Recent recommendations are that older adults increase their dietary protein intake to intakes higher than are currently recommended to mitigate sarcopenia-induced muscle loss caused in part by anabolic resistance. Protein supplementation may serve as an effective strategy to meet protein intake goals; however, protein supplements vary in their quality, which may impact muscle protein turnover. Protein quality is determined by the digestibility and content of essential amino acids in a protein source and may play an important role in mitigating the loss of muscle mass and muscle protein synthesis (MPS) during energy restriction (ER), acute reductions in physical activity, which we modeled using enforced step reduction (SR), and during recovery from SR. We aimed to determine whether the quality of a protein supplement – whey protein (higher quality) versus collagen peptides (lower quality) – would impact the reduction in fat-free bone-free mass (FBFM) and MPS (Study 1), and also to compare differences in functional variables: strength loss in men and women, and single fibre function with SR in men (Study 2). In Studies 1 and 2 we compared supplementation with whey protein (WP) and collagen peptides (CP), higher and lower quality proteins respectively, as part of a higher protein diet provided to older adults during one week of ER (-500 kcal/d), two weeks of step reduction (< 750 steps/d) (ER+SR) and one week of recovery (RC). Two weeks of ER+SR significantly reduced FBFM in both the WP and CP groups with greater FBFM recovery with WP. MPS was significantly reduced following ER in both groups and did not decrease further during ER+SR. MPS was increased above ER+SR following 1 week of RC in the WP group only. ER+SR significantly reduced maximum voluntary contraction (MVC) in both men and women; however, following RC men fully recovered their strength and women did not. In Study 3, we aimed to determine the impact of WP and CP supplementation combined with unilateral resistance exercise (RE) to augment the acute and longer term MPS response in healthy older women. Acutely, rates of MPS were elevated following WP+RE and with WP alone while MPS was elevated only in CP+RE. Six days of supplementation increased MPS in WP and WP+RE with no increase in MPS with CP or CP+RE. Collectively, these studies demonstrate that protein quality is an important variable to consider in selecting a protein supplement for older adults and for recovering from inactivity. / Thesis / Doctor of Science (PhD) / At the end of the 5th decade of life, adults will have lost an appreciable amount of muscle mass and strength versus what they had in their 3rd decade of life. This age-related loss of muscle mass and strength is known as sarcopenia. Additionally, as they age, adults will experience brief periods of reduced physical activity due to illness, injury, or recovery from surgery. Such periods are associated with a rapid loss of muscle and strength creating a brief period of ‘accelerated sarcopenia’. Strategies to combat the loss of muscle and strength in these periods include increasing protein intake and even periodic exercise which may help to reduce the negative impact of physical inactivity. In particular, higher quality protein sources (protein derived from animal sources or soy) and weightlifting may better help muscles recover from inactivity. Our main findings were that consuming high quality protein (whey protein) stimulated the process of muscle building that is normally reduced with inactivity. Importantly, when combined with resistance exercise, we were able to increase the rate at which healthy older women built muscle with whey protein in comparison to a lower quality protein source (collagen peptides). These findings provide novel and insightful information for the recommendations of protein supplement types to older adults to increase daily protein intake to preserve muscle mass with age.
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/24849 |
| Date | January 2019 |
| Creators | Oikawa, Sara Y. |
| Contributors | Phillips, Stuart M., Kinesiology |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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