Browsing by Author "Zoughaib, William S."

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    Beetroot juice supplementation and exercise performance: is there more to the story than just nitrate?
    (Frontiers Media, 2024-02-20) Zoughaib, William S.; Fry, Madison J.; Singhal, Ahaan; Coggan, Andrew R.; Exercise & Kinesiology, School of Health and Human Sciences
    This mini-review summarizes the comparative effects of different sources of dietary nitrate (NO3-), beetroot juice (BRJ) and nitrate salts (NIT), on physiological function and exercise capacity. Our objectives were to determine whether BRJ is superior to NIT in enhancing exercise-related outcomes, and to explore the potential contribution of other putatively beneficial compounds in BRJ beyond NO3-. We conducted a comparative analysis of recent studies focused on the impact of BRJ versus NIT on submaximal oxygen consumption (VO2), endurance performance, adaptations to training, and recovery from muscle-damaging exercise. While both NO3- sources provide benefits, there is some evidence that BRJ may offer additional advantages, specifically in reducing VO2 during high-intensity exercise, magnifying performance improvements with training, and improving recovery post-exercise. These reported differences could be due to the hypothesized antioxidant and/or anti-inflammatory properties of BRJ resulting from the rich spectrum of phytonutrients it contains. However, significant limitations to published studies directly comparing BRJ and NIT make it quite challenging to draw any firm conclusions. We provide recommendations to help guide further research into the important question of whether there is more to the story of BRJ than just NO3-.
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    Short-term beetroot juice supplementation improves muscle speed and power but does not reduce blood pressure or oxidative stress in 65–79 y old men and women
    (Elsevier, 2023) Zoughaib, William S.; Hoffman, Richard L.; Yates, Brandon A.; Moorthi, Ranjani N.; Lim, Kenneth; Coggan, Andrew R.; Exercise & Kinesiology, School of Health and Human Sciences
    We have previously demonstrated that acute ingestion of inorganic nitrate (NO3-)-rich beetroot juice (BRJ), a source of nitric oxide (NO) via the NO3- → nitrite (NO2-) → NO pathway, can improve muscle speed and power in older individuals. It is not known, however, whether this effect is maintained or perhaps even enhanced with repeated ingestion, or if tolerance develops as with organic nitrates, e.g., nitroglycerin. Using a double-blind, placebo-controlled, crossover design, we therefore studied 16 community-dwelling older (age 71 ± 5 y) individuals after both acute and short-term (i.e., daily for 2 wk) BRJ supplementation. Blood samples were drawn and blood pressure was measured periodically during each ∼3 h experiment, with muscle function determined using isokinetic dynamometry. Acute ingestion of BRJ containing 18.2 ± 6.2 mmol of NO3- increased plasma NO3- and NO2- concentrations 23 ± 11 and 2.7 ± 2.1-fold over placebo, respectively. This was accompanied by 5 ± 11% and 7 ± 13% increases in maximal knee extensor speed (Vmax) and power (Pmax), respectively. After daily supplementation for 2 wk, BRJ ingestion elevated NO3- and NO2- levels 24 ± 12 and 3.3 ± 4.0-fold, respectively, whereas Vmax and Pmax were 7 ± 9% and 9 ± 11% higher than baseline. No changes were observed in blood pressure or in plasma markers of oxidative stress with either acute or short-term NO3- supplementation. We conclude that both acute and short-term dietary NO3- supplementation result in similar improvements in muscle function in older individuals. The magnitudes of these improvements are sufficient to offset the decline resulting from a decade or more of aging and are therefore likely to be clinically significant.
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    The influence of acute dietary nitrate supplementation on skeletal muscle fatigue and recovery in older women.
    (Wiley, 2023-05) Zoughaib, William S.; Hoffman, Richard L.; Yates, Brandon A.; Moorthi, Ranjani N.; Lim, Kenneth; Coggan, Andrew R.; Kinesiology, School of Health and Human Sciences
    Older individuals fatigue more rapidly during, and recover more slowly from, dynamic exercise. Women are particularly vulnerable to these deleterious effects of aging, which increases their risk of falling. We have shown that dietary nitrate (NO ), a source of nitric oxide (NO) via the NO → nitrite (NO ) → NO pathway, enhances muscle speed and power in older individuals in the non-fatigued state; however, it is unclear if it reduces fatigability and/or improves recoverability in this population. Using a double-blind, placebo-controlled, crossover design, we studied 18 older (age 70 ± 4 y) women who were administered an acute dose of beetroot juice (BRJ) containing either 15.6±3.6 or <0.05 mmol of NO . Blood samples were drawn throughout each ∼3 h visit for plasma NO and NO analysis. Peak torque was measured during, and periodically for 10 min after, 50 maximal knee extensions performed at 3.14 rad/s on an isokinetic dynamometer. Ingestion of NO -containing BRJ increased plasma NO and NO concentrations by 21±8 and 4±4 fold, respectively. However, there were no differences in muscle fatigue or recovery. Dietary NO increases plasma NO and NO concentrations but does not reduce fatigability during or enhance recoverability after high intensity exercise in older women.