Novel insights on caffeine supplementation, CYP1A2 genotype, physiological responses and exercise performance.

Caffeine is a popular ergogenic aid due to its primary physiological effects that occur through antagonism of adenosine receptors in the central nervous system. This leads to a cascade of physiological reactions which increases focus and volition, and reduces perception of effort and pain, contributing to improved exercise performance. Substantial variability in the physiological and performance response to acute caffeine consumption is apparent, and a growing number of studies are implicating a single-nucleotide polymorphism in the CYP1A2 gene, responsible for caffeine metabolism, as a key factor that influences the acute responses to caffeine ingestion. However, existing literature regarding the influence of this polymorphism on the ergogenic effects of caffeine is controversial. Fast caffeine metabolisers (AA homozygotes) appear most likely to benefit from caffeine supplementation, although over half of studies showed no differences in the responses to caffeine between CYP1A2 genotypes, while others even showed either a possible advantage or disadvantage for C-allele carriers. Contrasting data are limited by weak study designs and small samples sizes, which did not allow separation of C-allele carriers into their sub-groups (AC and CC), and insufficient mechanistic evidence to elucidate findings. Mixed results prevent practical recommendations based upon genotype while genetic testing for CYP1A2 is also currently unwarranted. More mechanistic and applied research is required to elucidate how the CYP1A2 polymorphism might alter caffeine's ergogenic effect and the magnitude thereof, and whether CYP1A2 genotyping prior to caffeine supplementation is necessary.

Nutritional therapy for hospitalized patients with COVID-19: A narrative and integrative review.

Hospitalized patients affected by coronavirus disease 19 (COVID-19) have a sustained pro-inflammatory state and recurrent gastrointestinal symptoms that correlate with a decline in the nutritional status, which is directly related to poor immune response and clinical evolution. Nutritional therapy has proven crucial in COVID-19 treatment through the provision of adequate amounts of nutrients. Since the beginning of the pandemic, medical societies have mobilized to provide practical nutritional guidelines to support decision-making; despite this, there are only a few studies dedicated to compiling the most relevant recommendations. In this narrative review, we aimed to summarize and stratify the current scientific literature on nutritional support for hospitalized COVID-19 patients. We carried out a literature review from three databases between January 2020 and July 2021, using nutrition therapy (or medical nutrition or enteral nutrition or parental nutrition or nutritional support) and COVID-19 (SARS-CoV-2 infection) as the search terms. Only those studies that evaluated adult hospitalized patients with admissions to wards, specific clinics, or intensive care units were included. The nutritional intervention considered was that of specific nutritional support via oral, enteral, or parenteral modes. A total of 37 articles were included. In general, the nutritional care provided to COVID-19 patients follows the same premises as for other patients, i.e., it opts for the most physiological route and meets nutritional demands based on the clinical condition. However, some protocols that minimize the risk of contamination exposure for the health team have to be considered. Energy requirements varied from 15 kcal/kg/day to 30 kcal/kg/day and protein goals from 1.2 g/kg/day to 2 g/kg/day. In both cases, the ramp protocol for increased supply should be considered. In cases of enteral therapy, ready-to-use diet and continuous mode are recommended. Attention to refeeding syndrome is essential when parenteral nutrition is used.

Can I Have My Coffee and Drink It? A Systematic Review and Meta-analysis to Determine Whether Habitual Caffeine Consumption Affects the Ergogenic Effect of Caffeine.

OBJECTIVE: The aim was to quantify the proportion of the literature on caffeine supplementation that reports habitual caffeine consumption, and determine the influence of habitual consumption on the acute exercise response to caffeine supplementation, using a systematic review and meta-analytic approach. METHODS: Three databases were searched, and articles screened according to inclusion/exclusion criteria. Three-level meta-analyses and meta-regression models were used to investigate the influence of habitual caffeine consumption on caffeine's overall ergogenic effect and within different exercise types (endurance, power, strength), in men and women, and in trained and untrained individuals. Sub-analyses were performed according to the following: acute relative dose (< 3, 3-6, > 6 mg/kg body mass [BM]); whether the acute caffeine dose provided was lower or higher than the mean daily caffeine dose; and the caffeine withdrawal period prior to the intervention (< 24, 24-48, > 48 h). RESULTS: Sixty caffeine studies included sufficient information on habitual consumption to be included in the meta-analysis. A positive overall effect of caffeine was shown in comparison to placebo (standard mean difference [SMD] = 0.25, 95% confidence interval [CI] 0.20-0.30; p < 0.001) with no influence of relative habitual caffeine consumption (p = 0.59). Subgroup analyses showed a significant ergogenic effect when the caffeine dose was < 3 mg/kg BM (SMD = 0.26, 95% CI 0.12-0.40; p = 0.003) and 3-6 mg/kg BM (SMD = 0.26, 95% CI 0.21-0.32; p < 0.0001), but not > 6 mg/kg BM (SMD = 0.11, 95% CI - 0.07 to 0.30; p = 0.23); when the dose was both higher (SMD = 0.26, 95% CI 0.20-0.31; p < 0.001) and lower (SMD = 0.21, 95% CI 0.06-0.36; p = 0.006) than the habitual caffeine dose; and when withdrawal was < 24 h, 24-48 h, and > 48 h. Caffeine was effective for endurance, power, and strength exercise, with no influence (all p ≥ 0.23) of relative habitual caffeine consumption within exercise types. Habitual caffeine consumption did not modify the ergogenic effect of caffeine in male, female, trained or untrained individuals. CONCLUSION: Habitual caffeine consumption does not appear to influence the acute ergogenic effect of caffeine.