Vegetarian diets may increase hip fracture risk by 50%

T​his prospective cohort study included over 400,000 participants. Researchers used data from the UK Biobank, which includes individuals from England, Scotland, and Wales ages 40–69 years.

Researchers looked at the risk for hip fractures, following up with participants an average of twelve and a half years later. They excluded participants based on specific criteria, including if they had a previous hip fracture or osteoporosis history.

Based on food frequency questionnaires, researchers divided participants into four key groups:

• Regular meat-eaters: These participants reported eating meat five or more times weekly.
• Occasional meat-eaters: These participants ate meat less than five times each week.
• Pescatarians: These participants ate fish but otherwise did not eat meat.
• Vegetarians: These participants all ate no meat. However, the group included those who ate dairy or eggs and those who did not eat eggs or dairy (vegans).

Researchers chose to combine the vegan and vegetarian groups because only a few participants were vegan.

Researchers accounted for many confounders, including the participants’ sex, ethnicity, regular use of nutritional supplements, activity level, smoking status, and alcohol consumption. They then looked at the associated risk for hip fractures among these different nutrition groups.

The findings indicated that people who followed a vegetarian diet were at a 50% higher risk of experiencing a hip fracture compared to meat-eater groups and pescatarians.

Researchers noted that some of this heightened risk might be explained by the lower body mass index of participants who followed a vegetarian diet. The authors speculated that a lower BMI could mean poor health of muscles and bones or reduced cushioning from impact forces during a fall from lack of fat.

But most of the reasons for the risk association were unclear. The authors speculate the increased hip fracture risk could be related to lower levels of protein and other key nutrients among vegetarians.

Dr. Emily Leeming, a registered dietitian and nutrition scientist, who was not involved in the study, offered her explanations to Medical News Today:

“We know that being at a slightly higher BMI is protective against risk of fractures from other studies, so this could be partially explained by differences in bone mass density. In this study, people who ate a vegetarian diet had, on average, a lower BMI than the other diet groups. However, as the study shows, there are likely other factors at play too.”

“The vegetarian group were less likely to reach their protein intake requirements than the other diet groups, with adequate protein intake essential for building and maintaining bone mass. This may also be exacerbated by poor intakes of other nutrients involved in bone health.”
— Dr. Emily Leeming

Despite the higher risk for hip fracture among vegetarians, this doesn’t mean people should avoid a vegetarian diet. James Webster, first study author, explained to MNT:

“We found that vegetarians were at a 50% greater risk of hip fracture than regular meat-eaters, regardless of sex. Lower BMI in vegetarians explained some of this risk difference…Importantly, the 50% greater risk in vegetarians translated to three more hip fractures per 1,000 people over 10 years.”

“The health benefits of a vegetarian diet, including a lower risk of cancer and cardiovascular disease, may therefore outweigh any increases in hip fracture risk. Additionally, since there was no difference in risk between occasional and regular meat-eaters, reducing meat intake from the diet doesn’t seem to affect hip fracture risk.”
— James Webster, study author

The study did have a number of limitations. First, this study cannot prove that following a vegetarian diet causes hip fractures.

Researchers could not independently assess vegans, who may not get enough protein and calcium in their diets. Within each group, there is also the potential for varied quality of diets, which could influence the risk for hip fractures.

Most participants were below the average ages of people with hip fractures, which may have affected the results.

The age of participants could also have influenced why researchers didn’t observe changes in risk based on age.

Researchers did not distinguish between traumatic or fragility hip fractures because data on the cause of hip fractures were unavailable. Residual confounding is possible, as well as some of the data of participants to have changed from baseline.

Finally, there are limits on how much the results can be generalized because UK Biobank participants are healthier than the general U.K. population, and most of the participants are white.

“Since this study was an observational study, our findings cannot show causality. Further studies are needed to confirm if vegetarian diets cause an increase in hip fracture risk and to identify why that might be. This information will help to inform risk mitigation strategies,” Webster further noted.

People seeking to follow a vegetarian diet must understand how to incorporate key nutrients and what nutrients a vegetarian diet is most likely to lack. They may need to find alternative plant sources of nutrients that are more common in animal sources.

For example, calcium may be harder for vegetarians to get if they don’t consume dairy. There are some products fortified with calcium, like certain cereals or orange juice. Plant options like broccoli, almonds, or white beans can also provide calcium.

Vegetarian diets can also lack vitamin B12. Vegetarians who allow for dairy products can find dairy sources of vitamin B12, such as milk or cheese. Strict vegans may need to consume fortified foods like nutritional yeast to meet their vitamin B12 requirements.

“Vegetarians can speak with their doctor or registered dietitian to ensure that they’re eating a balanced diet and meeting their nutrient requirements. Having a varied diet with plenty of plant protein like beans, legumes, nuts, and seeds, as well as dietary or supplementary sources of iron, B12, and vitamin D can help support having an optimum nutrition intake and for bone health.”
— D​r. Emily Leeming