Plain language summary
Ageing is associated with the progressive loss of muscle, which can result in impaired movement, an increased risk for falls and disrupted energy production. During ageing there is a decrease in one of the substrates involved in producing energy known as NAD+. Studies in animals have shown that supplementing with a precursor of NAD+ promotes longevity and energy production. In humans supplementation with a precursor of NAD+ has been shown to improve heart health and be of benefit to individuals with obesity. This randomised control trial aimed to determine the effect of supplementing the NAD+ precursors, tryptophan, nicotinic acid, and nicotinamide on muscle function in 14 older adults with impaired physical function. The results showed that supplementation had no effect on NAD+ and had no effect on muscular energy production nor exercise performance following a cycling test. It was concluded that supplementation with an NAD+ precursor does not improve muscle function. This study could be used by healthcare professionals to understand that a combination supplement of tryptophan, nicotinic acid, and nicotinamide may not benefit the physical function of older adults.
Abstract
BACKGROUND Boosting NAD+ via supplementation with niacin equivalents has been proposed as a potential modality capable of promoting healthy aging and negating age-dependent declines of skeletal muscle mass and function. OBJECTIVES We investigated the efficacy of NAD+-precursor supplementation (tryptophan, nicotinic acid, and nicotinamide) on skeletal muscle mitochondrial function in physically compromised older adults. METHODS A randomized, double-blind, controlled trial was conducted in 14 (female/male: 4/10) community-dwelling, older adults with impaired physical function [age, 72.9 ± 4.0 years; BMI, 25.2 ± 2.3 kg/m2]. Participants were supplemented with 207.5 mg niacin equivalents/day [intervention (INT)] and a control product (CON) that did not contain niacin equivalents, each for 32 days. The primary outcomes tested were mitochondrial oxidative capacity and exercise efficiency, analyzed by means of paired Student's t-tests. Secondary outcomes, such as NAD+ concentrations, were analyzed accordingly. RESULTS Following supplementation, skeletal muscle NAD+ concentrations [7.5 ± 1.9 compared with 7.9 ± 1.6 AU, respectively] in INT compared with CON conditions were not significantly different compared to the control condition, whereas skeletal muscle methyl-nicotinamide levels were significantly higher under NAD+-precursor supplementation [INT, 0.098 ± 0.063 compared with CON, 0.025 ± 0.014; P = 0.001], suggesting an increased NAD+ metabolism. Conversely, neither ADP-stimulated [INT, 82.1 ± 19.0 compared with CON, 84.0 ± 19.2; P = 0.716] nor maximally uncoupled mitochondrial respiration [INT, 103.4 ± 30.7 compared with CON, 108.7 ± 33.4; P = 0.495] improved under NAD+-precursor supplementation, nor did net exercise efficiency during the submaximal cycling test [INT, 20.2 ± 2.77 compared with CON, 20.8 ± 2.88; P = 0.342]. CONCLUSIONS Our findings are consistent with previous findings on NAD+ efficacy in humans, and we show in community-dwelling, older adults with impaired physical function that NAD+-precursor supplementation through L-tryptophan, nicotinic acid, and nicotinamide does not improve mitochondrial or skeletal muscle function. This study was registered at clinicaltrials.gov as NCT03310034.
Methodological quality
Jadad score
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3
Allocation concealment
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No
