Tuesday July 5 2011
Protein drinks are popular but their benefits are unclear
“Protein drinks ‘are no help for athletes and aren’t better than a balanced diet’,” according to the Daily Mail. The Independent also reported that there is “no benefit from protein sports drinks”, and that the finding comes from a scientific review of their use.
These newspapers have reported only one side of an article intended to present arguments both for and against the idea of adding protein to carbohydrate energy drinks. The “narrative review” was written by two researchers who each selected and discussed research articles that either supported or challenged the view that adding protein to sports drinks has no effect. The research paper did not offer a definitive review of the use of supplements and did not reach a conclusion in favour of either argument.
This study exemplifies the potential downside of narrative reviews, which only consult selected sources of information and are therefore potentially biased. Given this potential for bias and the possibility that important information sources are ignored, this approach cannot definitively confirm the effects of protein in carbohydrate sports drinks. The only way to address this is to systematically gather together all studies that have assessed the effects of adding protein to energy drinks and critically appraise them as a whole.
Where did the story come from?
The study was carried out by researchers from the University of Bath and Northumbria University. No funding source was stated. The study was published in the journal Medicine & Science in Sports & Exercise.
This study was covered poorly and unevenly by the Daily Mail and The Independent, neither of which stated that it was a narrative review. Both reports only included the views of one side of a structured debate intended to present two opposing views on the use of protein drinks.
What kind of research was this?
This was a narrative review addressing whether or not there are any additional benefits to including protein in carbohydrate-rich sports drinks.
Narrative reviews may present a researcher’s views using citations of selected research to support that viewpoint. Because narrative reviews do not gather evidence in a systematic way (which would involve the inclusion of all relevant studies, regardless of their findings), there is the risk that not all relevant articles are included in narrative reviews.
This particular narrative review was unusual in that it was essentially two reviews in one, providing two distinct sets of evidence that either supported or challenged the suggestion that there are potential benefits to adding protein to sports drinks. The journal publishing the article says that the article intended to showcase “contrasting perspectives”.
On one side the “prevailing view” says that there is no compelling scientific evidence to support adding protein to sports drinks, which was compared against the “challenging view” that there are benefits to be had from consuming protein in sports drinks. This study highlights the way that narrative reviews can be biased by an author simply acknowledging studies that support their particular viewpoint. However, in this instance the narrative review was used to present two sides of an argument and highlight the lack of definitive evidence on the matter.
What did the research involve?
The two researchers presented the two opposing views in adjacent columns. Each viewpoint was written by a different author. Both the authors then wrote their response to points raised by the other author.
Both researchers discussed studies that had compared carboyhydrate-only drinks to drinks containing both protein and carbohydrate, and how protein from supplements taken around the time of exercise compared to dietary protein in terms of their effect on the body. The review also considered whether sports drinks containing protein had any effect on recovery during rest between exercise sessions.
What were the basic points of the arguments?
The “prevailing view” was argued by Dr James Betts of the University of Bath. His main points state that:
- Although some studies (four cited) have shown positive effects on exercise performance when protein is added to a carbohydrate drink, the prevailing view is that there is no benefit (nine studies cited).
- There is no empirically supported mechanism to explain why ingesting protein during exercise would be expected to improve athletic performance.
- The process of recovery after exercise may mean that athletes have a slightly increased daily protein requirement; however, the vast majority of athletes in westernised societies exceed their recommended protein intake even without supplementation, and almost all meet their long-term protein requirements without supplementation.
- Dr Betts said that studies that have shown that eating precise types of protein or amino acids close to finishing exercise governs both protein synthesis rates and chronic accrual of lean tissue, but that supplementation is not necessarily required to obtain them; drinking milk, which contains appropriate proteins, may be sufficient.
- Whole foods can also bring about these effects while simultaneously being more likely to provide a variety of other important nutrients.
The “challenging view” was presented by Dr Emma Stevenson of Northumbria University. Her main points stated that:
- There are five studies that have shown a positive effect on exercise performance when protein is added to carbohydrate drinks, compared to four that have shown no effect. Dr Stevenson said that although the evidence for and against was “equivocal”, adding protein to carbohydrate drinks was not likely to be detrimental to performance.
- Drinking proteins during prolonged endurance exercise has been shown to improve protein balance by increasing protein synthesis and decreasing protein breakdown, resulting in a positive net protein balance during exercise.
- Some studies have found that protein affects perceived soreness or concentrations of creatine kinase (a protein found in muscles and a measure of muscle damage) after exercise.
- Some studies have suggested that adding protein to carbohydrate drinks improves fluid retention during rehydration after exercise.
In response to the prevailing view, Dr Stevenson said that, although protein in sports drinks may not improve athletic performance specifically, there might be other benefits.
In response to the challenging view, Dr Betts said that adding protein or anything else to sports supplements was a “just in case” approach and that there was no reason why the potential benefits discussed by Dr Stevenson couldn’t be achieved using nutritionally balanced whole foods instead of supplementation.
This was a debate between two researchers who selected published studies to support their respective arguments for and against adding protein to carbohydrate drinks to improve exercise performance or recovery.
This kind of approach cannot definitively determine whether adding protein to carbohydrate sports drinks is beneficial, or what effect this has on the body. However, it does highlight the lack of consensus on the matter, as well as how easily selected research can be used to build a compelling argument that is not necessarily reflective of the balance of evidence overall.
To reach a consensus it would be necessary to perform a systematic review to critically appraise all studies that have assessed the effects of protein supplementation. These should preferably be randomised controlled trials that have compared groups of people who took a protein-supplemented energy drink against those who drank a protein-free energy drink. Such a critical appraisal would need to be systematic, including all relevant studies, regardless of their results.
Both the Daily Mail and The Independent have presented the “prevailing view” from the article, reporting that there was no greater benefit from adding protein to sports drinks than would be expected from consuming protein as part of the diet. However, the research paper presents each argument as having equal merit, so it is unclear why the media has chosen to focus on only one perspective.