Vegetarian women are at a higher risk of hip fracture

by University of Leeds

Credit: University of Leeds

A study of over 26,000 middle-aged UK women reveals those with a vegetarian diet had a 33% higher risk of hip fracture compared to regular meat-eaters.

03 sept 2022--University of Leeds research, published Thursday, August 11 in the journal BMC Medicine, investigated the risk of hip fracture in occasional meat-eaters; pescatarians, people who eat fish but not meat; and vegetarians compared to regular meat-eaters.

Among 26,318 women, 822 hip fracture cases were observed over roughly 20 years—that represented just over 3% of the sample population. After adjustment for factors such as smoking and age, vegetarians were the only diet group with an elevated risk of hip fracture.

This study is one of very few studies to compare risk of hip fracture in vegetarians and meat-eaters where the occurrence of hip fracture was confirmed from hospital records.

The scientists stress the need for more research into the exact causes of why vegetarians were at a greater risk of hip fracture.

Vegetarian diets can be 'healthy or unhealthy'

Study lead author James Webster, a doctoral researcher from the School of Food Science and Nutrition at Leeds, said, "Our study highlights potential concerns regarding risk of hip fracture in women who have a vegetarian diet. However, it is not warning people to abandon vegetarian diets. As with any diet, it is important to understand personal circumstances and what nutrients are needed for a balanced healthy lifestyle.

"Vegetarian diets can vary widely from person to person and can be healthy or unhealthy, just like diets that include animal products.

"However, it is concerning that vegetarian diets often have lower intakes of nutrients that are linked with bone and muscle health. These types of nutrients generally are more abundant in meat and other animal products than in plants, such as protein, calcium, and other micronutrients.

"Low intake of these nutrients can lead to lower bone mineral density and muscle mass, which can make you more susceptible to hip fracture risk. This makes it especially important for further research to better understand factors driving the increased risk in vegetarians, whether it be particular nutrient deficiencies or weight management, so that we can help people to make healthy choices."

Plant-based diets growing in popularity

Vegetarian diets have gained popularity in recent years, with a 2021 YouGov survey putting the size of the UK vegetarian population at roughly 5-7%. It is often perceived as a healthier dietary option, with previous evidence that shows a vegetarian diet can reduce the risks of several chronic diseases, including diabetes, heart disease, and cancer compared to omnivorous diets.

There is also a worldwide call for reducing the consumption of animal products in an effort to tackle climate change.

Understanding hip fracture risk in vegetarians is therefore becoming increasingly important to public health.

Study co-author Professor Janet Cade, leader of the Nutritional Epidemiology Group in the School of Food Science and Nutrition at Leeds, said, "Hip fracture is a global health issue with high economic costs that causes loss of independence, reduces quality of life, and increases risk of other health issues.

"Plant-based diets have been linked with poor bone health, but there has been a lack of evidence on the links to hip fracture risk. This study is an important step in understanding the potential risk plant-based diets could present over the long-term and what can be done to mitigate those risks."

The team used data from the UK Women's Cohort Study to investigate possible links between diet and hip fracture risk. The national cohort of middle-aged women was established at the University of Leeds to explore links between diet and chronic disease, encompassing a wide range of different eating patterns. Dietary information was collected using a food frequency questionnaire and was validated using a 4-day food diary in a subsample of women.

At the time they were recruited into the cohort study, the women ranged in age from 35 to 69 years.

Effect of low BMI

The research team found that the average BMI among vegetarians was slightly lower than the average among the regular meat eaters. Previous research has shown a link between low BMI and a high risk of hip fracture.

Lower BMI can indicate people are underweight, which can mean poorer bone and muscle health, and higher risk of hip fracture. Further investigation is needed to determine if low BMI is the reason for the observed higher risk in vegetarians.

Study co-author Dr. Darren Greenwood, a biostatistician in the School of Medicine at Leeds, said, "This study is just part of the wider picture of diet and healthy bones and muscles in older age.

"Further research is needed to confirm whether there could be similar results in men, to explore the role of body weight, and to identify the reasons for different outcomes in vegetarians and meat-eaters."

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More information: Risk of hip fracture in meat-eaters, pescatarians, and vegetarians: results from the UK Women's Cohort Study, BMC Medicine (2022). DOI: 10.1186/s12916-022-02468-0

Provided by University of Leeds

Vitamin D Concentration Linked to Hip Fracture Risk

By Todd Neale
PITTSBURGH, 19 aug 2008 -- In postmenopausal women, low serum vitamin D concentrations were associated with an increased risk for hip fracture in a nested case-control study here.
Women with the lowest serum concentrations of 25-hydroxyvitamin D were 71% more likely to have a hip fracture than those with the highest (OR 1.71, 95% CI 1.05 to 2.79), Jane Cauley, Dr.P.H., of the University of Pittsburgh, and colleagues, reported in the Aug. 19 issue of Annals of Internal Medicine.
Adjusting for C-terminal telopeptide of type I collagen -- a marker for bone resorption -- seemed to eliminate the association (OR 1.58, 95% CI 0.97 to 2.60), the researchers said, but the overall trend remained significant in a multivariate model (P=0.029).
"Our findings suggest that low serum 25-hydroxyvitamin D concentrations might help identify women at high risk for hip fracture," they said.
Past studies examining the link between serum vitamin D concentrations and risk of fracture have yielded mixed results, they said.
To explore the issue, the researchers turned to the Women's Health Initiative Observational Study, a large prospective cohort study of participants ages 50 to 79.
They selected 400 women who had an incident hip fracture and 400 controls from 40 clinical centers around the U.S. for a case-control study nested within the larger study.
All of the participants were postmenopausal (mean age 71, 95% white) and were not using estrogens or other osteoporosis medications.
Serum vitamin D concentrations were measured at baseline and the participants were followed annually with questionnaires for a mean of 7.1 years (range 0.7 to 9.3).
At baseline, concentrations were lower in the case patients than in the controls (55.95 nmol/L versus 59.60 nmol/L, P=0.007).
For each 25-nmol/L decrease in vitamin D concentration, the risk of hip fracture was increased by 33% (OR 1.33, 95% CI 1.06 to 1.68).
Risk of hip fracture decreased significantly from women in the lowest quartile of vitamin D concentration (≤ 47.5 nmol/L) to those in the highest (≥ 70.7 nmol/L) (P=0.016 for trend).
The association did not vary by age and remained significant when adjusted for the number of falls, physical function, frailty, renal function, sex-steroid hormone levels, geographic location, and obesity.
The researchers said that the mechanism of the association remained unclear but suggested several ways that serum vitamin D concentration and fractures could be related.
Vitamin D concentration could influence muscle strength and balance, and consequently, falls and disability, they said.
In addition, they said, the relationship could be influenced by sex-steroid hormones, bone turnover, and renal insufficiency, which has been linked to both fracture risk and vitamin D deficiency.
The authors acknowledged several limitations of the study, including the possibility of seasonal variability in the blood tests, the fact that almost all participants were white, the lack of distinction between 25-hydroxyvitamin D2 and D3, the failure to measure parathyroid hormone, the inclusion of few women with a serum vitamin D concentration greater than 75 nmol/L, and potential residual confounding.
In addition, they did not measure bone mineral density, which may provide varying information on fracture risk so they could not determine whether 25(OH) vitamin D concentrations give different information about fracture risk than that offered by bone-mineral density.
The Women's Health Initiative was funded by the National Heart, Lung, and Blood Institute. Additional support was provided by U.S. Public Health Service Research grants. One of Dr. Cauley's co-authors is supported by a grant from the National Center for Research Resources.
Dr. Cauley and her co-authors reported potential conflicts of interest with Novartis, Eli Lilly, Merck, Roche Diagnostics, Johnson & Johnson, Procter & Gamble, Amgen, GlaxoSmithKline, Zelos, sanofi-aventis, General Electric, Pfizer, MicroMRI, and Abbott.
Primary source: Annals of Internal MedicineSource reference:Cauley J, et al "Serum 25-hydroxyvitamin D concentrations and risk for hip fractures" Ann Intern Med 2008; 149: 242-250.