Diet, Nutrition, Lifestyle and Health in Older Chinese Adults

By Professor Jean Woo

The relationship of lifestyle factors such as diet, physical activity, smoking, and alcohol intake, to chronic diseases is well known. With increasing life expectancy and ageing of the population all over the world, the concomitant increase in the burden of chronic diseases and disability has resulted in growing emphasis being placed on primary preventive measures such as lifestyle modifications. In China, with economic development, the prevalence and mortality rate of non-communicable diseases will become a long-term economic burden. Between 1930-80, the rate of increase in the contribution of stroke, cancer and heart disease to mortality in China is steeper than in the United States. By 2030, the annual deaths from coronary heart disease, stroke, and lung cancer are estimated to reach 800,000, 3 million, and 1.7 million respectively.¹ In the (industrialized) Special Administrative Region of Hong Kong, the three primary causes of mortality are cancer, coronary heart disease and stroke. Among older people, diseases having the largest contribution to disability are stroke, dementia, fractures, Parkinson's disease, and diabetes mellitus.² These diseases tend to present as functional or cognitive impairment and frequent falls, Lifestyle modifications have a role in preventing the occurrence of diseases, in delaying deterioration, or in maximizing residual function even in the presence of disease. This article describes the relationship between some lifestyle factors (diet, physical activity, and smoking) and health problems in the older Chinese population.

Undernutrition: There are few surveys regarding this problem among the Chinese population, Data is available mainly from Hong Kong, where protein-energy malnutrition and poor nutritional status in older persons have been documented both in long term care institutions and on acute medical wards.^3,4 Poor nutrition may result in loss of muscle strength (predisposing older persons to falls resulting in fractures), impaired immunity, poor functional ability and increased health care utilization.

Figure 1. Increases in the consumption in higher-fat diets from 1989 to 1993 according to income

Source: Adapted from Guo X, Popkin BM and Zhai F, Patterns of change in food consumption and dietary fat intake in Chinese adults, 1989-1993 (1999 September) Food and Nutrition Bulletin 20(3):344-353.

Hypertension: The prevalence of hypertension and stroke is high for older Chinese persons. The positive association between salt intake and blood pressure is well documented. Many countries recommend that daily intakes of sodium chloride be limited to 5-6g (about 2 000 mg of sodium/day). A reduction in the blood pressure of a population is likely to result in a decreased prevalence of stroke, as well as in multi-infarct dementia. The traditional Northern Chinese diet consisting, in part, of preserved vegetables has an average salt content of about 15g per day. The prevalence of hypertension between northern and southern parts of China may differ by more than three-fold, and that for stroke by two-fold.⁶

Coronary Heart Disease: The prevalence of coronary heart disease among the Chinese is lower than that for Caucasians. It is suspected that the low percentage of fat in the traditional Chinese diet, which falls within the recommended guidelines for prevention of CHD (<?? 30% of total daily kilocalories), may account for the difference. Other dietary factors may contribute to the lower prevalence of CHD. Because the Chinese populations in China consume a high amount of vegetables, fish, seafood, and few dairy products, their diets may contain more folate, anti-oxidant vitamins, omega-3 fatty acids, and phytoestrogens than Caucasian diets.⁷ Urinary phytoestrogen concentration is also higher in Asian populations, reflecting the high consumption of soy products.

Osteoporotic Fractures: Low bone mineral density and falls predispose older persons to fractures, which constitute a major cause of disability as well as mortality. Certain features in the Chinese diet are known to predispose the body to bone loss: the low consumption of dairy products results in low calcium intake, and the high salt intake increases obligatory urinary calcium excretion, hence increasing the calcium requirement. Throughout China calcium intake values range from 300 mg to 800 mg per day and are considered low compared to the recommended requirement for North Americans of 1 200 mg per day (800 mg per day for those over 50 years of age). Although the calcium intake appears lower when compared to Western women, Chinese women have a smaller body size, so that when the intake is adjusted for body size, calcium intake is really no less than that for US women.⁷ A recent study suggested that absorption of calcium may be higher for subjects with habitually low calcium intake and higher than that for whites or blacks.⁸ Based on these observations, it has been suggested that the recommended calcium intake may be lower for Chinese populations. Definitive conclusions cannot be made, however, since the calcium isotope used for the absorption studies was not mixed with food⁷ (unlike the studies in Western women), and ideally, recommendations should be made based on calcium balance studies.⁹ Although the consumption of dairy products is lower in the Chinese population, vegetables and soy products provide 41% of the calcium intake, and calcium absorption from some of these vegetables is higher than that from milk.⁹ The study by Kung et al.⁸ also showed a higher urinary calcium excretion among older osteoporotic subjects (in spite of similar parathyroid hormone levels and creatinine clearance values in older normal subjects), and this may be compatible with higher salt consumption in the osteoporotic subjects' increasing obligatory renal calcium loss. Other dietary factors affecting bone health include a negative association between protein and vitamin K intake which increases the risk of hip fractures;^10,11 and vegetarianism, a feature of some Chinese religious sects, is associated with low protein intake and low bone mineral density.¹² These dietary factors may be ameliorated by genetic factors, in that there is a low prevalence of the vitamin D receptor BB genotype noted to be associated with osteoporosis in Caucasians.¹³

Cancer. The changing patterns of cancer in China (decreasing incidence of oesophagus and cervical cancer; rising incidence of lung, colorectal and breast cancers) parallel changes in the national Chinese diet towards consumption of more fat, oil, meat and foods of animal origin. Large scale epidemiological studies are in progress to examine the relationship between diet and disease. It is likely that the shift towards a more Western dietary pattern may be associated with the changing patterns of cancer.

Physical Activity: A higher level of physical activity has been associated with increased survival, delay in the progression of disability, loss of functional ability, improved balance and strength, reduced incidence of falls (and thus fractures), as well as the quality of life. There is a general decrease, however, in the level of physical activity with an urban lifestyle, resulting in an increased prevalence of obesity. For older persons, the age-related loss of muscle mass, "sarcopenia", (see page 27) is thought to be a major contributor to the development of this metabolic syndrome, which may be retarded by high resistance exercise. Physical inactivity is a risk factor for coronary heart disease in elders, predisposing them to hypertension, an adverse lipid and haemostatic profile, and left ventricular dysfunction. In subjects with heart failure, physical training improves endothelial dysfunction. Weight bearing exercise is also important in the prevention of osteoporosis. While physical inactivity will not be a problem for rural populations in a large part of China, it is a significant problem for people living in cities such as Hong Kong. The design of the city is such that few people use stairs or walk any distance on steeply graded roads. For cities in other parts of China, the widespread use of bicycles results in a higher level of physical activity. It is important to promote the health benefits of exercise to the public. Traditionally, Chinese elders regularly practice some form of exercise in the morning, whether it is a walk, Tai-Chi or related exercises. It is important to encourage this practice, and at the same time to carry out studies to document the health benefits associated with exercises that are acceptable and practical for the majority of the population. Walking or similar aerobic exercises will improve cardiovascular fitness. The benefits of Tai-Chi are now being documented: Tai-Chi improves balance, reduces falls and probably the risk of fractures. Its effect on the prevention of sarcopenia is uncertain. It is possible that resistance exercises will also be needed to maintain optimal health. With more studies on the health benefits of different types of exercises practiced by older Chinese persons, evidence-based exercise regimes that are likely to be practiced by the majority of the population can be more easily promoted.

Smoking: Adverse health effects of smoking have also been documented in China,¹⁴ yet the tobacco companies, under increasing pressure from developed countries, have intensified marketing effects in Asia. The prevalence of smoking is much higher in men (about 50%) than women (less than 10%). Even in persons more than 70 years old, the effect of smoking on health is still apparent. In a three year longitudinal study of 2030 Hong Kong Chinese subjects age 70 years and older, elevated mortality risks from all causes were observed for current smokers of both sexes. Eighty percent of deaths were due to cancer, cardiovascular and respiratory diseases, for which smoking is an established risk factor. Therefore smoking cessation is beneficial even in the older population.

Conclusion: The Chinese population can modify their lifestyles not only to prevent chronic diseases, but to minimize their accompanying disease and disability burden. Steps to be taken to achieve this goal include raising the awareness of the magnitude of the problem among health care workers and the general public, and disseminating clear, healthy lifestyle messages. Further research is needed to decide on the methods which will have the greatest impact.

References

1.	Chen CM (1995). Eating patterns - a prognosis for China. Asia Pacific Journal of Clinical Nutrition 4 S1:24-28.
2.	Woo J, Ho SC, Yu LM, Lau J, Yuen YK (1998). Impact of chronic diseases on functional limitations in elderly Chinese aged 70 years and over a cross sectional and longitudinal survey. Journal of Gerontology: Medical Sciences 35A:102-106.
3.	Woo J, Ho SC, Cheung CK, Mak YT, Swaminathan R (1989) (b). Protein calorie malnutrition in elderly chronic care institutions in Hong Kong. Nutrition Reports International, 40:1011-1018.
4.	Woo J, Mak YT, Swaminathan R (1991). Nutritional Status of General Medical patients - influence of age and disease. Journal of Nutritional Biochemistry 2:274-280.
5.	Guo X, Popkin BM, Zhai F (1999) Patterns of change in food consumption and dietary fat intake in Chinese adults, 1989-1993 Food and Nutrition Bulletin 20(3):344-353.
6.	Chen CM, Shao ZM (1994) Food, Nutrition and Health Status of Chinese in 7 Provinces, 1990. China Statistical Publishing House, Beijing, China.
7.	Heaney RP (1999) Age-related osteoporosis in Chinese women American Journal of Clinical Nutrition 69:1291-1292.
8.	Kung AWC, Luk KDK, Chu LW, Chiu PKY (1998) Age-related osteoporosis In Chinese: an evaluation of the response of Intestinal calcium absorption and calcitropic hormones to dietary calcium deprivation American Journal of Clinical Nutrition 68:1291-1297.
9.	Weaver CM (1998) Calcium requirements: the need to understand racial differences. American Journal of Clinical Nutrition 68:1153-1154.
10.	Munger RG, Cerhan JR, Chiu B C-H (1999) Prospective study of dietary protein intake and risk of hip fracture in postmenopausal women American Journal of Clinical Nutrition 69:147-152.
11.	Feskanich D, Wber P, Wilett WC, Rockett H, Booth SL, Colditz GA (1999) Vitamin K intake and hip fracture in women: a prospective study American Journal of Clinical Nutrition 69:74-79.
12.	Lau E, Kwok T, Woo J, Ho SC (1998) Bone mineral density in elderly female Chinese vegetarians and omnivores European Journal of Clinical Nutrition 52:60-64.
13.	Young RP, Lau EMC, Birjandi Z, Critchley JAJH, Woo J (1996) Incidence of hip fracture In women and the vitamin D receptor gene polymorphism Lancer 348:688-689.
14.	Lopez AD (1998) Counting the dead in China British Medical Journal 317:1399-1400.

Dr J Woo, Head, Division of Geriatrics, The Chinese University of Hong Kong, The Prince of Wales Hospital, Shatin, NT, Hong Kong; tel 852 2632 3127; fax 852 2645 1699; email jeanwoowong@cuhk.edu.hk