A food frequency questionnaire for use in the Chinese population in Hong Kong: Description and examination of validity

Hypertension is the most important known risk factor for stroke. Clinical, experimental, and epidemiologic evidence suggests that a high dietary intake of potassium is associated with lower blood pressure. In hypertensive rats, a high intake of potassium is reported to protect against stroke, even though blood pressure is not affected. We examined the relation between the 24-hour dietary potassium intake at base line and subsequent stroke-associated mortality in a population-based cohort of 859 men and women (aged 50 to 79 years) in Southern California. After 12 years, 24 stroke-associated deaths had occurred. The relative risks of stroke-associated mortality in the lowest tertile of potassium intake, as compared with that in the top two tertiles combined, were 2.6 (P = 0.16) in men and 4.8 (P = 0.01) in women. In multivariate analyses, a 10-mmol increase in daily potassium intake was associated with a 40 percent reduction in the risk of stroke-associated mortality (P less than 0.001). This effect was independent of other dietary variables, including the intake of calories, fat, protein, fiber, calcium, magnesium, and alcohol. The effect was also apparently independent of known cardiovascular risk factors, including age, sex, blood pressure, blood cholesterol level, obesity, fasting blood glucose level, and cigarette smoking. These findings support the hypothesis that a high intake of potassium from food sources may protect against stroke-associated death.

To develop predictive equations for basal metabolic rate (BMR) in healthy Chinese adults and to evaluate factors that may influence BMR. Measuring the BMR of Chinese adults by indirect calorimetry. Selected subjects were randomly assigned to a validation sample and a cross-validation sample. The validation sample was used to develop predictive equations that were cross-validated using the other sample. Two hundred twenty-three healthy Chinese adults (102 men and 121 women) participated in the study. Their ages ranged from 20 to 78 years old (mean = 43.8 +/- 14.3 years). BMR was measured by indirect calorimetry. Body composition was assessed by skinfold fat thicknesses, bioelectrical impedance analysis, and urinary creatinine excretion. Student's t test, Pearson correlation coefficients, linear regression analyses, and the best subset were used for statistical analyses. The better-fitting equation for predicting BMR in Chinese adults is BMR = 13.88 x weight (kg) + 4.16 x height (cm) - 3.43 x age (years) - 112.40 x sex (men = 0; women = 1) +54.34. Men had higher BMR values than women because men had greater fat-free mass, body cell mass, and muscle mass. BMR correlated best with body composition, which correlated highly with anthropometric measurements. Therefore, accurate determination of body weight and body height are beneficial in predicting a person's BMR. All of the currently available predictive equations overestimated BMR (P = .0001) for healthy Chinese adults. The equations developed in this study predict BMR more accurately for Chinese adults. The equations developed in this study are recommended for clinical use in healthy Chinese adults who are within normal limits for body weight.

Laboratory and epidemiological studies suggest that the antioxidants, vitamin E and beta-carotene, protect against coronary heart disease. In a European multicentre case-control study alpha-tocopherol and beta-carotene concentrations were measured in adipose-tissue samples collected in 1991-92 from 683 people with acute myocardial infarction and 727 controls. Mean adipose-tissue beta-carotene concentration was 0.35 microgram/g in cases and 0.42 in controls, with age-adjusted and centre-adjusted mean difference 0.07 microgram/g (95% confidence interval [CI] 0.04-0.10). Mean alpha-tocopherol concentrations were 193 micrograms/g and 192 micrograms/g for cases and controls, respectively. The age-adjusted and centre-adjusted odds ratio for risk of myocardial infarction in the lowest quintile of beta-carotene as compared with the highest was 2.62 (95% CI 1.79-3.83). Additional control for body-mass index and smoking reduced the odds ratio to 1.78 (95% CI 1.17-2.71); other established risk factors did not substantially alter this ratio. The increased risk was mainly confined to current smokers: the multivariate odds ratio in the lowest beta-carotene quintile in smokers was 2.39 (95% CI 1.35-4.25), whereas it was 1.07 for people who had never smoked. A low alpha-tocopherol concentration was not associated with risk of myocardial infarction. Our results support the hypothesis that high beta-carotene concentrations within the normal range reduce the risk of a first myocardial infarction. The findings for alpha-tocopherol are compatible with previous observations of reduced risk among vitamin E supplement users only. The consumption of beta-carotene-rich foods such as carrots and green-leaf vegetables may reduce the risk of myocardial infarction.