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A compelling case — the role of dairy in bone health

Over 4,000 delegates descended on the beautiful and historic city of Florence for this year’s World Congress on Osteoporosis, Osteoarthritis and Musculoskeletal Diseases. The largest meeting worldwide that focuses solely on osteoporosis, uniquely, it discusses and debates both the clinical and economic aspects of these diseases.

Indeed, one clear theme running through this year’s Congress was the bad press that dairy is currently receiving and the danger of falling dairy intakes within ageing populations.

It is estimated that osteoporotic fractures currently cost the Irish economy upwards of €650 million per year, with an estimated 300,000 people thought to have the condition. The Congress heard that Ireland’s rate of hip fractures among women is the sixth-highest globally, while 20 per cent of people over the age of 60 who fracture a hip will die within six-to-12 months.

New Irish data released at the Congress painted a picture of a pivotal role for yogurt consumption in maintaining bone density in the elderly. Dr Miriam Casey, Consultant Geriatrician at St James’s Hospital, Dublin, and the Mercers Institute for Successful Ageing (MISA), led the research, which used data from the Trinity Ulster Department of Agriculture (TUDA) ageing cohort study. This was a large study of older Irish community-dwelling adults aged over 60, designed to investigate nutritional factors, related gene-nutrient interactions and a range of health and lifestyle factors in the development of chronic diseases of ageing.

The study observed significant positive associations of increased frequency of yogurt intake with bone health and measures of physical function. This has “huge” policy implications, Dr Casey told the Medical Independent (MI).

“To have a study that clearly shows a reduction of that strength in the risk of developing osteoporosis achieved by a simple food product like yogurt is very impressive.

“Some of the milder drugs to treat osteoporosis would be on a par with these results. Yogurts are easier to take than tablets and they are ‘cheap and cheerful’.”

These findings must be viewed within the demographics of Ireland’s ageing population, Dr Casey pointed out. “Addressing both dairy and yogurt intakes as part of Irish health policy could be a valuable and cost-effective health measure for maintaining bone health and ultimately possibly reducing fracture risk among older adults.”

The findings

The study, carried out in the North and South of Ireland, found that every increase in yogurt intake in females was associated with a 29 per cent lower risk of osteopaenia and a 37 per cent lower risk of osteoporosis, while men were 51 per cent less likely to develop osteoporosis.

In addition, blood concentrations of vitamin B12 biomarkers, red cell folate, vitamin B2 and vitamin B6 were significantly worse in those with the lowest tertile of dairy intake compared to those in the highest tertile. Total hip and femoral neck bone mineral density (BMD) in females were also significantly higher among those with the highest yogurt intakes compared to the lowest, as were the Timed Up and Go (TUG) scores — a score that reflects mobility and muscle function.

Females with the highest yogurt intakes had significantly higher BMD concentrations and better physical function scores compared to individuals with the lowest intakes, added Dr Casey. “Overall, their health was enhanced,” she said.

A previous study published in the BMJ in 2014 had shown that yogurt and fermented dairy products were linked with a 10-to-15 per cent reduction in mortality and hip fracture rates in women. The Irish data shows this impact in both men and women. “We show for the first time that, after adjustment for covariate predictors, each unit increase in yogurt intake significantly decreased the odds of being characterised as osteopaenic or osteoporotic in both men and women. What is needed now is a randomised, controlled study to see what it is about these older people and their genetics that allows yogurt to have such a strong effect in such a high proportion of people,” explained Dr Casey.

Yet just 3.5 per cent of the elderly group involved in the study were achieving the recommended intake of three servings of dairy products a day. According to Dr Casey, the trend to reduce dairy intakes has increased in recent years and is due to a myriad of factors, including health concerns over certain dairy components, such as saturated fatty acids, the decrease in family meal consumption and, more recently, to meet climate change targets.

Cost-effective

Improving both dairy and yogurt intakes could be a valuable and cost-effective health measure for maintaining bone health and ultimately possibly reducing fracture risk, said Dr Casey. “In addition, it could also provide a source of micronutrients and reducing frailty in older adults.”

This research also highlights opportunities for the food industry in developing micronutrient-rich, acceptable dairy products for the elderly consumer, she added.

International Osteoporosis Foundation co-founder, Belgium’s Prof Jean Yves Reginster, told delegates at the Congress that there has been “much media-bashing” of dairy products and attempted to differentiate between “fact and fantasy” when it came to dairy products and their perceived risk and benefits. The evidence shows that both calcium and vitamin D are needed to decrease fracture risk and data shows that there is a high prevalence of vitamin D insufficiency in the elderly, with dietary calcium low in many postmenopausal osteoporotic women, he stated.

“Despite the established benefits for bone health, some people avoid dairy in their diet due to beliefs that dairy may be detrimental to health, especially in those with weight or digestion concerns, or trying to avoid cardiovascular disease and cancer,” he told delegates.

Contrary to popular belief, meta-analyses of observational studies support the positive role of dairy for weight control, particularly during energy restriction, he explained.

The evidence also shows that dairy products do not increase the risk of cardiovascular disease or cancer when consumed at the recommended dose of three servings per day as part of a balanced diet, he added.

The professor also presented evidence to show that dairy products are not associated with weight gain, with research showing they can actually increase lean muscle mass. A meta-analysis of 22 randomised, controlled trials showed that people who engaged in resistance training and then took a supplement containing whey proteins gained significantly more lean muscle mass than those who were given a placebo — the mean fat-free mass gain was more pronounced in younger people (0.8kg) than it was in older adults (0.5kg). Similar studies comparing whey protein to soy protein showed significantly more muscle mass gain with whey protein; this shows there is clearly a difference in the quality of the protein taken in terms of its capacity to induce synthesis of new muscle, added Prof Reginster.

The professor also rubbished misperceptions surrounding the supposed “acid-ash” hypothesis — this suggests foods containing acid-forming substances (such as animal protein from milk or meat and some plant foods) cause the blood pH to drop or become less alkaline and leads to release of calcium from bones, and eventually osteoporosis. “There is no evidence at all to prove this hypothesis,” he told the audience.

In addition, lactose maldigestion is not necessarily lactose intolerance, noted the professor: “Lactose-intolerant individuals may not need to eliminate dairy products from their diet; most of them can tolerate up to 12g of lactose (240ml of milk) and both yogurt and hard cheese are well tolerated.”

“Overall, the proven benefits of dairy foods on bone health greatly outweigh unproven harms,” he stated.

The economic impact

Even dairy products can be at the mercy of health economics and Prof Mickaël Hiligsmann, Assistant Professor in Health Economics and Health Technology Assessment at Maastricht University in the Netherlands delivered a presentation titled ‘Saving lives and resources by preventing osteoporotic fractures with dairy products’.

In addition to clinical evidence, assessing the public health and economic impact of fortified dairy products is important to help policy-makers in evaluating and making decisions about preventive programmes, especially in the context of limited healthcare resources, explained Prof Hiligsmann.

The professor was recently involved in a study in France, which estimated using a simulation model the lifetime health impacts of the recommended intake of dairy products in the general French population aged over 60 years for one year. They found that the total lifetime number of fractures decreased by 64,932 for the recommended intake of dairy products in the general population over 60 years old, of which 15,087 and 4,413 hip fractures could be prevented in women and men, respectively. This resulted in a gain of 29,169 life years and of 32,569 years in perfect health (QALYs).

Prof Hiligsmann explained the cost per QALY gained of appropriate dairy intake in the general population aged over 60 years was estimated at the border of efficiency (€58,244) and dairy products were found to be highly cost-effective (ICER <€30,000 per QALY gained) in women aged over 70 years and in men aged over 80 years.

“The use of vitamin D-fortified dairy products could substantially reduce the burden of osteoporotic fractures and seems to be an economically beneficial strategy,” he concluded.

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