¹Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, New Territories, Hong Kong

Correspondence: T C Y Kwok, Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, New Territories, Hong Kong. E-mail: tkwok@cuhk.edu.hk

^*Guarantor: TCY Kwok.

^†Contributors: TCY Kwok, TYK Chan, J Woo.

Received 11 April 2002; Revised 7 June 2002; Accepted 11 June 2002.

Abstract

Objective: To examine the associations of dietary sodium and potassium, as reflected by the urinary sodium/potassium excretion, and calcium intake with blood pressure and the prevalence of hypertension among older Chinese vegetarians in Hong Kong.

Design: Cross-sectional study.

Setting: Research clinic in a teaching hospital in Hong Kong.

Subjects: A total of 111 ambulatory vegetarians over the age of 55 were recruited from members of religious organizations or old age hostels.

Main outcome measures: Hypertension was defined as supine blood pressure >140/90 mmHg or a history of hypertension. Dietary sodium, potassium and calcium intakes were assessed by 24 h recall method or fasting urinary sodium or potassium/creatinine ratios.

Results: Seventy-one subjects (64%) were found to have hypertension. Compared with normotensive subjects, hypertensive subjects had lower calcium intake (411s.d. 324 vs 589428 mg, P=0.04), but higher urinary sodium/creatinine ratio (32.619.3 vs 21.012.4, P=0.00) and sodium/potassium ratio (4.72.8 vs 3.42.3, P=0.02). Among 88 subjects not taking diuretics or antihypertensive drugs, systolic blood pressure was related to calcium intake (r=-0.40), urinary sodium/creatinine ratio (r=0.39), urinary sodium/potassium ratio (r=0.30) and age (r=0.23). Diastolic blood pressure was related to urinary sodium/creatinine (r=0.29). Twenty-three subjects with high urinary sodium/potassium and low calcium intake and 16 subjects with low urinary sodium/potassium ratio and high calcium intake differed markedly with respect to systolic blood pressure (15926 vs 13015 mmHg) and prevalence of hypertension (78% vs 25%).

Conclusion: Older Chinese vegetarians are predisposed to hypertension because of their sodium-rich but calcium-deficient diets.