Influence of exercise and degenerative vertebral changes on BMD: a cross-sectional study in Japanese men

Greater milk intake is associated with lower bone turnover, higher bone density, and higher bone microarchitecture index in a population of elderly Japanese men with relatively low dietary calcium intake: Fujiwara-kyo Osteoporosis Risk in Men (FORMEN) Study

The effects of milk intake on bone health are not clear in elderly Asian men with low dietary calcium intake. This study showed that greater milk intake is associated with lower bone turnover, higher bone density, and higher bone microarchitecture index in community-dwelling elderly Japanese men.

INTRODUCTION

The consumption of milk or dairy products is widely recommended for maintaining bone health regardless of gender or age. However, little evidence exists on the beneficial effects of milk intake on bone health in elderly Japanese men characterized with relatively low dietary calcium intake. Here we examined whether or not greater milk intake was associated with lower bone turnover, higher bone density, and stronger bone microarchitecture in community-dwelling elderly Japanese men.

METHODS

Interviews were conducted to obtain information on medical history and lifestyle, including the amount of habitual milk intake, nutrient intake calculations based on a 1-week food diary, and measurements of areal bone mineral density (aBMD) at the lumbar spine (LS), total hip (TH), and femoral neck (FN) by dual-energy x-ray absorptiometry (DXA), trabecular bone score (TBS) using DXA images at LS, and biochemical markers of bone turnover in sera. Participants with a history of diseases or medications that affect bone metabolism, or with missing data, were excluded from the analysis.

RESULTS

The median intake of milk in the 1479 participants (mean age, 73.0 ± 5.1 years) was one glass of milk per day. Bone turnover markers showed a decreasing trend (p < 0.05) and aBMD at TH (p = 0.0019) and FN (p = 0.0057) and TBS (p = 0.0017) showed increasing trends with greater milk intake after adjusting for demographic and behavioral confounding factors. This association was attenuated after further adjusting for nutrient intake, in particular, calcium intake.

CONCLUSIONS

Greater milk intake was associated with lower bone turnover, higher aBMD, and higher TBS in community-dwelling elderly Japanese men.

Dairy foods and bone health: examination of the evidence

It is unclear whether dairy foods promote bone health in all populations and whether all dairy foods are equally beneficial. The objective of this review was to determine whether scientific evidence supports the recommendation that dairy foods be consumed daily for improved bone health in the general US population. Studies were reviewed that examined the relation of dairy foods to bone health in all age, sex, and race groups. Outcomes were classified according to the strength of the evidence by using a priori guidelines and were categorized as favorable, unfavorable, or not statistically significant. Of 57 outcomes of the effects of dairy foods on bone health, 53% were not significant, 42% were favorable, and 5% were unfavorable. Of 21 stronger-evidence studies, 57% were not significant, 29% were favorable, and 14% were unfavorable. The overall ratio of favorable to unfavorable effects in the stronger studies was 2.0 (4.0 in <30-y-olds, 1.0 in 30-50-y-olds, and 1.0 in >50-y-olds). Males and ethnic minorities were severely underrepresented. Dairy foods varied widely in their content of nutrients known to affect calcium excretion and skeletal mass. Foods such as milk and yogurt are likely to be beneficial; others, such as cottage cheese, may adversely affect bone health. Of the few stronger-evidence studies of dairy foods and bone health, most had outcomes that were not significant. However, white women <30 y old are most likely to benefit. There are too few studies in males and minority ethnic groups to determine whether dairy foods promote bone health in most of the US population.

Calcium, dairy products and osteoporosis

Osteoporosis is a multifactorial disorder in which nutrition plays a role but does not account for the totality of the problem. 139 papers published since 1975 and describing studies of the relationship of calcium intake and bone health are briefly analyzed. Of 52 investigator-controlled calcium intervention studies, all but two showed better bone balance at high intakes, or greater bone gain during growth, or reduced bone loss in the elderly, or reduced fracture risk. This evidence firmly establishes that high calcium intakes promote bone health. Additionally, three-fourths of 86 observational studies were also positive, indicating that the causal link established in investigator-controlled trials can be found in free-living subjects as well. The principal reason for failure to find an association in observational studies is the weakness of the methods available for estimating long-term calcium intake. While most of the investigator-controlled studies used calcium supplements, six used dairy sources of calcium; all were positive. Most of the observational studies were based on dairy calcium also, since at the time the studies were done, higher calcium intakes meant higher dairy intakes. All studies evaluating the issue reported substantial augmentation of the osteoprotective effect of estrogen by high calcium intakes. Discussion is provided in regard to the multifactorial complexity of osteoporotic response to interventions and to the perturbing effect in controlled trials of the bone remodeling transient, as well as about how inferences can validly be drawn from the various study types represented in this compilation.

Bone loss in Great Britain and Japan: a comparative longitudinal study

Hip fracture incidence is lower in Japan than in the West. Although differences have been found in peak bone mass and hip geometry between white and Japanese populations, these do not fully explain the difference in hip fracture rates. Variation in the rates of involutional bone loss may be an additional contributing factor. We address this issue in a prospective epidemiological study comparing bone loss rate among elderly people in Britain and Japan. Two population-based studies of bone loss rate in a British and a Japanese cohort were performed. Annual bone loss rates were obtained for 172 Hertfordshire men and 143 Hertfordshire women of mean age 66 years, and a questionnaire administered to obtain information on known confounding lifestyle factors. Eighty-six Japanese men and 90 Japanese women of mean age 69 years completed a similar study in Taiji, Japan. British men and women were heavier than Japanese men and women. Differences in lifestyle were also evident; the British men were less likely to smoke and the women more likely to consume alcohol than their Japanese counterparts. The British population also spent more time walking outdoors. Statistically significant differences between the two populations were apparent in baseline bone mineral density at lumbar spine (p < 0.05) and trochanter (p < 0.001) in men and women with Japanese subjects having lower values. There were also significant differences in bone density at the femoral neck (p < 0.001) between British and Japanese males. Men gained bone at the lumbar spine over the follow-up period in both populations. Bone loss rates were generally greater in the British female population than in Japanese women: the difference was statistically significant at the femoral neck (p < 0.05) and femoral trochanter (p < 0.001). These differences all remained significant after adjustment for differences in age between the two populations. Japanese subjects appear to have lower peak bone mass, but slower bone loss rates in later life than their European counterparts. These differences in bone loss rate help to explain the relatively low hip fracture rates found in Japan.