Vitamin D in athletes: focus on physical performance and musculoskeletal injuries

[Purpose]The aim of this review was to discuss the effects of vitamin D on physical performance and musculoskeletal injuries in athletes and provide information on the field applications of vitamin D. [Methods]A systematic review was conducted to identify studies on vitamin D in athletes that assessed serum vitamin D levels, vitamin D and physical performance, vitamin D and musculoskeletal injuries, and practical guidelines for supplementation of vitamin D. [Results]Several studies reported that a high proportion of athletes had vitamin D insufficiency or deficiency. Low serum levels of vitamin D in athletes were more pronounced in winter than in other seasons, and indoor athletes had lower serum vitamin D levels than outdoor athletes. Low vitamin D levels have been demonstrated to have negative effects on muscle strength, power, and endurance; increase stress fractures and other musculoskeletal injuries; and affect acute muscle injuries and inflammation following high-intensity exercises. Therefore, periodic assessment and monitoring of vitamin D levels are necessary in athletes; the recommended serum level of 25(OH)D is > 32 ng/mL and the preferred level is > 40 ng/mL (-1). In those with low levels of vitamin D, exposure to sunlight and an improved diet or supplements may be helpful. Particularly, 2000–6000 IU of supplemental vitamin D3 can be consumed daily. [Conclusion]Vitamin D is a potential nutritional factor that can significantly affect physical performance and musculoskeletal injuries in athletes. The importance and role of vitamin D in athletes should be emphasized, and the current levels of vitamin D should be assessed. Therefore, it is essential to periodically evaluate and monitor serum vitamin D levels in athletes.     

Dietary cholesterol increases paraoxonase 1 enzyme activity

HDL-associated paraoxonase 1 (PON1) activity has been consistently associated with cardiovascular and other diseases. Vitamins C and E intake have previously been positively associated with PON1 in a subset of the Carotid Lesion Epidemiology and Risk (CLEAR) cohort. The goal of this study was to replicate these findings and determine whether other nutrient intake affected PON1 activity. To predict nutrient and mineral intake values, 1,402 subjects completed a standardized food frequency survey of their dietary habits over the past year. Stepwise regression was used to evaluate dietary and covariate effects on PON1 arylesterase activity. Five dietary components, cholesterol (P < 2.0 × 10⁻¹⁶), alcohol (P = 8.51 × 10⁻⁸), vitamin C (P = 7.97 × 10⁻⁵), iron (P = 0.0026), and folic acid (0.037) were independently predictive of PON1 activity. Dietary cholesterol was positively associated and predicted 5.5% of PON1 activity, second in variance explained. This study presents a novel finding of dietary cholesterol, iron, and folic acid predicting PON1 activity in humans and confirms prior reported associations, including that with vitamin C. Identifying and understanding environmental factors that affect PON1 activity is necessary to understand its role and that of HDL in human disease.     

The effects of royal jelly protein on bone mineral density and strength in ovariectomized female rats

[Purpose]Sex hormones deficiency leads to dramatically bone loss in particular postmenopausal women. Royal jelly has anti-osteoporosis effect due to maintain bone volume in that condition. We hypothesized that royal jelly protein (RJP, a latent residue after extracting royal jelly) also prevents bone deficient in ovariectomized (OVX) female rats, the animal model of postmenopausal women. [Methods]Female Sprague-Dawley rats (n = 30, 6 weeks age old) were sham operated (Sham; sham operated group, n = 7), OVX control group (OC, n = 7), OVX with low RJP intake group (ORL, n = 8), and OVX with high RJP intake group (ORH, n = 8) during 8 weeks experimental periods. In the end point of this experiment, the bone samples (lumbar spine, tibia, and femur) were surgically removed under anesthesia. These bone samples were evaluated bone mineral density (BMD) and bone strength.[Results]BMD of lumbar spine in RJP intake groups (ORL, ORH) were higher than that in OC group (p < 0.05 and p < 0.01) in RJP intake volume dependent manner. BMD of tibial proximal metaphysis and diaphysis in RJP intake groups were also higher than these in OC group (p < 0.01 and p < 0.01 / p < 0.05 and p < 0.001). In addition, breaking force of femur in RJP intake groups were significantly increase compared with that in OC group (p < 0.001 respectively). [Conclusion]These findings indicate that RJP contribute to prevent sex hormone related bone abnormality     

Changes in physical activity and energy intake according to abdominal obesity in Korean adult men before and after COVID-19: Data from 2019 and 2020 Korea National Health and Nutrition Examination Survey (KNHANES)

[Purpose] This study aimed to investigate changes in physical activity and energy intake according to abdominal obesity in Korean adult men before and after COVID-19.[Methods] Using data from the 2019 and 2020 KNHANES, the physical activity level measured by the Global Physical Activity Questionnaire (GPAQ) the physical activity level by GPAQ, number of days of walking and strength training, aerobic exercise, and total energy, protein, fat, carbohydrate, dietary fiber, and sugar intake for a total of 2,799 participants were analyzed.[Results] There were no changes in energy intake during the pandemic. The number of days of weekly walking was higher (2019, p = 0.006; 2020, p = 0.012) and strength training was significantly higher (2019, p < 0.0001; 2020 p < 0.0001) in the non-abdominal obesity group than in the abdominal obesity group before and after COVID-19. Strength training at least once a week suppressed abdominal obesity (0.628 times in 2019, p < 0.0001; 0.605 times in 2020, p < 0.0001). In addition, even when the total energy intake and age were adjusted for, strength training influenced the suppression of abdominal obesity (0.634 times in 2019, p < 0.0001; 0.614 times in 2020, p < 0.0001).[Conclusion] Even with the change in the physical activity level, such as walking and aerobic exercise, due to the influence of social distancing measures, strength training influenced the suppression of abdominal obesity, regardless of the COVID-19 pandemic.     

APOA2 ?256T>C polymorphism interacts with saturated fatty acids intake to affect anthropometric and hormonal variables in type 2 diabetic patients

Recent studies have established the interaction between APOA2 −256T>C polymorphism and dietary saturated fatty acids intake in relation to obesity on healthy individuals. In the current study, we investigate the effects of this interaction on anthropometric variables and serum levels of leptin and ghrelin in patients with type 2 diabetes. In this cross-sectional study, 737 patients with type 2 diabetes mellitus (290 males and 447 females) were recruited from diabetes clinics in Tehran. The usual dietary intake of all participants during the last year was obtained by validated semiquantitative food frequency questionnaire. APOA2 genotyping was performed by real-time PCR on genomic DNA. No significant relation was obtained by univariate analysis between anthropometric variables and APOA2 genotypes. However, after adjusting for age, gender, physical activity and total energy intake, we identified a significant interaction between APOA2-saturated fatty acids intake and body mass index (BMI). After adjusting for potential confounders, serum levels of ghrelin in CC genotype patients were significantly higher than T allele carriers (p = 0.03), whereas the case with leptin did not reveal a significant difference. The result of this study confirmed the interaction between APOA2 −256T>C polymorphism and SFAs intake with BMI in type 2 diabetic patients. In fact, homozygous patients for the C allele with high saturated fatty acids intake had higher BMI. The APOA2 −256T>C polymorphism was associated with elevated levels of serum ghrelin.     

Sclerostin as a novel marker of bone turnover in athletes

Sclerostin is a protein secreted by osteocytes that acts as an inhibitor of bone formation. It has been shown that physical activity affects sclerostin concentration and thus bone remodelling. The aim of the study was to evaluate serum concentrations of sclerostin, selected bone turnover markers (PTH, P1NP), 25(OH)D3 and the intake of calcium and vitamin D in physically active versus sedentary men. A total of 59 healthy men aged 17-37 were enrolled in the study (43 athletes and 16 non-athletes). The mean sclerostin concentration in the group of athletes (A) was significantly higher than in non-athletes (NA) (35.3±8.9 vs 28.0±5.6 pmol·l^-1, p= 0.004). A compared with NA had higher concentrations of P1NP (145.6±77.5 vs 61.2±22.3 ng·ml^-1, p= <0.0001) and 25(OH)D3 (16.9±8.4 vs 10.3±4.3 ng·ml^-1, p= 0.004) and lower concentrations of PTH (25.8±8.3 vs 38.2±11.5 pg·ml^-1, p= <0.0001). Vitamin D deficiency was found in 77% of A and 100% of NA. A and NA had similar daily energy intake. They did not differ as to the intake of calcium and vitamin D. We observed a negative correlation between the serum concentrations of sclerostin and calcium in the studied subjects. Our results suggest that regular, long-lasting physical training may be associated with higher concentration of sclerostin. It seems that increased sclerostin is not related to other bone turnover markers (PTH, P1NP).     

Comparative analysis of energy intake and physical activity according to household type and presence of metabolic syndrome in middle-aged men based on data from the 7th Korea national health and nutrition examination survey (KNHANES) (2016-2018)

[Purpose] This study analyzed data from the 7^th Korean National Health and Nutrition Examination Survey (2016‒2018) to compare the differences in energy intake and physical activity (PA) levels in middle-aged Korean men aged 40-59 years according to household type and the presence of metabolic syndrome (MetS).[Methods] Data from 2,266 young adults (aged >39 years and <60 years) were obtained from the KNHANES. We analyzed the differences in energy intake and PA levels according to household type and MetS. The presence or absence of MetS was determined by measuring waist circumference, blood pressure, fasting blood glucose, triglyceride, and HDL-C levels.[Results] Regarding total nutritional intake, no relationship with MetS was observed regardless of household type (interaction between MetS and household type: p = 0.875). No differences in total PA were observed between multiple- and single-person households (interaction between MetS and household type: p = 0.122). The relationship between MetS and MetS components according to nutritional intake showed that participants with a higher energy intake had a 27% lower prevalence of low high-density lipoprotein cholesterol (HDL-C) (p < 0.05) and a 36% higher prevalence of high blood pressure (p < 0.01). The relationship between MetS and MetS components according to the PA level showed significantly reduced prevalence of MetS by approximately 39%, 35%, and 43% (p < 0.01, 0.01, and 0.001) in subjects who were somewhat active, active, and very active, respectively, compared to inactivity.[Conclusion] Middle-aged men showed no difference in nutritional intake and PA between multiple- and single-person households. However, the risk of MetS was significantly higher in participants with approximately 1.5 times the energy intake compared to the group with the lowest energy intake. Moreover, higher levels of PA had a marked positive effect on the risk factors and prevalence of MetS. Therefore, we suggest that reducing the total energy intake and increasing total PA are important for preventing MetS in middle-aged men regardless of household type.     

Associations of maternal dietary inflammatory potential and quality with offspring birth outcomes: An individual participant data pooled analysis of 7 European cohorts in the ALPHABET consortium

BackgroundAdverse birth outcomes are major causes of morbidity and mortality during childhood and associate with a higher risk of noncommunicable diseases in adult life. Maternal periconception and antenatal nutrition, mostly focusing on single nutrients or foods, has been shown to influence infant birth outcomes. However, evidence on whole diet that considers complex nutrient and food interaction is rare and conflicting. We aim to elucidate the influence of whole-diet maternal dietary inflammatory potential and quality during periconceptional and antenatal periods on birth outcomes.Methods and findingsWe harmonized and pooled individual participant data (IPD) from up to 24,861 mother–child pairs in 7 European mother–offspring cohorts [cohort name, country (recruitment dates): ALSPAC, UK (1 April 1991 to 31 December 1992); EDEN, France (27 January 2003 to 6 March 2006); Generation R, the Netherlands (1 April 2002 to 31 January 2006); Lifeways, Ireland (2 October 2001 to 4 April 2003); REPRO_PL, Poland (18 September 2007 to 16 December 2011); ROLO, Ireland (1 January 2007 to 1 January 2011); SWS, United Kingdom (6 April 1998 to 17 December 2002)]. Maternal diets were assessed preconceptionally (n = 2 cohorts) and antenatally (n = 7 cohorts). Maternal dietary inflammatory potential and quality were ranked using the energy-adjusted Dietary Inflammatory Index (E-DII) and Dietary Approaches to Stop Hypertension (DASH) index, respectively. Primary outcomes were birth weight and gestational age at birth. Adverse birth outcomes, i.e., low birth weight (LBW), macrosomia, small-for-gestational-age (SGA), large-for-gestational-age (LGA), preterm and postterm births were defined according to standard clinical cutoffs. Associations of maternal E-DII and DASH scores with infant birth outcomes were assessed using cohort-specific multivariable regression analyses (adjusted for confounders including maternal education, ethnicity, prepregnancy body mass index (BMI), maternal height, parity, cigarettes smoking, and alcohol consumption), with subsequent random-effects meta-analyses.Overall, the study mothers had a mean ± SD age of 29.5 ± 4.9 y at delivery and a mean BMI of 23.3 ± 4.2 kg/m². Higher pregnancy DASH score (higher dietary quality) was associated with higher birth weight [β(95% CI) = 18.5(5.7, 31.3) g per 1-SD higher DASH score; P value = 0.005] and head circumference [0.03(0.01, 0.06) cm; P value = 0.004], longer birth length [0.05(0.01, 0.10) cm; P value = 0.010], and lower risk of delivering LBW [odds ratio (OR) (95% CI) = 0.89(0.82, 0.95); P value = 0.001] and SGA [0.87(0.82, 0.94); P value < 0.001] infants. Higher maternal prepregnancy E-DII score (more pro-inflammatory diet) was associated with lower birth weight [β(95% CI) = −18.7(−34.8, −2.6) g per 1-SD higher E-DII score; P value = 0.023] and shorter birth length [−0.07(−0.14, −0.01) cm; P value = 0.031], whereas higher pregnancy E-DII score was associated with a shorter birth length [−0.06(−0.10, −0.01) cm; P value = 0.026] and higher risk of SGA [OR(95% CI) = 1.18(1.11, 1.26); P value < 0.001]. In male, but not female, infants higher maternal prepregnancy E-DII was associated with lower birth weight and head circumference, shorter birth length, and higher risk of SGA (P-for-sex-interaction = 0.029, 0.059, 0.104, and 0.075, respectively). No consistent associations were observed for maternal E-DII and DASH scores with gestational age, preterm and postterm birth, or macrosomia and LGA. Limitations of this study were that self-reported dietary data might have increased nondifferential measurement error and that causality cannot be claimed definitely with observational design.ConclusionsIn this cohort study, we observed that maternal diet that is of low quality and high inflammatory potential is associated with lower offspring birth size and higher risk of offspring being born SGA in this multicenter meta-analysis using harmonized IPD. Improving overall maternal dietary pattern based on predefined criteria may optimize fetal growth and avert substantial healthcare burden associated with adverse birth outcomes.

In this cohort analysis, Ling-Wei Chen and colleagues explore associations of maternal dietary patterns with offspring birth outcomes.     

Maternal dietary intake of folate,vitamin B12 and MTHFR 677C>T genotype: their impact on newborn’s anthropometric parameters

In this study, we evaluated the effects of dietary intake of vitamin B₁₂ and folate during pregnancy and their interactions with maternal polymorphism of MTHFR (677C>T; 1298A>C) on intrauterine development. Anthropometric parameters were obtained from 231 newborns that belong to a prospective birth cohort in Morelos, Mexico. Maternal dietary intake of vitamin B₁₂ and folate was assessed using a semi-quantitative questionnaire administered during the first and third trimesters of the pregnancy. Maternal MTHFR 677C>T and 1298 A>C genotypes were determined by PCR–RFLP. The associations between deficient dietary intake of vitamin B₁₂ (<2.0 μg/d) and folate (<400 μg/d) in the first and third trimesters and maternal polymorphisms of MTHFR on anthropometric parameters at birth were estimated using a multivariate linear regression model. During pregnancy, the deficient dietary intake was roughly 60 % for folate and 19 % for vitamin B₁₂. Allelic frequencies of 677T and 1298C were 59 and 10 %, respectively. After adjusting for confounders, deficiency in maternal dietary intake of vitamin B₁₂ (<2.0 μg/d) was associated with a significant reduction in length (β ~ −2.4; 95 % CI −4.3; −0.6) and length-for-age at birth (β ~ −1.2; 95 % CI −2.3; −0.1) among infants whose mothers were carriers of the 677TT genotype (p for interaction = 0.02). In contrast, no association was observed between deficiency in maternal dietary intake of folate (<400 μg/d) and any anthropometric parameter of newborns. These results suggest that supplementation with vitamin B₁₂ during pregnancy could have a favorable impact on intrauterine fetal development mainly in populations that are genetically susceptible.     

Association of dietary and serum selenium concentrations with glucose level and risk of diabetes mellitus: A cross sectional study of national health and nutrition examination survey, 1999-2006

BackgroundThe associations among dietary selenium intake, serum selenium concentration, plasma glucose and glycosylated hemoglobin levels, and diabetes risk remain controversial. This study aimed to evaluate these associations in adults from the United States.MethodsWe conducted a cross-sectional study of participants aged 18 years and older who participated in the National Health and Nutrition Examination Survey. Between 1999 and 2006, a total of 41,474 participants were initially included in this study. Multivariable linear or logistic regression analysis was used to investigate the association between dietary selenium intake and serum selenium concentrations, glucose level, and diabetes risk.ResultsThe average age of the participants was 30.32 ± 23.95 years, and 48.72 % were men. Their mean dietary selenium intake and mean serum selenium concentration were 98 ± 55 μg per day and 129 ± 22 ng/mL, respectively. Compared with t he lowest quartile of dietary selenium intake, the highest quartile was associated with elevated plasma glucose levels (β = 2.412, 95 % confidence interval [CI]: 0.420, 4.403, P = 0.018), glycosylated hemoglobin levels (β = 0.080, 95 % CI: 0.041, 0.119, P < 0.001), and diabetes risk (odds ratio [OR] = 2.139, 95 % CI: 1.763, 2.596, P < 0.001). Higher serum selenium was also associated with increased plasma glucose levels (β = 12.454, 95 % CI: 4.122, 20.786, P = 0.003) and glycosylated hemoglobin levels (β = 0.326, 95 % CI: 0.187, 0.465, P < 0.001). A generalized additive model with a spline curve suggested a nonlinear relationship between dietary selenium intake, serum selenium and glucose levels, and diabetes risk.ConclusionsDietary selenium intake and serum selenium were positively associated with elevated levels of plasma glucose and glycosylated hemoglobin, and the relationships were nonlinear. Additional selenium supplementation for patients with diabetes may not be recommended.     

Decrease in Vitamin D Status in the Greenlandic Adult Population from 1987–2010

Background

Low vitamin D status may be pronounced in Arctic populations due to limited sun exposure and decreasing intake of traditional food.

Objective

To investigate serum 25(OH)D3 as a measure of vitamin D status among adult Inuit in Greenland, predictors of low serum 25(OH)D3 concentrations and the trend from 1987 to 2005–2010.

Design

A total of 2877 randomly selected Inuit (≥18 years) from the Inuit Health in Transition study were included. A sub-sample (n = 330) donated a blood sample in 1987 which allowed assessment of time trends in vitamin D status.

Results

The geometric mean serum 25(OH)D3 (25[OH]D2 concentrations were negligible and not reported) in 2005–2010 was lowest among the 18–29 year old individuals (30.7 nmol/L; 95% CI: 29.7; 31.7) and increased with age. In all age-groups it decreased from 1987 to 2005–2010 (32%–58%). Low 25(OH)D3 concentrations (<50 nmol/L) were present in 77% of the 18–29 year old and decreased with age. A characteristic seasonal variation in 25(OH)D3 concentrations was observed (range 33.2–57.1 nmol/L, p<0.001), with the highest concentrations in August to October. Age (2.0% per year increase; CI: 1.7, 2.2), female gender (7.1%; CI: 2.0; 12.5), alcohol intake (0.2% per increase in drinks/week; 0.0; 0.4), and traditional diet (10.0% per 100 g/d increase; CI: 7.9; 12.1) were associated with increased serum 25(OH)D3, whereas smoking (−11.6%; CI: −16.2; −6.9), BMI (−0.6%; CI: −1.1; −0.2) and latitude (−0.7% per degree increase; CI: −1.3; −0.2) were associated with decreased concentrations.

Conclusion

We identified a remarkable decrease in vitamin D status from 1987 to 2005–2010 and a presently low vitamin D status among Inuit in Greenland. A change away from a traditional diet may well explain the observed decline. The study argues for the need of increased dietary intake of vitamin D and supplementation might be considered.     

Vitamin K Intake and Plasma Desphospho-Uncarboxylated Matrix Gla-Protein Levels in Kidney Transplant Recipients

Vitamin K is essential for activation of γ-carboxyglutamate (Gla)-proteins including the vascular calcification inhibitor matrix Gla-protein (MGP). Insufficient vitamin K intake leads to production of uncarboxylated, mostly inactive proteins and contributes to an increased cardiovascular risk. In kidney transplant recipients, cardiovascular risk is high but vitamin K intake and status have not been defined. We investigated dietary vitamin K intake, vascular vitamin K status and its determinants in kidney transplant recipients. We estimated vitamin K intake in a cohort of kidney transplant recipients (n = 60) with stable renal function (creatinine clearance 61 [42–77] (median [interquartile range]) ml/min), who were 75 [35–188] months after transplantation, using three-day food records and food frequency questionnaires. Vascular vitamin K status was assessed by measuring plasma desphospho-uncarboxylated MGP (dp-ucMGP). Total vitamin K intake was below the recommended level in 50% of patients. Lower vitamin K intake was associated with less consumption of green vegetables (33 vs 40 g/d, p = 0.06) and increased dp-ucMGP levels (621 vs 852 pmol/L, p<0.05). Accordingly, dp-ucMGP levels were elevated (>500 pmol/L) in 80% of patients. Multivariate regression identified creatinine clearance, coumarin use, body mass index, high sensitivity-CRP and sodium excretion as independent determinants of dp-ucMGP levels. In a considerable part of the kidney transplant population, vitamin K intake is too low for maximal carboxylation of vascular MGP. The high dp-ucMGP levels may result in an increased risk for arterial calcification. Whether increasing vitamin K intake may have health benefits for kidney transplant recipients should be addressed by future studies.     

Osteocalcin Induces Release of Glucagon-Like Peptide-1 and Thereby Stimulates Insulin Secretion in Mice

The uncarboxylated form (ucOC), but not the γ-carboxylated form (GlaOC), of the bone-derived protein osteocalcin stimulates insulin secretion and regulates energy metabolism in insulin target tissues. Glucagon-like peptide–1 (GLP-1) is an insulin secretagogue that is released from the gut in response to food intake. We have now found that Gprc6a, a putative ucOC receptor, is expressed in epithelial cells of the mouse small intestine as well as in STC-1 enteroendocrine cells. Secretion of GLP-1 by STC-1 cells was stimulated by ucOC but not by GlaOC. The serum GLP-1 concentration in mice was increased by intraperitoneal or oral administration of ucOC, whereas GlaOC was effective in this regard only after oral application. Serum insulin levels were also increased by ucOC, and this effect was potentiated by an inhibitor of dipeptidyl peptidase IV and blocked by a GLP-1 receptor antagonist. Intravenous injection of ucOC in mice increased the serum GLP-1 concentration, and also increased the serum level of insulin. Our results suggest that ucOC acts via Gprc6a to induce GLP-1 release from the gut, and that the stimulatory effect of ucOC on insulin secretion is largely mediated by GLP-1.     

Incidence of exercise-associated hyponatremia during a high-altitude 161-km ultramarathon

[Purpose]Exercise-associated hyponatremia (EAH) is a well-known condition among endurance athletes at low altitudes. The incidence of EAH during ultramarathons at high altitudes warrants further investigation. This prospective observational study was conducted on the participants of the Leadville Trail 100 run, a 161-km race held at a high altitude (2,800 m-3,840 m).[Methods]Venous blood samples were collected before and immediately after the race. The participants completed an electronic survey after the race. Our main outcome measure was the post-race serum sodium ([Na⁺]) level.[Results]Of the 672 athletes who started the race, 351 (52%) successfully completed the event within the 30-hour cut-off. Post-race blood samples were collected from 84 runners (66 finishers). Both pre- and post-race blood samples were collected from 37 participants. Twenty percent of the post-race participants had EAH. Only one post-race participant had a [Na⁺] level of <130 mmol/L. All participants with EAH were asymptomatic. One participant had an abnormal pre-race [Na⁺] level (134 mmol/L). Female participants had a significantly higher rate of EAH than male participants (40% vs. 16%; p=0.039). Age, body mass index, weight changes, race completion status, nonsteroidal anti-inflammatory drug use, and urine specific gravity were not associated with the development of EAH. Lower postrace [Na⁺] levels were associated with higher serum creatine kinase values (R²=0.1, p<0.005).[Conclusion]High altitude (3,840 m peak) does not appear to enhance the incidence of EAH after an ultramarathon footrace. This suggests that ambient temperature (low temperatures reduce risk), sex (female predilection), endurance running, and overhydration are more prominent risk factors for EAH than high altitude.     

Effect of sodium bicarbonate supplementation on two different performance indicators in sports: a systematic review with meta-analysis

[Purpose]Sodium bicarbonate shows ergogenic potential in physical exercise and sports activities, although there is no strong evidence which performance markers show the greatest benefit from this supplement. This study evaluated the effects of sodium bicarbonate supplementation on time trial performance and time to exhaustion in athletes and sports practitioners.[Methods]A systematic review was conducted using three databases, including 17 clinical trials. Among these clinical trials, 11 were considered eligible for the meta-analysis according to the criteria for the assessment of methodological quality using the PEDro Scale. Time to exhaustion was assessed in six studies, while time trial performance was evaluated in five studies.[Results]A significant beneficial effect of supplementation on time to exhaustion was found in a random effects model (1.48; 95% confidence interval [CI], 0.49 to 2.48). There was no significant effect of supplementation on time trial performance in a fixed effects model (slope = −0.75; 95% CI, −2.04 to 0.55) relative to a placebo group.[Conclusion]Sodium bicarbonate has the potential to improve sports performance in general, especially in terms of time to exhaustion.     

Osteocalcin Levels on Oral Glucose Load in Women being Investigated for Polycystic Ovary Syndrome

ObjectiveOsteocalcin (OC) might play a hormone-like role in energy metabolism and the regulatory circuit between the pancreas and osteoblasts. Effects of a 75-g oral glucose tolerance test (OGTT) on total OC, undercarboxylated (ucOC), and carboxylated osteocalcin (cOC) in insulin-resistant (IR) and noninsulin-resistant (nIR) premenopausal women was evaluated, and the relationships of changes in OC, ucOC, and cOC with area under the curve (AUC) insulin and the Matsuda index were examined.MethodsIn this cross-sectional study, 105 premenopausal women underwent OGTT; 18 were IR (homeostatic model assessment of insulin resistance [HOMA-IR] > 2.6; (2 with type 2 diabetes, 2 with impaired glucose tolerance), and 87 were nIR (3 with impaired glucose tolerance). Changes in total OC, ucOC, and cOC were evaluated 60 and 120 minutes after glucose loading.ResultsAt baseline, IR subjects had significantly lower levels of total OC, cOC, and ucOC. In nIR women, total OC decreased by 19% from 18.0 ng/mL (14.5-24.7) at baseline to 14.6 ng/mL (10.9-17.8) after 120 minutes, ucOC decreased by 22% from 3.2 ng/mL (2.1-4.5) to 2.5 ng/mL (1.7-3.5), and cOC decreased by 26% from 14.9 ng/mL (12.1-20.4) to 11.1 ng/mL (9.0-14.5) (P < .001, respectively). No significant decreases were noted in IR subjects. The declines in OC and cOC predicted AUCinsulin (ΔOC: β = 0.301, P = .001; ΔcOC: β = 0.315, P < .001) and the Matsuda index (ΔOC: β = − 0.235, P = .003; ΔcOC: β = − 0.245, P = .002).ConclusionsGlucose intake lowers levels of OC, ucOC, and cOC in nIR women, the extent of which predicts IR and insulin sensitivity in premenopausal women. OC parameters seem suppressed in IR women. There might be a differential osteoblast response to oral glucose in IR and nIR women, with OC reflecting this finding. (Endocr Pract. 2014;20:5-14)     

Taxed and untaxed beverage intake by South African young adults after a national sugar-sweetened beverage tax: A before-and-after study

BackgroundIn an effort to prevent and reduce the prevalence rate of people with obesity and diabetes, South Africa implemented a sugar-content-based tax called the Health Promotion Levy in April 2018, one of the first sugar-sweetened beverage (SSB) taxes to be based on each gram of sugar (beyond 4 g/100 ml). This before-and-after study estimated changes in taxed and untaxed beverage intake 1 year after the tax, examining separately, to our knowledge for the first time, the role of reformulation distinct from behavioral changes in SSB intake.Methods and findingsWe collected single-day 24-hour dietary recalls from repeat cross-sectional surveys of adults aged 18–39 years in Langa, South Africa. Participants were recruited in February–March 2018 (pre-tax, n = 2,459) and February–March 2019 (post-tax, n = 2,489) using door-to-door sampling. We developed time-specific food composition tables (FCTs) for South African beverages before and after the tax, linked with the diet recalls. By linking pre-tax FCTs only to dietary intake data collected in the pre-tax and post-tax periods, we calculated changes in beverage intake due to behavioral change, assuming no reformulation. Next, we repeated the analysis using an updated FCT in the post-tax period to capture the marginal effect of reformulation. We estimated beverage intake using a 2-part model that takes into consideration the biases in using ordinary least squares or other continuous variable approaches with many individuals with zero intake. First, a probit model was used to estimate the probability of consuming the specific beverage category. Then, conditional on a positive outcome, a generalized linear model with a log-link was used to estimate the continuous amount of beverage consumed. Among taxed beverages, sugar intake decreased significantly (p < 0.0001) from 28.8 g/capita/day (95% CI 27.3–30.4) pre-tax to 19.8 (95% CI 18.5–21.1) post-tax. Energy intake decreased (p < 0.0001) from 121 kcal/capita/day (95% CI 114–127) pre-tax to 82 (95% CI 76–87) post-tax. Volume intake decreased (p < 0.0001) from 315 ml/capita/day (95% CI 297–332) pre-tax to 198 (95% CI 185–211) post-tax. Among untaxed beverages, sugar intake increased (p < 0.0001) by 5.3 g/capita/day (95% CI 3.7 to 6.9), and energy intake increased (p < 0.0001) by 29 kcal/capita/day (95% CI 19 to 39). Among total beverages, sugar intake decreased significantly (p = 0.004) by 3.7 (95% CI −6.2 to −1.2) g/capita/day. Behavioral change accounted for reductions of 24% in energy, 22% in sugar, and 23% in volume, while reformulation accounted for additional reductions of 8% in energy, 9% in sugar, and 14% in volume from taxed beverages. The key limitations of this study are an inability to make causal claims due to repeat cross-sectional data collection, and that the magnitude of reduction in taxed beverage intake may not be generalizable to higher income populations.ConclusionsUsing a large sample of a high-consuming, low-income population, we found large reductions in taxed beverage intake, separating the components of behavioral change from reformulation. This reduction was partially compensated by an increase in sugar and energy from untaxed beverages. Because policies such as taxes can incentivize reformulation, our use of an up-to-date FCT that reflects a rapidly changing food supply is novel and important for evaluating policy effects on intake.

Rina Swart and co-authors use real world data to demonstrate that sugar-sweetened beverage tax was associated with reduced sugary drink intake in a low-income population within a middle-income country.     

Lower Serum Irisin Levels Are Associated with Increased Osteoporosis and Oxidative Stress in Postmenopausal

Background:Irisin as an exercise-induced myokine was proposed to improve bone health. This study investigated the role of serum irisin (s-irisin) in patients with osteoporosis (OP) through correlating to most biological bone markers and oxidative stress.Methods:A cross-sectional study recruited an eligible 175 postmenopausal women at Al-Hussien Teaching Hospital, Iraq. They were scanned by DEXA and stratified into two groups based on T-score; the first 95 patients as control group (GI) with −1 ≤ T-score and the second 80 patients as cases group (GII) with T-score ≤ −2.5. Demographic criteria were age, bone mineral density (BMD, g/cm2) and T-score. Serum irisin, total serum calcium (s-calcium), serum inorganic phosphate (s-phosphate), serum alkaline phosphatase (s-ALP), serum 25 [OH] vitamin D, the serum parathyroid hormone (s-PTH), serum Carboxy terminal collagen crosslinks (CTx), serum procollagen type I C-termidnal peptide (s-PICP), serum malondialdehyde (s-MDA) and serum superoxide dismutase (s-SOD) were collected from blood samples.Results:Serum irisin were 31.84 ± 2.65 vs. 20.88 ± 2.71 ng/mL for control and trial groups, respectively. Lower levels of BMD, T-score, 25 [OH] vitamin D, and s-irisin along with a higher serum levels of PTH, CTx, PICP, MDA and SOD were observed in patients with osteoporosis. All parameters were statistically meaningful upon correlation (p< 0.0001), except age and s-calcium (p= 0.0088 and p= 0.187, respectively).Conclusion:The results showed that, a significantly lower serum irisin levels among osteoporosis women, was intimately correlated to most bone turnover markers and it can be considered as encouraging results for clinical application in prediction and treatment of osteoporosis.Key Words: Bone turnover markers, DEXA scan, Irisin, T-score, BMD, osteoporosis, post-menopause     

Essential Amino Acids in the Gluten-Free Diet and Serum in Relation to Depression in Patients with Celiac Disease

IntroductionCeliac disease (CD) is associated with an increased risk of major depressive disorder, possibly due to deficiencies in micronutrients in the gluten-free diet. We aimed to investigate whether essential amino acids (i.e., the precursors of serotonin, dopamine and other neurotransmitters) are depleted in the diet and serum of CD patients with major depressive disorder.MethodsIn a cross-sectional study we assessed dietary intake of amino acids and serum levels of amino acids, in 77 CD patients on a gluten-free diet and in 33 healthy controls. Major depressive disorder was assessed with structured interviews (using the Mini International Neuropsychiatric Interview Plus). Dietary intake was assessed using a 203-item food frequency questionnaire.ResultsParticipants had a mean age of 55 years and 74% were women. The intake of vegetable protein was significantly lower in CD patients than in healthy controls (mean difference of 7.8 g/d; 95% CI: 4.7–10.8), as were serum concentrations of tyrosine, phenylalanine and tryptophan (all p < 0.005). However, within the CD patient group, the presence of major depressive disorder (n = 42) was not associated with intake or serum levels of essential amino acids.ConclusionsPatients with CD on a long-term gluten-free diet, with good adherence, consume significantly less vegetable protein than controls, and their serum levels of several essential amino acids were also lower. Despite its potential adverse effect, intake and serum levels of essential amino acids were not related to major depression.