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

Soft drinks, fructose consumption, and the risk of gout in men: prospective cohort study.

Hyon K Choi, Gary Curhan

Objective: To examine the relation between intake of sugar sweetened soft drinks and fructose and the risk of incident gout in men.

Design: Prospective cohort over 12 years.

Setting: Health professionals follow-up study.

Participants: 46 393 men with no history of gout at baseline who provided information on intake of soft drinks and fructose through validated food frequency questionnaires.

Main Outcome Measure: Incident cases of gout meeting the American College of Rheumatology survey criteria for gout.

Results: During the 12 years of follow-up 755 confirmed incident cases of gout were reported. Increasing intake of sugar sweetened soft drinks was associated with an increasing risk of gout. Compared with consumption of less than one serving of sugar sweetened soft drinks a month the multivariate relative risk of gout for 5-6 servings a week was 1.29 (95% confidence interval 1.00 to 1.68), for one serving a day was 1.45 (1.02 to 2.08), and for two or more servings a day was 1.85 (1.08 to 3.16; P for trend=0.002). Diet soft drinks were not associated with risk of gout (P for trend=0.99). The multivariate relative risk of gout according to increasing fifths of fructose intake were 1.00, 1.29, 1.41, 1.84, and 2.02 (1.49 to 2.75; P for trend <0.001). Other major contributors to fructose intake such as total fruit juice or fructose rich fruits (apples and oranges) were also associated with a higher risk of gout (P values for trend <0.05).

Conclusions: Prospective data suggest that consumption of sugar sweetened soft drinks and fructose is strongly associated with an increased risk of gout in men. Furthermore, fructose rich fruits and fruit juices may also increase the risk. Diet soft drinks were not associated with the risk of gout.

Source: Br Med J. Jan 2008 [Epub ahead of print].

Cardiorespiratory fitness and adiposity as mortality predictors in older adults.

X Sui, MJ LaMonte, JN Laditka, et al.

Context: Although levels of physical activity and aerobic capacity decline with age and the prevalence of obesity tends to increase with age, the independent and joint associations among fitness, adiposity, and mortality in older adults have not been adequately examined.

Objective: To determine the association among cardiorespiratory fitness ("fitness"), adiposity, and mortality in older adults.

Design, Setting and Patients: Cohort of 2603 adults aged 60 years or older (mean age, 64.4 [SD, 4.8] years; 19.8% women) enrolled in the Aerobics Center Longitudinal Study who completed a baseline health examination during 1979-2001. Fitness was assessed by a maximal exercise test, and adiposity was assessed by body mass index (BMI), waist circumference, and percent body fat. Low fitness was defined as the lowest fifth of the sex-specific distribution of maximal treadmill exercise test duration. The distributions of BMI, waist circumference, and percent body fat were grouped for analysis according to clinical guidelines.

Main Outcome Measure: All-cause mortality through December 31, 2003.

Results: There were 450 deaths during a mean follow-up of 12 years and 31 236 person-years of exposure. Death rates per 1000 person-years, adjusted for age, sex, and examination year were 13.9, 13.3, 18.3, and 31.8 across BMI groups of 18.5-24.9, 25.0-29.9, 30.0-34.9, and > or =35.0, respectively (P = .01 for trend); 13.3 and 18.2 for normal and high waist circumference (> or =88 cm in women; > or =102 cm in men) (P = .004); 13.7 and 14.6 for normal and high percent body fat (> or =30% in women; > or =25% in men) (P = .51); and 32.6, 16.6, 12.8, 12.3, and 8.1 across incremental fifths of fitness (P < .001 for trend). The association between waist circumference and mortality persisted after further adjustment for smoking, baseline health status, and BMI (P = .02) but not after additional adjustment for fitness (P = .86). Fitness predicted mortality risk after further adjustment for smoking, baseline health, and either BMI, waist circumference, or percent body fat (P < .001 for trend).

Conclusions: In this study population, fitness was a significant mortality predictor in older adults, independent of overall or abdominal adiposity. Clinicians should consider the importance of preserving functional capacity by recommending regular physical activity for older individuals, normal-weight and overweight alike.

Source: JAMA. Dec 5, 2007;298(21):2507-16.

Diet and physical activity in lung cancer risk prediction for current, former, and never smokers.

M.R. Forman, C. Etzel, S. Mahabir, et al.

The potential public health benefits of individualized estimates of the probability of developing lung cancer are large. Using data from an ongoing case-control study, we recently developed separate epidemiologic risk assessment models for lung cancer in current, former, and never smokers. Exposures to second-hand smoke and to dust, family history of cancer, history of respiratory disease in the index patient, and smoking history were strong risk factors. These models had only modest discriminatory power and did not include data on diet or physical activity. We have therefore expanded the model to evaluate the added benefit of incorporating these variables. Lung cancer patients were recruited from the University of Texas M.D. Anderson Cancer Center, while healthy controls, who were matched on cases by age, gender, ethnicity and smoking status, were recruited at the Kelsey Seybold Clinics, the largest private physician group in the greater Houston area. Dietary data were collected on patients for the year prior to diagnosis and on controls for the year prior to interview using a 129-item modified National Cancer Institute-Block food frequency questionnaire, and responses were categorized according to the 2006 USDA guideline for pyramid food groups. Physical activity was reported for sports and other forms throughout adult years. We developed multiple variable models using backward elimination (P < 0.10) for diet and physical activity while retaining the original risk factors by smoking status. Among never smokers, the odds ratios (O.R.) for lung cancer were O.R. = 2.09 (95% CI 1.03, 4.21) and an O.R. = 2.15 (95% CI 1.17, 3.95) for participants who ate three servings or less than three servings of green salad per week, respectively, compared to those who consumed 4+ servings; and working in the garden once or twice per week, compared to those who did not report gardening, reduced risk by 40 to 46%. A similar model appeared for former smokers. Among current smokers, the O.R. of lung cancer was: 2.73 (95% CI 1.44,4.18) for consumption of three or fewer servings of carrots per week, compared to those who reported 4+ servings, and gardening once again reduced risk by 33 to 45%. Our new risk prediction models have a discriminatory power of 64%, 67%, and 71% respectively for never, former and current smokers, and were statistically significantly better than baseline models. This is the first lung cancer risk prediction model that examines both diet and physical activity, using the USDA pyramid serving guidelines and therefore provides easily applicable public health modalities for intervention strategies.

Source: Abstract No. B143, Frontiers in Cancer Prevention Research, Dec. 2-8, 2007 in Philadelphia.

Early determinants of fruit and vegetable acceptance.

CA Forestell, JA Mennella

Objective: Our goal was to evaluate the effects of breastfeeding and dietary experiences on acceptance of a fruit and a green vegetable by 4- to 8-month-old infants.

Methods: Forty-five infants, 44% of whom were breastfed, were assigned randomly to 1 of 2 treatment groups. One group was fed green beans, and the other was fed green beans and then peaches at the same time of day for 8 consecutive days. Acceptance of both foods, as determined by a variety of measures, was assessed before and after the home-exposure period.

Results: During the initial exposure, infants ate more calories from peaches than from green beans. Breastfed infants showed greater liking of peaches, as did their mothers, who ate more fruits in general than did mothers who formula fed. Although formula-feeding mothers ate more green beans, there was no difference in their infants' acceptance of this vegetable. For breastfed and formula-fed infants, repeated dietary exposure to green beans, with or without peaches, resulted in greater consumption of green beans (56.8 vs 93.6 g). Only infants who experienced green beans with peaches displayed fewer facial expressions of distaste during feeding. Mothers were apparently unaware of these changes in acceptance.

Conclusions: Breastfeeding confers an advantage in initial acceptance of a food, but only if mothers eat the food regularly. Once weaned, infants who receive repeated dietary exposure to a food eat more of it and may learn to like its flavor. However, because infants innately display facial expressions of distaste in response to certain flavors, caregivers may hesitate to continue offering these foods. Mothers should be encouraged to provide their infants with repeated opportunities to taste fruits and vegetables and should focus not only on their infants' facial expressions but also on their willingness to continue feeding.

Source: Pediatrics. Dec 2007;120(6):1247-54.

Prospective study of cured meats consumption and risk of chronic obstructive pulmonary disease in men.

R Varraso, R Jiang, RG Barr, et al.

Cured meats are high in nitrites. Nitrites generate reactive nitrogen species that may cause damage to the lung. The objective is to assess the relation between frequent consumption of cured meats and the risk of newly diagnosed chronic obstructive pulmonary disease (COPD). Between 1986 and 1998, the authors identified 111 self-reported cases of newly diagnosed COPD among 42,915 men from the Health Professionals Follow-up Study. The cumulative average intake of cured meats consumption (processed meats, bacon, hot dogs) was calculated from food frequency questionnaires administrated in 1986, 1990, and 1994 and divided according to servings per week (never/almost never, <1 serving/week, 1-3 servings/week, 4-6 servings/week, at least once/day). After adjustment for age, smoking status, pack-years, pack-years squared, energy intake, race/ethnicity, US region, body mass index, and physical activity, the consumption of cured meats was positively associated with the risk of newly diagnosed COPD (for highest vs. lowest intake: relative risk = 2.64, 95% confidence interval: 1.39, 5.00; p(trend) = 0.002). In contrast to these findings, the consumption of cured meats was not associated with the risk of adult-onset asthma. These data suggest that cured meat may worsen the adverse effects of smoking on risk of COPD.

Source: Am J Epidemiol. Dec 15, 2007;166(12):1438-45.

Mediterranean Dietary Pattern and Prediction of All-Cause Mortality in a US Population: Results From the NIH-AARP Diet and Health Study.

PN Mitrou, V Kipnis, AC Thiébaut, et al.

Background: The Mediterranean diet has been suggested to play a beneficial role for health and longevity. However, to our knowledge, no prospective US study has investigated the Mediterranean dietary pattern in relation to mortality.

Methods: Study participants included 214 284 men and 166 012 women in the National Institutes of Health (NIH)-AARP (formerly known as the American Association of Retired Persons) Diet and Health Study. During follow-up for all-cause mortality (1995-2005), 27 799 deaths were documented. In the first 5 years of follow-up, 5985 cancer deaths and 3451 cardiovascular disease (CVD) deaths were reported. We used a 9-point score to assess conformity with the Mediterranean dietary pattern (components included vegetables, legumes, fruits, nuts, whole grains, fish, monounsaturated fat-saturated fat ratio, alcohol, and meat). We calculated hazard ratios (HRs) and 95% confidence intervals (CIs) using age- and multivariate-adjusted Cox models.

Results: The Mediterranean diet was associated with reduced all-cause and cause-specific mortality. In men, the multivariate HRs comparing high to low conformity for all-cause, CVD, and cancer mortality were 0.79 (95% CI, 0.76-0.83), 0.78 (95% CI, 0.69-0.87), and 0.83 (95% CI, 0.76-0.91), respectively. In women, an inverse association was seen with high conformity with this pattern: decreased risks that ranged from 12% for cancer mortality to 20% for all-cause mortality (P = .04 and P < .001, respectively, for the trend). When we restricted our analyses to never smokers, associations were virtually unchanged.

Conclusion: These results provide strong evidence for a beneficial effect of higher conformity with the Mediterranean dietary pattern on risk of death from all causes, including deaths due to CVD and cancer, in a US population.

Source: Arch Intern Med. Dec 10, 2007;167(22):2461-8.

Weight loss in overweight Mexican American children: a randomized, controlled trial.

Johnston CA, Tyler C, McFarlin BK, et al.

Objectives: Childhood overweight has increased significantly in the past 20 years, with the highest rates noted among Mexican Americans. Although this minority group is in significant need of intervention, few programs have demonstrated actual decreases in weight. In this study we evaluated an intensive healthy lifestyle program designed to result in weight reduction for overweight Mexican American children. We hypothesized that children randomly assigned to an intensive intervention would significantly reduce their standardized BMI when compared with children randomly assigned to a self-help condition.

Patients and Methods: A total of 60 children (33 boys; 55%) between the ages of 10 and 14 years at or above the 85th percentile for BMI were randomly assigned to a 6-month intensive-intervention or self-help condition.

Results: Children in the intensive-intervention condition significantly reduced their standardized BMI when compared with the children in the self-help condition. The change in standardized BMI was significantly different at both 3 and 6 months, with intensive-intervention participants showing greater decreases in weight.

Conclusions: Overall, the results were promising, suggesting that an intensive, individualized intervention may be an effective means for promoting weight loss in overweight Mexican American children.

Source: Pediatrics. 2007 Dec;120(6):e1450-7.

Green tea consumption and prostate cancer risk in Japanese men: a prospective study.

N Kurahashi, S Sasazuki, M Iwasaki, et al.

The incidence of prostate cancer is much lower in Asian than Western populations. Given that environmental factors such as dietary habits may play a major role in the causation of prostate cancer and the high consumption of green tea in Asian populations, this low incidence may be partly due to the effects of green tea. The JPHC Study (Japan Public Health Center-based Prospective Study) was established in 1990 for cohort I and in 1993 for cohort II. The subjects were 49,920 men aged 40-69 years who completed a questionnaire that included their green tea consumption habit at baseline and were followed until the end of 2004. During this time, 404 men were newly diagnosed with prostate cancer, of whom 114 had advanced cases, 271 were localized, and 19 were of an undetermined stage. Green tea was not associated with localized prostate cancer. However, consumption was associated with a dose-dependent decrease in the risk of advanced prostate cancer. The multivariate relative risk was 0.52 (95% confidence interval: 0.28, 0.96) for men drinking 5 or more cups/day compared with less than 1 cup/day (p(trend) = 0.01). Green tea may be associated with a decreased risk of advanced prostate cancer.

Source: Am J Epidemiol. Jan 1, 2008;167(1):71-7.

Effect of physical activity on menopausal symptoms among urban women.

DB Nelson, MD Sammel, EW Freeman, et al.

Purpose: To determine whether physical activity, measured by expended kilocalories per week (kcal.wk), decreases the risk of menopausal symptoms among African American and Caucasian women.

Methods: Level of physical activity and menopausal symptoms, including hot flashes, depression, anxiety, stress, and vasomotor, physiological, and somatic symptom summaries were measured in 401 women during an 8-yr period. Tertiles of physical activity at each assessment were defined as kilocalories per week: top third (>or= 1450 kcal x wk(-1)), middle third (< 1450 to 644 kcal x wk(-1)), and bottom third (< 644 kcal x wk(-1)). Regression models were used to estimate the independent effect of physical activity at each time period on menopausal symptoms after adjusting for covariates and hormone levels. Results were also stratified by race, smoking status, and menopausal status.

Results: Overall, only perceived stress was related to level of physical activity, with women in both the middle and top tertiles of physical activity reporting lower mean levels of stress compared with women in the lowest tertile of activity. In the analysis by menopausal stage, active postmenopausal women continued to report lower mean levels of anxiety, stress, and depressive symptoms compared with inactive postmenopausal women. We did not find an association between level of physical activity and reports of hot flashes, even after adjusting for the variability in the hormonal changes.

Conclusions: Among a cohort of community-dwelling women, high levels of physical activity were related to lower levels of stress during an 8-yr follow-up period. In addition, levels of anxiety, stress, and depression were lowest among physically active postmenopausal women compared with inactive women in the same menopausal grouping.

Source: Med Sci Sports Exerc. 2008 Jan;40(1):50-8.

Treating hot flushes in menopausal women with homeopathic treatment-Results of an observational study.

M Bordet, A Colas, P Marijnen, et al.

Objective: There is great controversy concerning treatment for menopausal symptoms. We evaluated homeopathic treatments for hot flushes and their effect on quality of life in menopausal women.

Methods: Open, multi-national prospective, pragmatic and non-comparative observational study of homeopathic treatments prescribed and their effectiveness, observing their impact on quality of life.

Results: Ninety-nine physicians in 8 countries took part in this study and included 438 patients with an average age of 55. Homeopathic medicines were prescribed to all patients; 98% of the prescription lines were for homeopathic medicines. Lachesis mutus, Belladonna, Sepia officinalis, Sulphur and Sanguinaria canadensis were the most prescribed. A non-homeopathic treatment and/or food supplement prescribed for 5% of the patients. This observational study revealed a significant reduction (p<0.001) in the frequency of hot flushes by day and night and a significant reduction in the daily discomfort they caused (mean fall of 3.6 and 3.8 points respectively, on a 10cm visual analogue scale; p<0.001). Ninety percent of the women reported disappearance or lessening of their symptoms, these changes mostly taking place within 15 days of starting homeopathic treatment.

Conclusions: The results of this observational study suggest that homeopathic treatment for hot flushes in menopausal women is effective. Further studies including randomized controlled trials should be conducted.

Source: Homeopathy. 2008 Jan;97(1):10-5.

Broccoli: a unique vegetable that protects mammalian hearts through the redox cycling of the thioredoxin superfamily.

Subhendu Mukherjee, Hiranmoy Gangopadhyay, Dipak K. Das

Epidemiological evidence indicates several health benefits of the consumption of broccoli, especially related to chemoprevention. Because broccoli contains high amounts of selenium and glucosinolates (particularly glucoraphanin and isothiocyanate sulforaphane), which can produce redox-regulated cardioprotective protein thioredoxin (Trx), it was reasoned that consumption of broccoli could be beneficial to the heart. To test this hypothesis, a group of rats were fed broccoli (slurry made with water) through gavaging; control animals were gavaged water only. After 30 days, the rats were sacrificed; isolated hearts perfused via working mode were made ischemic for 30 min followed by 2 h of reperfusion. The results demonstrated significant cardioprotection with broccoli as evidenced by improved postischemic ventricular function, reduced myocardial infarct size, and decreased cardiomyocyte apoptosis accompanied by reduced cytochrome c release and increased pro-caspase 3 activities. Ischemia/reperfusion reduced both RNA transcripts and protein levels of the thioredoxin superfamily including Trx1, Trx2, glutaredoxin Grx1, Grx2, and peroxiredoxin (Prdx), which were either restored or enhanced with broccoli. Broccoli enhanced the expression of Nrf2, a cytosolic suppressor of Keap1, suggesting a role of antioxidant response element (ARE) in the induction of Trx. Additionally, broccoli induced the expression of another cardioprotective protein, heme oxygenase (HO)-1, which could be transactivated during the activation of Trx. Examination of the survival signal revealed that broccoli caused the phosphorylation of Akt and the induction of Bcl2 in concert with the activation of redox-sensitive transcription factor NFκB and Src kinase, indicating a role of Akt, Bcl2, and cSrc in the generation of survival signal. Taken together, the results of the present study indicate that the consumption of broccoli triggers cardioprotection by generating a survival signal through the activation of several survival proteins and by redox cycling of thioredoxins.

Source: J Agric Food Chem. 2008;56(2):609-17.

Cranberries for preventing urinary tract infections.

RG Jepson, JC Craig.

Background: Cranberries have been used widely for several decades for the prevention and treatment of urinary tract infections (UTIs).

Objectives: To assess the effectiveness of cranberry products in preventing UTIs in susceptible populations.

Search Strategy: We searched MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials (CENTRAL in The Cochrane Library) and the Internet. We contacted companies involved with the promotion and distribution of cranberry preparations and checked reference lists of review articles and relevant studies.

Date of Last Search: January 2007.

Selection Criteria: All randomized controlled trials (RCTs) or quasi-RCTs of cranberry products for the prevention of UTIs in all populations.

Data Collection and Analysis: Two authors independently assessed and extracted information. Information was collected on methods, participants, interventions and outcomes (UTIs - symptomatic and asymptomatic, side effects, adherence to therapy). Relative risk (RR) were calculated where appropriate, otherwise a narrative synthesis was undertaken. Quality was assessed using the Cochrane criteria.

Main Results: Ten studies (n = 1049, five cross-over, five parallel group) were included. Cranberry/cranberry-lingonberry juice versus placebo, juice or water was evaluated in seven studies, and cranberries tablets versus placebo in four studies (one study evaluated both juice and tablets). Cranberry products significantly reduced the incidence of UTIs at 12 months (RR 0.65, 95% CI 0.46 to 0.90) compared with placebo/control. Cranberry products were more effective reducing the incidence of UTIs in women with recurrent UTIs, than elderly men and women or people requiring catheterisation. Six studies were not included in the meta-analyses due to methodological issues or lack of available data. However, only one reported a significant result for the outcome of symptomatic UTIs. Side effects were common in all studies, and dropouts/withdrawals in several of the studies were high.

Authors' Conclusions: There is some evidence that cranberry juice may decrease the number of symptomatic UTIs over a 12 month period, particularly for women with recurrent UTIs. It's effectiveness for other groups is less certain. The large number of dropouts/withdrawals indicates that cranberry juice may not be acceptable over long periods of time. It is not clear what is the optimum dosage or method of administration (e.g. juice, tablets or capsules). Further properly designed studies with relevant outcomes are needed.

Source: Cochrane Database of Systematic Reviews 2008,1:CD001321.

Exercise capacity and mortality in Black and White men.

P Kokkinos, J Myers, JP Kokkinos, et al.

Exercise capacity is inversely related to mortality risk in healthy individuals and those with cardiovascular diseases. This evidence is based largely on white populations, with little information available for blacks. Methods and Results-We assessed the association between exercise capacity and mortality in black (n=6749; age, 58+/-11 years) and white (n=8911; age, 60+/-11 years) male veterans with and without cardiovascular disease who successfully completed a treadmill exercise test at the Veterans Affairs Medical Centers in Washington, DC, and Palo Alto, Calif. Fitness categories were based on peak metabolic equivalents (METs) achieved. Subjects were followed up for all-cause mortality for 7.5+/-5.3 years. Among clinical and exercise test variables, exercise capacity was the strongest predictor of risk for mortality. The adjusted risk was reduced by 13% for every 1-MET increase in exercise capacity (hazard ratio, 0.87; 95% confidence interval, 0.86 to 0.88; P<0.001). Compared with those who achieved <5 METs, the mortality risk was approximately 50% lower for those with an exercise capacity of 7.1 to 10 METs (hazard ratio, 0.51; 95% confidence interval, 0.47 to 0.56; P<0.001) and 70% lower for those achieving >10 METs (hazard ratio, 0.31; 95% confidence interval, 0.26 to 0.36; P<0.001). The findings were similar for those with and without cardiovascular disease and for both races. Conclusions-Exercise capacity is a strong predictor of all-cause mortality in blacks and whites. The relationship was inverse and graded, with a similar impact on mortality outcomes for both blacks and whites.

Source: Circulation. 2008 Jan 22 [Epub ahead of print].

Dietary intake and the development of the metabolic syndrome. The Atherosclerosis Risk in Communities study.

PL Lutsey, LM Steffen, J Stevens

The role of diet in the origin of metabolic syndrome (MetSyn) is not well understood; thus, we sought to evaluate the relationship between incident MetSyn and dietary intake using prospective data from 9514 participants (age, 45 to 64 years) enrolled in the Atherosclerosis Risk in Communities (ARIC) study. Methods and Results-Dietary intake was assessed at baseline via a 66-item food frequency questionnaire. We used principal-components analysis to derive "Western" and "prudent" dietary patterns from 32 food groups and evaluated 10 food groups used in previous studies of the ARIC cohort. MetSyn was defined by American Heart Association guidelines. Proportional-hazards regression was used. Over 9 years of follow-up, 3782 incident cases of MetSyn were identified. After adjustment for demographic factors, smoking, physical activity, and energy intake, consumption of a Western dietary pattern (Ptrend=0.03) was adversely associated with incident MetSyn. After further adjustment for intake of meat, dairy, fruits and vegetables, refined grains, and whole grains, analysis of individual food groups revealed that meat (Ptrend<0.001), fried foods (Ptrend=0.02), and diet soda (Ptrend=< 0.001) also were adversely associated with incident MetSyn, whereas dairy consumption (Ptrend=0.006) was beneficial. No associations were observed between incident MetSyn and a prudent dietary pattern or intakes of whole grains, refined grains, fruits and vegetables, nuts, coffee, or sweetened beverages. Conclusions-These prospective findings suggest that consumption of a Western dietary pattern, meat, and fried foods promotes the incidence of MetSyn, whereas dairy consumption provides some protection. The diet soda association was not hypothesized and deserves further study.

Source: Circulation. 2008 Jan 22 [Epub ahead of print].

The association between physical activity in leisure time and leukocyte telomere length.

LF Cherkas, JL Hunkin, BS Kato, et al.

Background: Physical inactivity is an important risk factor for many aging-related diseases. Leukocyte telomere dynamics (telomere length and age-dependent attrition rate) are ostensibly a biological indicator of human aging. We therefore tested the hypothesis that physical activity level in leisure time (over the past 12 months) is associated with leukocyte telomere length (LTL) in normal healthy volunteers.

Methods: We studied 2401 white twin volunteers, comprising 2152 women and 249 men, with questionnaires on physical activity level, smoking status, and socioeconomic status. Leukocyte telomere length was derived from the mean terminal restriction fragment length and adjusted for age and other potential confounders.

Results: Leukocyte telomere length was positively associated with increasing physical activity level in leisure time (P < .001); this association remained significant after adjustment for age, sex, body mass index, smoking, socioeconomic status, and physical activity at work. The LTLs of the most active subjects were 200 nucleotides longer than those of the least active subjects (7.1 and 6.9 kilobases, respectively; P = .006). This finding was confirmed in a small group of twin pairs discordant for physical activity level (on average, the LTL of more active twins was 88 nucleotides longer than that of less active twins; P = .03).

Conclusions: A sedentary lifestyle (in addition to smoking, high body mass index, and low socioeconomic status) has an effect on LTL and may accelerate the aging process. This provides a powerful message that could be used by clinicians to promote the potentially anti-aging effect of regular exercise.

Source: Arch Intern Med. 2008 Jan 28;168(2):154-8.

Examining an integrative model of physical activity and healthy eating self-perceptions and behaviors among adolescents.

Sabiston CM, Crocker PR

Purpose: This study tested a comprehensive model of physical activity and healthy eating behavior.

Methods: A sample of older adolescents (boys n = 206, girls n = 326) volunteered to complete a scientifically supported questionnaire assessing physical activity and healthy eating perceptions of competence, values, and behaviors once during class time.

Results: Confirmatory factor analysis suggested the data fit the model well. Tests of group differences supported factorial invariance, and revealed higher physical activity perceptions of competence, value, and behavior as well as lower healthy diet value and behavior for adolescent boys compared with girls. Perceptions of competence for healthy diet were also higher among boys. Path modeling demonstrated a good model fit, whereby behavior-specific perceptions of competence and values were significant correlates of physical activity for the total sample and subsamples of boys and girls (R(2) = .41-.53). Perceptions of competence and values were also significant correlates of healthy diet for the total sample (R(2) = .34) and boys (R(2) = .42). Subjective values were significant correlates of healthy diet for girls (R(2) = .30). Structural invariance suggested that the models were not significantly different for adolescent boys and girls.

Conclusions: These results demonstrate the saliency of the comprehensive model in understanding physical activity and healthy eating behaviors among older adolescents. Further tests of the model are needed to advance theory exploring both physical activity and healthy eating behaviors, and to inform intervention strategies targeting adolescent health.

Source: J Adolesc Health. 2008 Jan;42(1):64-72.