DASH diet

DASH — Dietary Approaches to Stop Hypertension — is the eating pattern built and tested to lower blood pressure, and it does lower it — modestly. The effect is smaller than the famous number: a few millimetres of mercury (mmHg), larger in the first trial's participants with high blood pressure, though later trials found no such difference.

If your blood pressure is high or creeping up, eat DASH-style — fruit, vegetables, whole grains, low-fat dairy, little red meat or sugary drink — and cut salt as well. Expect a few points off, not a replacement for medication you need.

What it is

DASH is high in fruit, vegetables, whole grains and low-fat dairy, moderate in fish, poultry, beans and nuts, and low in saturated fat, red meat and sugar-sweetened drinks. It overlaps heavily with the Mediterranean diet; the main differences are that the Mediterranean diet leans harder on olive oil and fish, while DASH emphasises low-fat dairy and, in its stricter version, cutting salt.

The original trial, and where the famous number comes from

The first DASH trial provided every meal to 459 people for eight weeks, holding salt and body weight constant, so it measured the diet eaten properly rather than the result of advice. Systolic pressure (the top number) fell by about 11 mmHg in the 133 people with hypertension, but only by about 3.5 mmHg in the 326 without it — most of whom had high-normal pressure.^[1] The widely quoted ~6 mmHg is the average across the whole trial, not the effect in people with normal pressure.

What later trials show

Across 30 randomised trials and 5,545 participants, the typical effect is smaller still: about 3 mmHg systolic and 2.5 mmHg diastolic. Unlike in the first trial, it did not differ by whether people had hypertension.^[2] A real effect, but a small one.

Salt: helps more, but overlaps

A follow-up feeding trial varied salt on top of the diet. Going from high to low sodium lowered systolic pressure by about 6.7 mmHg on an ordinary diet but by about 3.0 mmHg on DASH.^[3] The two levers overlap rather than add up: doing both beats either alone, but by less than the sum.

Does it help you live longer?

Possibly, but the evidence is observational. Pooling 17 cohort estimates from 13 publications, each 5-point step up a DASH adherence score tracked with about 5% lower mortality from any cause and about 4% lower cardiovascular mortality. The studies varied widely, and all relied on people reporting what they ate, so read this as "people who eat this way die later", not as a proven effect of the diet.^[4]

What to do

Build meals on fruit, vegetables, whole grains and beans, with low-fat dairy, and keep red meat and sugary drinks low.
Cut salt too, mostly by eating less processed food; the gain on top of DASH is smaller than on an ordinary diet but still real.
Treat it as one lever among several. The wider plan is on Blood pressure, and how DASH compares with the other named diets on Dietary patterns.