Hypertension: time always for prevention via dietary salt reduction.

Hypertension is defi ned as a systolic blood pressure (BP) of 140 mmHg or higher or a diastolic BP of 90 mmHg or higher.1 However, health declines in persons whose blood pressure is above 115/75 mmHg. Hypertension is linked to an increased risk of stroke, myocardial infarction, heart failure, renal failure, and cognitive impairment.1,2 Globally, a systolic BP above 115 mmHg is the top determinant of the risk of death,1 and the absolute number of annual cardiovascular deaths approaches 8 millons.2 The restricted intake of sodium chloride (table salt) in heart failure is an old and effective treatment, whose success depends on limiting volume expansion of the circulating plasma (due to retention of sodium-linked free water). Dietary restriction of sodium (2 to 3 grams daily) is recommended in most patients with heart failure (HF); further restriction to <2 grams daily may be considered in severe HF. Fluid restriction to <2 litres/day is considered in hyponatremic patients (plasma sodium <130 mmol/L) and in those with hard-to-regulate fl uid retention.3 Sodium is also a powerful pressor substance, and a widely available hypertensive agent. However, the idea that cutting the dietary intake of sodium, both table salt and the monosodium glutamate which underpins the new ‘umami taste,’ effectively decreases the blood pressure only took hold after a long lag-time.4,5 The dietary prevention of hypertension is attractive, yet notoriously diffi cult to translate into effective public health strategy.6 There is no doubt that salt restriction will lower the BP by a small but effective amount, about 4/2 mmHg, in the long term.4-6 A greater BP reduction (about 7/3 mmHg) occurs when the non-drug regime includes loss of body mass, and reductions in the intake of total calories, and of fats and sugars.7 The so-called ‘healthful dietary pattern’ shown to lower the BP comprises less salt, and more fruits, vegetables, whole grains, low-fat dairy products, fi sh, nuts, and unsaturated vegetable oils.6,8 The mean BP falls further still when these reductions are enhanced by regular aerobic exercise.9 Obviously the whole ‘lifestyle package’ is best — it lowers the BP as much as one antihypertensive drug.1 However, in contrast to physical exercise, cutting salt is a change many people can sustain in the long term. What