While supplements such as nitrate and caffeine returned sufficient evidence supporting their acute beneficial effects on muscle strength, Spanish researchers found mixed or unclear evidence for several popular supplements including branched-chain amino acids.
The team also found “weak or scarce” evidence for supplements such as glutamine and resveratrol and “no evidence” for other supplements such as ornithine or α-ketoglutarate.
“Despite their popularity, most of the supplements available on the market lack scientific support for their alleged effects and some have even proved ineffective or have been found to give rise to serious adverse effects,” the review stated.
“Although some supplements have shown promising results in the basic research field, their effects in humans have not been consistently analysed in the scientific literature.”
Responding to the review article, Dr Emma Derbyshire, public health nutritionist and adviser to the Health & Food Supplements Information Service (HSIS) noted, “While this a valuable publication its findings should not be communicated out of context.”
“The paper was looking at supplements in relation to “muscle mass” and “strength”. This is an interesting but rather broad area ranging from roles in sport, exercise performance and recovery to sarcopenia prevention in ageing or lack of muscle use. This broad approach could have potentially ‘diluted’ the findings.”
Published in the European Journal of Nutrition, the review team first performed a non-systematic review in PubMed using the name of the supplement and terms such as muscle mass, strength, body composition, hypertrophy or muscle atrophy.
Reference lists of relevant articles and reviews were also examined to find additional publications on the topic.
The team, made up of researchers from the Spanish Agency for Health Protection in Sport (AEPSAD), University of Alcalá and the European University of Madrid, then began listing the potential mechanisms by which each of the supplements might provide benefits on muscle mass or strength based on mechanistic studies
‘A focus on RCTs and meta-analyses’
“We then summarised the results of relevant studies assessing the effectiveness of each supplement in humans (if available), with a priority focus on randomised controlled trials (RCTs) and meta-analyses, when available,” the team said.
“Finally, the main weaknesses of each supplement (e.g., side effects, lack of evidence in humans) are presented. Based on this information, the evidence supporting the beneficial effects of each supplement on muscle mass/strength was categorised (A to D).”
While evidence of nitrate, caffeine, creatine, protein and polyunsaturated fatty acids’ effect on muscle mass and strength was classed as an ‘A,’ branched-chain amino acids, adenosine triphosphate, and citrulline, were classed as evidence level B - not enough evidence of the benefits of these supplements on muscle mass or strength.
Conjugated linoleic acid, glutamine, resveratrol, tribulus terrestris or ursolic acid were classed as evidence level C - not enough evidence of the supplement’s benefits and should not be recommended for the promotion of muscle mass or strength.
Finally, supplements such as ornithine or α-ketoglutarate were classed as evidence D - insufficient evidence to be categorised in levels A to C and are not be recommended for the promotion of muscle mass or strength.
Individual physiological status a factor
“Their effects could depend on doses (e.g., a linear relationship between protein intake and lean body mass (LBM) gains has been observed up to a maximum of 1.6 g/kg/day),” the study concluded.
“Also type (not all protein or creatine supplements forms provide the same benefits), and on the individual’s physiological status (higher protein doses are required in elderly people or athletes).”
“There is a clear need for studies designed to examine the effectiveness of supplements in terms of improving muscle mass and strength gains in healthy subjects or attenuating muscle wasting during catabolic states such as those produced in situations of ageing, injury or inactivity.”
Dr Derbyshire summarised by saying further research and super studies (meta-analyses) were needed which collated and statistically pooled data from underpinning studies.
“In the meantime it is worth considering that the supplements reviewed in this paper need to be tested on ‘specific populations’.
“There were huge differences in studies included and supplements ideal for individuals partaking in sport and exercise are not necessarily ideal for those with sarcopenia – broad findings cannot necessarily be extrapolated”.
Source: European Journal of Nutrition
Published online: doi.org/10.1007/s00394-018-1882-z
“Supplements with purported effects on muscle mass and strength.”
Authors: Pedro Valenzuela, Javier Morales, Enzo Emanuele, Helios Pareja-Galeano, Alejandro Lucia