Lunch-time food source is associated with school hour and school day diet quality among Canadian children.

BACKGROUND: There is limited research on the dietary behaviours of Canadian children at school, including where students obtain food from during school hours or whether lunch-time food source influences diet quality. METHODS: Nationally representative cross-sectional data from 24-h dietary recalls were analysed from the 2004 Canadian Community Health Survey (n = 4589). Dietary outcomes included school hour and school day dietary intakes and School Healthy Eating Index (S-HEI) scores. Survey-weighted covariate-adjusted linear regression models examined differences in dietary outcomes across lunch-time food source groups. RESULTS: The majority of children (72.8%) reported bringing lunch from home, whereas fewer students obtained lunch from off-campus locations (11.6%), schools (9.6%) or skipped lunch (5.9%). Compared to off-campus lunches, home-packed lunches were significantly higher in fibre, vitamins A, D and C, thiamin, magnesium, iron, grains, vegetables and fruit, but lower in total calories, fat and calories from minimally nutritious foods. Average school hour diet quality required improvement for all age groups, although S-HEI scores did not differ significantly by lunch-time food source among 6-8-year-old children. However, for children age 9-17 years, bringing a home-packed lunch was associated with significantly higher S-HEI scores compared to students obtaining lunch from off-campus locations. After adjusting for age and sex, lunch-time food source was also significantly associated with whole day dietary quality. CONCLUSIONS: Although the nutritional quality of off-campus lunches was lower than home-packed lunches, the quality of foods was suboptimal, regardless of food source. Strategies are needed to enhance access to nutritious foods on campus and improve the nutritional quality of packed lunches, which supply the majority of lunch-time foods consumed by Canadian children.

The effect of inflammation on serum zinc concentrations and the prevalence estimates of population-level zinc status among Congolese children aged 6-59 months.

BACKGROUND/OBJECTIVES: Zinc is a negative acute-phase reactant; hence, its concentration decreases in the presence of inflammation. There is no current consensus on how to control for the effect of inflammation on serum zinc, which has implications for accurate estimates of population-level zinc status. We aimed to measure the association between inflammation and serum zinc concentrations and to compare the means and the prevalence of zinc deficiency using unadjusted and inflammation-adjusted serum zinc concentrations among Congolese children. SUBJECTS/METHODS: Non-fasting blood was collected in the afternoon in trace element-free vacutainers from 744 apparently healthy children aged 6-59 months in the Democratic Republic of the Congo. Serum was analyzed for zinc, C-reactive protein (CRP) and α-1 acid glycoprotein (AGP) for 665 children with complete data for all three biomarkers. Linear regression was used to generate correction factors (CFs) based on three stages of inflammation: incubation (CRP >5 mg/l and normal AGP), early convalescence (CRP >5 mg/l and AGP >1 g/l) and late convalescence (AGP >1 g/l and normal CRP), relative to no inflammation. RESULTS: Overall unadjusted mean±s.d. serum zinc concentration was 9.4±2.1 µmol/l. Study-generated CFs (95% confidence interval) for incubation, early and late convalescence were 1.01 (0.88, 1.14), 1.15 (1.11, 1.21) and 1.07 (1.03, 1.11), respectively. After applying the CFs, overall adjusted mean±s.d. serum zinc concentration was 10.1±2.2 µmol/l, and prevalence of zinc deficiency (<8.7 µmol/l) decreased from 35% (n=234/665) to 24% (n=160/665). CONCLUSIONS: Adjustment of zinc concentrations for inflammation is warranted when assessing population-level zinc status.European Journal of Clinical Nutrition advance online publication, 23 August 2017; doi:10.1038/ejcn.2017.127.

Associations of Protein Intake and Protein Source with Bone Mineral Density and Fracture Risk: A Population-Based Cohort Study.

UNLABELLED: High dietary protein has been hypothesized to cause lower bone mineral density (BMD) and greater fracture risk. Previous results are conflicting and few studies have assessed potential differences related to differing protein sources. OBJECTIVE: To determine associations between total protein intake, and protein intake by source (dairy, non-dairy animal, plant) with BMD, BMD change, and incident osteoporotic fracture. DESIGN/SETTING: Prospective cohort study (Canadian Multicentre Osteoporosis Study). Participants/Measures: Protein intake was assessed as percent of total energy intake (TEI) at Year 2 (1997-99) using a food frequency questionnaire (N=6510). Participants were contacted annually to ascertain incident fracture. Total hip and lumbar spine BMD was measured at baseline and Year 5. Analyses were stratified by group (men 25-49 y, men 50+ y, premenopausal women 25-49 y, and postmenopausal women 50+ y) and adjusted for major confounders. Fracture analyses were limited to those 50+ y. RESULTS: Intakes of dairy protein (with adjustment for BMI) were positively associated with total hip BMD among men and women aged 50+ y, and in men aged 25-49. Among adults aged 50+ y, those with protein intakes of <12% TEI (women) and <11% TEI (men) had increased fracture risk compared to those with intakes of 15% TEI. Fracture risk did not significantly change as intake increased above 15% TEI, and was not significantly associated with protein source. CONCLUSIONS: In contrast to hypothesized risk of high protein, we found that for adults 50+ y, low protein intake (below 15% TEI) may lead to increased fracture risk. Source of protein was a determinant of BMD, but not fracture risk.

Longitudinal changes in calcium and vitamin D intakes and relationship to bone mineral density in a prospective population-based study: the Canadian Multicentre Osteoporosis Study (CaMos).

OBJECTIVES: Our objective was to study changes in calcium and vitamin D intakes over time, and their cross-sectional and longitudinal associations with bone mineral density (BMD). METHODS: We followed 9382 women and men aged ≥25 and 899 aged 16-24, for 10 and 2 years respectively. RESULTS: Calcium and vitamin D intakes increased over time in adults, but decreased in women aged 16-18. The increased intakes in adults were largely attributable to the increased use of calcium and/or vitamin D supplements. Both the percentage of supplement users and average dose among users increased over time. There was nevertheless a high prevalence of calcium and vitamin D intake below the estimated average requirement. At baseline, higher calcium and vitamin D intakes were associated with higher total hip and femoral neck BMD in young men, and cumulatively high levels of calcium and vitamin D intakes over time contributed to better BMD maintenance at lumbar spine and hip sites in adult women. CONCLUSIONS: Although total intakes, particularly of vitamin D, frequently fell below the Institute of Medicine recommendations despite an increase over time in supplement use, we found some positive associations between total calcium and vitamin D intake and bone health.

Healthy midlife Canadian women: how bone health is considered in their food choice systems.

BACKGROUND: The incidence of osteoporosis is predicted to increase as Western populations age. Diet is considered to be an important modifiable factor in bone health, yet the diets of many women are insufficient in calcium and vitamin D, which comprise two key nutrients for bone health. This focus group study explored ways in which midlife women consider bone health in their personal food choice systems. METHODS: Data were obtained in six audio-recorded focus groups from a total of 36 women from upper, middle and lower income neighbourhoods. Open and axial coding and thematic analysis revealed shared and unique themes across and within the income groups. Use of member checks, peer debriefing, and independent and team data analysis enhanced rigour in the findings. RESULTS: All participants were aware of osteoporosis. Most women idealised making simple food decisions and eating for 'holistic' health, but not specifically for bone health. Most midlife women were not motivated to change their diets, few had deliberately increased their intake of calcium and vitamin D through foods and supplements, and few others had simplified their food decisions. CONCLUSIONS: Midlife women in the present study did not make eating for bone health a priority in their food choice systems. Instead, women wanted to eat for 'holistic' health, and only by implication bone health.

Energy recommendations for normal weight, overweight and obese children and adolescents: are different equations necessary?

In 2002/2005, separate energy requirement equations were generated by the Institute of Medicine's (IOM) Dietary Reference Intake process for normal weight and overweight/obese children and adolescents. The current paper questions the theoretical rationale of having two sets of equations (based solely on body-weight classification): when body weight is considered, overweight and obese children and adolescents do not seem to differ from their normal weight counterparts in energy expended for basal metabolism or physical activity tasks. However, energy needs for weight maintenance among overweight/obese girls were consistently higher when predicted using the equations for overweight/obese individuals compared with those developed for normal weight individuals. In contrast, among overweight/obese boys, they were consistently lower. Although the differences are within the variability of the estimates, even theoretical support for a higher energy intake (as occurs in girls) seems unwise because of the potential contribution to a higher body mass in children who are already at risk. It is the opinion of the authors that the IOM revisit the use of two separate equations and generate one set that is appropriate for all children and adolescents.

Self-reported lifetime physical activity and areal bone mineral density in healthy postmenopausal women: the importance of teenage activity.

Girls who exercise athletically have higher bone mass than their sedentary counterparts, and this difference may be sustained in adulthood. However, whether moderate physical activity during youth confers lasting benefits for bone is unclear. We explored lifetime physical activity and current areal bone mineral density (aBMD) in 78 postmenopausal women with no known history of osteoporosis. Subjects reported physical activity for four age periods (12-18, 19-34, 35-49, > or = 50 years) using the Historical Leisure Activity Questionnaire, completed two 3-day food records, had measurements of height and weight, and aBMD assessed using dual-energy X-ray absorptiometry at the lumbar spine (L1-4) and proximal femora. Low aBMD was detected at the lumbar spine in 43 (56%) women and at the proximal femora in 38 (49%) women. Teenage physical activity, but not activity during other age periods, was associated with current aBMD at both sites (lumbar spine r = 0.31, P < 0.01; mean proximal femora r = 0.33, P < 0.01). Weight-bearing physical activity (WBPA) at age 12-18 years was the only predictor of current lumbar spine aBMD (R (2) = 0.110, P = 0.004). Current proximal femoral aBMD was positively predicted by physical activity at age 12-18 years and negatively predicted by current age (R (2) = 0.175, P = 0.001). Subjects above the median of teen WBPA had 5-8% higher current aBMD than those reporting less teen WBPA and were less likely to be classified with osteopenia or osteoporosis. Moderate physical activity during years of peak bone acquisition appears to have lasting benefits for lumbar spine and proximal femoral aBMD in postmenopausal women.

Canadian dietitians' views and practices regarding obesity and weight management.

OBJECTIVE: To provide insight into Canadian dietitians' attitudes and practices regarding obesity and weight management. DESIGN: Cross-sectional mail survey of a stratified random sample of members of Canadian dietetic associations. SUBJECTS: A total of 514 dietitians (74% of those surveyed), 350 (69%) of whom actively counselled overweight/obese clients. MEASUREMENTS: Participants received a questionnaire to assess dietitians' attitudes regarding obesity and overweight, views regarding their role in weight management, counselling practices, and the criteria used to judge success. Demographic variables were collected. RESULTS: Most dietitians believed that obesity contributes to morbidity and mortality, and that small weight losses produced important health benefits. However, 80% agreed that health indicators other than weight loss should be the focus of obesity management, and 55% specifically recommended that clients not weigh themselves. Instead, weight management was promoted by recommending healthy eating and increased physical activity. Three-quarters agreed that they are the profession best trained to manage obesity but two-thirds believed their time would be better spent preventing rather than managing obesity. Dietitians most valued education received from on-the-job support and mentoring from other dietitians. Participants reported wanting to learn more about motivational and behavioural modification counselling techniques. CONCLUSIONS: Canadian dietitians follow a lifestyle approach to weight management. Studies are required to formally assess the effectiveness of various aspects of this approach.

Nutrition and physical activity--why we must move from a casual acquaintance to a lifelong partnership. 2001 Ryley-Jeffs memorial lecture.

Both nutrition and physical activity have important roles in health promotion and disease prevention, and are viewed by the public as closely related and synergistic. However, the present level of interaction between professionals in the two areas is limited, and could be described as a "casual acquaintance." Using heart disease, osteoporosis and obesity as examples of chronic conditions that affect the health and well-being of Canadians, reasons why the level of interaction between nutrition and exercise professionals must move to a "lifelong partnership" are discussed. For each, evidence for the roles of nutrition and physical activity in prevention and management is presented, along with data to support the concept that attention to both factors is likely to be more beneficial than attention to either alone. Obesity is presented as a risk factor for inactivity rather than a chronic disease per se: when fitness level is controlled, data suggest that lean and obese men have similar mortality rates. However, the prevalence of low fitness is much higher among obese individuals. Moving from a casual acquaintance to a lifelong partnership will require modification of the education of nutrition and fitness professionals, as well as a personal commitment by members of both groups.

Dietary restraint, exercise, and bone density in young women: are they related?

PURPOSE: Women with high scores for dietary restraint have been found to have higher 24-h urinary cortisol excretion and a higher prevalence of subclinical ovulatory disturbances, both of which may be risk factors for bone loss. The purpose of this study was to explore relationships between dietary restraint and bone health in regularly menstruating young women. METHODS: 62 women (age: 21.7 +/- 2.5 yr) had body composition and total body and lumbar spine bone mineral density (BMD) and content (BMC) assessed using dual-energy x-ray absorptiometry. Dietary restraint was assessed using the restraint subscale from the Three-Factor Eating Questionnaire: 29 women had low restraint (LR; restraint score 0--5), 33 had high restraint (HR; restraint score 13--21). Exercise (h x wk(-1)) was assessed by questionnaire on two occasions. RESULTS: LR and HR women were similar in age and body composition (fat mass = 15.0 +/- 4.7 kg, lean mass = 40.9 +/- 4.9 kg), but HR women exercised more (3.4 +/- 1.7 vs 2.2 +/- 1.8 h x wk(-1), P < 0.05). Exercise was correlated with BMD and BMC, and when it was included as a covariate, total body BMC was significantly lower in HR than LR women. In multiple regression analysis, weekly hours of exercise and restraint score were significant predictors of total body BMD and BMC. CONCLUSION: The observations of this cross-sectional study suggest that high levels of cognitive dietary restraint, or associated factors such as higher cortisol, may attenuate the positive effects of exercise on bone in young women.

Eating attitudes and habitual calcium intake in peripubertal girls are associated with initial bone mineral content and its change over 2 years.

This 2-year prospective study examined associations among bone mineral acquisition and physical, maturational, and lifestyle variables during the pubertal transition in healthy girls. Forty-five girls, initially 10.5+/-0.6 years, participated. Body composition and bone mineral content (BMC) at the spine and total body (TB) were assessed at baseline and annually thereafter using dual-energy X-ray absorptiometry (DXA). Nutrient intakes were assessed using 3-day diet records and a calcium food frequency questionnaire (FFQ), physical activity by questionnaire, sexual maturation using Tanner's stages of breast and pubic hair maturation, growth by height and weight, and eating attitudes using the children's Eating Attitudes Test (Children's EAT). Mean children's EAT subscale scores (dieting, oral control [OC], and bulimia) were stable over time. Median split of OC subscale scores was used to form high and low OC groups. Groups had similar body composition, dietary intake, activity, and Tanner stage at baseline and 2 years. Using height, weight, and Tanner breast stage as covariates, girls with low OC scores had greater TB BMC at baseline (1452+/-221 g vs. 1387+/-197 g; p = 0.030) and 2 years (2003+/-323 g vs. 1909+/-299 g; p = 0.049) and greater lumbar spine (LS) BMC at 2 years (45.2+/-8.8 g vs. 41.2+/-9.6 g; p = 0.042). In multiple regression analysis, OC score predicted baseline, 2 years, and 2-year change in TB and spinal BMC, contributing 0.9-7.6% to explained variance. Calcium intake predicted baseline, 2 years, and 2-year change in TB BMC, explaining 1.6-5.3% of variance. We conclude that both OC and habitual calcium intake may influence bone mineral acquisition.

Cognitive dietary restraint is associated with higher urinary cortisol excretion in healthy premenopausal women.

BACKGROUND: Cognitive dietary restraint, assessed by the Three-Factor Eating Questionnaire restraint subscale, is associated with subclinical menstrual cycle disturbances. This association may be mediated by stress-activated cortisol release. OBJECTIVE: We assessed whether 24-h urinary cortisol excretion differs between women with high and low restraint scores. DESIGN: Participants (aged 21.6+/-2.5 y; n = 62) with normal-length menstrual cycles and high (n = 33) or low (n = 29) restraint scores completed a questionnaire describing weight history, dietary practices, and exercise. Cortisol, calcium, and creatinine were measured in urine collected over 24 h on a day when all food and beverages were provided and measured. Previously, 3-d food records and anthropometric measurements were obtained. RESULTS: Age, height, weight, body mass index, and length of menstrual cycle were similar between groups. The reported amount of exercise was higher (3.4+/-1.7 compared with 2.2+/-1.8 h/wk; P<0.05) and energy intakes (assessed from 3-d and 24-h food records) were lower in the high- than in the low-restraint group. Ratios of urinary cortisol (nmol) to creatinine (mmol) were higher in the high-restraint than in the low-restraint group (42.9+/-12.9 compared with 36.3+/-8.9; P<0.05), whereas ratios of urinary calcium (mmol) to creatinine were lower (0.3+/-0.1 compared with 0.4+/-0.2; P<0.05) in the high-restraint group. Urinary cortisol was not associated with exercise, nutrient intakes, or anthropometric measurements. CONCLUSIONS: High dietary restraint scores are associated with urinary cortisol, a biological marker of stress, and high cortisol excretion may affect bone health. Our results suggest that further research is warranted to clarify these associations and to determine whether they persist over time.

Effects of increased consumption of fluid milk on energy and nutrient intake, body weight, and cardiovascular risk factors in healthy older adults.

OBJECTIVE: To assess the impact of increased consumption of milk, without other dietary advice, on older adults' energy and nutrient intakes, weight, cardiovascular risk factors (blood pressure, plasma lipid levels), and quality of life. SUBJECTS/SETTING: Two hundred four healthy men and women, aged 55 to 85 years, who consumed fewer than 1.5 dairy servings per day were chosen from six US academic health centers. DESIGN: Randomized, controlled open trial. INTERVENTION: Advice to increase skim or 1% milk intake by 3 cups per day (n = 101) or to maintain usual diet (n = 103) for 12 weeks after a 4-week baseline period. MAIN OUTCOME MEASURES: Changes in energy and nutrient intake assessed from 3-day food records, body weight, blood pressure, and plasma lipid levels. STATISTICAL ANALYSES PERFORMED: Group-by-time analysis of variance with repeated-measures, chi 2 test. RESULTS: Compliance with the intervention was good. Compared with controls, participants in the milk-supplemented group significantly increased energy, protein, cholesterol, vitamins A, D, and B-12, riboflavin, pantothenate, calcium, phosphorus, magnesium, zinc, and potassium intakes. Prevalence of nutrient inadequacy, assessed for nutrients with Estimated Average Requirements, decreased among women in the milk group for magnesium (40% at baseline vs 13% at 12 weeks, P < .001) and vitamin B-12 (6% vs 0%, P < .05) and tended to decrease (P < .10) for protein and thiamin (women) and magnesium and vitamin B-6 (men). The milk group gained 0.6 kg more than control group (P < .01); however, weight gain was less than predicted, which suggests some compensation for the added energy from milk. Blood pressure decreased similarly over time in both groups. Total and low-density lipoprotein cholesterol levels, and the ratio of total cholesterol to high-density lipoprotein cholesterol, were unchanged. Triglyceride levels increased within the normal range in the milk group (P = .002). Quality of life scores were high at baseline and remained high throughout. APPLICATIONS/CONCLUSIONS: Older adults can successfully increase milk intake, thereby meaningfully improving their nutrient intakes. Dietitians can play a key role in disseminating this advice.

Augmented trochanteric bone mineral density after modified physical education classes: a randomized school-based exercise intervention study in prepubescent and early pubescent children.

BACKGROUND: Of the few exercise intervention studies focusing on pediatric populations, none have confined the intervention to the scheduled physical education curriculum. OBJECTIVE: To examine the effect of an 8-month school-based jumping program on the change in areal bone mineral density (aBMD), in grams per square centimeter, of healthy third- and fourth-grade children. STUDY DESIGN: Ten elementary schools were randomized to exercise (n = 63) and control groups (n = 81). Exercise groups did 10 tuck jumps 3 times weekly and incorporated jumping, hopping, and skipping into twice weekly physical education classes. Control groups did regular physical education classes. At baseline and after 8 months of intervention, we measured aBMD and lean and fat mass by dual-energy x-ray absorptiometry (Hologic QDR-4500). Calcium intake, physical activity, and maturity were estimated by questionnaire. RESULTS: The exercise group showed significantly greater change in femoral trochanteric aBMD (4.4% vs 3.2%; P <.05). There were no group differences at other sites. Results were similar after controlling for covariates (baseline aBMD change in height, change in lean, calcium, physical activity, sex, and ethnicity) in hierarchical regression. CONCLUSIONS: An easily implemented school-based jumping intervention augments aBMD at the trochanteric region in the prepubertal and early pubertal skeleton.

Relative weight, weight loss efforts and nutrient intakes among health-conscious vegetarian, past vegetarian and nonvegetarian women ages 18 to 50.

OBJECTIVE: To compare relative weight, weight loss efforts and nutrient intakes among similarly health-conscious vegetarian, past vegetarian and nonvegetarian premenopausal women. METHODS: Demographic data, lifestyle practices and weight loss efforts (by questionnaire), body mass index (BMI;kg/m2) and dietary intake (via multiple-pass 24-hour diet recall) were compared in a convenience sample of 90 current vegetarians, 35 past vegetarians and 68 nonvegetarians. RESULTS: Age (31.9 +/- 8.8), educational attainment, smoking status, alcohol use, physical activity and perceived health status were similar among the three groups of women. BMI did not differ by dietary pattern and averaged 23.7 +/- 4.7 for all women combined. Participants had intentionally lost > or = 10 pounds a mean of 2.1 times, and 39% of women perceived themselves to be overweight; again, no differences were observed among dietary groups. Dietary intakes of vegetarians and current nonvegetarians were consistent with current recommendations for macronutrient composition (< 30% fat, < 10% saturates). Compared to current nonvegetarians, current vegetarians had lower intakes of protein, saturated fat, cholesterol, niacin, vitamins B12 and D, and higher fiber and magnesium intakes. Vegetarians' mean vitamin B12 and D intakes were well below recommendations. CONCLUSIONS: Relative weight and weight loss efforts do not differ by dietary pattern among similarly health-conscious vegetarian and nonvegetarian women. The only differences in nutrient intake with potential health implications were vitamins D and B12.

Energy balance in women with breast cancer during adjuvant treatment.

OBJECTIVE: To compare weight, body composition, and major determinants of energy balance of women treated with adjuvant chemotherapy (n = 8) using Adriamycin and cyclophosphamide (AC), or radiation therapy (n = 10). DESIGN: The study used a nonrandomized prospective design. Pretreatment and posttreatment measurements, obtained at baseline and 12 weeks, respectively, included weight, body composition (determined using dual-energy x-ray absorptiometry), energy intake (determined using 3-day food records), resting energy expenditure (determined in indirect calorimetry), and physical activity (determined using 3-day physical activity records). Poststudy follow-up weights were obtained for 13 women. SUBJECTS/SETTING: Eighteen premenopausal women with breast cancer in the early stage, recruited from outpatient clinics, participated in and completed the study. STATISTICAL ANALYSES PERFORMED: Unpaired Student t tests or X2 tests were used to test for differences in baseline subject characteristics, and repeated measures analysis of variance was used to compare groups before and after treatment. RESULTS: Body weight was unchanged in both treatment groups during the study, although poststudy follow-up weights (n = 13) suggested a tendency for weight gain in both groups. Significant changes in body composition for both groups included a mean loss of 0.8 kg total lean body mass (LBM), a mean loss of 0.4 kg LBM in the leg region, and a mean 1.3% increase in percent body fat, from 40.0% to 41.3%. Overall, no between-group differences were observed in any factors associated with energy balance. APPLICATIONS: In this short-term study, AC chemotherapy using fewer antineoplastic agents and number of treatments than most chemotherapy protocols for breast cancer, did not result in weight gain during treatment. Regardless of weight gain, changes in body composition may occur in women with breast cancer during or after treatment. These potential changes have important implications for preventive nutrition counseling.

Dietary changes favorably affect bone remodeling in older adults.

OBJECTIVE: To determine whether dietary counseling to increase milk intake could produce useful changes in the calcium economy and what, if any, other nutrition-related changes might be produced. DESIGN: Randomized, open trial. SUBJECTS/SETTING: Two hundred four healthy men and women, aged 55 to 85 years, who habitually consumed fewer than 1.5 servings of dairy foods per day. Six academic health centers in the United States. INTERVENTION: Subjects were instructed to consume 3 servings per day of nonfat milk or 1% milk as a part of their daily diets, or to maintain their usual diets, for a 12-week intervention period, which followed 4 weeks of baseline observations. MAIN OUTCOME MEASURES: Energy and nutrient intake assessed from milk intake logs and 3-day food records; serum calciotrophic hormone levels at baseline and at 8 and 12 weeks; urinary excretion of calcium and N-telopeptide at 12 weeks. STATISTICAL ANALYSES: Repeated-measures analysis of variance. RESULTS: In the milk-supplemented group, calcium intake increased by 729 +/- 45 mg/day (mean +/- standard error), serum parathyroid hormone level decreased by approximately 9%, and urinary excretion of N-telopeptide, a bone resorption marker, decreased by 13%. Urine calcium excretion increased in milk-supplemented subjects by 21 +/- 7.6 mg/day (mean +/- standard error), less than half the amount predicted to be absorbed from the increment in calcium intake. All of these changes were significantly different from baseline values in the milk group and from the corresponding changes in the control group. Bone-specific alkaline phosphatase level (a bone formation marker) fell by approximately 9% in both groups. Serum level of insulin-like growth factor-1 (IGF-1) rose by 10% in the milk group (P < .001), and the level of insulin-like growth factor binding protein-4 (IGFBP-4) fell slightly (1.9%) in the milk group and rose significantly (7.9%) in the control group (P < .05). APPLICATIONS/CONCLUSIONS: The changes observed in the calcium economy through consumption of food sources of calcium are similar in kind and extent to those reported previously for calcium supplement tablets. The increase in IGF-1 level and the decrease in IBFBP-4 level are new observations that are beneficial for bone health. Important improvements in skeletal metabolism can feasibly occur in older adults by consumption of food sources of calcium. Dietitians can be confident that food works, and that desired calcium intakes can be achieved using food sources.

Vegetarianism and menstrual cycle disturbances: is there an association?

The question of whether menstrual disturbances are more common in vegetarian than in nonvegetarian women is complex. Disturbances of the cycle may be clinical (ie, amenorrhea or oligomenorrhea) or subclinical (i.e., normal-length cycles with anovulation or a short or defective luteal phase). Detection of the latter requires that the menstrual cycle be monitored, but may help prevent recruitment bias in studies comparing vegetarians with nonvegetarians because vegetarians with menstrual disturbances may be more likely to volunteer for a study on menstrual disturbances and vegetarianism. Three general mechanisms that could contribute to menstrual disturbances that may differ between vegetarians and nonvegetarians include energy imbalances associated with body-weight disturbances or exercise, psychosocial and cognitive factors, and dietary components. Evidence for each of these mechanisms is reviewed and studies comparing menstrual function between vegetarians and nonvegetarians are described in this article. Although results from several cross-sectional studies suggest that clinical menstrual disturbances may be more common in vegetarians, a prospective study that controlled for many potential confounders found that subclinical disturbances were less common in weight-stable, healthy vegetarian women. Because the sample studied may not be representative of all vegetarian women, however, these results cannot be generalized. Population studies are needed to draw definitive conclusions.

Running and ovulation positively change cancellous bone in premenopausal women.

PURPOSE: Exercise is understood to exert positive effects on bone. However cancellous bone has not been shown to increase with exercise. Previous results of our 1-yr observational prospective study in ovulatory women related 20% of the change in cancellous spinal bone mineral density (BMD), measured by quantitative computed tomography (QCT), to luteal phase length (the time from ovulation to menstruation, LL). METHODS: The 66 women who documented exercise daily included normally active women (N = 23) and those who ran consistently or were increasing running in preparation for a marathon (N = 43). Exercise did not affect BMD change in the women as a whole. We re-evaluated those data to determine whether exercise-related effects on spinal cancellous BMD change in regularly cycling premenopausal women were related to ovulatory characteristics. The potential relationship of exercise to BMD change was reanalyzed by stratifying women into tertiles according to average LL documented by quantitative basal temperature analysis. RESULTS: Repeated-measures ANOVA indicated independent positive effects of both luteal length (P = 0.001) and activity (P = 0.041). The 11 runners with LL > 10.9 d had a nonsignificant 0.5% increase in lumbar BMD while the 15 who averaged short LL (<9.9 d) experienced a significant 3.6% loss. In the runners as a group, however, kilometers run per week was negatively related to BMD change throughout (r = -0.347, P = 0.024). CONCLUSIONS: These data are the first to indicate that, in women with regular cycles, luteal length and exercise independently and positively affect change in spinal cancellous BMD.

Effects of dehydration on exercise performance.

Dehydration refers both to hypohydration (dehydration induced prior to exercise) and to exercise-induced dehydration (dehydration that develops during exercise). The latter reduces aerobic endurance performance and results in increased body temperature, heart rate, perceived exertion, and possibly increased reliance on carbohydrate as a fuel source. Although the negative effects of exercise-induced dehydration on exercise performance were clearly demonstrated in the 1940s, athletes continued to believe for years thereafter that fluid intake was not beneficial. More recently, negative effects on performance have been demonstrated with modest (<2%) dehydration, and these effects are exacerbated when the exercise is performed in a hot environment. The effects of hypohydration may vary, depending on whether it is induced through diuretics or sauna exposure, which substantially reduce plasma volume, or prior exercise, which has much less impact on plasma volume. Hypohydration reduces aerobic endurance, but its effects on muscle strength and endurance are not consistent and require further study.