Plant-based Diets Not Associated with Fracture in Postmenopausal Women

Decreased bone density is one of the most common concerns among postmenopausal women and for a good reason. On average, 1 in 3 women over the age of 50 will experience a fragility fracture, which is most seen in the hip, spine or wrists.

Previous studies have reported that plant-based diets contribute to these fractures, but what they failed to explore was the quality of the diet; a plant-based diet does not necessarily mean it is healthy.

A research team led by Mercedes Sotos Prieto, Ph.D., adjunct assistant professor of Environmental Health at Harvard University, studied data from 70,285 postmenopausal women who participated in the U.S. Nurses’ Health Study from 1984 to 2014. Researchers found that 2,038 hip fractures were reported during this time.

The Nurses’ Health Study is a large, ongoing study made up of female nurses and nursing school students. It was founded in 1976 to study women’s health issues long term and is currently in its third generation.

Prieto’s findings were published in JAMA Network on Feb. 29, 2024.

To measure the potential correlation, women in the study were given surveys about their diet every four years. Participants were asked about how much of each food group they had consumed. Hip fractures were reported on separate, biennial questionnaires. Data on age, body mass index and smoking status were also collected biennially.

Plant-based diets were separated into two categories. The first was the healthful Plant-Based Diet Index (hPDI), which included whole grains, fruits and vegetables. The second was the unhealthful Plant-Based Diet Index (uPDI), which consisted of refined grains, potatoes and fruit juices.

Participants with higher hPDI scores were less likely to smoke, more likely to have a lower BMI and more likely to be physically active.

The role of animal protein in bone density remains controversial. Protein is essential for bone strength but it’s unclear whether it must be animal or plant protein. Some researchers argue that a lack of animal protein contributes to bone fragility, but results are inconsistent whether this is true.

“The most recent intake of a healthy plant-based diet was associated with 21% lower risk of fracture, whereas the most recent intake of an unhealthy plant-based diet was associated with 28% higher risk of fracture,” the study reads. “Future research should clarify whether the associations observed with recent dietary intake are due to short-term effects of these dietary patterns, reverse causality, or both.”

This study has several limitations. Only white women were included in the analysis, so the results may not be universal. All data was also self-reported. Antiosteoporotic medication use was also not included due to a lack of information.