Lifetime milk consumption and bone mineral density in older women

Milk consumption in older Americans

OBJECTIVES

The purpose of this study was to identify individual characteristics associated with types and frequency of milk consumption in older American adults.

METHODS

A national probability-based sample (response rate = 91%) completed a telephone survey. Generalized logit and cumulative logit analyses were used to identify predictors of and barriers to fluid milk consumption in 494 elderly people.

RESULTS

The likelihood of drinking skim or 1% milk rather than whole milk increased with nutrition knowledge, income, trying to reduce cholesterol intake, and being female (P < .05). Frequency of milk consumption was higher with nutrition knowledge, frequency of milk consumption during adolescence, and following a diabetic diet but was lower with milk intolerance.

CONCLUSIONS

The present results could be used to develop intervention strategies for improving milk consumption rates among older adults. These strategies might focus on increasing elderly people's awareness of milk intolerance and lactose-reduced milk products and their concern about cholesterol. The relationship between current and adolescent milk consumption suggests that intervention strategies should begin early in life.

Appendicular bone density, biochemical markers of bone turnover and lifestyle factors in female teachers of Southern Italy

The present study was designed to investigate relationships between urinary free pyridinolines (F-Pyr), serum osteocalcin (OC) and appendicular bone mineral density (BMD). Furthermore, possible correlations between such variables and putative risk factors for low bone density were also analysed. We were not able to find any relationships between biochemical markers of bone turnover and appendicular BMD or putative risk factors for osteoporosis at multivariate analysis. Multivariate analysis showed a significant decrease of BMD when age increases (p < 0.001), with menopause and time since menopause (p < 0.001), while number of pregnancies (p = 0.018) was associated with a higher value of BMD. Age, menopause and time since menopause were significantly associated with urinary excretion of F-Pyr. Indeed age was an inverse effect modifier of the relationship between urinary excretion of F-Pyr and time since menopause.

Calcium intake and the incidence of forearm and hip fractures among men

High calcium intakes are thought to be associated with strong bones and lower risk of fractures. However, findings from epidemiologic studies have not been consistent. In addition, the vast majority of such studies were conducted among women, leading to a relative lack of data concerning men. The objective of this study therefore was to investigate the relation between adult calcium intake and risk of fractures among men in the Health Professionals Follow-up Study (HPFS). During 331,234 person-years of follow-up over an 8-y period, 201 forearm and 56 hip fractures due to low or moderate trauma were reported among 43,063 men 40-75 y of age in 1986 when they first completed a questionnaire about diet and lifestyle factors. After controlling for age, smoking status, body mass index (BMI), physical activity, alcohol consumption and total energy intake, the relative risk (RR) of forearm fractures for men in the highest quintile of calcium intake (from foods plus supplements) compared with those in the lowest quintile was 0.98 [95% confidence interval (CI) = 0.59-1.61; P for trend = 0.78]; for hip fractures, the comparable RR was 1.19 (95% CI = 0.42-3.35; P for trend = 0.58). Relative risks for consuming >2.5 glasses (600 mL) of milk per day compared with one (240 mL) or fewer per week were 1.06 (95% CI = 0.69-1.62; P for trend = 0.82) for forearm fractures and 0.97 (95% CI = 0.39-2.42; P for trend = 0.56) for hip fractures. In conclusion, these results do not support a relation between calcium intake and the incidence of forearm or hip fractures in men.

Calcium and osteoporosis

Calcium is an essential nutrient that is involved in most metabolic processes and the phosphate salts of which provide mechanical rigidity to the bones and teeth, where 99% of the body's calcium resides. The calcium in the skeleton has the additional role of acting as a reserve supply of calcium to meet the body's metabolic needs in states of calcium deficiency. Calcium deficiency is easily induced because of the obligatory losses of calcium via the bowel, kidneys, and skin. In growing animals, it may impair growth, delay consolidation of the skeleton, and in certain circumstances give rise to rickets but the latter is more often due to deficiency of vitamin D. In adult animals, calcium deficiency causes mobilization of bone and leads sooner or later to osteoporosis, i.e., a reduction in the "amount of bone in the bone" or apparent bone density. The effects of calcium deficiency and oophorectomy (ovariectomy) are additive. In humans, osteoporosis is a common feature of aging. Loss of bone starts in women at the time of the menopause and in men at about age 55 and leads to an increase in fracture rates in both sexes. Individual fracture risk is inversely related to bone density, which in turn is determined by the density achieved at maturity (peak bone density) and the subsequent rate of bone loss. At issue is whether either or both of these variables is related to calcium intake. The calcium requirement of adults may be defined as the mean calcium intake needed to preserve calcium balance, i.e., to meet the significant obligatory losses of calcium through the gastrointestinal tract, kidneys, and skin. The calcium allowance is the higher intake recommended for a population to allow for individual variation in the requirement. The mean requirement defined in this way, calculated from balance studies, is about 20 mmol (800 mg) a day on Western diets, implying an allowance of 25 mmol (1000 mg) or more. Corresponding requirements and allowances have been calculated for pregnancy and lactation and for children and adolescents, taking into account the additional needs of the fetus, of milk production, and of growth. There is a rise in obligatory calcium excretion at menopause, which increases the theoretical calcium requirement in postmenopausal women to about 25 mmol (1000 mg) and implies an allowance of perhaps 30 mmol (1200 mg) or even more if calcium absorption declines at the same time. At issue here, however, is whether menopausal changes in calcium metabolism are the cause or the result of postmenopausal bone loss. The first interpretation relies on evidence of a positive action of estrogen on the gastrointestinal absorption and renal tubular reabsorption of calcium; the latter interpretation relies on evidence of a direct inhibitory effect of estrogen on bone resorption. The calcium model for postmenopausal bone loss tends to be supported by the effect of calcium therapy. An analysis of the 20 major calcium trials in postmenopausal women reported in the last 20 years yielded a mean rate of bone loss of 1.00% per annum (p.a.) in the controls and 0.014% p.a. (NS) in the treated subjects (P < 0.001). However, trials in which calcium and estrogen have been directly compared have shown that the latter is generally more effective than calcium in that it produces a small, but often significant bone gain. This superiority of estrogen over calcium could be due to the former's dual action on calcium absorption and excretion or to a direct action of estrogen on bone itself. In older women, the importance of calcium intake is overshadowed by the strong association between vitamin D insufficiency and hip fracture. Whether this insufficiency arises primarily from lack of exposure to sunlight or to a progressive failure to activate the vitamin D precursor in the skin or both is uncertain but it is compounded by a general decline in dietary vitamin D intake with age. The biological effect is probably an impairment of calcium absorption and c

Milk, dietary calcium, and bone fractures in women: a 12-year prospective study

OBJECTIVES

This study examined whether higher intakes of milk and other calcium-rich foods during adult years can reduce the risk of osteoporotic fractures.

METHODS

This was a 12-year prospective study among 77761 women, aged 34 through 59 years in 1980, who had never used calcium supplements. Dietary intake was assessed with a food-frequency questionnaire in 1980, 1984, and 1986. Fractures of the proximal femur (n = 133) and distal radius (n = 1046) from low or moderate trauma were self-reported on biennial questionnaires.

RESULTS

We found no evidence that higher intakes of milk or calcium from food sources reduce fracture incidence. Women who drank two or more glasses of milk per day had relative risks of 1.45 for hip fracture (95% confidence interval [CI] = 0.87, 2.43) and 1.05 for forearm fracture (95% CI = 0.88, 1.25) when compared with women consuming one glass or less per week. Likewise, higher intakes of total dietary calcium or calcium from dairy foods were not associated with decreased risk of hip or forearm fracture.

CONCLUSIONS

These data do not support the hypothesis that higher consumption of milk or other food sources of calcium by adult women protects against hip or forearm fractures.

Do dairy products improve bone density in adolescent girls?

Previous studied have shown that when calcium is supplemented in adolescents who normally consume less than 1000 mg calcium, bone mineral accretion improves between 1 and 5%. This increment in bone accretion is improved up to 10% when dairy products are used as a source of supplemental calcium in adolescent girls. Because the addition of dairy foods is a simple, inexpensive intervention that carries no risk and because it substantially increases bone accretion with potential long-term benefits, adolescents should be encouraged to include dairy products in their diet.

An 18-year prospective study of dietary calcium and bone mineral density in the hip

The object of this study was to determine whether a single 24-hour diet recall of calcium intake obtained an average of 18 years previously would predict bone mineral density (BMD) in the hip in older men and women. A prospective population-based cohort study was done in Rancho Bernardo, California. Between 1973 and 1975, a 24-hour diet recall was obtained in 140 men and 220 women aged 45 and older by a trained interviewer using food models and containers. Responses were coded by the Nutrition Coordinating Center, University of Minnesota. Between 1988 and 1991, BMD in the femoral neck, trochanter, and intertrochanter was measured using dual-energy x-ray absorptiometry. Results showed that age-adjusted mean BMD levels increased significantly with increasing tertile of calcium intake at all hip sites in women, with the most striking difference at the femoral neck. These associations persisted after adjustment for body mass index, smoking, exercise, alcohol intake, use of estrogen replacement therapy, and number of years postmenopausal. No significant trends were seen for men at any hip site. It is concluded that low dietary calcium predicts low BMD in older women independent of other major determinants of BMD.