Adding salt to food linked to higher osteoporosis risk, 32% higher in those who always did

Some people salt their food before they have tasted it, and some never reach for the shaker at all. In a study of nearly half a million British adults, the ones who always added salt at the table were more likely to be diagnosed with osteoporosis over the following decade and a half.

Researchers at the Second Xiangya Hospital of Central South University in Changsha, China, used UK Biobank, a long-running study of adults recruited between 2006 and 2010, to follow 491,428 people who did not have osteoporosis when they joined. The more often people salted their food, the higher their risk of a later diagnosis, and those who always did it were about a third more likely to be diagnosed than those who never or rarely did. The study, led by Xukun Luo with Jian Zhou as senior author, was published in September in The Journal of Nutrition, Health and Aging. The authors describe it as the first prospective study to explore this association, meaning the first to record the habit and then follow people forward in time to see who developed the disease.

What did the salt and osteoporosis study ask?

Osteoporosis is a loss of bone mass that leaves bones fragile and quick to break, and a 2025 review in JAMA notes that worldwide 1 in 3 women and 1 in 5 men older than 50 will have a fracture caused by it. Known risk factors for osteoporosis include older age, female sex and a parent’s hip fracture, none of which anyone can change. That is why researchers keep hunting for risk factors that can be changed.

Salt has been a suspect for a long time. Experiments have shown that more sodium can enhance urinary calcium excretion, the loss of calcium through the kidneys, and calcium is the mineral that gives bone its strength. Population studies have been less clear. The Changsha team notes that the salting habit’s association with bone health has remained unexplored in studies that follow people forward to a diagnosis of osteoporosis, although a genetic study, described below, had looked at salting and bone density.

Their measure was one question. On joining UK Biobank, participants used a touchscreen to say how often they added salt to their food, excluding salt used in cooking: never or rarely, sometimes, usually or always. The authors picked it as a marker of a person’s long-term preference for salty taste that is largely separate from the salt already inside processed food. An earlier UK Biobank analysis by a different research group found that people who salted more often also had higher concentrations of spot urinary sodium, so the habit shows up in what the body excretes.

Most participants answered at the low end. Of the 491,428, a total of 272,375 (55.4%) never or rarely added salt, about 28% did so sometimes and about 12% usually. Only 23,846 people, just under 5%, said they always did.

How much higher was the osteoporosis risk?

Over a median follow-up of 14.7 years, 15,953 osteoporosis cases were documented, roughly 3 in every 100 participants, each one counted when the diagnosis appeared in hospital inpatient records linked to that person.

Compared with people who never or rarely salted their food, those who usually did had about 9% higher risk, and those who always did had about 32% higher risk. Those figures already allow for age, sex, ethnicity, deprivation, diet quality, smoking, alcohol, body weight, physical activity, and vitamin D and calcium intake. The authors report a positive graded association between the frequency of adding salt to food and osteoporosis, which means the risk climbed as salting became more frequent. It held when they set aside cases diagnosed in the first two years of follow-up, which makes it less likely that early, undiagnosed illness had changed what people ate before the study recorded it.

Fractures moved in the same direction, with one exception. Salting more often was associated with total and vertebral fractures, the second meaning breaks in the spine, while hip fractures showed no link.

The link was much stronger in men. Men who always salted their food had about 67% higher risk of osteoporosis than men who rarely did, while among women the figure was about 22%. The association was also stronger in White participants and in those with a higher body mass index. The authors offer one possible reason for the gap between the sexes, which they did not test. Because osteoporosis in men is often under-recognized and insufficiently prevented, they suggest, a harmful habit may go on for longer before anyone checks or treats their bones, leaving more time for damage to build up.

Genes added another layer. The team scored each participant’s inherited risk with a genetic risk score, a tally of the gene variants that earlier studies tied to osteoporosis, and split them into thirds. People in the highest third who always added salt carried about 2.7 times the risk of those in the lowest third who rarely did. Luo and Zhou caution against making too much of that. The statistical test for whether salt mattered more in people with high genetic risk came up empty, and they write that the joint result should not be overinterpreted as evidence of a gene-environment interaction. Genes and salting each added to the risk on their own; the study cannot say that salt does extra harm to the genetically vulnerable.

The same habit also tracked with the heart. In the same 491,428 participants, the study found that people who always salted their food had about 18% higher risk of dying from cardiovascular disease and about 21% higher risk of a heart attack, stroke or similar event. The authors take that as a sign that adding salt may be a modifiable behavior relevant to multiple age-related diseases.

Why would salt matter to bones?

The best-supported route runs through the kidneys. Extra sodium means the kidneys hold back less calcium, which the Changsha team describes as increasing urinary calcium loss and contributing to chronic negative calcium balance. Over years, that becomes a slow drain in which the body loses more calcium than it takes in and makes up the difference from bone.

A small feeding trial measured that drain directly. Eleven women completed a randomized cross-over trial in which they ate carefully controlled diets, low and moderately high in salt, in turn for five weeks at a time. The higher-salt diet, about 11 grams of salt a day, brought an increase in urinary calcium excretion, and when the women were also eating plenty of calcium, the extra salt tipped their bones from gaining calcium to losing it.

There is a less biological explanation too, and the Changsha researchers raise it themselves. Frequent salting may also reflect a broader unhealthy dietary pattern, a taste for processed, energy-dense food that could harm bone in other ways. When they joined the study, the more frequent salters already weighed more, were less active and eating a poorer diet with less calcium and vitamin D. The analysis adjusted for those differences as they were measured, but one diet score cannot capture a whole way of eating.

Does other research on salt and bone agree?

Only partly, which is what makes a large study of the question worth having. A 2018 review that pooled earlier studies found a positive link between sodium intake and a diagnosis of osteoporosis, yet no clear correlation between sodium intake and BMD, or bone mineral density, the scan measure doctors use to diagnose the condition. The reviewers also found the studies disagreed widely with one another. The Changsha authors also cite a meta-analysis of nearly 40,000 participants that put the risk of osteoporosis about 20% higher with high dietary sodium intake.

The largest earlier test of measured sodium pointed the other way. The Women’s Health Initiative followed 69,735 postmenopausal women for an average of 11 years. Once body weight was taken into account, sodium intake showed no link to bone density changes at any skeletal site, and none to fractures. Its authors concluded that current sodium recommendations are unlikely to significantly affect osteoporosis.

Genetic evidence has given only a faint signal. A 2025 study used a method called Mendelian randomization, which treats inherited gene variants as a natural experiment, to test whether the UK Biobank salting habit could cause lower bone density. It found a suggestive association between higher frequency of adding salt to foods and decreased total-body bone density in Europeans over 60, but no causal effect was detected on BMD in other age groups or skeletal sites.

The salting question itself has a track record. In the earlier analysis of more than 500,000 UK Biobank participants, people who always added salt were more likely to die early, with about 1.5 and 2.3 years lower life expectancy at the age of 50 in women and men respectively. The new study adds bone to a list of outcomes that already included the heart and early death.

What the UK Biobank salt study leaves open

The researchers set out the gaps themselves. Salting was measured by a single self-reported question at baseline, which says nothing about total sodium from all foods, and anyone who changed their habits over 15 years was still counted by their first answer. Hidden differences, what epidemiologists call residual confounding, cannot be fully excluded given the observational design, so something else that separates heavy and light salters could explain part of the link. UK Biobank volunteers were mostly White and European, which may limit how far the result travels.

Osteoporosis was also counted only when it reached a hospital record. Reliance on inpatient records may have missed people diagnosed and treated entirely by family doctors or outpatient clinics.

What the salt finding means for everyday eating

The study changes no recommendation, but it sits comfortably beside the ones that exist. The World Health Organization recommends less than 2000 mg/day of sodium for adults, equal to under 5 grams of salt or just under a teaspoon. The global mean intake in 2021 was about 11 grams of salt a day, more than double that. The agency already lists osteoporosis among the conditions tied to diets high in sodium, and notes that in many countries much of the sodium in the diet comes from processed foods rather than the shaker.

The Changsha authors call adding salt a simple behavioral target relevant to healthy aging, because unlike age or genes it is a habit that can change. Whether changing it would protect anyone’s bones has not been tested in a trial. Whether a person’s bone health needs checking is assessed by their doctor, usually with a bone density scan and a look at other risk factors.

The salt shaker now joins the list of habits linked to weaker bones in a large observational study, with a plausible reason behind the link and earlier research that has not settled whether salt itself is to blame.