naturopathydigest.com -- Critical Research

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Critical Research

Critical Research is a regular feature in Naturopathy Digest. Each month, we provide abstracts from studies published in the top peer-reviewed journals; each abstract includes the complete citation and an online link to the journal. Whenever possible, this link directs you to a page where you can order the full text of the study, if desired.

This Month's Featured Abstract

A pilot study of an environmental intervention to increase physical activity in inner-city children.

Thomas A. Farley, Rebecca A. Meriwether, Erin T. Baker, et al.

Objectives: We evaluated the effect of providing a safe play space on the physical activity level of inner-city schoolchildren.

Methods: In 1 of 2 matched neighborhoods, we opened a schoolyard and provided attendants to ensure children’s safety. Over the next 2 years we directly observed the number of children and their physical activity levels in the schoolyard, as well as in the surrounding intervention and comparison neighborhoods. We also surveyed children in the schools in the intervention and comparison neighborhoods regarding sedentary activities.

Results: After the schoolyard was opened, a mean of 71.4 children used it on weekdays and 25.8 used it on weekends during the school year. When observed, 66% of these children were physically active. The number of children who were outdoors and physically active was 84% higher in the intervention neighborhood than the comparison neighborhood. Survey results showed that children in the intervention school reported declines relative to the children in the comparison school in watching television, watching movies and DVDs, and playing video games on weekdays.

Conclusion: When children were provided with a safe play space, we observed a relative increase in their physical activity. Provision of safe play spaces holds promise as a simple replicable intervention.

Source: Am J Public Health, July 31, 2007 [Epub ahead of print].

Tobacco smoke exposure of pregnant mothers and blood pressure in their newborns. Results from the Wheezing Illnesses Study Leidsche Rijn Birth Cohort.

CC Geerts, DE Grobbee, CK van der Ent, et al.

There is evidence to suggest that exposure of pregnant women to tobacco smoke is related to higher childhood blood pressure in their offspring. It is not well known whether this association is set in utero or by shared postnatal environments. The objective of this study was to assess the association between tobacco smoke exposure of pregnant mothers and blood pressure and heart rate of their newborns. In an unselected birth cohort, blood pressure and heart rate were measured in 456 infants at approximately 2 months of age. Smoking exposure of mothers in pregnancy was obtained by questionnaire. Of 456 mothers whose infants had blood pressure measured, 363 (79.6%) were not exposed to tobacco smoke in pregnancy, 63 (13.8%) did not smoke in pregnancy but were exposed by others, and 30 (6.6%) smoked. Infant offspring of mothers who had smoked during pregnancy had 5.4 mm Hg (95% CI: 1.2 to 9.7; P=0.01) higher systolic blood pressure levels than offspring of mothers who were not exposed to tobacco smoke in pregnancy, taking account of birth weight, infant age, gender, nutrition, and age of mother. No associations were found between maternal exposure to tobacco smoke in pregnancy and diastolic blood pressure. A positive association between maternal exposure to tobacco smoke and heart rate was largely explained by confounding. It can be concluded that maternal exposure to tobacco smoke in pregnancy has a substantial increasing effect on systolic blood pressure in early infancy.

Source: Hypertension, July 30; 2007 [Epub ahead of print].

A prospective study of overall diet quality and risk of type 2 diabetes in women.

TT Fung, M McCullough, RM van Dam, FB Hu

Objective: The aim of this article was to assess the association between the Alternate Healthy Eating Index (AHEI) and risk of type 2 diabetes in women.

Research Design and Methods: A total of 80,029 women aged 38-63 years in the Nurses' Health Study were followed from 1984 to 2002. The AHEI score was computed from dietary information collected from five repeated food frequency questionnaires administered between 1984 and 1998. Relative risks (RRs) for type 2 diabetes were calculated using Cox proportional hazards models and adjusted for known diabetes risk factors. We also examined how changes in score in 4, 6-8, and 10-12 years are associated with diabetes risk.

Results: We ascertained 5,183 incident cases of type 2 diabetes during 18 years of follow-up. Women who scored high on the AHEI had a lower risk (RR comparing top to bottom score quintile 0.64 [95% CI 0.58-0.71], P(trend) < 0.0001) for diabetes. Women with consistently high AHEI scores throughout follow-up, compared with those with consistently low scores, had the lowest risk for diabetes. In addition, women whose AHEI scores improved during follow-up, even during recent years, had a lower risk of diabetes than did women whose (low) score did not change.

Conclusions: A higher AHEI score is associated with a lower risk of type 2 diabetes in women. Therefore, the AHEI score may be a useful clinical tool to assess diet quality and to recommend for the prevention of diabetes.

Source: Diabetes Care, July 2007;30(7):1753-7.

Children's preference for large portions: prevalence, determinants, and consequences.

CK Colapinto, A Fitzgerald, LJ Taper, PJ Veugelers

Background: Proliferation of large portions of snack and fast foods parallels dramatic increases in childhood obesity. This study investigates the prevalence, determinants, and consequences of large portions in children's diets.

Methods: As part of the 2003 Children's Lifestyle and School-performance Study, we surveyed 4,966 children in Nova Scotia regarding their usual portion sizes of French fries, meats, vegetables, and potato chips using three-dimensional graduated food models. We measured heights and weights and assessed dietary intake with the Harvard Youth Adolescent Food Frequency Questionnaire. Diet quality was summarized using the Diet Quality Index International (DQI-I). Parents were surveyed on food habits and socioeconomic background.

Statistical Analysis: We used multilevel regression methods to examine determinants of children's large portion size choice and to evaluate the effect of this selection on energy intake, diet quality, and overweight.

Results: Children reported preference for portions of French fries, meats, and potato chips that are larger and vegetable portions that are smaller than what is recommended. Children from socio-economically disadvantaged families or who frequently eat while watching television and in fast-food restaurants preferred larger portions of French fries and potato chips. Consequences of consuming large portions of these foods included poor diet quality and increased energy intake. Consuming large portions of vegetables was associated with lower energy intake and better diet quality.

Conclusions: Successful marketing of large portions of French fries and potato chips may be at the expense of diet quality and appropriate energy intake. Policy regulations and nutrition education emphasizing appropriate portion sizes provide opportunities to prevent overweight and improve future health.

Source: J Am Diet Assoc, July 2007;107(7):1183-90.

Milk and dairy consumption, diabetes and the metabolic syndrome: the Caerphilly Prospective Study.

PC Elwood, JE Pickering, AM Fehily

Objectives: To report a negative association between milk or dairy consumption and the metabolic syndrome and to examine associations within the Caerphilly cohort.

Setting: A representative sample of men aged 45-59 years in Caerphilly, UK. Participants and data: Data on fasting blood glucose and plasma insulin, fasting plasma triglycerides and high-density lipoprotein cholesterol, body mass index, and blood pressure were used to define the metabolic syndrome in terms of levels of two or more variates within the top 10%. The clinical importance of the syndrome was assessed from 20-year incidence of diabetes, vascular events and deaths. The relationships between the syndrome and the consumption of milk and dairy products was examined using data from both a semiquantitative food frequence questionnaire, and from a 7-day weighed intake record which had been kept by a 1:3 subsample of the men.

Main Results: There were 2375 men without diabetes in the cohort. The prevalence of the metabolic syndrome was 15%. Men with the syndrome had significantly increased risks of a subsequent ischaemic heart disease event, death or diabetes. Negative relationships were shown between both the consumption of milk and dairy produce, and the syndrome. Adjusted odds ratio in men who regularly drank a pint of milk or more daily was 0.38 (0.18 to 0.78) and that for dairy food consumption was 0.44 (0.21 to 0.91). Milk intake showed no significant trend with incident diabetes.

Conclusions: The consumption of milk and dairy products is associated with a markedly reduced prevalence of the metabolic syndrome, and these items therefore fit well into a healthy eating.

Source: J Epidemiol Community Health, Aug 2007;61(8):695-8.

Psychosocial experiences of breast cancer survivors involved in a dragon boat program: exploring links to positive psychological growth.

Catherine Sabiston; Meghan H. McDonough; Peter R.E. Crocker

This study explored psychosocial experiences of breast cancer survivors involved in dragon boat programs. Twenty women (M age = 58.69, SD = 6.85) were interviewed for 45–60 min about their experiences as members of survivor dragon boat teams. Interviews were analyzed using constructivist grounded theory methods. The dragon boat program facilitated social support from women with common challenges and a shared understanding of survivorship. It also provided opportunities to (re)gain a sense of personal control, develop new identities as athletes, and overcome physical challenges. Together these elements contributed to positive psychological growth and linked to the literature on posttraumatic growth. Future physical activity interventions targeting breast cancer survivors may benefit from developing strategies that share key characteristics of dragon boating.

Source: J Sport Exerc Psychol, August 2007;29(4):419-38.

Enzymes and receptors of prostaglandin pathways with arachidonic acid-derived versus eicosapentaenoic acid-derived substrates and products.

M Wada, CJ Delong, YH Hong, et al.

Dietary fish oil containing omega3 highly unsaturated fatty acids has cardioprotective and anti-inflammatory effects. Prostaglandins (PGs) and thromboxanes are produced in vivo both from the omega6 fatty acid arachidonic acid (AA) and the omega3 fatty acid eicosapentaenoic acid (EPA). Certain beneficial effects of fish oil may result from altered PG metabolism resulting from increases in the EPA/AA ratios of precursor phospholipids. Here we report in vitro specificities of prostanoid enzymes and receptors toward EPA-derived, 3-series versus AA-derived, 2-series prostanoid substrates and products. The largest difference was seen with PG endoperoxide H synthase (PGHS)-1. Under optimal conditions purified PGHS-1 oxygenates EPA with only 10% of the efficiency of AA, and EPA significantly inhibits AA oxygenation by PGHS-1. Two- to 3-fold higher activities or potencies with 2-series versus 3-series compounds were observed with PGHS-2, PGD synthases, microsomal PGE synthase-1 and EP1, EP2, EP3, and FP receptors. Our most surprising observation was that AA oxygenation by PGHS-2 is only modestly inhibited by EPA (i.e. PGHS-2 exhibits a marked preference for AA when EPA and AA are tested together). Also unexpectedly, TxA(3) is about equipotent to TxA(2) at the TPalpha receptor. Our biochemical data predict that increasing phospholipid EPA/AA ratios in cells would dampen prostanoid signaling with the largest effects being on PGHS-1 pathways involving PGD, PGE, and PGF. Production of 2-series prostanoids from AA by PGHS-2 would be expected to decrease in proportion to the compensatory decrease in the AA content of phospholipids that would result from increased incorporation of omega3 fatty acids such as EPA.

Source: J Biol Chem, Aug 3, 2007;282(31):22254-66.

Impact of repeated dietary counseling between infancy and 14 years of age on dietary intakes and serum lipids and lipoproteins: the STRIP study.

H Niinikoski, H Lagström, E Jokinen, et al.

Background: Atherosclerosis development might be delayed or prevented by dietary measures. The aims of the present study were to evaluate the effect of low-saturated-fat, low-cholesterol dietary counseling on fat intakes, growth, serum cholesterol values, and pubertal development in children and adolescents.

Methods and Results: In the randomized prospective Special Turku Coronary Risk Factor Intervention Project (STRIP), a low-saturated-fat, low-cholesterol diet was introduced to intervention infants (n=540) at 7 months of age, and control children (n=522) received an unrestricted diet. Dietary intakes, serum cholesterol values, somatic growth, and development were followed up throughout childhood and adolescence. Saturated fat intakes, serum total cholesterol, and low-density lipoprotein cholesterol values were lower (P<0.001) in the intervention than in control children during the 14 years, whereas high-density lipoprotein cholesterol values in the 2 study groups showed no difference. Boys had lower total and low-density lipoprotein cholesterol concentrations than girls throughout childhood (P<0.001), and the intervention effect on serum cholesterol concentration was larger in boys than girls. The 2 study groups showed no difference in growth, body mass index, pubertal development, or age at menarche (median, 13.0 and 12.8 years in the intervention and control girls, respectively; P=0.52). The cholesterol values decreased as puberty progressed. Mean concentrations of total and high-density lipoprotein cholesterol decreased from approximately 4.5 and approximately 1.4 mmol/L, respectively, in Tanner stage 1 (prepubertal) boys to approximately 3.9 and approximately 1.1 mmol/L in Tanner stage 4 (late pubertal) boys.

Conclusions: Repeated dietary counseling remains effective in decreasing saturated fat and cholesterol intake and serum cholesterol values at least until 14 years of age. Puberty markedly influences serum cholesterol concentrations.

Source: Circulation. 2007 Aug 28;116(9):1032-40.

Whole grain, bran, and germ intake and risk of type 2 diabetes: a prospective cohort study and systematic review.

JS de Munter, FB Hu, D Spiegelman, et al.

Background: Control of body weight by balancing energy intake and energy expenditure is of major importance for the prevention of type 2 diabetes, but the role of specific dietary factors in the etiology of type 2 diabetes is less well established. We evaluated intakes of whole grain, bran, and germ in relation to risk of type 2 diabetes in prospective cohort studies.

Methods and Findings: We followed 161,737 US women of the Nurses' Health Studies (NHSs) I and II, without history of diabetes, cardiovascular disease, or cancer at baseline. The age at baseline was 37-65 y for NHSI and 26-46 y for NHSII. Dietary intakes and potential confounders were assessed with regularly administered questionnaires. We documented 6,486 cases of type 2 diabetes during 12-18 y of follow-up. Other prospective cohort studies on whole grain intake and risk of type 2 diabetes were identified in searches of MEDLINE and EMBASE up to January 2007, and data were independently extracted by two reviewers. The median whole grain intake in the lowest and highest quintile of intake was, respectively, 3.7 and 31.2 g/d for NHSI and 6.2 and 39.9 g/d for NHSII. After adjustment for potential confounders, the relative risks (RRs) for the highest as compared with the lowest quintile of whole grain intake was 0.63 (95% confidence interval [CI] 0.57-0.69) for NHSI and 0.68 (95% CI 0.57-0.81) for NHSII (both: p-value, test for trend <0.001). After further adjustment for body mass index (BMI), these RRs were 0.75 (95% CI 0.68-0.83; p-value, test for trend <0.001) and 0.86 (95% CI 0.72-1.02; p-value, test for trend 0.03) respectively. Associations for bran intake were similar to those for total whole grain intake, whereas no significant association was observed for germ intake after adjustment for bran. Based on pooled data for six cohort studies including 286,125 participants and 10,944 cases of type 2 diabetes, a two-serving-per-day increment in whole grain consumption was associated with a 21% (95% CI 13%-28%) decrease in risk of type 2 diabetes after adjustment for potential confounders and BMI.

Conclusions: Whole grain intake is inversely associated with risk of type 2 diabetes, and this association is stronger for bran than for germ. Findings from prospective cohort studies consistently support increasing whole grain consumption for the prevention of type 2 diabetes.

Source: PLoS Med. Aug 28, 2007;4(8):e261.

The relationship between relative weight and school attendance among elementary schoolchildren.

AB Geier, GD Foster, LG Womble, et al.

Objective: To determine the relationship between relative weight and school attendance among elementary schoolchildren.

Research Methods and Procedures: A total of 1069 fourth to sixth graders from nine elementary schools in the inner city of Philadelphia, PA, were part of an ongoing randomized control trial to assess prevention strategies for obesity. The mean rate of students eligible for free/reduced meals was 82.9 +/- 11.5%. Weight was measured in the second semester of the academic year. Absentee data for the entire academic year were recorded by homeroom teachers. Participants were classified into relative weight categories described by the Institute of Medicine: underweight, normal-weight, overweight, and obese.

Results: ANOVA showed that overweight children were absent significantly more than normal-weight children (12.2 +/- 11.7 days vs.10.1 +/- 10.5 days) (p < 0.05). Linear regression showed that the obese category remained a significant contributor to the number of days absent even after adjusting for age, race/ethnicity, and gender.

Discussion: These data suggest that in addition to the medical and psychosocial consequences of being overweight, heavier children have greater risk for school absenteeism than their normal-weight peers. As the rate of childhood obesity increases, parallel increases in school absenteeism should be expected.

Source: Obesity (Silver Spring). Aug 2007;15(8):2157-61.

Use of calcium or calcium in combination with vitamin D supplementation to prevent fractures and bone loss in people aged 50 years and older: a meta-analysis.

BM Tang, GD Eslick, C Nowson, et al.

Background: Whether calcium supplementation can reduce osteoporotic fractures is uncertain. We did a meta-analysis to include all the randomized trials in which calcium, or calcium in combination with vitamin D, was used to prevent fracture and osteoporotic bone loss.

Methods: We identified 29 randomized trials (n=63 897) using electronic databases, supplemented by a hand-search of reference lists, review articles, and conference abstracts. All randomized trials that recruited people aged 50 years or older were eligible. The main outcomes were fractures of all types and percentage change of bone-mineral density from baseline. Data were pooled by use of a random-effect model.

Findings: In trials that reported fracture as an outcome (17 trials, n=52 625), treatment was associated with a 12% risk reduction in fractures of all types (risk ratio 0.88, 95% CI 0.83-0.95; p=0.0004). In trials that reported bone-mineral density as an outcome (23 trials, n=41 419), the treatment was associated with a reduced rate of bone loss of 0.54% (0.35-0.73; p<0.0001) at the hip and 1.19% (0.76-1.61%; p<0.0001) in the spine. The fracture risk reduction was significantly greater (24%) in trials in which the compliance rate was high (p<0.0001). The treatment effect was better with calcium doses of 1200 mg or more than with doses less than 1200 mg (0.80 vs 0.94; p=0.006), and with vitamin D doses of 800 IU or more than with doses less than 800 IU (0.84 vs 0.87; p=0.03).

Interpretation: Evidence supports the use of calcium, or calcium in combination with vitamin D supplementation, in the preventive treatment of osteoporosis in people aged 50 years or older. For best therapeutic effect, we recommend minimum doses of 1200 mg of calcium, and 800 IU of vitamin D (for combined calcium plus vitamin D supplementation).

Source: Lancet. Aug 25, 2007;370(9588):657-66.

Prepregnancy obesity as a risk factor for structural birth defects.

DK Waller, GM Shaw, SA Rasmussen et al.

Objective: To describe the relation between maternal obesity, overweight and underweight status, and 16 categories of structural birth defects.

Design: An ongoing multisite, case-control study. Clinical geneticists reviewed all of the cases, excluding those that had or were strongly suspected to have a single-gene disorder or chromosomal abnormality. Mothers with preexisting diabetes were also excluded. Body mass index was based on maternal report of height and weight prior to pregnancy.

Setting: Eight participating states in the United States.

Participants: Mothers enrolled in the National Birth Defects Prevention Study who had index pregnancies between October 1, 1997, and December 31, 2002.

Main Exposure: Maternal obesity.

Main Outcome Measures: Crude and adjusted odds ratios.

Results: Mothers of offspring with spina bifida, heart defects, anorectal atresia, hypospadias, limb reduction defects, diaphragmatic hernia, and omphalocele were significantly more likely to be obese than mothers of controls, with odds ratios ranging between 1.33 and 2.10. Mothers of offspring with gastroschisis were significantly less likely to be obese than mothers of controls.

Conclusions: To our knowledge, this is the first population-based study of its scale to examine prepregnancy obesity and a range of structural birth defects. These results suggest a weak to moderate positive association of maternal obesity with 7 of 16 categories of birth defects and a strong inverse association with gastroschisis. The mechanisms underlying these associations are not yet understood but may be related to undiagnosed diabetes.

Source: Arch Pediatr Adolesc Med, Aug 2007;161(8):745-50.

Protective effect of fruits, vegetables and the Mediterranean diet on asthma and allergies among children in Crete.

L Chatzi, G Apostolaki, I Bibakis, et al.

Background: Atopy is not uncommon among children living in rural Crete, but wheeze and rhinitis are rare. A study was undertaken to examine whether this discrepancy could be attributed to a high consumption of fresh fruit and vegetables or adherence to a traditional Mediterranean diet.

Methods: A cross-sectional survey was performed in 690 children aged 7-18 years in rural Crete. Parents completed a questionnaire on their child's respiratory and allergic symptoms and a 58-item food frequency questionnaire. Adherence to a Mediterranean diet was measured using a scale with 12 dietary items. Children underwent skin prick tests with 10 common aeroallergens.

Results: 80% of children ate fresh fruit (and 68% vegetables) at least twice a day. The intake of grapes, oranges, apples, and fresh tomatoes-the main local products in Crete-had no association with atopy but was protective for wheezing and rhinitis. A high consumption of nuts was found to be inversely associated with wheezing (OR 0.46; 95% CI 0.20 to 0.98), whereas margarine increased the risk of both wheeze (OR 2.19; 95% CI 1.01 to 4.82) and allergic rhinitis (OR 2.10; 95% CI 1.31 to 3.37). A high level of adherence to the Mediterranean diet was protective for allergic rhinitis (OR 0.34; 95% CI 0.18 to 0.64) while a more modest protection was observed for wheezing and atopy.

Conclusion: The results of this study suggest a beneficial effect of commonly consumed fruits, vegetables and nuts, and of a high adherence to a traditional Mediterranean diet during childhood on symptoms of asthma and rhinitis. Diet may explain the relative lack of allergic symptoms in this population.

Source: Thorax, Aug 2007;62(8):677-83.

Vitamin D supplementation and total mortality: a meta-analysis of randomized controlled trials.

Philippe Autier, MD; Sara Gandini, PhD

Background: Ecological and observational studies suggest that low vitamin D status could be associated with higher mortality from life-threatening conditions including cancer, cardiovascular disease, and diabetes mellitus that account for 60% to 70% of total mortality in high-income countries. We examined the risk of dying from any cause in subjects who participated in randomized trials testing the impact of vitamin D supplementation (ergocalciferol [vitamin D2] or cholecalciferol [vitamin D3]) on any health condition.

Methods: The literature up to November 2006 was searched without language restriction using the following databases: PubMed, ISI Web of Science (Science Citation Index Expanded), EMBASE, and the Cochrane Library.

Results: We identified 18 independent randomized controlled trials, including 57 311 participants. A total of 4777 deaths from any cause occurred during a trial size–adjusted mean of 5.7 years. Daily doses of vitamin D supplements varied from 300 to 2000 IU. The trial size–adjusted mean daily vitamin D dose was 528 IU. In 9 trials, there was a 1.4- to 5.2-fold difference in serum 25-hydroxyvitamin D between the intervention and control groups. The summary relative risk for mortality from any cause was 0.93 (95% confidence interval, 0.87-0.99). There was neither indication for heterogeneity nor indication for publication biases. The summary relative risk did not change according to the addition of calcium supplements in the intervention.

Conclusions: Intake of ordinary doses of vitamin D supplements seems to be associated with decreases in total mortality rates. The relationship between baseline vitamin D status, dose of vitamin D supplements, and total mortality rates remains to be investigated. Population-based, placebo-controlled randomized trials with total mortality as the main end point should be organized for confirming these findings.

Source: Arch Intern Med, Sept 10, 2007;167(10):1730-1737.

The relationship of dietary carotenoid and vitamin A, E, and C intake with age-related macular degeneration in a case-control study: AREDS Report No. 22.

Age-Related Eye Disease Study Research Group, JP San Giovanni, EY Chew, et al.

Objective: To evaluate the relationship of dietary carotenoids, vitamin A, alpha-tocopherol, and vitamin C with prevalent age-related macular degeneration (AMD) in the Age-Related Eye Disease Study (AREDS).

Methods: Demographic, lifestyle, and medical characteristics were ascertained on 4519 AREDS participants aged 60 to 80 years at enrollment. Stereoscopic color fundus photographs were used to categorize participants into 4 AMD severity groups and a control group (participants with < 15 small drusen). Nutrient intake was estimated from a self-administered semiquantitative food frequency questionnaire at enrollment. Intake values were energy adjusted and classified by quintiles. The relationship between diet and AMD status was assessed using logistic regression analyses.

Results: Dietary lutein/zeaxanthin intake was inversely associated with neovascular AMD (odds ratio [OR], 0.65; 95% confidence interval [CI], 0.45-0.93), geographic atrophy (OR, 0.45; 95% CI, 0.24-0.86), and large or extensive intermediate drusen (OR, 0.73; 95% CI, 0.56-0.96), comparing the highest vs lowest quintiles of intake, after adjustment for total energy intake and non-nutrient-based covariates. Other nutrients were not independently related to AMD.

Conclusion: Higher dietary intake of lutein/zeaxanthin was independently associated with decreased likelihood of having neovascular AMD, geographic atrophy, and large or extensive intermediate drusen.

Source: Arch Ophthalmol, Sept 2007;125(9):1225-32.