Melatonin supplementation reduces nighttime blood pressure but does not affect blood pressure reactivity in normotensive adults on a high-sodium diet

Abstract

High-sodium diets (HSDs) can cause exaggerated increases in blood pressure (BP) during physiological perturbations that cause sympathetic activation, which is related to cardiovascular risk. Melatonin supplementation has been shown to play a role in BP regulation. Our aim was to examine the effects of melatonin taken during an HSD on 24-h BP and BP reactivity during isometric handgrip (IHG) exercise, postexercise ischemia (PEI), and the cold pressor test (CPT). Twenty-two participants (11 men/11 women, 26.5 ± 3.1 yr, BMI: 24.1 ± 1.8 kg/m², BP: 111 ± 9/67 ± 7 mmHg) were randomized to a 10-day HSD (6,900 mg sodium/day) that was supplemented with either 10 mg/day of melatonin (HSD + MEL) or placebo (HSD + PL). Twenty-four-hour ambulatory BP monitoring was assessed starting on day 9. Mean arterial pressure (MAP) was quantified during the last 30 s of IHG at 40% of maximal voluntary contraction and CPT, and during 3 min of PEI. Melatonin did not change 24-h MAP (HSD + PL: 83 ± 6 mmHg; HSD + MEL: 82 ± 5 mmHg; P = 0.23) but decreased nighttime peripheral (HSD + PL: 105 ± 10 mmHg; HSD + MEL: 100 ± 10 mmHg; P = 0.01) and central systolic BP (HSD + PL: 97 ± 9 mmHg; HSD + MEL: 93 ± 8 mmHg; P = 0.04) on the HSD compared with the HSD + PL. The absolute and percent change in MAP during IHG was not different between conditions (all P > 0.05). In conclusion, melatonin supplementation did not alter BP reactivity to the perturbations tested on an HSD but may be beneficial in lowering BP in young healthy normotensive adults.NEW & NOTEWORTHY BP reactivity was assessed during isometric handgrip (IHG) exercise, postexercise ischemia (PEI), and the cold pressor test (CPT) after 10 days of a high-sodium diet with and without melatonin supplementation. Melatonin did not alter BP reactivity in healthy normotensive men and women. However, melatonin did decrease nighttime peripheral and central systolic BP, suggesting it may be beneficial in lowering BP even in those with a normal BP.

Keywords: ambulatory blood pressure; blood pressure reactivity; melatonin; sodium.

Figure 1.

Twenty-four-hour ambulatory blood pressure at the end of the high-sodium diet plus placebo condition (HSD + PL) and high-sodium diet plus melatonin conditions (HSD + MEL). Twenty-four-hour systolic blood pressure (SBP) (A); 24-h diastolic blood pressure (DBP) (B); 24-h mean arterial pressure (MAP) (C); daytime SBP (D); daytime DBP (E); daytime MAP (F); nighttime SBP (G); nighttime DBP (H); and nighttime MAP (I). n = 18 (9 M/9 W). Data were analyzed using paired t tests and are presented as average and individual data points. Data points from a single participant are connected. *P < 0.05 between conditions.

Figure 2.

Effect of high-sodium diet plus placebo (HSD + PL) and high-sodium diet plus melatonin (HSD + MEL) on the blood pressure responses to isometric handgrip (IHG) exercise, postexercise ischemia (PEI), and the cold pressor test (CPT). Change in mean arterial pressure (MAP) (Δ) in response to IHG (A); percent change in MAP to IHG (B); change in MAP (Δ) in response to PEI (C); percent change in MAP in response to PEI (D); change in MAP (Δ) in response to CPT (E); percent change in MAP in response to CPT (F). n = 22 (11 M/11 W) for IHG and PEI; n = 19 (11 M/8 W) for CPT. Data were analyzed using paired t tests and are presented as average and individual data points. Data points from a single participant are connected.