As we age, the risk of frailty increases. Though difficult to define, Fried et al (1) define frailty as a clinical syndrome diagnosed when three or more of the following are present: unintentional weight loss of greater than 10 lbs in the past year, exhaustion, weakness, slow walking speed, and low physical activity. Another way to characterize frailty, according to Rockwood et al (2), is through an accumulation of deficits in symptoms, signs, function, and laboratory measures, with more deficits indicating greater risk. Regardless of how frailty is diagnosed, community-dwelling older adults who experience frailty have sarcopenia, a decline in mental and physical function, and a decrease in dietary intake that puts them at greater risk of institutionalization and mortality. Medium-chain triglycerides (MCT) comprise medium-chain fatty acids that are 6 to 12 carbons in length. Because of their shorter chain lengths, MCT are oxidized for energy rather than stored, with evidence showing stimulation of hormones that promote skeletal muscle protein synthesis. Previous studies have indicated MCT supplementation to be potentially beneficial in enhancing strength and recovery in hospitalized patients and the elderly. Thus, the 2023 article by Kojima et al in Nutrients aims to investigate whether continuous MCT supplementation in healthy middle-aged and older adults undergoing a moderate-intensity walking routine prevents the loss of, or maintains, skeletal muscle mass. (3)
For this 12-week supplementation study, 120 sedentary normal-weight adults between 60 and 75 years old were randomized to receive test foods containing either: 1) Control (6 g/d long-chain triglycerides in the form of canola oil), 2) Decanoic acid (6 g/d 10:0, MCT), 3) Low octanoic acid (4 g/d canola oil + 2 g/d 8:0 MCT), or 4) High octanoic acid (6 g/d 8:0 MCT). The daily dosage was divided into two food packets (containing 3 g each of the test fat) to be consumed after two meals of the participant’s choosing. For the exercise intervention, the participants were asked to walk outside for about 40 minutes twice a week at a usual pace and to record any other activities performed. Diet history (brief-type self-administered diet history questionnaire), body composition via bioelectrical impedance, grip strength, knee extension, and walking ability were measured at baseline and 4-week intervals throughout the study.
The authors report that after 12 weeks of supplementation, there was an improvement in knee extension in all three groups that supplemented with MCT. However, there were also improvements from baseline, albeit not as great, in knee extension in the control group. The final measured values at 12 weeks from the higher dose MCT groups were also greater than those of the control group. Though there were no differences at baseline, the lower dose MCT group appears to have lower baseline values. Grip strength improved in the higher MCT group only, though not enough to indicate a difference between groups. It should be noted that these improvements in strength were despite no differences in body composition between time points or groups, and all groups improved walking ability equally. Excluding the test food, there were no differences in nutrient intake at baseline and throughout the study period.
Overall, the study provides some evidence that MCT supplementation may beneficially improve strength with exercise. The canola placebo provided was appropriate and the study design was strong. The authors used appropriate measures for strength. The study was limited in that there are more robust ways of measuring dietary intake and body composition. The exercise prescribed in this study was light and unsupervised. In comparison, according to the Centers for Disease Control, adults greater than 65 years old should be walking 30 minutes per day, five days per week. Why such a low level of exercise was prescribed is unclear. Also, the reporting of results was rather difficult to understand. There were 120 participants included with only one dropout reported, but in the end, results from 112 participants seem to be reported. The reason for excluding an additional seven participants is unclear, as it is merely stated that they were excluded per the criteria of the statistical analysis plan. Another thing to be aware of is that the study was funded by the Nisshin OiliO Group, the company providing the supplements. It is not clear what is in the food packages provided that contain the MCT supplements, thus, one cannot determine whether it is the contents of the food packages that might have affected the study results. Despite these limitations, the provision of food packets containing the MCT was a strength of the study. The fact that the study was double-blinded, randomized, and placebo-controlled also reduced any bias associated with study conduct, analyses, and interpretation of the results.
In sum, this study provides limited evidence of the potentially beneficial effects of MCT supplementation on improving strength and reducing the risk of frailty in adults over 60 years old. Further studies will be needed to determine whether MCT should be recommended for supplementation to improve strength and thus, prevent frailty in this age group.
1. Fried LP, Tangen CM, Walston J, Newman AB, Hirsch C, Gottdiener J, et al. Frailty in older adults: evidence for a phenotype. The journals of Gerontology Series A, Biological Sciences and Medical Sciences. 2001;56(3):M146-56.
2. Rockwood K, Stadnyk K, MacKnight C, McDowell I, Hebert R, Hogan DB. A brief clinical instrument to classify frailty in elderly people. Lancet. 1999;353(9148):205-6.
3. A Randomized, Double-Blind, Controlled Trial Assessing If Medium-Chain Triglycerides in Combination with Moderate-Intensity Exercise Increase Muscle Strength in Healthy Middle-Aged and Older Adults