The main and novel finding of the present study is that beta-alanine supplementation is able to increase the muscle carnosine concentration in elderly (60–80 yrs) subjects. Importantly, the study also showed compelling evidence indicating that the increase in muscle carnosine was paralleled by an improvement in exercise tolerance with no evidence of any adverse effect. The present data is in accordance with a growing body of evidence obtained in younger subjects suggesting that beta-alanine supplementation results in increased carnosine synthesis in muscle (Harris et al. 2006
; Hill et al. 2007
). The present data further demonstrate that within the age group measured, ageing does not impair intramuscular beta-alanine uptake or intramuscular carnosine synthesis.
Although one study (Kim 2009
) demonstrated a normal muscle carnosine content in older individuals with glucose intolerance, Tallon et al. (2007
) reported a 53% reduction in carnosine in type II, but not in type I muscle fibres, in older subjects with osteoarthritis when compared with younger healthy subjects. Similarly Stuerenburg and Kunze (1999
) reported a significant age-related reduction in skeletal muscle carnosine. These dissonant findings may be explained, at least in part by dietary differences, as the Korean population studied by Kim (2009
) is described as eating a typical Korean diet including chicken, pork and beef meat, as well as fish. As noted by Kim (2009
) Korean cooking is typically done “in the pot” or by barbeque with the result that loss of dipeptides is minimal. Changing dietary patterns in the elderly due to loss of appetite will reduce beta-alanine intake from the ingestion of histidine containing dipeptides (carnosine, anserine and balenine). Even where dietary intake of protein may be adequate, dietary levels of beta-alanine may fall. Declining levels of carnosine in muscle may also occur with preferential loss of type II muscle fibres with age, or with a reduction in cross sectional area of type II muscle fibres, since in humans these have up to two times the level of carnosine compared to type I (Harris et al. 1998
; Hill et al. 2007
). In such circumstances beta-alanine supplementation could be beneficial in maintaining or even elevating muscle carnosine levels with possible improvements in physical exercise capacity and life quality.
In the present study the mean increase of 85.4% in muscle carnosine content after 12 weeks beta-alanine supplementation was almost identical to the increase observed after 10 weeks by Hill et al. (2007
), albeit using a dosing level twice that used in this study. Hill et al. (2007
) administered beta-alanine in a hard gelatin capsule, which disintegrates rapidly on ingestion and gave rise to a peak in the plasma concentration after 30 to 45 min. In the present study a proprietary sustained-release tablet formulation was used, which for the same dose results in a lower and later peak plasma concentration and reduced urinary loss, but generates the same area-under-the-plasma-concentration curve (Stellingwerff et al. 2011
). By slowing the rate of beta-alanine release, less is excreted in urine with a greater percentage retained for carnosine synthesis in muscle.
Importantly in the present study changes in TLIM and TTE were positively correlated to the changes in muscle carnosine. Similar correlations have been shown in younger subjects with improved performances in cycling (Hill et al. 2007
) and rowing (Baguet et al. 2010
) tracking the increase in muscle carnosine content with beta-alanine supplementation. Although Stout et al. (2008
) have earlier shown an improvement in the time to neuromuscular fatigue in the elderly with beta-alanine supplementation, the absence of carnosine measurements did not enable comparison to any increase in the muscle carnosine content. The emerging correlations in the current study, between carnosine increase and exercise performance, are consistent with the role of carnosine as an intramuscular H+
buffer. In the context of the elderly, those still active in such activities as cycling, skating, mountain climbing, even gardening, as examples of strenuous leisure activities involving bouts of intense isometric and dynamic exercise, are likely to gain both immediate benefits from an increase in muscle carnosine, as well as long-term benefits if the current high level of activity can be extended into more senior years. Whether much less active older people are able to derive a similar level of benefit remains to be shown but many simple tasks, for instance stair climbing, which in earlier years might have been accomplished by aerobic exercise, invoke increasing levels of anaerobic effort as muscle mass progressively declines.
In the present study there were no improvements in the “timed-stands” and “timed-up-and-go” tests. Although these have previously been validated to measure improvements in daily-life activities (Podsiadlo and Richardson 1991
, Newcomer et al. 1993
) this is based on the study of populations far less active than investigated here. The lack of changes in the quality of life may be due to the fact that subjects were healthy and functional at baseline. A future goal, therefore, should be to study the effects of beta-alanine supplementation in patients who are less active and demonstrate a greater degree of sarcopenia and frailty, and poor quality of life.
In any decade, whether it is 60+, 70+ or even 90+, there will be a broad spectrum of activity levels set against a background of declining musculo-skeletal function. Moderating the rate of decline would help maintain active participation in leisure activities and independence. Regular exercise involving some form of resistance training is considered the most effective treatment in slowing the progression of sarcopenia (Snijders et al. 2009
; Verdijk et al. 2009a
). We suggest that beta-alanine supplementation by increasing the capacity for resistance exercise and lessening the fatigue burden associated with this, whether performed as part of a prescriptive training programme, in the course of leisure, or simply as part of normal everyday activities, will encourage prolongation of an active life style in elderly people. This assumption needs to be tested in future studies.
In conclusion the present study indicates that beta-alanine supplementation is effective in increasing the muscle carnosine content in the elderly (60–80 years) with improvements in physical exercise capacity. Benefits in maintaining a high muscle carnosine content may be both immediate and long-term, if this encourages subjects to maintain a more active life. Beta-alanine supplementation possibly represents one of the few evidenced-based dietary interventions which may help delay the decline in muscle function with ageing.