overweight, obesity and related chronic diseases have increased in both children and adults in the past 20 years and are now a major public health problem in China. In view of China’s rapid nutrition transition, it is necessary to provide better guidance to the public to enable them to make rational dietary choices and take measures to control their high intakes of dietary fat and cholesterol - factors that are very significant in the prevention and control of chronic diseases.

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