Omega-3 Fatty Acid Adds Little Benefit to Resistance Training for Older Adults
Abstract & Commentary
By Dónal P. O'Mathúna, BS (Pharm), MA, PhD
Synopsis: A randomized, double-blind study found that alpha-linolenic acid (an omega-3 fatty acid) supplementation provided few additional benefits for older adults participating in a 12-week resistance-training program.
Source: Cornish SM, Chilibeck PD. Alpha-linolenic acid supplementation and resistance training in older adults. Appl Physiol Nutr Metab 2009;34:49-59.
The purpose of this randomized, double-blind, controlled trial was to evaluate whether alpha-linolenic acid (ALA) supplementation provides additional benefits during 12 weeks of resistance training in older adults. The hypothesis was that ALA might counteract the chronic low-grade inflammation that can contribute to decreased muscle mass and strength in older people.
The participants were 60 healthy, untrained adults older than 60 years of age (mean, 65.4 ± 0.8 years). They were randomly assigned to supplement their diet with either 30 mL flaxseed oil (containing about 14 g/day ALA) or 30 mL placebo (corn oil) for 12 weeks. The oil was to be added to other foods. Fifty-one people completed the study, 28 men and 23 women. The resistance-training program involved 13 activities, which exercised all major muscle groups. Participants exercised three days a week and were monitored and supervised. The load in each exercise was increased as participants were able to complete all prescribed exercises.
Outcomes were measured at baseline and after 12 weeks. Blood samples were taken to measure cytokine levels, muscle strength was evaluated using maximum chest press and leg press, muscle thickness was measured by ultrasound of the knee and elbow flexors and extensors, and body composition was measured using dual energy X-ray absorptiometry.
ALA supplementation led to reductions in the concentrations of only one inflammatory cytokine, interleukin-6 (IL-6) and only among men, not women (P = 0.003). The supplements had minimal effect on muscle mass and strength during resistance training. While chest and leg press strength, lean tissue mass, muscle thickness, hip bone mineral content and density, and total bone mineral content significantly increased, and percent fat and total body mass decreased with the resistance training program (P < 0.05), the two groups differed from one another in only one outcome: The males in the ALA group had a significantly greater increase in knee flexor muscle thickness (P < 0.05). Total-body bone mineral density improved in the placebo group, with no change in the ALA group (P = 0.05).
Loss of muscle mass and strength is a significant problem for older men and women. Such loss has been linked with chronic low-grade inflammation. Increased concentrations of the inflammatory cytokines, tumor necrosis factor-alpha (TNF-a) and interleukin-6 (IL-6), are associated with reduced muscle mass, strength, and fiber number in older adults. Strength training can improve muscle mass and strength, and preserve bone mass. Some, but not all, studies have found that resistance training in older adults also can increase the levels of anti-inflammatory cytokines.
ALA is an essential omega-3 polyunsaturated fatty acid, which acts as a precursor to other, longer-chain omega-3 fatty acids. However, the conversion from ALA to the other omega-3 fatty acids such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) is quite inefficient. The relatively high ratio of omega-6 to omega-3 fatty acids in the Western diet is associated with an increased risk of chronic diseases, including inflammatory diseases.1 Therefore, ALA supplementation has been proposed as a method of reducing the risk of chronic inflammatory diseases. The hypothesis for this study was that ALA might have an additive effect on the benefits of resistance training. This would lead to both a reduction in the low-grade inflammation associated with aging and an increase in muscle mass and strength.
The study was well-designed and clearly reported, although with some limitations. The method of randomization was not reported, and intention-to-treat analysis was not used. Of the 60 participants who started, nine were lost to follow-up. Reasons for not completing the study were obtained. Only one person stopped for reasons to do with the study an inability to tolerate the supplement. The study measured several outcomes, which could be problematic as multiple hypothesis testing can lead to positive findings due to chance alone. This was not a problem here as few measurements showed significant differences between the two groups.
The study found that older men, but not older women, had reduced levels of IL-6 after ALA supplementation with 12 weeks of resistance training. The TNF-a levels were reduced, but not to a statistically significant degree. A post-hoc power analysis showed that a much larger number of subjects would have been needed to show significant changes. The reason for the gender differences was not known.
The results of the study provided further data to demonstrate the value of resistance training for older adults. However, ALA supplementation did not add any further benefit. Even though supplementation reduced IL-6 levels in older men, only knee flexor muscle thickness showed additional benefits. However, it is possible that 12 weeks of supplementation is not long enough to show beneficial effects. Other omega-3 fatty acids such as EPA and DHA are more prevalent in fish oils and may have a greater anti-inflammatory effect compared to the flaxseed oil tested in this study. Such hypotheses would need to be tested in future studies.
The bottom line from this study is that patients can be encouraged to undertake at least three days of resistance training per week to help off-set loss of muscle mass and strength. This study provides little evidence that supplementation with ALA will provide additional benefits for musculature. While there is some evidence of an anti-inflammatory benefit for older men who take ALA and engage in strength training, further research is needed to confirm these findings.
1. Lecerf JM. Fatty acids and cardiovascular disease. Nutr Rev 2009;67:273-283.