Many would recognise ‘frailty’ in our older population. Clinical definitions of frailty typically involve physical criteria including weight loss, fatigue, physical activity, walking distance and grip strength. Frailty is characterised by diminished strength and endurance, and reduced function that increases vulnerability for higher dependency and deterioration in health.
Although malnutrition and frailty are distinct, it is recognised they are overlapping conditions, with presentations of muscle and weight loss in both. And for both conditions, early identification and treatment is important in prevention or delay in development.
But what can we learn from the scientific literature about the association of nutrition and frailty?
A greater understanding of which nutrition aspects are of most importance may help us start to identify the best way nutrition could be used as part of prevention and treatment of frailty.
This has been explored in a new systematic review looking at studies published since 2005 on nutritional determinants of frailty in older adults. The largest number of studies in this area have looked at the relationship between malnutrition or risk of malnutrition (measured through a screening tool) and frailty, and all found significant associations. But the review also explored whether poor micro- and macronutrient intakes may be linked with frailty.
Micronutrients and Macronutrients
The review found a small number of studies that investigated the association of vitamin intake or status with frailty. These studies largely looked at antioxidant vitamins (vitamins C and E, as well as carotenoids like beta carotene), B vitamins and vitamin D, and suggest that lower dietary intake or lower levels in the blood were associated with higher risk of frailty. A few studies have also looked at protein, with the majority (but not all) showing an association between low intake and frailty. Interestingly one study found that it was the overall distribution of the protein throughout daily meals that was significantly associated with frailty, suggesting the importance on ingesting a sufficient amount of protein with each meal.
Quality and Quantity
Other studies included in the review have investigated the association of frailty with diet quality, including both broad healthy dietary patterns as well as the inclusion of foods high in antioxidants such as fruit and vegetables. In total these suggest, in accordance with previous findings, that a high-quality diet with foods rich in antioxidant nutrients and with sufficient energy intake, and adequate and timely intake of protein are important in reducing the risk of frailty.
However, this review has a major limitation in that most studies are cross-sectional in nature (taking place at a point in time) which makes it difficult to establish what is cause and what is effect. If nutritional factors are associated with frailty, is that because these factors are contributing to frailty, or because people that are frail reduce their intake? And it is likely that there are other confounding variables that are not accounted, like the need for feeding assistance or swallowing difficulties that may be contributing to the findings.
So whilst the evidence we have is suggestive, it cannot determine conclusively the impact of nutrition on frailty, and more studies are needed to further understand the potential role of nutrition in the prevention, postponement and reversal of frailty. However, this should not in any way deter from the provision of diets in care homes that are both sufficient in energy and protein and that supply important micronutrients.
