Degree Name

Master of Philosophy


School of Medicine


Background: As adults age, there is a progressive decline in cardiovascular and skeletal muscle function that directly impacts on physical capacity and exercise tolerance. In the elderly, an increase in energy cost of walking is associated with slower walking speeds and augmented fatigue. Both cardiovascular function, and in particular heart rate, and physical function such as walking speed have strong predictability on longevity in this cohort.

Evidence supports that the long chain omega-3 polyunsaturated fatty acid (LC n-3 PUFA), docosahexaenoic acid (DHA), incorporates into cardiac and skeletal muscle at a dose that is achievable via fatty fish consumption. In the case of skeletal muscle there is certainly evidence supporting the improvement of muscular strength at high doses. In fact, population health is improved by the regular consumption of fatty fish and this is reinforced by direct measures of physical capacity. In the laboratory, the effect of elevating the omega-3 status of an individual includes improved heart and skeletal muscle function especially when physiological strain is increased and supports the need for increased intake of LC n-3 PUFA, especially DHA which is found in abundance in contractile cells.

Objective: This study sought to determine whether low dose (2g/day), DHA-rich fish oil could elevate the red blood cell (RBC) omega-3 status and as a result modify heart function and improve physical capacity in physically active and healthy older adults.

Design: Using randomised placebo-controlled trial, physically fit older adults aged 60-85 years were supplemented with either 2g/d of DHA-rich fish oil (FO) (delivering 560mg/d DHA and 140mg/d eicosapentaenoic acid (EPA)), or 2g/d of placebo oil (control) (Sunola oil) for 16 weeks. Omega-3 index (RBC EPA+DHA) was measured before and after supplementation. Participants completed a series of physical function tests, including walking speed over distances of 20-400m. In addition, a submaximal treadmill ramp protocol was conducted to evaluate the heart rate and oxygen cost of walking. Most importantly, heart rate was measured during both rest (including overnight sleep), exercise states and recovery.

Results: In physically fit and healthy older adults (mean walking speed >1.5m/s), the omega-3 index (%) was significantly increased (P0.05). There was no effect of increasing the omega-3 index on the oxygen cost of walking (P>0.05) which might help to explain the non-modification to walking speed (P>0.05) in this already very active group. Additionally, physical function tasks, including grip strength and timed up and go were not substantially modified as a result of fish oil supplementation (P>0.05) and may too be due the high physical function in this group.

Conclusions: This study established that a DHA-rich fish oil dose that is reproducible through consumption of two fish meals per week significantly improves the omega-3 index (RBC EPA+DHA) in older adults. This increase in the omega-3 index resulted in improved cardiovascular function as reflected by the lowering of heart rate, particularity during fast walking. This study has supported the need to further promote LC n-3 PUFA in the diets of older adults and highlights this can be achieved via the consumption of regular fish that is rich in DHA.