The research, published in the Nutrients journal, revealed that supplementation with short-term high-dose nitrate (NO3−) reduced systolic blood pressure and mean arterial pressure in the study group during submaximal exercise.
“These findings have extended the knowledge regarding the BP-lowering impact of NO3− with multiple-day supplementation during isometric and ischemic exercise in healthy adults,” the study authors wrote.
Published with financial support from the European Union, the study was carried out by researchers from universities in the United Kingdom, Czech Republic and Turkey.
The nitrate effect
Nitrate-rich beetroot juice has been the subject of extensive scientific study and is used as a popular nutritional intervention by athletes to enhance physical performance, stamina and recovery.
Benefits are attributed to nitrate’s capacity to increase the bioavailability of nitric oxide (NO) in the body, an essential molecule that confers ergogenic and cardioprotective effects by relaxing blood vessels to increase blood flow.
Other vegetables naturally high in nitrate include spinach, lettuce, celery, arugula, fennel and radishes.
Over two 5-day supplementation periods, separated by a washout period, 14 healthy active young males consumed 70 mL of concentrated nitrate-rich beetroot juice or a depleted placebo twice daily. Both were provided by Beet It Sport, a subsidiary of UK-based James White Drinks Ltd, which has developed a process to standardize nitrate content in each shot.
Researchers measured beat-by-beat blood pressure at pre- and post-exercise rest, during a 20-second isometric knee extensor contraction at 25% maximal strength, and throughout a three-minute sustained ischemic contraction. Blood samples were collected at least 2 ½ hours post-meal to measure plasma nitrate (NO2−) concentration.
“Plasma NO2− concentration was elevated following 5 days of NO3− supplementation, and this elevation was 245% higher compared to placebo, which suggests considerably improved potential for NO bioavailability via reduction of NO2− to NO,” the study stated.
While results conform to other research in this area and indicate the potential for nitric oxide bioavailability to reduce exercise-induced augmentation of blood pressure, the researchers say that they are novel in that they demonstrate the effects of a high nitrate dose (12.8 mmol/day) on blood pressure responses during large muscle mass (e.g., the vastus lateralis muscle in the thigh) isometric exercise.
Room for further study
The researchers noted multiple limitations of the study and called for a host of future trials to investigate the effects on blood pressure in women compared to men, as well as the mechanism of action-related parameters of the blood pressure-lowering effect of NO3− supplementation during exercise.
They also acknowledged the need for a longer-term intervention to understand the acute effect of a double dose on testing day, the limitations of self-reported data and if supplement-induced improved exercise and/or physical capacity might have affected outcomes in this trial.
2022, 14(17), 3645 doi: 10.3390/nu14173645
“High-Dose Nitrate Supplementation Attenuates the Increased Blood Pressure Responses to Isometric Blood Flow Restriction Exercise in Healthy Males”
Authors: Ozcan Esen et al