Antoneta Granic, Nuno Mendonca, Avan Aihie Sayer, Tom R Hill, Karen Davies, Ashley Adamson, Mario Siervo, John C Mathers, Carol Jagger

Clinical Nutrition 2017 Nov 9 (Article in Press).

As they age adults experience a progressive decline in muscle mass and strength which puts them at increased risk of falls, frailty, disability and death. Physical inactivity and a poor diet can accelerate this loss of muscle mass and strength. We aimed to investigate the relationship between an important part of the diet for muscle, protein intake, and muscle strength and physical performance in very old adults (aged 85 years) as they aged further. Our study, the Newcastle 85+ Study, was based in North East England, and involved 722 people aged 85 years old, with diet assessed by 24h recalls on two non-consecutive days. Low protein intake was defined as less than 1 g per kg of adjusted body weight per day (or around 65 g per day for an average weight individual). Muscle strength was measured by grip strength (squeezing a dynamometer for 5s) and physical performance was measured by the Timed Up-and-Go test (getting up, walking 3 m, walking back, and sitting again). Both grip strength and Timed-Up-and-Go were measured at age 85, 87.5, 88 and 90 years of age.

We found that very old women who had low protein intake had lower grip strength and Timed-Up-and-Go at baseline, but grip strength and Timed-Up-and-Go declined at the same rate as in women with adequate protein intake (1 g per kg of adjusted body weight or more). For men, there was no difference in the baseline measures or decline in grip strength and Timed-Up-and-Go between those with low or adequate protein intake. We found an added benefit of combining adequate protein intake (above 1 g per kg of adjusted body weight per day) with medium/high physical activity on muscle strength. This positive effect was not observed if medium/high physical activity was combined with low protein intake. We conclude that (a) low protein intake may negatively affect muscle strength and physical performance in late life, especially in older women and before age 85, independently of other important factors; and (b) a combination of adequate protein intake and physical activity may be necessary to reduce the loss of muscle strength in the very old.

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