Usual Calcium Intake Research Articles

Variables related to urinary calcium excretion in young girls.

The relations among dietary and calcium kinetic factors and 24-h urinary mineral excretion were evaluated in a group of 89 healthy girls (51 white and 38 black) aged 4.9-16.7 years. Nutrient intakes were calculated for each participant using a weighed intake of all food and beverage on the day of the 24-h urine collection study and two subsequent 24-h food records. A significant relation was noted between urinary calcium and sodium excretion (r = 0.55; p < 0.0001). No significant relations were found between urinary calcium and (a) calcium intake (r = 0.08), (b) protein intake (r = 0.14), or (c) phosphorus intake (r = 0.11). Urinary calcium was not significantly related to fractional calcium absorption (r = 0.03) or net calcium absorption (r = 0.11), but was significantly associated with the bone calcium deposition rate (r = 0.24; p < 0.03). Using a multiple regression model, both urinary sodium and the bone calcium deposition rate were independent predictors of urinary calcium excretion in this population (r = 0.57; p = 0.0001). A substantial number of the children in this population had urinary calcium excretion > 4 mg/kg/day (12%). The incidence of hypercalciuria differed between the racial groups and was markedly higher in the white than in the black children (17.6 vs. 5.3%). Over a range of usual calcium intakes, during the rapid-bone-growth period in childhood and early adolescence, urinary calcium appears relatively unaffected by calcium intake and is most strongly associated with urinary sodium levels.

Dietary lentils and calcium balance in adult men

The effect of dietary lentils on calcium balance was evaluated in nine healthy male subjects. The Control and Experimental (+ 130 g dry lentils) diets were each fed for three weeks in a cross-over design. Study diets were matched to subjects' usual calcium and energy intakes, and balanced for protein and phytate. Complete fecal collections were made for all weeks and 24-hour urine collections were made in Week 3 of each period. Calcium balance was maintained during both the Control (0.4 ± 0.8 mmol/day, mean ± SEM) and Experimental periods (− 0.6 ± 0.9 mmol/day); fecal calcium remained unchanged (28.5 ± 1.7 mmol/day, 29.7 ± 1.5 mmol/day, respectively). Urinary excretion, however, varied from Control to Experimental periods for the following: calcium decreased from 5.43 ± 0.44 to 4.53 ± 0.41 mmol/day (P < 0.0001); sodium (Na) decreased from 149 ± 4 to 133 ± 3 mmol/day (P = 0.0003); potassium (K) increased from 90.8 ± 4.7 to 102.5 ± 3.1 mmol/day (P = 0.015), respectively. Changes in urinary K and Na reflected dietary intake levels. There was no change in net acid excretion. The decrease in renal calcium excretion may be due to a protective role of dietary K as well as a decrease in renal Na excretion, independent of changes in endogenous acid. This study shows that adding lentils to the diet, while maintaining a constant phytate intake, does not adversely affect calcium balance.

Associations of social and demographic variables with calcium intakes of high school students

Objective To assess usual calcium intake of urban high school students and to assess the association of social and demographic variables with calcium intake. Design A self-administered survey instrument containing the following elements: a food frequency questionnaire (FFQ) developed to estimate calcium intake; questions to elicit demographic information; and scales to reflect taste enjoyment of dairy products, social reinforcement for consumption of milk, perceptions of others' opinions about milk, and behavioral modeling of milk consumption (ie, the frequency of observing friends' and family members' use of milk). The FFQ was shown to include major sources of calcium in diets of a pretest sample (n=130). Setting Urban high schools in a metropolitan setting. Subjects/samples Students in one class per grade level in six high schools (approximately 900 students) were asked to participate. Of the 856 questionnaires completed, 785 were usable. Main outcome measures Total calcium intake, as estimated using the FFQ. Statistical analyses performed Descriptive statistics, t tests, one-way analysis of variance, correlation analysis, and stepwise multiple regression analysis were used to assess relationships of independent variables with calcium intake. Results Mean estimated calcium intakes for male and female students were 1,146±41 mg/day (mean±standard error of the mean) and 815±26 mg/day ( P<.001), respectively, 59% of which was obtained from milk. Median intakes were 1,016 mg/day for boys and 676 mg/day for girls, and more than half the students had intakes that were below current recommendations. Multiple regression analysis revealed significant predictors of total calcium intake: gender (boys>girls); taste enjoyment of dairy products; number of meals and snacks per day; age; ethnicity (whites>Asians); behavioral modeling of milk consumption; perceptions of others' opinions, recommendations, and use of milk; and soft drink consumption (total adjusted R 2=.304). With the exception of age, these variables were positively associated with calcium intake. Regression equations developed for boys and girls separately revealed that different variables entered the equations. Applications/conclusions Most of the variability in adolescents' calcium intakes remained unexplained by the variables included in this study. Nevertheless, the results suggest that education programs focusing on taste enjoyment of dairy products and building on the influence of peers and family members may have a positive impact on calcium intake.

Reliability of a short and long version of the Block food frequency form for assessing changes in calcium intake

We tested the reliability of a modified version of the Block 98-item food frequency questionnaire (FFQ) and a short 40-item FFQ derived from the Block form to estimate usual calcium intake. Ninety-eight female volunteers completed both forms three times during a 6-month period; forms were initially completed by participants at a group meeting (T1) and, subsequently, 2 months (T2) and 4 months (T3) later, by mail. Both mean total energy intake in kilocalories and mean calcium intake derived from the long FFQ dropped significantly between T1 and T2. The nutrient density variable, calcium per 1,000 kcal, did not vary significantly between administrations. Pearson correlation coefficients were most uniform for pairwise comparisons of calcium per 1,000 kcal at the three times. Mean calcium intake derived from the short FFQ did not vary significantly between administrations, and Pearson correlation coefficients ranged from .70 to .77 for paired comparisons. When using the long FFQ, the nutrient density variable, calcium per 1,000 kcal, was a more reliable measure of usual calcium intake than was calcium in milligrams. The short FFQ provided reliable estimates of usual calcium intake in milligrams and captured more than 75% of the calcium intake measured by the long FFQ.

Genetic determinants of bone mass in adult women: A reevaluation of the twin model and the potential importance of gene interaction on heritability estimates

We estimated genetic effects on bone density in pre- and postmenopausal twins and critically considered the assumptions of the twin model. Bone mass in the radius, lumbar spine, and hip, anthropometric measurements, usual calcium and caffeine intake, tobacco and alcohol use, number of pregnancies and live births, menstrual history, usual physical activity, and medical history were measured in a volunteer sample of 171 twin pairs [124 monozygotic (MZ) and 47 dizygotic (DZ)], aged 25-80, free of diseases known to affect bone mass or mineral metabolism. At all skeletal sites, MZ intraclass correlations exceeded DZ correlations for both pre- and postmenopausal women, yielding highly significant estimates of heritability for bone mass. Adjustments for height, age, and environmental characteristics did not reduce the heritability estimates. However, many of these estimates were unrealistically high, suggesting some violation(s) of the assumptions of the twin model. Thus, the familial resemblance in bone mass is due primarily to genetic effects at all skeletal sites and at all ages, although the importance of genetic effects is diminished with aging, as evidenced by increasing within-MZ pair variability in older women. Because of failures in the assumptions of the twin model, however, particularly the greater MZ environmental similarity and the probability of gene interaction, heritability estimates are probably too high and require cautious interpretation.

The effect of dietary sodium on urinary calcium and potassium excretion in normotensive men with different calcium intakes

On the basis of their usual calcium intake, 12 healthy normotensive male students were divided into a low and a high calcium group. Both groups were provided with complete diets containing the same calculated quantities, expressed per MJ, of protein, fat, carbohydrate, sodium, potassium, phosphorus, and calcium. After an initial period of two weeks during which all participants received an additional 100 mmol sodium daily, 6 participants received an additional 22 mmol sodium/day (low sodium), the other 6 participants 178 mmol sodium/day (high sodium). After two weeks the sodium regimes were crossed over for a subsequent two-week period. When the second week of the low sodium period is compared with the second week of the high sodium period, the increase in the calcium/creatinine ratio, expressed on molar basis, was 0.059 for the low and 0.053 for the high calcium group (p less than 0.05). The increase in the molar potassium/creatinine ratio was 0.65 for the low and 0.03 for the high calcium group (p less than 0.025). However, after correcting for the calcium intake the effect in the low calcium group was found to be greater (p less than 0.05). Sodium supplementation was found to have no effect on blood pressure, but mean systolic (p less than 0.10) and diastolic in the high calcium group were lower. This suggests that calcium may well play a role in the regulation of blood pressure.

Calcium requirements in man: a critical review

Many official bodies give advice on desirable intakes of calcium but no clear evidence of a calcium deficiency disease in otherwise normal people has ever been given. In Western countries the usual calcium intake is of the order of 800-1000 mg/day; in many developing countries figures of 300-500 mg/day are found. There is no evidence that people with such a low intake have any problems with bones or teeth. It seems likely that normal people can adapt to have a normal calcium balance on calcium intakes as low as 150-200 mg/day and that this adaptation is sufficient even in pregnancy and lactation. Inappropriate concern about calcium intake may divert attention and resources from more important nutritional problems.

Calcium absorption in renal failure: its relationship to blood urea nitrogen, dietary calcium intake, time on dialysis, and other variables.

Abstract Calcium absorption was measured in 37 patients, 23 with azotemia not treated with hemodialysis and 14 on hemodialysis. Nine of the 14 were also studied after dialysis. Simultaneous measurements of serum calcium, serum phosphorus, blood urea nitrogen (BUN), serum creatinine, estimated usual calcium intake, and recorded time on dialysis treatments were obtained. In nondialyzed patients, when the BUN concentration was low, calcium absorption was negatively correlated with the BUN; at higher BUN levels, calcium absorption was normal or elevated. Mean calcium absorption in hemodialysis patients was significantly below normal before dialysis and not significantly different from normal after dialysis; however, the data were variable and no conclusion may be reached. Fractional calcium absorption was higher in patients with lower dietary calcium intakes which suggests that these patients retained the ability to regulate calcium absorption in response to body calcium needs. Higher fractional absorption was seen in patients who had been on chronic hemodialysis treatments for longer periods of time. While defective calcium absorption tends to be present in uremic patients, it is not an invariable finding; severe uremia may coexist with supernormal absorption.