Older adults who are deficient in vitamin D have poorer muscle function, the results of a new Irish study suggest.

According to researchers from Trinity College Dublin (TCD), maintaining muscle function throughout life is key to successful ageing as it promotes a good quality of life, mobility and independence. It also reduces the risk of falls and frailty.

While resistance exercise is known to preserve muscle function, increasing evidence suggests that maintaining adequate vitamin D levels also offers a protective effect. To investigate this further, the researchers analysed data relating to over 4,100 adults aged 60 or older living in the community.

They found that the prevalence of muscle weakness was twice as high among those who were deficient in vitamin D (40%) compared with those who had adequate levels of the vitamin (21%).

They also found that impaired muscle performance was three times higher among those deficient in the vitamin (25%) compared to those with adequate levels (almost 8%).

A more complex statistical analysis of the data also showed that deficiency greatly increased the likelihood of impaired muscle strength and performance.

The study also confirmed the beneficial impact of physical activity. Older adults who regularly undertook moderate physical activity had a much lower likelihood of poor muscle strength and physical performance.

"Overall our findings add weight to the evidence in favour of public health strategies to eliminate vitamin D deficiency in older populations. Future research should identify and focus on older adults with vitamin D deficiency and aim to better understand if reversing this deficiency improves skeletal muscle function," commented the study's first author, Dr Niamh Aspell.

Meanwhile, the study's co-author, Dr Eamon Laird, emphasised that vitamin D deficiency and physical activity are modifiable factors.

"Some countries, for example Finland, have successful implemented a vitamin D food fortification policy, which has all but eliminated deficiency in the population. Such a policy could similarly be implemented in the UK and Ireland for older populations," he explained.

Details of these findings are published in the journal, Clinical Investigations in Ageing.