Measurement of the daily dietary calcium and magnesium intake in Belgium, using duplicate portion sampling

Habitual high phosphorus intakes and foods with phosphate additives negatively affect serum parathyroid hormone concentration: a cross-sectional study on healthy premenopausal women

Objective

Foods can contain natural phosphorus (NP) and phosphate-containing food additives (AP). The main objective of the present study was to investigate whether NP and AP of habitual diets differ in their effects on markers of Ca metabolism. We also investigated the impact of total habitual dietary P intake on markers of Ca metabolism.

Design

Cross-sectional study. Fasting blood samples were collected and participants kept a 4 d food record, from which dietary intake of total P and the consumption of NP (milk and cheese, excluding processed cheese) and AP (processed cheese) sources were calculated. Participants were divided into groups according to their NP- and AP-containing food consumption and into quartiles according to their total P intake.

Setting

Southern Finland.

Subjects

One hundred and forty-seven healthy premenopausal women aged 31–43 years.

Results

Relative to the lowest total dietary P quartile, mean serum parathyroid hormone (S-PTH) concentration was higher (P = 0·048, analysis of covariance (ANCOVA)) and the mean serum ionized Ca concentration lower (P = 0·016, ANCOVA) in the highest P intake quartile. Mean S-PTH concentrations were higher among participants who consumed processed cheese (P = 0·027, ANCOVA) and less milk and other cheese than processed cheese (P = 0·030, ANCOVA).

Conclusions

High total habitual dietary P intake affected S-PTH unfavourably. Furthermore, phosphate additives may have more harmful effects on bone than other P sources, as indicated by higher mean S-PTH concentration among participants who consumed AP-containing foods. Because of the high dietary P intake and current upward trend in consumption of processed foods in Western countries, these findings may have important public health implications.

Low calcium:phosphorus ratio in habitual diets affects serum parathyroid hormone concentration and calcium metabolism in healthy women with adequate calcium intake

Excessive dietary P intake alone can be deleterious to bone through increased parathyroid hormone (PTH) secretion, but adverse effects on bone increase when dietary Ca intake is low. In many countries, P intake is abundant, whereas Ca intake fails to meet recommendations; an optimal dietary Ca:P ratio is therefore difficult to achieve. Our objective was to investigate how habitual dietary Ca:P ratio affects serum PTH (S-PTH) concentration and other Ca metabolism markers in a population with generally adequate Ca intake. In this cross-sectional analysis of 147 healthy women aged 31–43 years, fasting blood samples and three separate 24-h urinary samples were collected. Participants kept a 4-d food record and were divided into quartiles according to their dietary Ca:P ratios. The 1st quartile with Ca:P molar ratio ≤ 0·50 differed significantly from the 2nd (Ca:P molar ratio 0·51–0·57), 3rd (Ca:P molar ratio 0·58–0·64) and 4th (Ca:P molar ratio ≥ 0·65) quartiles by interfering with Ca metabolism. In the 1st quartile, mean S-PTH concentration (P = 0·021) and mean urinary Ca (U-Ca) excretion were higher (P = 0·051) than in all other quartiles. These findings suggest that in habitual diets low Ca:P ratios may interfere with homoeostasis of Ca metabolism and increase bone resorption, as indicated by higher S-PTH and U-Ca levels. Because low habitual dietary Ca:P ratios are common in Western diets, more attention should be focused on decreasing excessively high dietary P intake and increasing Ca intake to the recommended level.

Acute effects of calcium carbonate, calcium citrate and potassium citrate on markers of calcium and bone metabolism in young women

Both K and Ca supplementation may have beneficial effects on bone through separate mechanisms. K in the form of citrate or bicarbonate affects bone by neutralising the acid load caused by a high protein intake or a low intake of alkalising foods, i.e. fruits and vegetables. Ca is known to decrease serum parathyroid hormone (S-PTH) concentration and bone resorption. We compared the effects of calcium carbonate, calcium citrate and potassium citrate on markers of Ca and bone metabolism in young women. Twelve healthy women aged 22-30 years were randomised into four controlled 24 h study sessions, each subject serving as her own control. At the beginning of each session, subjects received a single dose of calcium carbonate, calcium citrate, potassium citrate or a placebo in randomised order. The diet during each session was identical, containing 300 mg Ca. Both the calcium carbonate and calcium citrate supplement contained 1000 mg Ca; the potassium citrate supplement contained 2250 mg K. Markers of Ca and bone metabolism were followed. Potassium citrate decreased the bone resorption marker (N-terminal telopeptide of type I collagen) and increased Ca retention relative to the control session. Both Ca supplements decreased S-PTH concentration. Ca supplements also decreased bone resorption relative to the control session, but this was significant only for calcium carbonate. No differences in bone formation marker (bone-specific alkaline phosphatase) were seen among the study sessions. The results suggest that potassium citrate has a positive effect on the resorption marker despite low Ca intake. Both Ca supplements were absorbed well and decreased S-PTH efficiently.

Increased calcium intake does not completely counteract the effects of increased phosphorus intake on bone: an acute dose–response study in healthy females

A high dietary P intake is suggested to have negative effects on bone through increased parathyroid hormone secretion, as high serum parathyroid hormone (S-PTH) concentration increases bone resorption. In many countries the P intake is 2- to 3-fold above dietary guidelines, whereas Ca intake is too low. This combination may not be optimal for bone health. In a previous controlled study, we found that dietary P dose-dependently increased S-PTH and bone resorption and decreased bone formation. The aim of the present study was to investigate the dose–response effects of Ca intake on Ca and bone metabolism with a dietary P intake higher than recommended. Each of the twelve healthy female subjects aged 21–40 years attended three 24-h study sessions, which were randomized with regard to a Ca dose of 0 (control day), 600 or 1200 mg, and each subject served as her own control. The meals on each study day provided 1850 mg P and 480 mg Ca. S-PTH concentration decreased (P < 0·001) and serum ionized Ca concentration increased (P < 0·001) with increasing Ca doses. The bone formation marker, serum bone-specific alkaline phosphatase, did not differ significantly (P = 0·4). By contrast, the bone resorption marker, urinary N-terminal telopeptide of collagen type I, decreased significantly with both Ca doses (P = 0·008). When P intake was above current recommendations, increased Ca intake was beneficial for bone, as indicated by decreased S-PTH concentration and bone resorption. However, not even a high Ca intake could affect bone formation when P intake was excessive.

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.

Dietary magnesium intake in type 2 diabetes

BACKGROUND

Magnesium deficiency is common in type 2 diabetes and may have a negative impact on glucose homeostasis and insulin resistance, as well as on the evolution of complications such as retinopathy, thrombosis and hypertension.

OBJECTIVE

To assess the dietary magnesium intake of patients with type 2 diabetes in Zurich, Switzerland and to compare the magnesium intake of diabetic and non-diabetic subjects.

DESIGN

The magnesium intake of 97 randomly selected patients with type 2 diabetes and 100 healthy, non-diabetic controls matched for age and sex was estimated using a diet history method. During winter and summer periods, mean daily magnesium intakes were calculated from detailed information given by the test subjects about their eating habits over the previous 2 months. The calculations were performed using EBIS, a computer program based on a German nutrient data base (BLS 2.3), with food items specific to Switzerland added or directly analysed when necessary.

RESULTS

The mean+/-s.d. daily magnesium intake of the male diabetic and male control subjects was 423.2+/-103.1 and 421.1+/-111.0 mg, respectively. The mean daily magnesium intake of the female diabetic and female control subjects was 419.1+/-109.7 and 383.5+/-109.7 mg, respectively. There were no significant differences in daily magnesium intake between the diabetic and the non-diabetic subjects and mean intakes in both groups exceeded Swiss recommended dietary intakes.

CONCLUSIONS

Dietary intake of magnesium appears sufficient in Swiss adults with type 2 diabetes and is unlikely to contribute to the aetiology of magnesium deficiency.

SPONSORSHIP

The Swiss Federal Institute of Technology, Zurich, Switzerland.

Daily dietary chromium intake in Belgium, using duplicate portion sampling

Daily dietary chromium intake in Belgium has been evaluated by sampling duplicate portions of food, heating them at an acidic pH in a microwave oven and then quantifying the chromium by atomic absorption spectrometry. The mean intake value (53 +/- 31 micrograms/day) is similar to levels found for most other countries and is situated at the lower end of the recommended range for a safe and adequate daily dietary intake.