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Calorie restriction is a primary dietary intervention demonstrated over many decades in cellular and animal models to modulate aging pathways, positively affect age-associated diseases and, in clinical studies, to promote beneficial health outcomes. Because long-term compliance with daily calorie restriction has proven problematic in humans several intermittent fasting regimens, including alternate day fasting and time-restricted feeding, have evolved revealing similar clinical benefits as calorie restriction. Despite significant research on the cellular and physiological mechanisms contributing to, and responsible for, these observed benefits, relatively little research has investigated the impact of these various fasting protocols on the gut microbiome (GM). Reduced external nutrient supply to the gut may beneficially alter the composition and function of a "fed" gut microflora. Indeed, the prevalent, obesogenic Western diet can promote deleterious changes in the GM, signaling intermediates involved in lipid and glucose metabolism, and immune responses in the gastrointestinal tract. This review describes recent preclinical and clinical effects of varying fasting regimens on GM composition and associated physiology. Although the number of preclinical and clinical interventions are limited, significant data thus far suggest fasting interventions impact GM composition and physiology. However, there are considerable heterogeneities of study design, methodological considerations, and practical implications. Ongoing research on the health impact of fasting regimens on GM modulation is warranted.

The microorganisms in the gastrointestinal tract play a significant role in nutrient uptake, vitamin synthesis, energy harvest, inflammatory modulation, and host immune response, collectively contributing to human health. Important factors such as age, birth method, antibiotic use, and diet have been established as formative factors that shape the gut microbiota. Yet, less described is the role that exercise plays, particularly how associated factors and stressors, such as sport/exercise-specific diet, environment, and their interactions, may influence the gut microbiota. In particular, high-level athletes offer remarkable physiology and metabolism (including muscular strength/power, aerobic capacity, energy expenditure, and heat production) compared to sedentary individuals, and provide unique insight in gut microbiota research. In addition, the gut microbiota with its ability to harvest energy, modulate the immune system, and influence gastrointestinal health, likely plays an important role in athlete health, wellbeing, and sports performance. Therefore, understanding the mechanisms in which the gut microbiota could play in the role of influencing athletic performance is of considerable interest to athletes who work to improve their results in competition as well as reduce recovery time during training. Ultimately this research is expected to extend beyond athletics as understanding optimal fitness has applications for overall health and wellness in larger communities. Therefore, the purpose of this narrative review is to summarize current knowledge of the athletic gut microbiota and the factors that shape it. Exercise, associated dietary factors, and the athletic classification promote a more "health-associated" gut microbiota. Such features include a higher abundance of health-promoting bacterial species, increased microbial diversity, functional metabolic capacity, and microbial-associated metabolites, stimulation of bacterial abundance that can modulate mucosal immunity, and improved gastrointestinal barrier function.

Carotenoids are regarded as a cornerstone of avian vitality and coloration. Currently, the antioxidant potential of dietary carotenoids is debated for birds. Although some studies support a protective role, others report either no effect or pro-oxidant effects. However, the majority of research on this topic has not analyzed the oxidative status of a series of tissues in animals nor considered a range of carotenoid dosages. We investigated the effects of three levels of carotenoid supplementation on plasma, liver, adipose, heart and breast muscle oxidative damage in two congeneric species of waterfowl that exhibit marked differences in carotenoid coloration. After a 6-week depletion period, captive adult northern pintail (Anas acuta) and mallard (A. platyrhynchos) ducks of both sexes were fed either a carotenoid-depleted diet (<3 μg/g xanthophylls, lutein and zeaxanthin), a carotenoid-supplemented diet (50 μg/g) within physiological range, or a carotenoid-rich diet (100 μg/g) within pharmacological range for 22 to 32 weeks. We hypothesized that these dosages of dietary carotenoids would differentially affect oxidative damage between species and sexes and among the tissues examined. We found that dietary xanthophyll supplementation had no significant effect on tissue pro-oxidation in males and females from both species. Moreover, sex or species differences in oxidative stress were only observed in two tissues (plasma and heart). Significant correlations in the levels of oxidative damage were not observed among the tissues examined. In conclusion, the current study does not support a consistent antioxidant role for dietary carotenoids in the tissues of these two waterfowl species. Instead, our results align with the notion that carotenoids play complex, tissue- and species-specific roles in oxidative status in birds., (Copyright © 2019 Elsevier Inc. All rights reserved.)