Nanci S. Guest

University of Toronto

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Ahmed El‐Sohemy

University of Toronto

Bibiana García‐Bailo

General Mills (United States)

Mary Rozga

Academy of Nutrition and Dietetics

Sudha Raj

Syracuse University

Matthew J. Landry

University of California, Irvine

Katelyn Senkus

University of Alabama

Roman Pawlak

East Carolina University

Marc Sicova

University of Toronto

Ann Reed Mangels

Santa Cruz County Office of Education

Deepa Handu

Academy of Nutrition and Dietetics

Cooperative Institutions

University of Toronto

University of Padua

University College London

Committee on Publication Ethics

Gdansk University of Physical Education and Sport

University of Cape Town

Sports Science Institute of South Africa

Liverpool John Moores University

University of Bologna

Universidad Rovira i Virgili

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Genetic Modifiers of Caffeine and Endurance Performance in Athletes

Nanci S. Guest

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Genetic variation related to caffeine metabolism or response during exercise

Journal of the International Society of Sports Nutrition (2015)

Nanci S. Guest Joseph Jamnik Christopher J. Womack Ahmed El‐Sohemy

Methods We examined whether a panel of 25 SNPs in 19 genes that might be related to caffeine metabolism or response modified exercise performance, or were associated with any physiologic outcomes during exercise. Subjects were trained male cyclists (n = 33) who underwent a doubleblind placebo-controlled crossover trial to test the effects of caffeine (6 mg/kg) on various performance parameters during a computer-simulated 40 km time trial. The 25 SNPs were genotyped using the Sequenom MassARRAY system, and caffeine-genotype interactions on time trial time, VO2 max, heart rate, respiratory exchange ratio and rate of perceived exertion were assessed using repeated measures analysis of variance.

Clinical nutrition

Variation (astronomy)

Sports medicine

10.1186/1550-2783-12-s1-p53

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Citations (1)

Effect of Caffeine on Endurance Performance in Athletes May Depend on HTR2A and CYP1A2 Genotypes

The Journal of Strength and Conditioning Research (2020)

Nanci S. Guest Paul Corey Pascal N. Tyrrell Ahmed El‐Sohemy

Guest, NS, Corey, P, Tyrrell, PN, and El-Sohemy, A. Effect of caffeine on endurance performance in athletes may depend on HTR2A and CYP1A2 genotypes. J Strength Cond Res 36(9): 2486-2492, 2022-This investigation determined whether variation in the HTR2A (serotonin receptor) gene modifies the ergogenic effects of caffeine on endurance and further modifies performance by the CYP1A2 genotype. Male athletes ( n = 100; 25 ± 4 years) completed 10-km cycling time trials under 3 conditions as follows: 0, 2, or 4 mg of caffeine per kg body mass. Using a randomized, double-blinded, placebo-controlled design, data were analyzed using analysis of covariance to compare changes in cycling time between placebo (0 mg·kg -1 ) and each caffeine dose and adjusted for the placebo trial and order of treatment. A significance of ρ ≤ 0.05 was used. Subjects were genotyped for HTR2A (rs6313) and CYP1A2 (rs762551). A significant caffeine- HTR2A interaction ( p = 0.003) was observed; however, after adjustment for placebo trials, the interaction was no longer significant ( p = 0.37). Because of the strong caffeine- CYP1A2 interaction ( p < 0.0001) previously reported in these subjects, where the 4-mg dose resulted in divergent effects (slower and faster) on the 10-km cycling time, we conducted a simplified model to examine these same factors by the HTR2A genotype. The post hoc analysis excluded HTR2A CT heterozygotes and 2-mg·kg -1 caffeine trials. Among CYP1A2 fast metabolizers alone, a significant difference (1.7 minutes; p = 0.006) was observed when comparing (4- vs. 0-mg·kg -1 caffeine trials) between the HTR2A CC ( n = 16; 2.4 minutes) and TT ( n = 7; 0.7 minutes) genotypes. Our results show that 4-mg·kg -1 caffeine improves performance in individuals with the HTR2A CC genotype but only in those who are also CYP1A2 AA fast metabolizers. This study was registered with clinicaltrials.gov (NCT02109783).

10.1519/jsc.0000000000003665

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International society of sports nutrition position stand: caffeine and exercise performance

Journal of the International Society of Sports Nutrition (2021)

Nanci S. Guest Trisha A. VanDusseldorp Michael T. Nelson Jozo Grgić Brad J. Schöenfeld

Following critical evaluation of the available literature to date, The International Society of Sports Nutrition (ISSN) position regarding caffeine intake is as follows:

Clinical nutrition

Sports medicine

Sports nutrition

10.1186/s12970-020-00383-4

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Applying Genomics for Personalized Nutrition in Clinical Practice

Oxford University Press eBooks (2019)

Nanci S. Guest Joseph Jamnik Bibiana García‐Bailo Daiva E. Nielsen Ahmed El‐Sohemy

The role of genetic variation in influencing an individual’s response to diet and nutritional interventions is being increasingly recognized in nutrition research and practice. Discoveries in the field of nutrigenomics and nutrigenetics have paved the way for personalized nutrition by enabling us to tailor dietary recommendations to an individual’s genotype. This level of personalization is expected to hold great benefit by better aligning dietary recommendations with an individual’s requirements and potentially motivating favorable dietary changes that impact chronic disease risk. In this review, we discuss key findings in the field of nutritional genomics, issues surrounding genetic testing for personalized nutrition, and the role health care providers will play in delivering the science to individuals.

Nutrigenomics

Personalized Medicine

10.1093/med/9780190933043.003.0027

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P14-078-23 Relationships Between Vegetarian or Vegan Dietary Patterns and Body Mass Index in the General Population: An Umbrella Review of Systematic Reviews

Current Developments in Nutrition (2023)

Mary Rozga Katelyn Senkus Nanci S. Guest Matthew J. Landry Sudha Raj

Objectives: American dietary quality (DQ), measured by the Healthy Eating Index (HEI), has remained stable and low since 2005 (∼56-60/100).The Dietary Guidelines for Americans 2020-2025 call for dietary pattern analysis to determine how guidelines might be altered to increase healthful eating.This study sought to determine the DQ of popular fad dietary patterns and the potential for improving their DQ, while staying within fad diet parameters.Methods: Two independent researchers determined a standard "fad diet" definition.Google Explore © was searched for popular diets, using search terms derived from the established definition.Nine dietary patterns were identified for inclusion.One-week sample menus were created for each by altering a DGAcompliant menu based on the fad diet's rules.Dietary analyses used the Automated Self-Administered 24-hour (ASA24 ® ) Dietary Assessment Tool and HEI 2015.Menu data were extracted and analyzed with SAS software (v8), using National Cancer Institute HEI 2015 code.Outcomes included HEI total scores, total available calories, adequacy, and moderation.Micronutrient analyses included calculating means and standard deviations compared to Dietary Reference Intakes for 19-50 yr old males and females.Results: The Ketogenic, Plant-based/Vegan, Fasting, Carnivore, Liquid, Military, Low-FODMAP, and Paleo Diets were included.Total HEI 2015 scores ranged from 26.7 (Carnivore) to 89.1 (Low-FODMAP).The six highest total HEI scores ranged from 77.1-89.1 out of 100 points.Scores for Carnivore and Liquid Diets were below average HEI ranges for Americans.Total kcals were the highest in the Liquid Diet (2143 kcal/d) and lowest in the Carnivore Diet (3102 kcal/d).Overall, adherence was high among adequacy components for fruits, vegetables, and protein, but low for whole grains.Sodium scores indicated submaximal adherence among all diets analyzed.Overall, the Carnivore and Ketogenic Diets had the potential for more nutritional inadequacies for vitamins and minerals compared to the other diets.Conclusions: The current analytical approach showed that most of the included popular fad dietary patterns have the potential to attain high DQ (HEI >80).Rather than suggesting one "best" diet or dietary pattern, there is opportunity to maximize DQ in the context of dietary patterns that are considered to be fad diets.

Vegan Diet

10.1016/j.cdnut.2023.100692

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Cognitive Dietary Restraint Is Associated with Stress Fractures in Women Runners

International Journal of Sport Nutrition and Exercise Metabolism (2005)

Nanci S. Guest Susan I. Barr

High levels of cognitive dietary restraint (CDR) have been associated with subclinical menstrual cycle irregularities and increased cortisol levels, both of which can affect bone mineral density (BMD). Low BMD has been implicated in stress fracture risk. We assessed CDR in female runners (> or = 20 km/wk) with a recent stress fracture (SF) and with no stress fracture history (NSF). A sample of 79 runners (n = 38 SF, 29 +/- 5 y; n = 41 NSF, 29 +/- 6 y) completed a 3-d food record and questionnaire assessing physical activity, menstrual cycle history, and perceived stress. SF and NSF runners had similar body mass index (21.2 +/- 1.8 vs. 22.0 +/- 2.5 kg/m2), physical activity (35.7 +/- 13.5 vs. 33.4 +/- 1.34 km/wk), perceived stress, and dietary intakes. CDR, however, was higher in SF runners (11.0 +/- 5.4 vs. 8.4 +/- 4.3, P < 0.05). Subclinical menstrual cycle disturbances and increased cortisol levels that are associated with high CDR, might in turn contribute to lowered BMD and increased stress fracture risk.

Subclinical infection

Stress Fractures

Affect

10.1123/ijsnem.15.2.147

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Citations (32)

Contributors

Elsevier eBooks (2019)

David Abraham Ildus I. Ahmetov Fatima Al‐Khelaifi Antoni Caimari Philipp Baumert

10.1016/b978-0-12-816193-7.09991-7

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Citations (0)

The Alleged Health-Protective Effects of Coffee

JAMA Internal Medicine (2018)

Bibiana García‐Bailo Nanci S. Guest Ahmed El‐Sohemy

Our website uses cookies to enhance your experience. By continuing to use our site, or clicking "Continue," you are agreeing to our Cookie Policy | Continue JAMA Internal Medicine HomeNew OnlineCurrent IssueFor Authors Podcast Publications JAMA JAMA Network Open JAMA Cardiology JAMA Dermatology JAMA Health Forum JAMA Internal Medicine JAMA Neurology JAMA Oncology JAMA Ophthalmology JAMA Otolaryngology–Head & Neck Surgery JAMA Pediatrics JAMA Psychiatry JAMA Surgery Archives of Neurology & Psychiatry (1919-1959) JN Learning / CMESubscribeJobsInstitutions / LibrariansReprints & Permissions Terms of Use | Privacy Policy | Accessibility Statement 2023 American Medical Association. All Rights Reserved Search All JAMA JAMA Network Open JAMA Cardiology JAMA Dermatology JAMA Forum Archive JAMA Health Forum JAMA Internal Medicine JAMA Neurology JAMA Oncology JAMA Ophthalmology JAMA Otolaryngology–Head & Neck Surgery JAMA Pediatrics JAMA Psychiatry JAMA Surgery Archives of Neurology & Psychiatry Input Search Term Sign In Individual Sign In Sign inCreate an Account Access through your institution Sign In Purchase Options: Buy this article Rent this article Subscribe to the JAMA Internal Medicine journal

10.1001/jamainternmed.2018.5807

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Nutrigenomics for Sport and Exercise Performance

Routledge eBooks (2020)

Nanci S. Guest Marc Sicova Ahmed El‐Sohemy

An athlete's dietary and supplement strategies can provide a valuable contribution to overall sport performance. Personalized nutrition for athletes and fitness enthusiasts aims to optimize nutrition status, body composition, and exercise performance by tailoring dietary recommendations to an individual's genetic profile. Sport dietitians and nutritionists have long been modifying the one-size-fits-all general population dietary guidelines in order to accommodate the needs of athletes. In general, high-performance sport requires the addition of carbohydrates to fuel training and higher protein intakes to repair muscle. However, generic recommendations still remain with regard to micronutrients, food intolerances, bone health, risk of muscle damage, and various other performance-related nutritional factors that deserve consideration. Genetic variation is known to affect absorption, metabolism, uptake, utilization, and excretion of nutrients and food bioactives, which can alter the activity of metabolic pathways. Nutrigenomics and nutrigenetics are experimental approaches that use genomic information and genetic testing technologies to examine the role of individual genetic differences in modifying an athlete's response to nutrients or substances in foods and supplements. With the exception of caffeine, there have been few randomized, controlled trials examining the effects of genetic variation on performance in response to dietary interventions or ergogenic aids. However, there is a growing foundation of research linking gene–diet interactions on biomarkers of health and nutritional status. This means that reaching specific targets for an athlete's nutritional status to optimize health and body composition will in turn beneficially affect exercise and sport performance. These concepts and their actions form the basis from which the field of sport nutrigenomics continues to develop. Here we review the current science that associates genetic modifiers with foods, nutrients and ergogenic aids, and their impact on athletic performance.

Nutrigenomics

10.4324/9781003123835-25

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