Osteoporosis Sufferers May Benefit From Mediterranean Diet

Liam Davenport

July 20, 2018

People with osteoporosis could experience benefit if they follow a Mediterranean diet rich in fruit and vegetables, olive oil, and fish, claim European researchers in the first clinical trial looking at the impact of the diet on bone health in older adults.

The NU-AGE study involved almost 1300 individuals from five European countries who were helped to follow a Mediterranean diet through regular dietary advice and the provision of foods.

The research, published online in the American Journal of Clinical Nutrition on July 11, showed that, overall, the intervention had no effect on bone mineral density (BMD).

However, participants who already had osteoporosis at the start of the study saw a significant increase in BMD at the femoral neck.

Senior author Susan J. Fairweather-Tait, PhD, Department of Nutrition and Preventive Medicine, Norwich Medical School, University of East Anglia, led the UK arm of the study.

She told Medscape Medical News that the impact of the Mediterranean diet on BMD was seen in people with osteoporosis "because they're losing bone at a faster rate and so they're a more sensitive population."

Fairweather-Tait also believes that the wholefood nature of the dietary intervention was the key to its effect.

"It's not a vitamin, a mineral, or anything else," she said. "They individually might have a tiny effect, but the effect is so small that you need the combination, and that’s the strength [of our study]."

However, doubts have been cast over the clinical significance of the findings, with one expert arguing that it is not possible to say at this stage whether the Mediterranean diet itself was responsible for the changes seen in BMD in those with osteoporosis.

Benjamin Z. Leder, MD, an endocrinologist at Massachusetts General Hospital in Boston and professor of medicine at Harvard University, told Medscape Medical News, "The finding that there were differences between the two groups in BMD...is difficult to interpret because it's a small subgroup analysis and I don't think they corrected for the multiple different variables."

Leder, who is also chair of the American Society for Bone and Mineral Research Professional Practice Committee, said: "My reading of this study is it's a negative study, and it's important to have negative studies published."

Less Bone Loss With Mediterranean Diet in Small Osteoporosis Subgroup

Numerous prospective studies have shown that following a Mediterranean diet is associated with a reduced incidence of cardiovascular disease and cancer, among other conditions.

There have been few studies, however, examining the potential of the diet to affect bone health and fracture risk, although a recent review suggested that greater adherence to the Mediterranean diet was linked to a lower risk of hip fractures (JAMA Intern Med. 2016;176:645-652).

Researchers conducted the randomized controlled NU-AGE trial in 1294 individuals aged 65–79 years from France, Italy, the Netherlands, Poland, and UK who were recruited between 2012 and 2014.

Participants in the intervention group received standardized dietary advice tailored to their location nine times a year, supported by mail or email, as well as commercially available foods, to help them meet the Mediterranean diet-type guidelines, including whole-grain pasta and olive oil.

In addition, they received low-dose vitamin D supplements to minimize the differences in serum total 25-hydroxyvitamin D levels between the study sites because of habitual diet and sunlight exposure.

Control participants received a leaflet detailing national dietary guidance but otherwise continued with their same eating pattern.

Three-day food diaries were completed at months 4 and 8. All participants completed 7-day food diaries at study entry and at the end of the 1-year intervention.

Mean age of participants was 70.9 years and 44% were men.

In all, 1142 individuals completed the trial, of whom 555 from the intervention group and 562 controls had whole-body dual-energy X-ray absorptiometry scans at baseline and follow-up.

The scans revealed that 8% (n = 54) of participants had osteoporosis at baseline.

Results showed that, at 1 year, diet had no effect on BMD at any site and was not associated with changes in free pyridinoline or free deoxypyridinoline levels.

Mean vitamin D levels increased significantly during follow-up in the group assigned to the Mediterranean diet, at +4.5 ng/mL, compared with relatively little change in the control group, at +0.5 ng/mL (P < .01 between groups).

In addition, serum parathyroid hormone levels were significantly reduced in the intervention group, at –1.4 pg/mL, compared with an increase of +3.9 pg/mL in the control group (P < .001 between groups).

When the team focused only on participants with osteoporosis at baseline, they found that BMD at the femoral neck increased in the intervention group during follow-up but decreased in the control group, at a mean difference of 0.9% (P = .04).

There was no impact of diet on BMD at the lumbar spine or in the whole body in individuals diagnosed with osteoporosis.

"A Mediterranean-like diet together with vitamin D3 supplements had no effect on BMD in the normal age-related range," they observe.

"However, it significantly reduced the rate of loss of bone at the femoral neck in individuals with osteoporosis."

"The significant and interesting findings of differences in response between individuals with BMD in the normal range and those with osteoporosis need to be verified in a future study," the researchers conclude.

No Evidence That Small Changes Seen Are Clinically Significant

Leder has a different assessment of the findings, however.

He told Medscape Medical News that, in his view, although the study was "well done" and the methodology was "solid", it wasn't powered to examine bone markers.

"What this study shows is that this dietary intervention over 1 year had no effect on bone density or really any other marker of bone metabolism," although he also pointed out that 1-year follow-up "is not a lot of time for bone."

"If there is an effect, it's probably very, very small — even the femoral neck bone density changes that were significant in the osteoporosis group were so small that I think...there's no evidence that it's clinically significant."

The study was supported by the European Union's Seventh Framework Program. The authors have reported no relevant financial relationships.

Am J Clin Nutr. Published online July 11, 2018. Abstract

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