Weak muscles in later life may reveal more than a loss of fitness, as researchers identify a possible nutritional clue.
Older adults with weak muscles are twice as likely to have a vitamin D deficiency, research suggests.
Skeletal muscles attach to bones and allow us to move, maintain balance and carry out everyday physical activities.
Preserving muscle health becomes increasingly important with age. Good muscle function supports mobility, reduces physical weakness and can help maintain quality of life.
Vitamin D deficiency can produce a range of symptoms, although some people have no obvious signs. Possible symptoms include:
- Tiredness and fatigue
- Muscle weakness and bone pain
- Depression
- Poor wound healing
- Hair loss
- Bone deformities
- Recurrent infections or illness
- Slow healing of wounds
- Soft or fragile bones
However, these symptoms can have many different causes, so they do not necessarily indicate a lack of vitamin D.
Vitamin D and strength
Maintaining adequate levels of 25-hydroxyvitamin D may be important for muscle function alongside activities that build strength, such as resistance and weight training.
Researchers examined the connection between vitamin D status and muscle function using data from 4,157 adults aged 60 and over.
Participants completed physical tests including the Short Physical Performance Battery (SPPB) and a hand-grip strength assessment. These measures provided an indication of both physical performance and muscle strength.
The researchers also measured participants’ blood levels of serum 25(OH)D to assess their vitamin D status.
For the purposes of the study, vitamin D deficiency meant having a serum concentration below 30 nmol/L, the threshold used in relation to bone disease.
The results showed that muscle weakness occurred at twice the rate among people with vitamin D deficiency compared with those whose vitamin D levels were adequate.
The researchers also found that poor physical performance and low muscle strength were three times as common among people with vitamin D deficiency.
The study’s co-author, Dr Maria O’Sullivan, said the findings link vitamin D deficiency with poorer muscle function in older adults while also highlighting the role of physical activity.
She added that maintaining muscle function is an important part of healthy ageing that can sometimes receive too little attention.
The researchers suggested that future work should investigate approaches combining physical activity with correcting vitamin D deficiency and addressing other changeable dietary and lifestyle factors.
Half may be deficient
Experts estimate that as many as 50 percent of people worldwide may have insufficient vitamin D.
Low vitamin D has been associated with a range of health problems, including poorer immune function, changes in sleep, low mood, muscle fatigue, problems with learning and memory, digestive difficulties and headaches.
Another study found that people with lower vitamin D levels tended to wake more frequently during the night and get less sleep overall.
Vitamin D status and physical activity are both potentially modifiable factors.
The study’s co-author, Dr Eamon Laird, pointed to Finland as an example of a country where adding vitamin D to foods has greatly reduced deficiency across the population.
He suggested that a similar approach could potentially be considered for older people in the UK and Ireland.
The study was published in the journal Clinical Interventions in Aging (Aspell et al., 2019).
