A lack of high-quality research is preventing the development of dietary advice that could reduce the number of hip fractures, a new study suggests.
Hip fracture is the most common serious injury among adults and current guidelines for prevention focus largely on the consumption of calcium, vitamin D and protein through food and supplements.
But researchers at Leeds have concluded that many dietary factors have the potential to reduce or heighten the risk of sustaining a hip fracture, although more research is needed to confirm this. Their paper, published in PLOS ONE, concludes that limitations in research studies mean there is not enough evidence to develop dietary recommendations.
More than 75,000 people have hip fractures in the UK each year. With average hospital stays of nearly three weeks and on-going care and support, the injury costs the NHS and social care system around £1 billion annually. Older people with weak bone structure are most at risk – often after a fall – but women of all ages are also disproportionately susceptible.
The Leeds research team analysed 16 systematic reviews with 34 meta-analyses. A meta-analysis is a statistical method that attempts to combine the results of all relevant studies into one single result. Their work was effectively a systematic review of earlier reviews of studies into the relationship between various foods, nutrients and diets and the risk of hip fracture.
The study concluded that while dietary factors may play a role in prevention of hip fracture, the quality of systematic reviews and meta-analyses is below international standards and there is a lack of high quality evidence.
Likely areas for fruitful research
The clearest link identified was that fruit and vegetables can help reduce the risk of hip fracture by around 8%, but even here the evidence is weak.
Some protective effects were found when people followed set healthy diets – such as the alternative healthy eating index and Mediterranean diet – or had a higher intake of yoghurt, protein, fruit and vegetables. Harmful effects were observed for heavy alcohol consumption and vitamin A. No effect was observed for other foods or nutrients, including most dairy products and calcium.
Given that calcium – found in dairy products – is seen as an important nutrient in bone strength, the team were surprised that the studies they reviewed found no clear link to risk of hip fracture. However, this probably underlines the limitations of the existing research, together with the wide range of dairy products now available.
Lead author James Webster, a postgraduate researcher from the School of Food Science, said: “Diet has the potential to reduce the risk of hip fracture throughout life. We could help people reduce their risk of this common injury by simply eating or avoiding certain foods, but the quality of evidence isn’t there yet.
“More high-quality studies and well-conducted reviews can point to promising areas for further research into hip fracture prevention through diet, and ultimately to new public health and clinical advice. This is particularly important with an ageing population which is leading to more hip fractures each year.”
Professor Janet Cade, also from the School of Food Science and head of the research group at Leeds, said: “Bringing all the evidence on diet and risk of hip fracture together helps highlight what is known on the topic. While the number of population-based studies was limited, we found that fruit and vegetables might be protective.
“Considering the amount of ill-health and cost to the NHS resulting from hip fracture, more emphasis should be placed on higher quality studies with better measures of food intakes to support public health advice.”
The research team is now embarking on a study of several dietary factors linked to hip fracture risk, involving around 30,000 women from the UK, and using NHS data on hip fractures. This will include assessing the impact of eating a variety of animal products and fruit and vegetables, and of following a vegetarian diet.
The paper, “Dietary risk factors for hip fracture in adults: An umbrella review of meta-analyses of prospective cohort studies”, was published in PLOS ONE on 10 November 2021 - https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0259144
The researchers studied systematic reviews with meta-analyses reporting summary risk estimates for associations between the incidence of hip fracture and dietary exposures. This included oral intake of a food, a food group, a beverage or nutrient or a specific dietary pattern. They drew on studies from Medline, Embase, Web of Science and the Cochrane Library.
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