Association between calcium ingested from drinking water and femoral bone density in elderly women: evidence from the EPIDOS cohort

Supplementing Low-Sodium Bicarbonate-Calcic (Lete)® Water: Effects in Women on Bone and Systemic Metabolism

Calcium (Ca) represents about 40% of the total mineral mass, mainly in the bone, providing mechanical strength to the skeleton and teeth. An adequate Ca intake is necessary for bone growth and development in children and adolescents and for maintaining bone mineral loss in elderly age. Ca deficiency predisposes to osteopenia and osteoporosis. Healthy nutrition, including an adequate intake of Ca-rich food, is paramount to prevent and cure osteoporosis. Recently, several clinical studies have demonstrated that, in conditions of Ca dysmetabolism, Ca-rich mineral water is beneficial as a valuable source of Ca to be used as an alternative to caloric Ca-rich dairy products. Although promising, these data have been collected from small groups of participants. Moreover, they mainly regard the effect of Ca-rich mineral water on bone metabolism. In contrast, an investigation of the effect of Ca supplementation on systemic metabolism is needed to address the spreading of systemic metabolic dysfunction often associated with Ca dysmetabolism. In the present study, we analyzed urine and blood sera of 120 women in perimenopausal condition who were subjected for six months to 2l daily consumption of bicarbonate-calcium mineral water marketed under ®Lete. Remarkably, this water, in addition to being rich in calcium and bicarbonate, is also low in sodium. A complete set of laboratory tests was carried out to investigate whether the specific water composition was such to confirm the known therapeutic effects on bone metabolism. Second, but not least, urine and blood sera were analyzed using NMR-based metabolomic procedures to investigate, other than the action on Ca metabolism, potential system-wide metabolic effects. Our data show that Lete water is a valid supplement for compensating for Ca dysmetabolism and preserving bone health and integrity.

Exploring the Potential Benefits of Natural Calcium-Rich Mineral Waters for Health and Wellness: A Systematic Review

This systematic review investigates the potential health and wellness benefits of natural calcium-rich mineral waters. It emphasizes the importance of dietary calcium sourced from natural mineral waters in promoting bone health, maintaining cardiovascular function, aiding in weight management, and enhancing overall well-being. The review process involved the comprehensive analysis of peer-reviewed articles, clinical trials, and experimental studies published within the last decade. Findings reveal that consuming calcium-rich mineral water can contribute significantly to daily calcium intake, particularly for those with lactose intolerance or individuals adhering to plant-based diets. The unique bioavailability of calcium from such waters also appears to enhance absorption, thus potentially offering an advantage over other calcium sources. The potential benefits extend to the cardiovascular system, with some studies indicating a reduction in blood pressure and the prevalence of cardiovascular diseases. Emerging evidence suggests that calcium-rich mineral water might have a role in body weight management, though further research is needed. The review identifies several areas requiring additional research, such as the potential interaction between calcium-rich mineral water and other dietary components, the effects on populations with specific health conditions, and the long-term effects of consumption. In conclusion, natural calcium-rich mineral waters show promise as a readily accessible and bioavailable sources of dietary calcium, potentially beneficial for a broad range of individuals. However, further investigation is required to fully understand its range of health impacts and define optimal intake levels.

Calcium and magnesium in China's public drinking water and their daily estimated average requirements

Calcium (Ca) and magnesium (Mg) in drinking water and the relevant health effects have been ignored for too long. This study aims to reveal the concentrations, spatial distributions, origins and contributions to the daily estimated average requirements of Ca and Mg in public drinking water. Using hydrochemical data of collected samples of public drinking water in 314 cities across China, the contributions of Ca and Mg intakes from public drinking water to their daily estimated average requirements (EARs) were assessed. And the significance of Ca/Mg ratio and total hardness (TH) was evaluated as well. The Ca and Mg concentrations of the samples were in the range of 2.5-155.1 mg/L and 0.2-81.9 mg/L, with an average of 40.4 mg/L and 12.4 mg/L, respectively. There exist obvious differences in Ca and Mg concentrations in different regions, under the impact of climate conditions and water-rock interactions. The intake of Ca via the consumption of public drinking water for adults may be twice as much as that for other age groups. In cities with high Ca levels in public drinking water, the Ca contributions to EAR could reach up to 51.59% for adults. By contrast, Mg in drinking water is an important and even the main pathway to ingest Mg for infants and children. Therefore, public drinking water is critical for Ca and Mg intake among urban residents of China. Besides, attention should be paid to the health effects of high Ca/Mg ratio and low TH in public drinking water, especially in southern China. This research is the first systematic and comprehensive national scale study of Ca and Mg in public drinking water and can provide an important reference to improve healthy public drinking water standards around the world.

Calculation of the contribution of water to calcium intake in low- and middle-income countries

Dietary calcium intake is low in many countries, particularly in low- and middle-income countries (LMICs). Water is often overlooked as a source of dietary calcium despite it being universally consumed and providing good calcium bioavailability. Our objective was to assess water distribution systems in LMICs and to develop a formula to simulate the contribution of different water sources to calcium availability. We calculated the contribution of drinking water considering different calcium concentration levels to estimate total calcium availability. We consider a country's households' access to drinking water sources and the distribution of the country's population by age and gender. Calcium availability could be increased by an average of 49 mg of calcium per person per day in the 62 countries assessed if calcium in drinking water was considered. In 22 (31%) of the countries studied, 80% of households are supplied by water sources that could increase calcium availability. Improving calcium concentration in water could be considered as a strategy in LMICs to slightly improve calcium availability.

Calcium and Bone

The maintenance of extracellular calcium levels within a narrow range is necessary for normal function of the nervous system, muscle, and coagulation, to maintain mineralization of the skeleton but to avoid calcification of soft tissues. Accordingly, absorption and excretion of calcium is closely regulated, and adult humans can adapt to a wide range of calcium intakes from 300 to 2,000 mg/day. The evidence that low calcium intakes contribute to osteoporosis development is weak, as is evidence that increasing these intakes significantly changes fracture risk. Consistent with this view, the United States Preventive Services Task Force does not support the use of calcium supplements in healthy community-dwelling adults. While some groups continue to recommend that supplements of calcium and vitamin D are given with drug treatments for osteoporosis, this view is not supported by clinical trials which demonstrate anti-fracture efficacy of estrogens and bisphosphonates in the absence of such supplementation. Thus, calcium supplements have only a minor place in contemporary medical practice.

Calcium Intake in Bone Health: A Focus on Calcium-Rich Mineral Waters

Calcium is an essential element that plays numerous biological functions in the human body, of which one of the most important is skeleton mineralization. Bone is a mineralized connective tissue in which calcium represents the major component, conferring bone strength and structure. Proper dietary calcium intake is important for bone development and metabolism, and its requirement can vary throughout life. The mineral composition of drinking water is becoming relevant in the modulation of calcium homeostasis. In fact, calcium present in mineral drinking waters is an important quantitative source of calcium intake. This, together with its excellent bioavailability, contributes to the maintenance of the bone health. This article aims to examine studies that assessed the bioavailability of the calcium contained in calcium-rich mineral waters and their impact on bone health, including original data collected in a recent study in humans.

Natural mineral waters: chemical characteristics and health effects

Water contributes significantly to health and a daily intake of 1.5 to 2 liters of water should be guaranteed, because a good hydration is essential to maintain the body water equilibrium, although needs may vary among people. However, worldwide population is far from the Recommended Allowance for water intake. Among the waters for human uses, there are 'waters (treated or not), intended for drinking, used for the food and beverages preparation or for other domestic purposes' and natural mineral waters, that are 'originated from an aquifer or underground reservoir, spring from one or more natural or bore sources and have specific hygienic features and, eventually, healthy properties'. According to the European Legislation (2009/54/EC Directive), physical and chemical characterization is used to make a classification of the different mineral waters, basing on the analysis of main parameters. Mineral composition enables to classify natural mineral waters as bicarbonate mineral waters, sulphate mineral waters, chloride mineral waters, calcic mineral waters, magnesiac mineral waters, fluorurate mineral waters, ferrous mineral waters and sodium-rich mineral waters. Although the concerns about bottled mineral waters (due to plasticizers and endocrine disruptors), many are the health effects of natural mineral waters and several studies explored their properties and their role in different physiological and pathological conditions.

Population data on calcium in drinking water and hip fracture: An association may depend on other minerals in water. A NOREPOS study

BACKGROUND

The Norwegian population has among the highest hip fracture rates in the world. The incidence varies geographically, also within Norway. Calcium in drinking water has been found to be beneficially associated with bone health in some studies, but not in all. In most previous studies, other minerals in water have not been taken into account. Trace minerals, for which drinking water can be an important source and even fulfill the daily nutritional requirement, could act as effect-modifiers in the association between calcium and hip fracture risk. The aim of the present study was to investigate the association between calcium in drinking water and hip fracture, and whether other water minerals modified this association.

MATERIALS AND METHODS

A survey of trace metals in 429 waterworks, supplying 64% of the population in Norway, was linked geographically to the home addresses of patients with incident hip fractures (1994-2000). Drinking water mineral concentrations were divided into "low" (below and equal waterworks average) and "high" (above waterworks average). Poisson regression models were fitted, and all incidence rate ratios (IRRs) were adjusted for age, geographic region, urbanization degree, type of water source, and pH of the water. Effect modifications were examined by stratification, and interactions between calcium and magnesium, copper, zinc, iron and manganese were tested both on the multiplicative and the additive scale. Analyses were stratified on gender.

RESULTS

Among those supplied from the 429 waterworks (2,110,916 person-years in men and 2,397,217 person-years in women), 5433 men and 13,493 women aged 50-85 years suffered a hip fracture during 1994-2000. Compared to low calcium in drinking water, a high level was associated with a 15% lower hip fracture risk in men (IRR=0.85, 95% CI: 0.78, 0.91) but no significant difference was found in women (IRR=0.98, 95%CI: 0.93-1.02). There was interaction between calcium and copper on hip fracture risk in men (p=0.051); the association between calcium and hip fracture risk was stronger when the copper concentration in water was high (IRR=0.52, 95% CI: 0.35, 0.78) as opposed to when it was low (IRR=0.88, 95% CI: 0.81, 0.94). This pattern persisted also after including potential confounding factors and other minerals in the model. No similar variation in risk was found in women.

CONCLUSION

In this large, prospective population study covering two thirds of the Norwegian population and comprising 19,000 hip fractures, we found an inverse association between calcium in drinking water and hip fracture risk in men. The association was stronger when the copper concentration in the water was high.

Calcium supplements: benefits and risks

Calcium is an essential element in the diet, but there is continuing controversy regarding its optimal intake, and its role in the pathogenesis of osteoporosis. Most studies show little evidence of a relationship between calcium intake and bone density, or the rate of bone loss. Re-analysis of data from the placebo group from the Auckland Calcium Study demonstrates no relationship between dietary calcium intake and rate of bone loss over 5 years in healthy older women with intakes varying from <400 to >1500 mg day(-1) . Thus, supplements are not needed within this range of intakes to compensate for a demonstrable dietary deficiency, but might be acting as weak anti-resorptive agents via effects on parathyroid hormone and calcitonin. Consistent with this, supplements do acutely reduce bone resorption and produce small short-term effects on bone density, without evidence of a cumulative density benefit. As a result, anti-fracture efficacy remains unproven, with no evidence to support hip fracture prevention (other than in a cohort with severe vitamin D deficiency) and total fracture numbers are reduced by 0-10%, depending on which meta-analysis is considered. Five recent large studies have failed to demonstrate fracture prevention in their primary analyses. This must be balanced against an increase in gastrointestinal side effects (including a doubling of hospital admissions for these problems), a 17% increase in renal calculi and a 20-40% increase in risk of myocardial infarction. Each of these adverse events alone neutralizes any possible benefit in fracture prevention. Thus, calcium supplements appear to have a negative risk-benefit effect, and so should not be used routinely in the prevention or treatment of osteoporosis.

Efficacy, effectiveness and side effects of medications used to prevent fractures

There is an increasing number of effective therapies for fracture prevention in adults at risk of osteoporosis. However, shortcomings in the evidence underpinning our management of osteoporosis still exist. Evidence of antifracture efficacy in the groups of patients who most commonly use calcium and vitamin D supplements is lacking, the safety of calcium supplements is in doubt, and the safety and efficacy of high doses of vitamin D give cause for concern. Alendronate, risedronate, zoledronate and denosumab have been shown to prevent spine, nonspine and hip fractures; in addition, teriparatide and strontium ranelate prevent both spine and nonspine fractures, and raloxifene and ibandronate prevent spine fractures. However, most trials provide little information regarding long-term efficacy or safety. A particular concern at present is the possibility that oral bisphosphonates might cause atypical femoral fractures. Observational data suggest that the incidence of this type of fracture increases steeply with duration of bisphosphonate use, resulting in concern that the benefit-risk balance may become negative in the long term, particularly in patients in whom the osteoporotic fracture risk is not high. Therefore, reappraisal of ongoing use of bisphosphonates after about 5 years is endorsed by expert consensus, and 'drug holidays' should be considered at this time. Further studies are needed to guide clinical practice in this area.

Nationwide data on municipal drinking water and hip fracture: could calcium and magnesium be protective? A NOREPOS study

Norway has a high incidence of hip fractures, and the incidence varies by degree of urbanization. This variation may reflect a difference in underlying environmental factors, perhaps variations in the concentration of calcium and magnesium in municipal drinking water. A trace metal survey (1986-1991) in 556 waterworks (supplying 64% of the Norwegian population) was linked geographically to hip fractures from hospitals throughout the country (1994-2000). In all, 5472 men and 13,604 women aged 50-85years suffered a hip fracture. Poisson regression models were fitted, adjusting for age, urbanization degree, region of residence, type of water source, and pH. The concentrations of calcium and magnesium in drinking water were generally low. An inverse association was found between concentration of magnesium and risk of hip fracture in both genders (IRR men highest vs. lowest tertile=0.80, 95% CI: 0.74, 0.87; IRR women highest vs. lowest tertile=0.90, 95% CI: 0.85, 0.95), but no consistent association between calcium and hip fracture risk was observed. The highest tertile of urbanization degree (city), compared to the lowest (rural), was related to a 23 and 24% increase in hip fracture risk in men and women, respectively. The association between magnesium and hip fracture did not explain the variation in hip fracture risk between city and rural areas. Magnesium in drinking water may have a protective role against hip fractures; however this association should be further investigated.

Bone remodelling is not affected by consumption of a sodium-rich carbonated mineral water in healthy postmenopausal women

This study was designed to investigate the possible effects of consuming Na-rich carbonated mineral water on bone remodelling and urinary mineral excretion in postmenopausal women. Women (n18) included were amenorrhoeic (>1 year), healthy and not obese (BMI <30 kg/m2). No woman was taking oestrogen replacement therapy, mineral and vitamin supplements, phyto-oestrogens or medications known to affect bone and lipid metabolism. In two consecutive interventions that lasted 8 weeks each, women drank 1 litre of control mineral water daily and 1 litre of carbonated mineral water, rich in Na, HCO–3inf super and Cl−, daily. Body weight and height were measured, BMI was calculated and blood pressure was measured. Blood samples were taken from fasting subjects and serum obtained to analyse the biochemical bone markers, procollagen I amino-terminal propeptide (PINP) and β-carboxy-terminal telopeptide of collagen (β-CTX). At the end of each period, 24 h urine samples were collected to determine Ca, Mg, P, Na+, K+, Cl−, urine excretion and urinary pH. No changes in body weight, BMI or blood pressure were observed during the experimental period. Ca excretion was lower after the intake of carbonated water than after intake of the control water (P=0·037) while P excretion was higher (P=0·015). Total urine, Na and Cl−excretion did not differ between the two periods but urinary pH was increased after the intake of carbonated mineral water. PINP and β-CTX did not differ between the two periods. Daily consumption of 1 litre of Na-rich carbonated mineral water for 8 weeks does not affect bone remodelling in healthy postmenopausal women.

Geometric indices of bone strength are associated with physical activity and dietary calcium intake in healthy older women

A population-based study on 1008 postmenopausal women identified that the 24% of women achieving high levels of PA and CI had 3.4-4.4% higher femoral bone strength in axial compression and 1.7-5.2% in bending than those achieving low levels, indicating that lifestyle factors influence bone strength in the proximal femur.

INTRODUCTION

Extensive research has shown that increased physical activity (PA) and calcium intake (CI) decrease the rate of bone loss; however, there is little research on how these lifestyle variables affect bone geometry. This study was designed to investigate the effects of modifiable lifestyle variables, habitual PA and dietary CI, on femoral geometry in older women.

MATERIALS AND METHODS

Femoral geometry, habitual PA, and dietary CI were measured in a population-based sample of 1008 women (median age+/-interquartile range, 75+/-4years) enrolled in a randomized controlled trial (RCT) of calcium supplementation. Baseline PA and CI were assessed by validated questionnaires, and 1-year DXA scans (Hologic 4500A) were analyzed using the hip structural analysis technique. Section modulus (Z), an index of bending strength, cross-sectional area (CSA), an index of axial compression strength, subperiosteal width (SPW), and centroid position, the position of the center of mass, were measured at the femoral neck (NN), intertrochanter (IT), and femoral shaft (FS) sites. These data were divided into tertiles of PA and CI, and the results were compared using analysis of covariance (ANCOVA), with corrections for age, height, weight, and treatment (calcium/placebo).

RESULTS AND CONCLUSIONS

PA showed a significant dose-response effect on CSA all hip sites (p<0.03) and Z at the narrow neck and intertrochanter sites (p<0.02). For CI, there was a dose-response effect for centroid position at the intertrochanter (p=0.03). These effects were additive, such that the women (n=240) with PA in excess of 65.5 kcal/day and CI in excess of 1039 mg/day had significantly greater CSA (NN, 4.4%; IT, 4.3%; FS, 3.4%) and Z (NN, 3.9%; IT, 5.2%). These data show a favorable association between PA and aspects of bone structural geometry consistent with better bone strength. Association between CI and bone structure was only evident in 1 of 15 variables tested. However, there was evidence that there may be additive effects, whereby women with high levels of PA and CI in excess of 1039 mg/day had significantly greater CSA (NN, 0.4%; FS, 2.1%) and Z (IT, 3.0%) than women with high PA but low CI. These data show that current public health guidelines for PA and dietary CI are not inappropriate where bone structure is the health component of interest.

A new proposed guidance system for beverage consumption in the United States

The Beverage Guidance Panel was assembled to provide guidance on the relative health and nutritional benefits and risks of various beverage categories. The beverage panel was initiated by the first author. The Panel's purpose is to attempt to systematically review the literature on beverages and health and provide guidance to the consumer. An additional purpose of the Panel is to develop a deeper dialog among the scientific community on overall beverage consumption patterns in the United States and on the great potential to change this pattern as a way to improve health. Over the past several decades, levels of overweight and obesity have increased across all population groups in the United States. Concurrently, an increased daily intake of 150-300 kcal (for different age-sex groups) has occurred, with approximately 50% of the increased calories coming from the consumption of calorically sweetened beverages. The panel ranked beverages from the lowest to the highest value based on caloric and nutrient contents and related health benefits and risks. Drinking water was ranked as the preferred beverage to fulfill daily water needs and was followed in decreasing value by tea and coffee, low-fat (1.5% or 1%) and skim (nonfat) milk and soy beverages, noncalorically sweetened beverages, beverages with some nutritional benefits (fruit and vegetable juices, whole milk, alcohol, and sports drinks), and calorically sweetened, nutrient-poor beverages. The Panel recommends that the consumption of beverages with no or few calories should take precedence over the consumption of beverages with more calories.

Small bowel absorption of magnesium and calcium sulphate from a natural mineral water in subjects with ileostomy

BACKGROUND

In many developed countries, magnesium and calcium intakes do not reach recommendations for a large part of the population. Mineral water may be a useful alternative source of dietary minerals, especially in groups of people at risk for developing deficiency due to low intakes.

AIM

To assess if the addition of a natural and mineral-rich water increased small bowel mineral absorption in people with ileostomy.

METHODS

A controlled randomised crossover study with two periods of two days each and a minimum 5 days of washout was performed in six ileostomy subjects. Apparent mineral absorption from 0.5 L of natural mineral water with either a high or a low mineral content consumed in the fasting state was compared. The daily addition of minerals corresponded to 2.3mmol magnesium, 6.9 mmol calcium and 7.7mmol sulphate. Ileostomy effluents were sampled and analysed for magnesium, calcium and total sulphate.

RESULTS

When compared with the control, the median absorbed amount of magnesium increased from 0.8 (0-1.34) mmol/d to 1.2 (0.8-1.9) mmol/d,which corresponded to a 30% increase (P = 0.028). Median amount of calcium absorbed increased from 8.3 (6.7-13.6) mmol/d to 14.8 (8.3-20.4) mmol/d, i. e. a 45% increase (P = 0.027). The sulphate absorption increased from 1.9 (1.3-2.2) mmol/d to 5.1 (4.2-6.8) mmol/d,which corresponded to 197 % increase (P = 0.028).

CONCLUSIONS

The mineral-rich water increased absorption of both magnesium and calcium and can therefore be used as an additional source of minerals. However, consumption with meals may be preferred.

Mineral water intake reduces blood pressure among subjects with low urinary magnesium and calcium levels

Background

Several previous epidemiological studies have shown a relation between drinking water quality and death in cardiovascular disease whereas others have not found such a relationship. An intervention study was undertaken to evaluate the effect of water with added magnesium and natural mineral water on blood pressure.

Methods

A group of 70 subjects with borderline hypertension was recruited and consumed 1) a water low in minerals, 2) magnesium enriched water or 3) natural mineral water, in a random, double blind fashion during four weeks.

Results

Among persons with an initial low excretion of magnesium or calcium in the urine, the urinary excretion of magnesium was increased in the groups consuming the two waters containing magnesium after 4 weeks. A significant decrease in blood pressure was found in the group consuming mineral water at 2 and 4 weeks.

Conclusion

The results suggest that minerals taken in water are significant for the body burden and that an intake of mineral water among persons with a low urinary excretion of magnesium or calcium may decrease the blood pressure. Further studies should investigate the extent of mineral deficiency in different populations and the efficiency of different vehicles for supplying minerals, particularly magnesium and calcium.

Effect of acute oral calcium load on serum PTH and bone resorption in young healthy subjects: an overnight study

OBJECTIVE

To investigate the effects of a 400 mg acute oral calcium dose on PTH and bone resorption markers in a young, healthy population.

DESIGN

Fasting serum parathyroid hormone (PTH), C-telopeptides (CTX), total calcium (Ca), albumin and urinary calcium/creatinine ratio (uCa/Cr) were measured on two separate days: one before and the other 10 h after oral administration of 400 mg calcium. Serum 25-hydroxy vitamin D (25-OHD) status was assessed at baseline. Dietary calcium intake was assessed using a food frequency questionnaire (FFQ).

SUBJECTS

A total of 32 healthy, young adults (17 female, 15 male; mean+/-s.e.m. age: 21+/-1 y) took part in this study. Their mean (s.e.m.) calcium intake was 1125 (+/-56) mg/day.

INTERVENTION

Effervescent Sandocal 400 tablets dissolved in water.

RESULTS

After the calcium challenge, mean Ca and uCa/Cr ratio increased significantly, and both PTH and CTX concentrations were significantly lower. Multiple regression analysis showed no relationship between the response to the 400 mg load and previous dietary calcium intake (as assessed by FFQ) or serum 25-OHD.

CONCLUSION

We have shown that in a young, healthy population, 400 mg oral calcium can inhibit bone resorption (as measured by serum CTX) and PTH, and this appears to be independent of previous dietary calcium intake and vitamin D status.

The Canadian Health Claim for Calcium, Vitamin D and Osteoporosis

To provide evidence for or against allowing a health claim for calcium in Canada, we undertook a review of the current U.S. health claim for calcium and osteoporosis, and also reviewed the scientific literature published since that health claim was first proposed and reviewed by the U.S. Food and Drug Administration in 1991 and adopted in 1993. Our objectives were 1) to determine if the science behind the claim was still valid, and if so, 2) to recommend any new wording to the claim, if warranted, prior to implementation in Canada. Based on a review of the evidence (to May 2000) related to the various claim elements, the following health claim for calcium has been established in Canada: A healthy diet with adequate calcium and vitamin D, and regular physical activity, help to achieve strong bones and may reduce the risk of osteoporosis. The compositional criteria for foods bearing this claim are that the food must provide at least 200 mg calcium per serving and that the phosphorus content (excluding that provided by phytate) must be less than the calcium content.

Contribution of mineral waters to dietary calcium and magnesium intake in a French adult population

OBJECTIVE

To assess the contribution of mineral water containing different amounts of calcium and magnesium to the total dietary intakes of these minerals

DESIGN

Matched case control study using data issued from the Supplementation en Vitamines et Minéraux Antioxydants (SU.VI.MAX) cohort.

SUBJECTS

Subjects were water consumers-240 men and 424 women-divided into the following 4 groups (n=166 per group): regular drinkers of a calcium-rich and magnesium-rich mineral water (calcium, 486 mg/L; magnesium, 84 mg/ L), drinkers of a water classified as a moderately mineralized content (calcium, 202 mg/L; magnesium, 36 mg/L), drinkers of 2 low-mineralized waters (calcium, 9.9 to 67.6 mg/L and magnesium, 1.6 to 2 mg/L, respectively), and drinkers of tap waters.

STATISTICAL ANALYSES

Quantitative data were compared using student's t test. Mean comparisons were performed in multivariate analysis by analysis of variance.

RESULTS

Dietary calcium intake provided by the various food groups did not differ between the 4 consumer groups, except for calcium provided by mineral water. According to its calcium concentration, mineral water may contribute to one fourth of the total daily calcium intake. Subjects who regularly drink mineral-rich water have a calcium intake that is significantly higher (P< 10(-3)) than those drinking either low-mineral-content water or tap water. Dietary magnesium intake provided by the various food groups did not differ between the 4 consumer groups, except for magnesium provided by mineral water. Depending on the magnesium concentration of the mineral water, it contributed 6% to 17% of total daily magnesium intake. Drinkers of magnesium-rich mineral water and water with a moderate mineral content had magnesium intakes significantly (P< 10(-3)) higher than those of drinkers on low-mineralized or tap water.

APPLICATIONS

Mineral-rich water may provide an important supplementary contribution to total calcium and magnesium intake. For dietetics professionals, it may provide-in place of the usual recommendations concerning the consumption of dairy products-a good way to improve calcium and magnesium intakes, particularly in subjects who don't like dairy products.

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.