Community-based prevention of stroke: nutritional improvement in Japan.

OBJECTIVES

(1) To demonstrate the importance of nutrition, especially sodium restriction and increased potassium and protein intakes, in the prevention of hypertension and stroke in a pilot study involving senior citizens. (2) To design a population-based intervention in the Shimane Prefecture of Japan concerning dietary factors such as low sodium and high potassium, protein, magnesium, calcium and dietary fibre in the prevention of stroke.

DESIGN AND METHODS

The intervention study was carried out at a senior citizens' residence and included general health education along with a reduction of dietary salt intake and increases in vegetable and protein, especially from seafood. Sixty-three healthy senior citizens (average age: 74.8 +/- 7.7 years) had their daily meals modified to a low sodium/potassium ratio for four weeks without their knowledge by the use of a potassium chloride substitute for salt, soy sauce and bean paste, which contains much less sodium and more potassium. Monosodium L-glutamate monohydrate used for cooking was changed to monopotassium L-glutamate monohydrate. Blood pressure was measured with the patient in the sitting position. Daily dietary sodium and potassium intakes were assessed by flame photometry from 24-hour urine specimens. Extensive intervention programs were introduced into the Shimane Prefecture, which has a population of 750,000, through health education classes for housewives, home visits by health nurses and an educational TV program for dietary improvement. The mortality from stroke was monitored for 10 years and compared with the average in Japan.

RESULTS

The blood pressure lowering effect of reducing the dietary sodium/potassium ratio was confirmed through a pilot intervention study at the senior citizens' residence. The mortality rates for stroke in the middle-aged population from the Shimane Prefecture during the 10 years after the introduction of dietary improvement had a steeper decline in hemorrhagic, ischemic and all strokes than the average for Japan.