DASH diet and sodium reduction: lower blood pressure during sleep too

Blood pressure measured over 24 hours

Participants were randomly assigned to either a control diet or the DASH diet. Within each group, they then followed three 30-day dietary periods with low, intermediate and high sodium levels, in random order.

Ambulatory blood pressure was measured at the end of each period. This method allowed researchers to distinguish between 24-hour, waking and sleeping values, rather than relying solely on a single reading.

The analysis included 335 participants with these measurements, 58% of whom self-identified as Black. The results were examined in this group and among non-Black participants.

Lower nighttime blood pressure with the low-sodium DASH diet

Compared with the high-sodium control diet, sodium reduction and the DASH diet, separately or together, reduced systolic and diastolic blood pressure over 24 hours, during waking hours and during sleep in both groups.

With the combination of DASH and low sodium intake, systolic blood pressure during sleep was an average of 8.0 mmHg lower among Black participants, with a 95% confidence interval of 4.8 to 11.2 mmHg. Among non-Black participants, the average reduction was 7.4 mmHg, with an interval of 3.9 to 11.0 mmHg.

These findings are group averages, not a guaranteed reduction for each person. Nevertheless, they show that the observed effect was not limited to waking hours.

Persistent differences, with no established explanation

Despite these reductions, differences in blood pressure during sleep persisted between Black and non-Black participants. The dietary intervention therefore did not eliminate the differences observed between these groups.

The abstract does not establish the causes. These self-reported categories do not, on their own, provide a biological explanation for the measured differences.

The study provides information about blood pressure after short dietary periods. The abstract reports neither cardiovascular events nor whether the effects were sustained over the long term. It is therefore not enough to turn these findings into a promise of prevention for individuals.

What we can take away

The DASH diet and sodium reduction also lower blood pressure during sleep in this trial. This finding demonstrates neither the elimination of differences between groups nor a long-term cardiovascular benefit.