Keto Means
Keto Means
Photo: Lisa Fotios
Despite these benefits, caffeine has been implicated in a number of adverse health outcomes possibly due to effects within the endocrine system, effects that may contribute to impaired reproductive function and low testosterone in men.
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Read More »Caffeine is the most widely used psychoactive drugs in the world, and estimates show that over 80% of Americans consume caffeine daily, with an average consumption of more than 200 mg/day [1]. Coffee and tea represent the main sources of caffeine (> 80% of daily intake), while soda, energy drinks, and chocolate are minor sources [2, 3]. Analysis of caffeine and its metabolites has been of great interest with respect to population-level caffeine exposure, utility in kinetic and metabolism studies of CYP450 enzymes, and for use in in vivo studies to estimate caffeine’s association with health outcomes [4]. Numerous benefits of caffeine consumption have been documented, including improved mood and wakefulness, weight loss, antioxidative properties, and potentially improved long-term memory [5,6,7]. Despite these benefits, adverse symptoms of high caffeine consumption including restlessness, insomnia, dehydration, and cardiac abnormalities are well-documented [8]. Additionally, reports of adverse effects on several organ systems including the cardiovascular, neurological, and endocrine systems have been published [8,9,10]. In the context of the endocrine system, there is preliminary evidence to suggest caffeine and its metabolites exert effects on various pathways, including those related to testosterone biosynthesis [11, 12]. Caffeine has a mean elimination half-life of 5 h, and virtually all of caffeine is metabolized in the body, with only 3% or less being excreted unchanged in urine [13]. The cytochrome P450 enzymes in the liver, mainly CYP1A2, are responsible for the metabolism of caffeine, and population level differences in P450 enzymes are known to contribute to variations in caffeine metabolism [14]. The main route of metabolism in humans (70–80%) is through N-3-demethylation to paraxanthine, also known as 1,7-dimethylxanthine or 17X. 1-N-demethylation of caffeine to theobromine accounts for approximately 7 to 8% of caffeine metabolism, and 7-N-demethylation to theophylline also around 7 to 8% [15]. The remaining 15% of caffeine undergoes C-8 hydroxylation to form 1,3,7-trimethyluric acid (Fig. 1). Fig. 1 Showing the metabolism of caffeine into its various metabolites. Theophylline, Paraxanthine, and Theobromine represent the major metabolites of caffeine, denoted by the bold arrows (4%, 84%, and 12% respectively) Full size image Testosterone plays an important role in men for the development of sexual features, brain function, muscle mass, and bone density [16, 17]. The most common symptoms associated with reduced serum testosterone (at or below 300 ng/dL) are decreased frequency of sexual thoughts and sexual desire, weight gain, and erectile dysfunction [18, 19]. In the U.S., the prevalence of low testosterone is as high as 40% in men over the age of 45 and is predicted to increase over the ensuing decades of life [20]. Paralleling the rise in low testosterone, there has been a decrease in fertilization rates both in the U.S. and worldwide [21]. Research shows that male factors such as hypogonadism account for over 40–50% of infertility cases [22,23,24]. A number of risk factors have been associated with low testosterone, including age, obesity, sedentary behavior, alcohol consumption, and certain medications [25, 26]. In addition to these risk factors, the potential role of the environment and dietary exposures, such as caffeine, on low testosterone etiology has come into light. A number of population level, in vitro, and in vivo studies have investigated the effects of caffeine on testosterone levels, yet results of these studies remain conflicting, inconclusive, and lack generalizability to the U.S. adult population. In a study by Park et al., prepubertal male rats that were exposed to caffeine over four weeks showed significant reductions in serum testosterone, as well as reductions in testicular mass. In a study by Friedman et al., rats exposed to theobromine and caffeine experienced significant testicular atrophy, and plasma concentrations of testosterone were elevated in theobromine and caffeine-fed rats. In a study of human participants, Wedick et al. (2012) investigated the association between caffeinated and decaffeinated coffee on sex hormone binding globulin and endogenous sex hormone levels. Over the period of 8 weeks, no significant associations were observed, however at the 4-week interval, men showed an increase in total testosterone, while females showed a decrease in total testosterone. A previous NHANES study by Lopez et. al. found non-linear associations between recall caffeine intake and testosterone, but insignificant linear associations. Based on data from these previous studies, and the potential for caffeine and its metabolites to dysregulate testosterone pathways experimentally, the researchers hypothesized that caffeine consumption is significantly associated with testosterone in men. In a representative sample of U.S. adult men, the researchers set out to quantify the strength and direction of the association between caffeine and testosterone.
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Tea, coffee, and herbal tea are a few options. Soda, sparkling water, low carb juices, sports drinks, and energy drinks are good options, too....
Read More »Methods for questionnaire data collection are described in the NHANES procedures guide [32]. Covariates related to low testosterone, as well as potential confounders were included and based on results from literature searches. Participants were classified according to highest level of education attainment, insurance coverage status, smoking status, alcohol use, diabetes status, and cholesterol status. Levels of education were based on responses by participants during the home interview. Insurance coverage status and smoking status were recorded as a yes or no response from the home interview. Alcohol use was divided into three categories of “non-drinker”, “moderate drinker”, and “heavy drinker.” Non-drinkers were defined by individuals stating they drank less than 1 alcoholic beverage a week. Moderate drinkers reported drinking between 2–8 drinks a week. Heavy drinkers were defined as drinking over 10 alcoholic drinks a week. Diabetes status was defined as a fasting serum glucose greater than 126 mg/dL, having answered yes to taking diabetic medications, or having been diagnosed by a physician with diabetes. Cholesterol status was defined by whether or not a person was told he/she has high cholesterol by a physician, if the serum total cholesterol was greater than 240 mg/dL, and/or if that person is currently taking hypercholesterolemia medications.
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