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Recent research: six studies on eating habits, obesity, vitamin D, lifestyle & dementia

Here are half a dozen studies on weight, bite size, vitamin D, dietary supplements, and ways of avoiding dementia.  Andrew et al report on the "Incident cancer burden attributable to excess body mass index in 30 European countries" estimating that about 6% of cancers could be avoided if we could maintain healthier weights (abstracts & links for all six articles mentioned appear further down this page).  Zijlstra and colleagues suggest a possible response!  They randomized subjects to eating with different bite (mouthful) sizes and different chewing times.  They found that " ... greater oral sensory exposure to a product, by eating with small bite sizes rather than with large bite sizes and increasing OPT (oral processing time), significantly decreases food intake."  As Mum might put it "Don't wolf your food!"

There are then a couple of articles on one of my "pet subjects" - vitamin D.  To review a series of other studies showing that we should all be at least considering taking extra vitamin D, click here.  In this new research Kumar et al investigated vitamin D levels in a nationally representative sample of over 6,000 U.S. children and adolescents.  They found "Overall, 9% of the pediatric population, representing 7.6 million US children and adolescents, were 25(OH)D deficient and 61%, representing 50.8 million US children and adolescents, were 25(OH)D insufficient."  They went on to comment that "after multivariable adjustment, 25(OH)D deficiency was associated with elevated parathyroid hormone levels (OR: 3.6; [1.8 to 7.1]), higher systolic blood pressure (OR: 2.24 mmHg [0.98 to 3.50 mmHg]), and lower serum calcium (OR: -0.10 mg/dL [-0.15 to -0.04 mg/dL]) and high-density lipoprotein cholesterol (OR: -3.03 mg/dL [-5.02 to -1.04]) levels compared with those with 25(OH)D levels > or = 30 ng/mL. Conclusions:  25(OH)D deficiency is common in the general US pediatric population and is associated with adverse cardiovascular risks."  This in the richest country in the world!  To hammer the point home, Reis et al looked at vitamin D and health in over 3,500 U.S. adolescents.  They found that average vitamin D levels were in the insufficient range and concluded that "Low serum vitamin D in US adolescents is strongly associated with hypertension, hyperglycemia, and metabolic syndrome ... "  The situation is likely to be just as bad in many other countries including the UK - see for example Hypponen & Power

Although these papers highlight the relevance of vitamin D supplements, Myung et al's paper demonstrates that other forms of supplementation may be unhelpful.  In their antioxidants and cancer study they conclude "The meta-analysis of randomized controlled trials indicated that there is no clinical evidence to support an overall primary and secondary preventive effect of antioxidant supplements on cancer. The effects of antioxidant supplements on human health, particularly in relation to cancer, should not be overemphasized because the use of those might be harmful for some cancer."  Happily the sixth paper in this sequence (by Scarmeas et al) highlights further action we can take to safeguard our health - this time to reduce our risk of developing dementia.  They demonstrated that either good adherence to a Mediterranean style diet or vigorous exercise both reduce the risk of developing Altzheimer's disease by about a third over 5.4 years of follow up.

Isn't it great that there are so many sensible ways that we can use to help our own health!

Andrew, G. R., S. Isabelle, et al. (2009). "Incident Cancer Burden Attributable to Excess Body Mass Index in 30 European countries." International Journal of Cancer 9999(999A): NA.  [Abstract/Full Text] 
Excess adiposity is associated with increased risks of developing adult malignancies. To inform public health policy and guide further research, the incident cancer burden attributable to excess body mass index (BMI ge 25 kg/m2) across 30 European countries were estimated. Population attributable risks (PARs) were calculated using European- and sex-specific risk estimates from a published meta-analysis and sex-specific mean BMI estimates from a World Health Organization Global Infobase. Country-specific numbers of new cancers were derived from Globocan2002. A ten-year lag-period between risk exposure and cancer incidence was assumed and 95% confidence intervals (CI) were estimated in Monte Carlo simulations. In 2002, there were 2,171,351 new all cancer diagnoses in the 30 countries of Europe. Estimated PARs were 2.5% (95% CI 1.5 - 3.6%) in men and 4.1% (2.3 - 5.9%) in women. These collectively corresponded to 70,288 (95% CI 40,069 - 100,668) new cases. Sensitivity analyses revealed estimates were most influenced by the assumed shape of the BMI distribution in the population and cancer-specific risk estimates. In a scenario analysis of a plausible contemporary (2008) population, the estimated PARs increased to 3.2% (2.1 - 4.3%) and 8.6% (5.6 - 11.5%), respectively, in men and women. Endometrial, post-menopausal breast and colorectal cancers accounted for 65% of these cancers. This analysis quantifies the burden of incident cancers attributable to excess BMI in Europe. The estimates reported here provide a baseline for future modelling, and underline the need for research into interventions to control weight in the context of endometrial, breast and colorectal cancer.

Zijlstra, N., R. de Wijk, et al. (2009). "Effect of bite size and oral processing time of a semisolid food on satiation." Am J Clin Nutr 90(2): 269-275.  [Abstract/Full Text]  
Background: Food texture plays an important role in food intake regulation. In previous studies we showed a clear effect of viscosity on ad libitum food intake and found indications that eating rate, bite size, and oral processing time (OPT) could play a role. Objective: The objective was to determine the effect of bite size and OPT of a food on satiation, defined as ad libitum food intake. Design: Twenty-two healthy subjects participated in all 7 test conditions. Bite sizes were free or fixed to small bite sizes (approx 5 g) or large bite sizes (approx 15 g). OPT was free (only in combination with free bite size) or fixed to 3 or 9 s. Subjects consumed chocolate custard through a tube, which was connected to a peristaltic pump. Sound signals indicated OPT duration. Results: Subjects consumed significantly more when bite sizes were large than when they were small (bite size effect: P < 0.0001) and when OPT was 3 s rather than 9 s (OPT effect: P = 0.008). Under small bite size conditions, mean ({+/-}SD) ad libitum intakes were 382 {+/-} 197 g (3-s OPT) and 313 {+/-} 170 g (9-s OPT). Under large bite size conditions, ad libitum intakes were much higher: 476 {+/-} 176 g (3-s OPT) and 432 {+/-} 163 g (9-s OPT). Intakes during the free bite size conditions were 462 {+/-} 211 g (free OPT), 455 {+/-} 197 g (3-s OPT), and 443 {+/-} 202 g (9-s OPT). Conclusion: This study shows that greater oral sensory exposure to a product, by eating with small bite sizes rather than with large bite sizes and increasing OPT, significantly decreases food intake.

Kumar, J., P. Muntner, et al. (2009). "Prevalence and Associations of 25-Hydroxyvitamin D Deficiency in US Children: NHANES 2001-2004." Pediatrics: peds.2009-0051.  [Abstract/Full Text] 
Objectives:  To determine the prevalence of 25-hydroxyvitamin D (25[OH]D) deficiency and associations between 25(OH)D deficiency and cardiovascular risk factors in children and adolescents. Methods With a nationally representative sample of children aged 1 to 21 years in the National Health and Nutrition Examination Survey 2001-2004 (n = 6275), we measured serum 25(OH)D deficiency and insufficiency (25[OH]D <15 ng/mL and 15-29 ng/mL, respectively) and cardiovascular risk factors. Results:  Overall, 9% of the pediatric population, representing 7.6 million US children and adolescents, were 25(OH)D deficient and 61%, representing 50.8 million US children and adolescents, were 25(OH)D insufficient. Only 4% had taken 400 IU of vitamin D per day for the past 30 days. After multivariable adjustment, those who were older (odds ratio [OR]: 1.16 [95% confidence interval (CI): 1.12 to 1.20] per year of age), girls (OR: 1.9 [1.6 to 2.4]), non-Hispanic black (OR: 21.9 [13.4 to 35.7]) or Mexican-American (OR: 3.5 [1.9 to 6.4]) compared with non-Hispanic white, obese (OR: 1.9 [1.5 to 2.5]), and those who drank milk less than once a week (OR: 2.9 [2.1 to 3.9]) or used >4 hours of television, video, or computers per day (OR: 1.6 [1.1 to 2.3]) were more likely to be 25(OH)D deficient. Those who used vitamin D supplementation were less likely (OR: 0.4 [0.2 to 0.8]) to be 25(OH)D deficient. Also, after multivariable adjustment, 25(OH)D deficiency was associated with elevated parathyroid hormone levels (OR: 3.6; [1.8 to 7.1]), higher systolic blood pressure (OR: 2.24 mmHg [0.98 to 3.50 mmHg]), and lower serum calcium (OR: -0.10 mg/dL [-0.15 to -0.04 mg/dL]) and high-density lipoprotein cholesterol (OR: -3.03 mg/dL [-5.02 to -1.04]) levels compared with those with 25(OH)D levels > or = 30 ng/mL. Conclusions:  25(OH)D deficiency is common in the general US pediatric population and is associated with adverse cardiovascular risks.

Reis, J. P., D. von Muhlen, et al. (2009). "Vitamin D Status and Cardiometabolic Risk Factors in the United States Adolescent Population." Pediatrics: peds.2009-0213.  [Abstract/Full Text] 
Objective:  Evidence on the association of vitamin D with cardiovascular risk factors in youth is very limited. We examined whether low serum vitamin D levels (25-hydroxyvitamin D [25(OH)D]) are associated with cardiovascular risk factors in US adolescents aged 12 to 19 years. Methods:  We conducted a cross-sectional analysis of 3577 fasting, nonpregnant adolescents without diagnosed diabetes who participated in the 2001-2004 National Health and Nutrition Examination Survey. Cardiovascular risk factors were measured using standard methods and defined according to age-modified Adult Treatment Panel III definitions. Results:  Mean 25(OH)D was 24.8 ng/mL; it was lowest in black (15.5 ng/mL), intermediate in Mexican American (21.5 ng/mL), and highest in white (28.0 ng/mL) adolescents (P < .001 for each pairwise comparison). Low 25(OH)D levels were strongly associated with overweight status and abdominal obesity (P for trend < .001 for both). After adjustment for age, gender, race/ethnicity, BMI, socioeconomic status, and physical activity, 25(OH)D levels were inversely associated with systolic blood pressure (P = .02) and plasma glucose concentrations (P = .01). The adjusted odds ratio (95% confidence interval) for those in the lowest (<15 ng/mL) compared with the highest quartile (>26 ng/mL) of 25(OH)D for hypertension was 2.36 (1.33-4.19); for fasting hyperglycemia it was 2.54 (1.01-6.40); for low high-density lipoprotein cholesterol it was 1.54 (0.99-2.39); for hypertriglyceridemia it was 1.00 (0.49-2.04); and for metabolic syndrome it was 3.88 (1.57-9.58). Conclusions:  Low serum vitamin D in US adolescents is strongly associated with hypertension, hyperglycemia, and metabolic syndrome, independent of adiposity.

Myung, S. K., Y. Kim, et al. (2009). "Effects of antioxidant supplements on cancer prevention: meta-analysis of randomized controlled trials." Ann Oncol: mdp286.  [Abstract/Full Text] 
Background: This meta-analysis aimed to investigate the effect of antioxidant supplements on the primary and secondary prevention of cancer as reported by randomized controlled trials. Methods: We searched Medline (PubMed), Excerpta Medica database, and the Cochrane Review in October 2007. Results: Among 3327 articles searched, 31 articles on 22 randomized controlled trials, which included 161 045 total subjects, 88 610 in antioxidant supplement groups and 72 435 in placebo or no-intervention groups, were included in the final analyses. In a fixed-effects meta-analysis of all 22 trials, antioxidant supplements were found to have no preventive effect on cancer [relative risk (RR) 0.99; 95% confidence interval (CI) 0.96-1.03). Similar findings were observed in 12 studies on primary prevention trials (RR 1.00; 95% CI 0.97-1.04) and in nine studies on secondary prevention trials (RR 0.97; 95% CI 0.83-1.13). Further, subgroup analyses revealed no preventive effect on cancer according to type of antioxidant, type of cancer, or the methodological quality of the studies. On the other hand, the use of antioxidant supplements significantly increased the risk of bladder cancer (RR 1.52; 95% CI 1.06-2.17) in a subgroup meta-analysis of four trials. Conclusions: The meta-analysis of randomized controlled trials indicated that there is no clinical evidence to support an overall primary and secondary preventive effect of antioxidant supplements on cancer. The effects of antioxidant supplements on human health, particularly in relation to cancer, should not be overemphasized because the use of those might be harmful for some cancer.

Scarmeas, N., J. A. Luchsinger, et al. (2009). "Physical Activity, Diet, and Risk of Alzheimer Disease." JAMA 302(6): 627-637.  [Abstract/Full Text] 
Context Both higher adherence to a Mediterranean-type diet and more physical activity have been independently associated with lower Alzheimer disease (AD) risk but their combined association has not been investigated. Objective To investigate the combined association of diet and physical activity with AD risk. Design, Setting, and Patients Prospective cohort study of 2 cohorts comprising 1880 community-dwelling elders without dementia living in New York, New York, with both diet and physical activity information available. Standardized neurological and neuropsychological measures were administered approximately every 1.5 years from 1992 through 2006. Adherence to a Mediterranean-type diet (scale of 0-9; trichotomized into low, middle, or high; and dichotomized into low or high) and physical activity (sum of weekly participation in various physical activities, weighted by the type of physical activity [light, moderate, vigorous]; trichotomized into no physical activity, some, or much; and dichotomized into low or high), separately and combined, were the main predictors in Cox models. Models were adjusted for cohort, age, sex, ethnicity, education, apolipoprotein E genotype, caloric intake, body mass index, smoking status, depression, leisure activities, a comorbidity index, and baseline Clinical Dementia Rating score. Main Outcome Measure Time to incident AD. Results A total of 282 incident AD cases occurred during a mean (SD) of 5.4 (3.3) years of follow-up. When considered simultaneously, both Mediterranean-type diet adherence (compared with low diet score, hazard ratio [HR] for middle diet score was 0.98 [95% confidence interval {CI}, 0.72-1.33]; the HR for high diet score was 0.60 [95% CI, 0.42-0.87]; P = .008 for trend) and physical activity (compared with no physical activity, the HR for some physical activity was 0.75 [95% CI, 0.54-1.04]; the HR for much physical activity was 0.67 [95% CI, 0.47-0.95]; P = .03 for trend) were associated with lower AD risk. Compared with individuals neither adhering to the diet nor participating in physical activity (low diet score and no physical activity; absolute AD risk of 19%), those both adhering to the diet and participating in physical activity (high diet score and high physical activity) had a lower risk of AD (absolute risk, 12%; HR, 0.65 [95% CI, 0.44-0.96]; P = .03 for trend). Conclusion In this study, both higher Mediterranean-type diet adherence and higher physical activity were independently associated with reduced risk for AD.

 

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