Biomedical subjects

C Ritenbaugh

Publications and source records attributed to C Ritenbaugh.

At least 37 records · Page 2Linked to original sources

PubMed1997

Errors in the interpretation of dietary assessments.

Two years ago, I reviewed the analytic effect of error in the estimation of dietary intake, describing the emphasis on the "random" day-to-day variation in reported intake. Interest in this area is increasing and there are signs of progress in analytic strategies. This paper focuses on two concerns about the use of dietary data in analyses. The effect of different methods of adjusting analyses of fat and a health outcome for energy is illustrated through an exploration of the association between fat intake and high body mass index in data sets from the US Department of Agriculture and a Dutch national survey. Both a shift in the analytic question and a change in the error structure occur as analysis strategies are changed, leading to confusion in interpretation. The paper also addresses the growing concern about bias in the estimation of intake and the possibility that differential bias moves with stratification variables of analytic interest. The increasing use of doubly labeled water estimates of energy expenditure as a gold standard for checking on overall bias in reporting is commendable. There will always be error in dietary assessments. The challenge is to understand, estimate, and make use of the error structure during analysis.

Bias↗

PubMed1997

Smoking experimentation and initiation among adolescent girls: qualitative and quantitative findings.

OBJECTIVE: To use qualitative and quantitative findings to describe patterns of smoking experimentation and initiation among adolescent girls. DESIGN: Ethnographic in-person interviews, focus groups, telephone interviews, and a survey questionnaire were used over a one-year period. The paper reports on cross-sectional data drawn from a three-year longitudinal study. SUBJECTS AND SETTING: 205 girls participated in the survey and interviews during year 3 of the study. Girls were drawn from two urban high schools in Tucson, Arizona (USA), and were in grades 10 and 11 (mean ages 16 and 17, respectively) during year 3. RESULTS: Overall, 30% (n = 61) of informants reported that they currently smoked, 7% (n = 15) were ex-smokers, and 63% (n = 129) were "non-smokers". The most frequently cited reasons for smoking were stress reduction and relaxation. Several stress-inducing situations, including family environment, social relations with classmates, and schoolwork, are discussed. The notion of peer pressure is re-examined in the light of teenagers' experience that there is little overt pressure to initiate smoking. Consonant with notions of adolescent autonomy, the theme of independence in smoking initiation and continuation permeated girls' narratives about their smoking behaviour. Girls projected the image that they could control their cigarettes rather than have their cigarettes control them. CONCLUSIONS: Smoking prevention and cessation programmes need to address and counter the smoking/relaxation association, which was identified as an important reason for smoking among adolescent girls. Questions typically used in surveys to measure smoking behaviour do not adequately define the smoking experience as described by teenagers.

Adolescent↗

PubMed1997

Fat or lean tissue mass: which one is the major determinant of bone mineral mass in healthy postmenopausal women?

The relative importance of fat and lean tissue mass in determining bone mineral mass among postmenopausal women was examined in this 1-year longitudinal study. Fifty postmenopausal Caucasian women entered the study; 45 of them completed a 1-year follow-up. Dual-energy X-ray absorptiometry was employed for measuring total and regional bone mineral density (BMD) and bone mineral content (BMC), fat tissue mass (FTM), lean tissue mass (LTM), and body weight. Results from linear regression analysis using the cross-sectional data (n = 50) of the study indicated that LTM explained a larger percentage of variation in bone mineral mass than did FTM. FTM and LTM were found to be moderately correlated (r = 0.55); when FTM was entered in the same predicting regression models, LTM was a significant predictor (p < 0.05) of the total and regional BMC, but not BMD. The percent FTM (and inversely %LTM) was correlated with BMD and BMC, but significant correlation was primarily found only for total body BMD (or BMC). Weight was the best predictor of total body BMD and BMC. Longitudinally (n = 45), annual changes in both FTM and weight were significantly associated with annual changes in regional BMD after adjustment for initial bone mineral values (p < 0.05). We conclude that bone mineral mass is more closely related to LTM than to FTM, while annual changes in regional BMD are more closely correlated with changes in FTM in healthy postmenopausal women. Meanwhile, increased body weight is significantly associated with increased bone mineral mass.

Absorptiometry, Photon↗

PubMed1997

The effect of wheat bran fiber and calcium supplementation on rectal mucosal proliferation rates in patients with resected adenomatous colorectal polyps.

Colorectal cancers continue as the second most common cause of death from cancer in the United States. Only a few prospective, randomized clinical trials have been performed to evaluate the potential preventive effects of dietary fiber or calcium in patients with an increased risk for the development or recurrence of colorectal cancer. We designed and conducted a double-blinded, placebo-controlled randomized trial involving supplementation of fiber and calcium intake and measurements of [3H]thymidine labeling index (LI) percentages in rectal mucosal biopsies obtained from patients with resected colorectal adenomas to examine the potential mechanisms by which dietary interventions might reduce colorectal cancer risk. We performed a randomized, double-blinded, Phase II study, using a factorial design to measure the effects of supplemental dietary wheat bran fiber (2.0 or 13.5 g/day) and calcium carbonate (250 or 1500 mg/day elemental calcium) supplementation on [3H]thymidine LI percentages in rectal mucosal crypts and 24-h in vitro outgrowth cultures. Measurements were made at baseline randomization (i.e., after a 3-month placebo run-in period using 2.0 g of wheat bran fiber plus 250 mg of calcium carbonate) and after 3 and 9 months on treatment in 100 randomized participants who had a history of colon adenoma resection. Neither the wheat bran fiber nor the calcium carbonate supplements significantly reduced [3H]thymidine LI percentages in rectal mucosal crypts (total or compartmental analysis) or 24-h in vitro outgrowth cultures at either 3 or 9 months of daily supplementation in the 93 evaluable participants. We conclude that 9 months of high-dose wheat bran fiber and calcium carbonate supplementation in study participants with a history of recently resected colorectal adenomas does not have a significant effect on cellular proliferation rates in rectal mucosal biopsies, comparing 3- and 9-month results to baseline results. Ultimately, there is great need for the evaluation of these two different nutrient interventions in the setting of Phase III studies wherein adenomatous polyp recurrence, rather than a rectal mucosal biomarker, serves as the primary end point.

Adenomatous Polyps↗

PubMed1997

Use of a food frequency questionnaire to screen for dietary eligibility in a randomized cancer prevention phase III trial.

Cancer prevention clinical trials use food frequency questionnaires (FFQs) to assist in eligibility screening. FFQ reliability and validity studies are available, but these studies do not evaluate FFQs as screening tools. The Wheat Bran Fiber Trial of the University of Arizona used a FFQ as an eligibility screen with the goal of screening out subjects whose true daily calcium intake was less than 500 mg per day (for safety) and whose true dietary fiber intake was greater than 30 g per day (for safety and trial efficiency). Subjects ineligible by FFQ were interviewed for final dietary eligibility determinations. A study was undertaken within the Wheat Bran Fiber Trial to evaluate the sensitivity, specificity, positive predictive value, and negative predictive value (NPV) of the FFQ used in this context. Four-day food records were collected on 183 potential participants before entry into the study. Using the 4-day averages as the "true" value, sensitivity, specificity, positive predictive value, and NPV were calculated for men and women separately under two screening conditions: using the target calcium and dietary fiber values and using "revised" values identified in interim analysis within the study. NPV was acceptable in all analyses. Sensitivity for low calcium intake was inadequate under the original criteria (0.33 for men and 0.09 for women) but acceptable under the revised criteria (0.80 for men and 0.81 for women). With the revised criteria, specificity declined, resulting in heavy screening burdens deemed worthwhile for the safety considerations. Dietary fiber eligibility screening worked well at target values. These differences were not predicted by reliability/validity studies.

Adult↗

PubMed1997

Development of a urinary riboflavin adherence marker for a wheat bran fiber community intervention trial.

Development of a reliable marker of adherence to high-fiber diets is essential for accurately assessing dietary fiber intake in community interventions and clinical trials. The objective of this study was to evaluate the feasibility of using a riboflavin tracer incorporated into wheat bran cereal to determine fiber intake and compare results to the more traditional methodology of measuring stool weight. The inpatient phase of the study established that the excretion of urinary riboflavin was highly correlated with the dose of the riboflavin-spiked wheat bran cereal (r = 0.95, P < 0.005) and could be used as a biomarker to validate fiber supplement intake. The outpatient clinical intervention included a group of seven African-American men and women, who were asked to incorporate 1/2 cup of wheat bran cereal (11.6 g of dietary fiber) into their daily diet for a 6-week period. The cereal was spiked with a 28-mg dose of riboflavin. Baseline measurements of urinary riboflavin and stool weight were compared to postintervention levels. Comparison of pre- and postintervention measures of riboflavin excretion showed a significant increase (0.8 +/- 0.1 versus 6.0 +/- 0.6 mg/day, P < 0.02), which confirmed a high level of adherence to the dietary intervention. Although wet stool weights at baseline were significantly lower than postintervention (106 +/- 20 versus 146 +/- 23 g/day; P < 0.03), differences in dry stool weights did not reach significant levels (28 +/- 4 versus 33 +/- 5 g/day, P < 0.30). Furthermore, pre- and poststool measurements overlapped and could not provide definitive data on participant adherence. These results indicate that the riboflavin tracer was a more sensitive biomarker of wheat bran fiber supplementation than stool weight and provided an accurate method for validating adherence to the dietary intervention. A riboflavin marker provides a valid technique for adherence assessment in large-scale community trials, in which collection of 3-day fecal samples is not a manageable option.

Aged↗

PubMed1996

Four Corners Research Consortium for Native Americans and cancer research.

Cancer morbidity and mortality in Native Americans in the Southwestern four-corners region of the United States (Arizona, Colorado, New Mexico, and Utah) is of critical concern to public health workers, health care providers, cancer researchers, and Native American communities of the region. As a follow-up to the national conference in Seattle, Washington, representatives from the Arizona, Colorado, New Mexico, and Utah Cancer Centers, the AMC Cancer Research Center, and the Indian Health Service participated in a regional conference on September 26, 1995. The primary reason for the "Four Corners Consortium" meeting was to assess cancer research activities in each state and to determine how Native American cancer research could be organized in the four-state region. One interest of the group was to determine strategies to explore why some cancers are more or less prevalent among Southwest Native American populations and to evaluate how the group might jointly establish research that would address the cancer needs of Southwestern tribes.

Arizona↗

PubMed1996

Analysis of multivariate reliability structures and the induced bias in linear model estimation.

Least squares provides consistent estimates of the regression coefficients beta in the model E[Y [symbol: see text] x] = beta x when fully accurate measurements of x are available. However, in biomedical studies one must frequently substitute unreliable measurements X in place of x. This induces bias in the least squares coefficient estimates. In the univariate case, the bias manifests itself as a shrinkage toward zero, but this result does not generalize. When x is multivariate, then there are no predictable relationships between the signs or magnitudes of actual and estimated regression coefficients. In this article, we characterize the estimation bias, and review a relatively simple adjustment procedure to correct it. We also show that several natural conjectures about the bias are false. We present three definitions of reliability coefficient matrices that generalize the univariate case, and we illustrate their application to dietary intake data from a cancer prevention study.

Bias↗

PubMed1996

A polysomnographic study of sleep disturbance in community elderly with self-reported environmental chemical odor intolerance.

Subjective sleep complaints and food intolerances, especially to milk products, are frequent symptoms of individuals who also report intolerance for low-level odors of various environmental chemicals. The purpose of the present study was to evaluate the objective nature of nocturnal sleep patterns during different diets, using polysomnography in community older adults with self-reported illness from chemical odors. Those high in chemical odor intolerance (n = 15) exhibited significantly lower sleep efficiency (p = .005) and lower rapid-eye-movement (REM) sleep percent (p = .04), with a trend toward longer latency to REM sleep (p = .07), than did those low in chemical intolerance (n = 15), especially on dairy-containing as compared with nondairy (soy) diets. The arousal pattern of the chemical odor intolerant group differed from the polysomnographic features of major depression, classical organophosphate toxicity, and subjective insomnia without objective findings. The findings suggest that community elderly with moderate chemical odor intolerance and minimal sleep complaints exhibit objectively poorer sleep than do their normal peers. Individual differences in underlying brain function may help generate these observations. The data support the need for similar studies in clinical populations with chemical odor intolerance, such as multiple chemical sensitivity patients and perhaps certain veterans with "Persian Gulf Syndrome."

Aged↗

PubMed1996

Time-dependent sensitization of plasma beta-endorphin in community elderly with self-reported environmental chemical odor intolerance.

This study examined plasma beta-endorphin as a marker of the physiological stress response in community elderly who were either high (n = 15) or low (n = 15) in self-rated frequency of illness from environmental chemical odors. Individuals who report nonatopic multiple sensitivities to or intolerances for low levels of environmental chemicals also claim high rates of comorbid food sensitivities or intolerances. Subjects gave 9 AM blood samples for plasma beta-endorphin 90 min after ingesting either 1% fat cow's milk or a soy-based nondairy drink, on six different mornings in the laboratory after all-night sleep recordings. The six sessions-were divided into three sets of two successive days each, with each set [involving baseline (ad lib milk), nondairy (soy-based), and dairy diets] separated from the next by 3 weeks. In the chemically tolerant subjects, stably lower beta-endorphin levels suggested that milk may have been a physiologically less stressful beverage than was the soy drink. In contrast, the chemical odor intolerant group exhibited a) increased levels of plasma beta-endorphin averaged over the 6 days (p = .02); and b) marked fluctuations in endorphin from one laboratory day to the next (Group x Diet x Day interaction, p = .005). The findings were consistent with time-dependent, context-dependent sensitization of beta-endorphin in the chemical odor intolerant individuals.

Aged↗

PubMed1996

Randomized, double-blinded, placebo-controlled study of effect of wheat bran fiber and calcium on fecal bile acids in patients with resected adenomatous colon polyps.

BACKGROUND: Ongoing epidemiologic and nutritional studies suggest that colorectal carcinogenesis is consistent with complex interactions between genetic susceptibility and environmental and dietary factors. Among the dietary components found to reduce colon cancer risk are high intakes of dietary fiber and calcium. PURPOSE: We designed and conducted a randomized, double-blinded, placebo-controlled trial involving supplementation of the customary dietary intake with fiber and calcium and measurements of fecal bile acids to examine the potential mechanisms by which added dietary interventions might reduce colorectal cancer risk. METHODS: In a randomized, double-blinded, phase II study, we used a factorial design to measure the effects of dietary wheat bran fiber (2.0 or 13.5 g/day) in the form of cereal and supplemental calcium carbonate (250 or 1500 mg/day elemental calcium) taken as a tablet on fecal bile acid concentrations and excretion rates. Measurements were made at base-line randomization (i.e., after a 3-month placebo run-in period using 2.0 g wheat bran fiber plus 250 mg calcium carbonate) and after 3 and 9 months on treatment in a randomly selected 52-patient subsample of the 95 fully assessable study participants who had a history of colon adenoma resection. Concentrations of fecal bile acids, total, primary (i.e., chenodeoxycholic and cholic), and secondary (i.e., deoxycholic, lithocholic, and ursodeoxycholic), were measured in 72-hour stool samples by gas-liquid chromatography. All P values resulted from two-sided tests. RESULTS: All geometric mean fecal bile acid concentrations and excretion rates were lower at 9 months than at 0 months or 3 months on treatment in the high-dose fiber, high-dose calcium, and high-dose fiber/high-dose calcium treatment groups. The high-dose fiber effect at 9 months of supplementation was statistically significant with respect to virtually all geometric mean fecal bile acid concentrations and excretion rates. For example at 9 months versus 0 months, high-dose fiber supplementation caused a reduction in fecal concentrations of total bile acids (52% reduction; P = .001) and deoxycholic acid (48% reduction; P = .003). High-dose calcium supplementation also had a significant, but lower, effect at 9 months versus 0 months on the geometric mean total bile acid (35% reduction; P = .044) and deoxycholic fecal bile acid (36% reduction; P = .052) concentrations. CONCLUSIONS: High-dose wheat bran fiber and calcium carbonate supplements given for 9 months are associated with statistically significant reductions in both total and secondary fecal bile acid concentrations and excretion rates in patients with resected colon adenomas. This study supports the hypothesis that one of the important ways in which a high intake of wheat bran fiber and calcium may reduce the risk of colorectal neoplasia and cancer is by reduction of the concentrations of fecal bile acids. IMPLICATION: Phase III studies of these agents in the prevention of adenoma recurrence are necessary to confirm this hypothesis and have now been initiated at multiple institutions.

Adenomatous Polyposis Coli↗

PubMed1996

Low-fat diet practices of older women: prevalence and implications for dietary assessment.

OBJECTIVE: To evaluate the importance of information on low-fat diet practices and consumption of reduced-fat foods for accurate assessment of energy and fat intakes using a semiquantitative food frequency questionnaire (FFQ). SUBJECTS: Subjects were 7,419 women, aged 50 to 79 years, who filled out an FFQ as part of eligibility screening for a diet modification component and/or a hormone replacement trial in a multicenter study of chronic disease prevention in postmenopausal women (Women's Health Initiative). STATISTICAL ANALYSIS: For 26 FFQ questions, we recoded the low-fat diet choices of participants to a high-fat counterpart and recalculated energy and fat intakes. We then determined the decrease in energy and nutrient estimates attributable to adding low-fat options to the FFQ. RESULTS: Low-fat diet practices were widespread in this population. For example, 69% of respondents rarely or never ate skin on chicken, 76% rarely or never ate fat on meat, 36% usually drank nonfat milk, 52% usually ate low-fat or fat-free mayonnaise, 59% ate low-fat chips/snacks, and 42% ate nonfat cheese. These low-fat choices had substantial effects on energy and nutrient estimates. Absolute decreases (and mean percentage decreases) for energy and nutrient measures attributable to adding low-fat diet options to the FFQ were 196 kcal (11.4%) energy, 9 percentage points in percentage energy from fat (22.3%), 23.2 g fat (29.0%), and 9.6 g saturated fat (32.5%). Black and Hispanic women and women of lower socioeconomic status reported significantly fewer low-fat diet practices than white women and women of higher socioeconomic status. CONCLUSION: Failure to collect information on low-fat diet practices with an FFQ will result in an upward bias in estimates of energy and fat intake, and the amount of error will vary by the personal characteristics of respondents.

Black or African American↗

PubMed1996

New carotenoid values for foods improve relationship of food frequency questionnaire intake estimates to plasma values.

Carotenoid consumption is of great interest in disease prevention studies. Until recently, carotenoid food composition data have not been available from a single laboratory source with high validity/reliability characteristics. With the availability of a new carotenoid food composition data base, we examined the impact of the new data base on the intake estimates as measured by a food frequency questionnaire and on the relationship of those estimates to plasma values to ascertain what, if any, improvement is achieved through use of the new values. Plasma samples were available for 162 healthy adults participating in cancer prevention studies at the Arizona Cancer Center, including men and women, smokers and nonsmokers. A single laboratory analyzed plasma samples for beta-carotene, alpha-carotene, lutein, and lycopene. All subjects had completed a modified version of the Block food frequency questionnaire, which calculates carotenoids using a literature-based algorithm. A new carotenoid composition data base using recently published data (A.R. Mangels et al., J. Am. Diet. Assoc., 93: 284-296, 1993) was then directly substituted for the Block data base. There were high correlations between intake estimates derived from the two data bases for all four carotenoids (range, r = 0.76-0.96). Average intake estimates based on the Mangels et al. data base were significantly higher for beta-carotene and lycopene; however, correlations between intakes and plasma values were significantly different only for beta-carotene (r = 0.44 for Mangels versus 0.32 for Block, P = 0.015).

Aged↗

PubMed1995

Effects of resistance training on regional and total bone mineral density in premenopausal women: a randomized prospective study.

This study was designed to assess the effects of 18 months of resistance exercise on regional and total bone mineral density (BMD) and soft tissue lean mass (STL) in premenopausal women aged 28-39 randomly assigned to an exercise or control group. Twenty-two exercise and 34 control subjects completed the 18-month training study. All subjects were previously inactive and untrained women. Initial, 5-, 12- and 18-month assessments were made of total and regional BMD and total and regional STL using dual energy X-ray absorptiometry. All subjects consumed a 500 mg/day elemental calcium supplement throughout the study. Initial Ca intake without supplement averaged 1,023 mg/day in total sample. Serum levels of bone osteocalcin and dietary assessments using 12 randomly assigned days of diet records were also completed. Muscular strength was assessed from both 1 repetition maximum (RM) testing of 10 weightlifting exercises and by peak torque for hip abduction/adduction and knee extension/flexion. Training increased strength by 58.1% based on 1 RM testing and by 33.8% based on isokinetic testing at 18 months versus baseline. BMD increased significantly above baseline at the lumbar spine for the exercise group at 5 months (2.8%), 12 months (2.3%), and 18 months (1.9%) as compared with controls. Femur trochanter BMD increased significantly (p < 0.05) in the exercise group at 12 months (1.8%) and 18 months (2.0%) but not at 5 months (0.7%) as compared with controls. No changes in total BMD, arm BMD, or leg BMD were found. There was a 20% increase in BGP in the exercise group as compared with controls at 5 months and this difference was maintained throughout the study. For STL, significant increases for total, arm, and leg were found at 5, 12, and 18 months for the exercise group versus control ranging from 1-6% over baseline. These results support the use of strength training for increasing STL and muscular strength with smaller but significant regional increases in BMD in the premenopausal population.

Absorptiometry, Photon↗

PubMed1995

Breast cancer incidence and screening practices among university faculty women.

Explore the source record for details and available documents.

Adult↗

PubMed1995

Dieting and "watching" behaviors among adolescent females: report of a multimethod study.

PURPOSE: This study posits a distinction between "watching what you eat" and dieting behaviors in a sample of adolescent females. Findings suggest that the dichotomy of dieter/nondieter fails to capture a range of healthful behaviors practiced by many adolescent girls. METHODS: Anthropologic and nutritional research methods were used in this study. Data were drawn from 1 year of a longitudinal study of food intake and dieting behaviors in a sample of 231 adolescent females. Multiple methods including one ethnographic interview, a survey questionnaire, a telephone interview, and food records were collected from each informant. RESULTS: Although 44% of the girls in this sample reported trying to lose weight on the day of the survey, only 8.6% of the food records reflected dieting days. In interviews, many identified "watching what they eat" as a health-promoting strategy that allowed them to maintain their weight. Analysis of food record data confirmed a trend toward higher intakes of micronutrients. CONCLUSIONS: Research concerned with adolescent weight loss behaviors has focused more on negative than positive health attitudes and behaviors. The present study identified the behavior of "watching" as distinct from dieting. "Watching" was widely utilized by girls in this sample as a way to maintain weight and promote health.

Adolescent↗

PubMed1995

Concentrations and plasma-tissue-diet relationships of carotenoids, retinoids, and tocopherols in humans.

Micronutrients, such as beta-carotene and vitamins A and E, are potential chemopreventive agents; however, their concentrations in human target tissues are largely unknown. Because these micronutrients may exert their action at the site of target tissues, the tissue concentrations of the micronutrients need to be determined. In this cross-sectional study, we have measured the concentrations of seven carotenoids, two retinoids, and two tocopherols in paired plasma, buccal mucosal cells (BMC), and skin samples from 96 healthy subjects (ages 26-82 yrs). The plasma-tissue, as well as the diet-plasma and diet-tissue relationships of the micronutrients, and the impact of various potential confounders on the micronutrient concentrations were evaluated. The micronutrient concentrations of plasma and BMC used in the evaluation were the average of three measurements over a one-month period. Our data indicated that 1) the correlations between the plasma and BMC (Spearman r = 0.40-0.91, p < 0.05) and the plasma and skin (r = 0.24-0.75, p < 0.05) concentrations of most micronutrients were significant in all subjects, suggesting that the status of these micronutrients in the BMC and skin may be estimated from their plasma concentrations; 2) the correlations between the diet and plasma/tissue concentrations of the micronutrients were generally not as strong as the plasma-tissue relationships; the diet-plasma and diet-tissue relationships of the carotenoids were particularly poor in the smokers; 3) the plasma and tissue concentrations of most micronutrients were lower in smokers than in nonsmokers and higher in vitamin supplement users than in nonsupplement users; the differences remained significant after adjustment for age, gender, and diet intake estimates; 4) among the seven carotenoids examined, lycopene was unique, because its concentration was not lower in smokers or higher in supplement users but was inversely associated with age.

Adult↗

PubMed1995

Nutrients, body composition and exercise are related to change in bone mineral density in premenopausal women.

This study determined relationships among total energy intake, nutrient intake, body composition, exercise group status, and annual rates of change (slopes) in bone mineral density in 66 Caucasian premenopausal women (mean age, 34.4 +/- 2.7) taking calcium supplements. Body composition components measured by dual-energy X-ray absorptiometry included fat mass, soft tissue lean mass, and bone mineral density (g/cm2) of total body, spine (lumbar vertebrae 2-4), and three femur sites measured at baseline, 5, 12, and 18 mo. Nutrients were not significant variables in regression models predicting bone mineral density slopes (rates of change) at any femur site. The only significant variable in models predicting Ward's triangle bone mineral density slope was the initial fat mass and, for trochanter, exercise. Significant variables (P < 0.05) in models predicting total body bone mineral density slope included the initial fat mass and fat mass slope plus either vitamin A, carotene, fiber, magnesium, or phosphorus (R2 from 0.31 to 0.25) and fat mass slope plus sodium (R2 = 0.24). The significant variable in the model predicting L2-4 slope was energy intake (R2 = 0.17, P < 0.05). We conclude that nutrient intake, exercise, and body composition are related to bone mineral density rate of change and that relations among these variables vary by bone site.

Absorptiometry, Photon↗