Since 1999 several groups have analyzed nutritional supplements with mass spectrometric methods (GC/MS, LC/MS/MS) for contaminations and adulterations with doping substances.These investigations showed that nutritional supplements contained prohibited stimulants as ephedrines, caffeine, methylenedioxymetamphetamie and sibutramine, which were not declared on the labels. An international study performed in 2001 and 2002 on 634 nutritional supplements that were purchased in 13 different countries showed that about 15% of the nonhormonal nutritional supplements were contaminated with anabolic-androgenic steroids (mainly prohormones). Since 2002, also products intentionally faked with high amounts of 'classic' anabolic steroids such as metandienone, stanozolol, boldenone, dehydrochloromethyl-testosterone, oxandrolone etc. have been detected on the nutritional supplement market. These anabolic steroids were not declared on the labels either. The sources of these anabolic steroids are probably Chinese pharmaceutical companies, which sell bulk material of anabolic steroids. In 2005 vitamin C, multivitamin and magnesium tablets were confiscated, which contained crosscontaminations of stanozolol and metandienone. Since 2002 new 'designer' steroids such as prostanozol, methasterone, androstatrienedione etc. have been offered on the nutritional supplement market. In the near future also cross-contaminations with these steroids are expected. Recently a nutritional supplement for weight loss was found to contain the b2-agonist clenbuterol. The application of such nutritional supplements is connected with a high risk of inadvertent doping cases and a health risk. For the detection of new 'designer' steroids in nutritional supplements, mass spectrometric strategies (GC/MS, LC/MS/MS) are presented.

Little is known about the prevalence and motives of supplement use among elite young athletes who compete on national and international levels. Therefore, the current survey was performed to assess information regarding the past and present use of dietary supplements among 164 elite young athletes (16.6 +/- 3.0 years of age). A 5-page questionnaire was designed to assess their past and present (last 4 weeks) use of vitamins, minerals, carbohydrate, protein, and fat supplements; sport drinks; and other ergogenic aids. Furthermore, information about motives, sources of advice, supplement sources, and supplement contamination was assessed. Eighty percent of all athletes reported using at least 1 supplement, and the prevalence of use was significantly higher in older athletes (p < .05). Among supplement users, minerals, vitamins, sport drinks, energy drinks, and carbohydrates were most frequently consumed. Only a minority of the athletes declared that they used protein/amino acids, creatine, or other ergogenic aids. Major motives for supplement use were health related, whereas performance enhancement and recommendations by others were less frequently reported. Supplements were mainly obtained from parents or by athletes themselves and were mostly purchased in pharmacies, supermarkets, and health-food stores. Among all athletes, only 36% were aware of the problem of supplement contamination. The survey shows that supplement use is common and widespread among German elite young athletes. This stands in strong contrast to recommendations by leading sport organizations against supplement use by underage athletes.

"Low energy availability in exercising men is associated with reduced leptin and insulin but not with changes in other metabolic hormones" (2016). Nutrition and Health Sciences --Faculty Publications. 85.

High-intensity interval training (HIIT) in junior and adult soccer has been shown to improve oxygen uptake (VO₂) and enhance soccer performance. The main purpose of this study was to examine the short term effects of a 5-week HIIT vs. high-volume training (HVT) program in 14-year-old soccer players regarding the effects on VO₂max and 1,000-m time (T₁₀₀₀) and on sprinting and jumping performance. In a 5-week period, 19 male soccer players with a mean (SD) age of 13.5 ± 0.4 years performed HIIT at close to ~90% of maximal heart rate. The HVT intensity was set at 60-75% of maximal heart rate. VO₂max increased significantly (7.0%) from pre to post in HIIT but not after HVT. T₁₀₀₀ decreased significantly after HIIT (~-10 vs. ~-5 seconds in HVT). Sprint performance increased significantly in both groups from pre to posttesting without any changes in jumping performance.

Brown adipose tissue (BAT) is a specialized fat tissue that has a high capacity to dissociate cellular respiration from ATP utilization, resulting in the release of stored energy as heat. Adult humans possess a substantial amount of BAT in the form of constitutively active brown fat or inducible beige fat. BAT activity in humans is inversely correlated with adiposity, blood glucose concentrations, and insulin sensitivity; this suggests that strategies aimed at BAT-mediated bioenergetics are an attractive therapeutic target in combating the continuing epidemic of obesity and diabetes. Despite advances in knowledge regarding the developmental lineage and transcriptional regulators of brown and beige adipocytes, our current understanding of environmental modifiers of BAT thermogenesis, such as diet, is limited. In this review, we consolidated the latest research on dietary molecules that may serve to promote BAT thermogenesis. Here, we summarized the thermogenic function of selected phytochemicals (e.g., capsaicin, resveratrol, curcumin, green tea, and berberine), dietary fatty acids (e.g., fish oil and conjugated linoleic acids), and all- retinoic acid, a vitamin A metabolite. We also delineated the proposed mechanisms whereby these dietary molecules promote BAT activity and/or browning of white adipose tissue. Characterizing thermogenic dietary factors may offer novel insight into revising nutritional intervention strategies aimed at obesity and diabetes prevention and management.

The carbon ((13)C/(12)C) and nitrogen ((15)N/(14)N) stable isotope ratios of human hair can be used for the interpretation of dietary habits and nutritional status in contemporary or past populations. Although the results of bulk or segmental isotope ratio analysis of human hair have been used for the reconstruction of an individual's diet for years, only limited data of controlled dietary changes on the carbon and nitrogen isotopic composition of human hair are available. Hair of four individuals, two males and two females, who participated in a dietary change experiment for 28 days was segmentally analysed for delta(13)C and delta(15)N. The dietary change included a change from C3 to C4 plant enriched diets and a simultaneous replacement of terrestrial animal products by marine products. This resulted in an increase in delta(13)C(diet) of +8.5 to +9.9 per thousand and in delta(15)N(diet) of +1.5 to +2.2 per thousand. All subjects showed significant increases in delta(13)C(hair) and delta(15)N(hair) during the dietary change period, although no subject reached a new steady state for either carbon or nitrogen. The change in delta(15)N(hair) was faster than the change in delta(13)C(hair) for all individuals. The magnitude of change of the isotopic composition during the dietary change period could be attributed to the degree of physical activity of the individuals, with a higher physical activity resulting in a faster change.

Energy availability (EA) is defined as the amount of dietary energy available to sustain physiological function after subtracting the energetic cost of exercise. Insufficient EA due to increased exercise, reduced energy intake, or a combination of both, is a potent disruptor of the endocrine milieu. As such, EA is conceived as a key etiological factor underlying a plethora of physiological dysregulations described in the female athlete triad, its male counterpart and the Relative Energy Deficiency in Sport models. Originally developed upon female-specific physiological responses, this concept has recently been extended to males, where experimental evidence is limited. The majority of data for all these models are from cross-sectional or observational studies where hypothesized chronic low energy availability (LEA) is linked to physiological maladaptation. However, the body of evidence determining causal effects of LEA on endocrine, and physiological function through prospective studies manipulating EA is comparatively small, with interventions typically lasting ≤ 5 days. Extending laboratory-based findings to the field requires recognition of the strengths and limitations of current knowledge. To aid this, this review will: (1) provide a brief historical overview of the origin of the concept in mammalian ecology through its evolution of algebraic calculations used in humans today, (2) Outline key differences from the ‘energy balance’ concept, (3) summarise and critically evaluate the effects of LEA on tissues/systems for which we now have evidence, namely: hormonal milieu, reproductive system endocrinology, bone metabolism and skeletal muscle; and finally (4) provide perspectives and suggestions for research upon identified knowledge gaps.

According to our results, the SWA does not provide valid results of TEE and ExEE in endurance athletes because of the underestimation of EE at higher exercise intensities. It seems necessary to develop exercise-specific prediction equations to improve EE measurements in athletes.