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Query: KEGG:D01453 (caffeine)
 21,611 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In view of the possible association between ingestion of caffeine (a constituent of coffee, tea, and several beverages) and osteoporosis, we have studied the effect of caffeine on bone resorption in vitro. Caffeine caused a dose-dependent increase of the spontaneous release of 45Ca from neonatal mouse calvarial bones. The effect of caffeine was less pronounced than that of parathyroid hormone (PTH), but of the same magnitude as that of theophylline, a structurally related methylxanthine. The enhancement of 45Ca release induced by caffeine and PTH was observed in 5 days culture. In 2 days culture, however, only PTH stimulated mineral mobilization. The delayed stimulatory effect of caffeine in long-term cultures was abolished by indomethacin and flurbiprofen. In indomethacin-treated bones, however, caffeine potentiated the stimulatory effect on 45Ca release induced by choleratoxin and forskolin. In contrast, caffeine did not potentiate 45Ca release stimulated by PTH. These data show that caffeine can stimulate calcium release from bone in vitro and that this effect is due to potentiation of a stimulatory action of a bone resorptive agonist acting via the adenylate cyclase-cyclic AMP system.
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PMID:Caffeine has the capacity to stimulate calcium release in organ culture of neonatal mouse calvaria. 145 Oct 9

Several life-style factors are known to or have been suggested to interact with calcium metabolism and bone turnover. Immobilization or a sedentary life-style may result in substantial bone loss, and physical exercise may increase bone mass, to different extents in different parts of the skeleton. Excessive training and/or slimming may lead to amenorrhoea, which is in turn complicated by rapid bone loss. While calcium supplementation probably cannot override the negative calcium balance induced by immobilization or amenorrhoea, the calcium requirement may be enhanced during recovery from these states. A high body mass index may to some extent protect against bone loss, particularly in post-menopausal women. Tobacco smoking and high alcohol consumption are probably detrimental to bone mass. Insufficient exposure to daylight and/or insufficient vitamin D intake occur mainly in infants and elderly people, and may impair calcium balance and cause rickets, osteomalacia or osteoporosis. Whether high intake of caffeine, protein, phosphate or fibre is detrimental to the bone mass has not yet been clarified. In many populations smoking and consumption of alcohol or caffeine are negatively correlated with calcium intake, and this exemplifies a source of confounding factors. Increased attention would be paid to important life-style factors during investigations of calcium requirements in different sex and age categories.
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PMID:Effect of calcium intake vs. other life-style factors on bone mass. 154 42

Dietary calcium is required for bone development during growth (attainment of peak bone mass), for maintenance of skeletal integrity during adult life, and thus for prevention of osteoporosis. The Recommended Dietary Allowance (RDA) of a nutrient for a particular group is considered to cover the needs of 98% of all individuals of that group, and thus takes into account a margin of safety to allow for interindividual variation in minimum requirements. It appears to be possible, on the basis of the available scientific literature, to calculate the daily amount of calcium that must be absorbed from the diet to compensate for the endogenous calcium losses (through urine, faeces and skin) and the calcium retention in bone. Similarly, it seems to be possible to obtain a reasonable estimate of calcium absorption for the different groups of the population. From these data, and taking into account a margin of safety, figures are obtained for calcium intake that are in reasonably close agreement with the authoritative 1989 RDAs of the USA Food and Nutrition Board, with the exception of the USA allowance for girls aged 19-25 years (probably too high) and older adults (possibly too low). With regard to optimal calcium intake, some important questions still remain unanswered. These bear upon the issue of calcium intake and peak bone mass development, and upon the effects of non-nutritional factors (e.g. genetics and physical activity) and nutritional factors (e.g. sodium, protein, alcohol and caffeine) on calcium requirements. Furthermore, it would appear that bone development and maintenance of bone health may not be the sole criteria for setting RDAs in the near future. These issues are briefly discussed.
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PMID:The scientific basis of recommended dietary allowances for calcium. 154 43

High caffeine consumption has been proposed as a risk factor for osteoporotic fracture, but the evidence associating high caffeine intake with low bone density is inconsistent. We therefore examined the influence of caffeine consumption on bone mineral at six skeletal sites in an age-stratified random sample of white women residing in Rochester, Minnesota. After age adjustment, there was no association between overall caffeine consumption and bone mineral at five of the six sites. In the femoral shaft, however, there was a statistically significant interaction between age and caffeine consumption so that high caffeine intake was associated with slight reductions in bone mineral among elderly subjects but with modestly increased bone mineral at younger ages. When caffeine intake was categorized by source, no consistent influence of coffee, tea, or other caffeinated beverage consumption could be detected on bone mineral. Caffeine intake was, however, positively associated with cigarette smoking and alcohol consumption. After adjusting for age, caffeine consumption was not correlated with biochemical indices of bone turnover, circulating concentrations of estradiol and estrone, or other dietary and musculoskeletal variables. These data suggest that caffeine intake in the range consumed by a representative sample of white women is not an important risk factor for osteoporosis. Among elderly women, however, in whom calcium balance performance is impaired, high caffeine intake may predispose to cortical bone loss from the proximal femur.
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PMID:Is caffeine consumption a risk factor for osteoporosis? 160 31

In a longitudinal study, we investigated the influence of risk factors on bone mass at menopause and postmenopausal bone loss in 121 healthy postmenopausal women. These women had completed a 2-year prospective study in 1979 and a follow-up examination in 1989. Measurements of the bone mineral content in the distal forearm (single photon absorptiometry) were performed 9 times during the initial study and once at the follow-up examination. Bone mass at menopause (initial measurement), rate of early postmenopausal bone loss, and the subsequent rate of bone loss over 10 years were thus determined. In addition, the bone mineral density of the lumbar spine and proximal femur was measured by dual-energy X-ray absorptiometry (DXA) in 1989. Information about risk factors was assessed by standardized questionnaires and included reproductive history and lifestyle factors (intake of calcium and vitamin D supplements, consumption of alcohol and caffeine, smoking habits, and physical activity). Lactation, oral contraceptive use, and dietary calcium intake above 1500 mg per day was associated with significantly increased bone mass at menopause. The number of pregnancies reduced the rate of early postmenopausal bone loss, whereas moderate alcohol consumption reduced the subsequent rate of bone loss. Smoking significantly reduced femoral bone mineral density. In conclusion, the present prospective study showed that some of the examined putative risk factors positively influenced bone mass at menopause, especially calcium intake, whereas the postmenopausal bone loss was virtually unaffected. Assessment of risk factors in postmenopausal women thus seems to have limited value for reducing future risk of osteoporosis.
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PMID:Potential risk factors for development of postmenopausal osteoporosis--examined over a 12-year period. 179 Mar 99

One common nutrient postulated to be protective against osteoporosis, hypertension, and colon cancer is dietary calcium. We report here nutrient patterns by calcium intake in older adult residents of a geographically defined community in Southern California. The analysis included all 426 men and 531 women aged 50-79 y with complete 24-h diet data. Nutrient-density-adjusted calcium intake was divided into tertiles: low intake (less than 284 mg/1000 kcal), mid intake (284-440 mg/1000 kcal), and high intake (greater than 440 mg/1000 kcal). The distribution of the reported 24-h nutrient density of protein, fat, fiber, caffeine, trace minerals, vitamin D, and vitamin C was examined in relation to the calcium-intake tertiles. In both men and women, the adjusted intakes of protein, saturated fatty acids, vitamin D, magnesium, and phosphorus were significantly higher in the high-calcium-intake group than in the low- and mid-calcium-intake groups. In both men and women, alcohol intake was significantly lower in the high-calcium-intake group. Studies postulating a protective role for calcium will need to consider the multicolinearity in the Western diet.
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PMID:Calcium intake: covariates and confounders. 184 36

Osteoporosis, a condition of decreased bone tissue that increases the likelihood of fracture, places a significant burden on our society in terms of health cost and morbidity. The most common type of osteoporosis is involutional, and two subtypes are recognized: type 1 and type 2. Type 1, or postmenopausal, osteoporosis is most commonly seen in perimenopausal and postmenopausal women from ages 51 to 75. Estrogen deficiency is the most dominant factor in the pathogenesis of this disorder. Type 2, or aging related, osteoporosis is seen in elderly women and men aged 70 or more. Bone loss in this group is related to aging, estrogen deficiency, negative calcium balance, and a variety of environmental and genetic factors. The best approach to the management of osteoporosis is to develop a lifelong strategy that maximizes peak bone mass and minimizes aging-related and postmenopausal bone loss. Estrogen is the only medication approved for the prevention of bone loss that is in general use. Other strategies to prevent bone loss (and maximize peak bone mass) include adequate calcium intake, adequate exercise, and avoidance of excess alcohol, tobacco, and caffeine use.
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PMID:Osteoporosis. 198 30

Transient hypercalciuria has been noted after high carbohydrate meals which is independent of dietary calcium and is probably due to impaired renal calcium reabsorption mediated by an increase in plasma insulin levels. Based on these observations, some investigators believe that long term intake of high carbohydrate diets may increase the risk of nephrolithiasis and possibly osteoporosis. Using a randomized cross-over design, we compared high carbohydrate diets (60% carbohydrate and 25% fat) with high fat diets (50% fat and 35% carbohydrate) for effects on metabolism of calcium and other minerals in eight normal subjects and eight euglycemic patients with noninsulin-dependent diabetes mellitus. All other dietary constituents, such as protein, fiber, fluid, minerals (including Ca, Mg, Na, K, and P), and caffeine intake, were kept constant. Despite higher daylong levels of plasma insulin on the high carbohydrate diets compared to the high fat diet in both normal and noninsulin-dependent diabetic subjects, no changes in daily urinary excretion of calcium or other constituents, associated with renal stone risk, were observed. Furthermore, there was no change in fractional intestinal 47Ca absorption. Although hypercalciuria may ensue transiently after high carbohydrate meals, we conclude that substitution of simple or complex carbohydrates for fats in an isocaloric manner for a longer duration does not result in significant urinary calcium loss, and therefore, high intakes of digestible carbohydrates may not increase the risk of nephrolithiasis or osteoporosis via this mechanism.
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PMID:Effects of dietary carbohydrates on metabolism of calcium and other minerals in normal subjects and patients with noninsulin-dependent diabetes mellitus. 215 83

Caffeine increases urinary calcium output and has been implicated as a risk factor for osteoporosis. The authors examined the effect of caffeine on hip fracture risk in 3,170 individuals attending the 12th (1971-1973) Framingham Study examination. Coffee and tea consumption, age, Framingham examination number, weight, smoking, alcohol consumption, and estrogen use were used to evaluate hip fracture risk according to caffeine intake. Hip fractures occurred in 135 subjects during 12 years of follow-up. Fracture risk over each 2-year period increased with increasing caffeine intake (one cup of coffee = one unit of caffeine, one cup of tea = 1/2 unit of caffeine). For intake of 1.5-2.0 units per day, the adjusted relative risk (RR) of fracture was not significantly elevated compared with intake of one or less units per day. Consumption of greater than or equal to 2.5 units per day significantly increased the risk of fracture. Overall, intake of greater than two cups of coffee per day (four cups of tea) increased the risk of fracture. In summary, hip fracture risk was modestly increased with heavy caffeine use, but not for intake equivalent to one cup of coffee per day. Since caffeine use may be associated with other behaviors that are, themselves, risk factors for fracture, the association may be indirect. Further studies should be performed to confirm these findings.
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PMID:Caffeine and the risk of hip fracture: the Framingham Study. 200 50

Caffeine has been cited as a risk factor for osteoporosis in humans. In rats, caffeine increases calcium absorption and excretion and raises parathyroid hormone (iPTH) levels. This study investigated the effect of chronic caffeine administration on bone histomorphometry and serum markers of bone mineral metabolism. Twenty-seven male Sprague Dawley rats weighing approximately 300 g were divided into three groups: Group A (n = 8) served as controls, Group B (n = 9) received 2.5 mg/100 g caffeine in their drinking water, and Group C (n = 10) received 10 mg/100 g body weight caffeine in their drinking water. Animals were bled serially for the 8 week study period: Ionized calcium was measured from tail vein blood and serum iPTH and osteocalcin (BGP) from orbital sinus blood. All three groups received two doses of tetracycline for bone histomorphometry which was performed on a right tibial section from each animal. Ionized calcium was not different among the three groups at any time point. No alteration in serum iPTH levels was demonstrated except for day 56 when the high-dose group (C) showed a raised level (mean = 59.1, SE = +/- 8.9 pg/ml (P less than 0.05). By week 8 Group C showed a failure to gain weight compared with Group A. Group C mean weight = 384.0 +/- 6.6 g, Group A 427.4 +/- 10.8 g (P less than 0.005). Serum BGP was significantly increased in Group C compared with control (P less than 0.001). No differences in bone histomorphometry were observed among the three groups.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The effect of chronic caffeine administration on serum markers of bone mineral metabolism and bone histomorphometry in the rat. 314 92


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