L-Carnitine: Main Functions

L-carnitine is a nutrient factor found mainly in foods of animal origin that plays a role in the use of fat as an energy source. Humans can also synthesise L-carnitine (L-b-hydroxy-c-N-trimethyl aminobutyric) acid in the liver, brain and kidneys from the amino acids lysine and methionine. The bioavailability of carnitine increases in vegetarians who do not obtain such high amounts from the diet, counteracting their lower intake to some extent. Skeletal and cardiac muscle have the highest concentrations of L-carnitine because these tissues utilise L-carnitine to help with energy production. L-Carnitine is used to shuttle long chain fatty acids into the mitochondria where oxidation of the fatty acids occurs to produce energy. L-Carnitine also activates the pyruvate dehydrogenase complex which converts pyruvate to acetyl-CoA, which is subsequently used to generate energy. Evidence suggests that L-carnitine can significantly improve weight loss when taken as a dietary supplement by overweight individuals. 

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Pooyandjoo, M., Nouhi, M., Shab‐Bidar, S., Djafarian, K. and Olyaeemanesh, A. 2016. The effect of (L‐) carnitine on weight loss in adults: a systematic review and meta‐analysis of randomized controlled trials. Obesity Reviews. 17(10): 970-976
Flanagan, J. L., Simmons, P. A., Vehige, J., Willcox, M. D. and Garrett, Q. 2010. Role of carnitine in disease. Nutrition and Metabolism. 7(1), 1-14
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The Effects of L-Carnitine Supplements on Weight Loss

L-carnitine is a nutrient factor that is present in the diet but also synthesised by cells. One of the functions of L-carnitine is to shuttle fatty acids into the mitochondria where they are oxidised to produce energy. Some evidence suggests that L-carnitine supplements may be useful for those that wish to lose weight. For example, in one study researchers administered a healthy diet to a group of overweight subjects with or without 3 grams per day of L-carnitine as a dietary supplement. The results of the study showed a significant increase in fatty acid oxidation in the subjects, and this was not accompanied by a detrimental increase in the breakdown of protein. L-carnitine may therefore have significant fat oxidation properties in overweight subjects. One thing to consider is that vitamin C is required for the synthesis of L-carnitine. L-carnitine supplements may therefore only work in those that are unable to produce enough of their own L-carnitine because they are already depleted in vitamin C. 

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Wutzke, K. D. and Lorenz, H. 2004. The effect of l-carnitine on fat oxidation, protein turnover, and body composition in slightly overweight subjects. Metabolism. 53(8): 1002-1006
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Does A Vitamin C Deficiency Reduce Fat Oxidation?

Vitamin C plays a role in the maintenance of correct body weight. One reason for this is that vitamin C is required for the biosynthesis of carnitine, a molecule that is necessary for the oxidation of fatty acids. A deficiency of vitamin C may decrease the synthesis of carnitine, and this may then affect the efficiency of fat oxidation. Around 15 % of adults in the United States are deficient in vitamin C and this may therefore explain the high rates of obesity. Researchers have investigated how the vitamin C status of an individual affects their ability to metabolise fat. In one study, researchers measured the vitamin C levels of healthy individuals and then asked them to run on a treadmill. The results showed that subjects with a marginal vitamin C status oxidised 25 % less fat during exercise compared to those subjects with an adequate vitamin C status. In addition, those with the best vitamin C levels also suffered less fatigue. Supplementation of depleted subjects with vitamin C caused a 4 fold increase in fat oxidation. 

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Johnston, C. S., Corte, C. and Swan, P. D. 2006. Marginal vitamin C status is associated with reduced fat oxidation during submaximal exercise in young adults. Nutrition and Metabolism.  3(1): 1-5
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Exercise Stress: The Effects of Antioxidants

Antioxidants may have significant benefits to athletes. Exercise is a form of stress, and the detrimental effects of exercise, at least in the short term, may be a significant increase in the generation of free radicals and oxidative stress. This oxidative stress may in turn have other physiological effects that include hormonal changes. Studies have investigated the effects of antioxidants in exercising athletes. For example in one study, researchers administered an antioxidant supplement, comprising 600 mg α-tocopherol, 1000 mg ascorbic acid and 32 mg β-carotene to healthy adults and then exposed them to their habitual training. The supplement caused significant increases in levels of α-tocopherol and β-carotene in the athletes, and this was associated with a significant reduction in oxidative stress. In addition, the anabolic to catabolic ratio of the athletes improved suggesting that the supplements had significantly improved the muscle building properties of the athletes.  

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Schröder, H., Navarro, E., Mora, J., Galiano, D. and Tramullas, A. 2001. Effects of α-tocopherol, β-carotene and ascorbic acid on oxidative, hormonal and enzymatic exercise stress markers in habitual training activity of professional basketball players. European Journal of Nutrition. 40(4): 178-184
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Magnesium Supplements as A Sleep Aid

Sleep deprivation is a common cause of poor health. In particular sleep deprivation may contribute towards the development of mood disorders and may also perpetuate them once present. Obtaining enough sleep is important because restorative processes occur during sleep, and those that are unable to obtain adequate sleep often deteriorate in their ability to cope with daily life. Supplemental magnesium has been shown to be highly beneficial at improving sleep and this may relate to the ability of magnesium to cause relaxation in muscle tissue. Further magnesium may also cause changes to neuronal firing rates that favours a state of relaxation over that of excitation. In one study, elderly subjects who were administered 500 mg of magnesium for 8 weeks had significant improvements in sleep time and sleep efficiency, as well as significant increases in melatonin levels. The magnesium also caused significant reductions in cortisol levels, suggesting that magnesium may have anti-stress properties. 

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Abbasi, B., Kimiagar, M., Sadeghniiat, K., Shirazi, M. M., Hedayati, M. and Rashidkhani, B. 2012. The effect of magnesium supplementation on primary insomnia in elderly: A double-blind placebo-controlled clinical trial. Journal of Research in Medical Sciences: the official journal of Isfahan University of Medical Sciences. 17(12): 1161
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Oxidative Stress and Cortisol Resistance

Cortisol is a stress hormone that is released in response to environmental stress. Cortisol is considered one of the major stress hormones in humans while corticosterone performs a similar role in animals. One of the functions of cortisol is to reduce the inflammatory response to injury and infection. Excessive oxidative stress can inhibit this process and prevent cortisol reducing inflammation in a process that has been termed cortisol resistance. Removal of the oxidative stress, through application of antioxidants may remove this cortisol resistance and allow cortisol to function effectively in its anti-inflammatory role. This may impart an explanation of the anti-inflammatory effects of antioxidants that have been consistently reported. By reducing cortisol resistance, antioxidants may lower plasma cortisol because the cortisol that is released becomes more effective, and negative feedback effects limit further release of cortisol. The flavonoid epicatechin has been shown to be particularly effective in this process. 

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Ruijters, E. J., Haenen, G. R., Weseler, A. R. and Bast, A. 2014. The cocoa flavanol (−)-epicatechin protects the cortisol response. Pharmacological Research. 79: 28-33
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Can Zinc Inhibit Cortisol Release?

The zinc status of an individual has been shown to cause changes to the adrenal secretions of an individual. Because zinc can regulate adrenal secretions, studies have investigated the effects of zinc supplements of stress hormone release. In one study, researchers administered 25, 37.5 or 60 mg of zinc to healthy subjects following a fast. The effects of the zinc supplements were observed as a significant reduction in the secretion of cortisol during the 4 hours of the study testing period. Therefore it may be that zinc supplements are able to lower blood levels of cortisol, and this may in part explain the mood elevating effects of zinc. It is known that the adrenal glands are rich in zinc and various disease states such as adrenal insufficiency and Cushing’s syndrome, that are characterised by low and high cortisol concentrations respectively, are also associated with alterations in zinc metabolism. Making sure that optimal zinc status is present may therefore be a pivotal strategy in effectively reducing stress levels. 

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Brandao-Neto, J., De Mendonca, B. B., Shuhama, T., Marchini, J. S., Pimenta, W. P. and Tornero, M. T. T. 1990. Zinc acutely and temporarily inhibits adrenal cortisol secretion in humans. Biological Trace Element Research. 24(1): 83-89
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Green Tea: Protective Effects Against Stress

Green tea is a rich source of polyphenolic phytochemicals. In particular it contains high amounts of the catechin variety of flavonoids. Evidence suggests that these catechins may have health benefits in humans and animals. One protective effect of green tea polyphenols may stem from their ability to protect the brain from the damaging effects of stress. For example, in one study researchers investigated the effects of green tea polyphenols on the cognitive performance of rats subjected to stress. The green tea polyphenols were significantly able to lower levels of stress hormones and prevent the stress induced degradation of cognitive processes in the brains of the rats. Therefore green tea polyphenols may confer significant protective effects against stressful environmental situations and this protective effect may in turn allow the brain to maintain its normal homeostatic function in terms of its cognitive performance. This may explain the mood elevating effects of green tea polyphenols that have been consistently demonstrated in studies. 

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Chen, W. Q., Zhao, X. L., Hou, Y., Li, S. T., Hong, Y., Wang, D. L. and Cheng, Y. Y. 2009. Protective effects of green tea polyphenols on cognitive impairments induced by psychological stress in rats. Behavioural Brain Research. 202(1): 71-76
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Tea: An Anti-Stress Drink

Tea is a healthy drink that has been shown to have a number of beneficial health effects. The beneficial health effects of tea are thought to stem from the presence of antioxidants in the tea. However, tea clearly has benefits that may not be explained by the presence of antioxidants. In particular, tea is a calming drink, and those who are under stress may derive significant benefits from consumption of tea. For example, in one study researchers administered tea to a group of healthy individuals over a period of 6 weeks. During this time the tea was able to significantly reduce blood pressure and heart rate elevations caused by the setting of specific behavioural  tasks. In addition, perceived stress levels also declined and relaxation levels increased, and this was accompanied by significant reductions in blood cortisol levels, suggesting that the tea had provided a significant anti-stress effect. Tea can therefore provide consumers with a relaxing and calming effect due to its ability to reduce stress levels. 

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Steptoe, A., Gibson, E. L., Vounonvirta, R., Williams, E. D., Hamer, M., Rycroft, J. A., Erusalimsky, J. D. and Wardle, J. 2007. The effects of tea on psychophysiological stress responsivity and post-stress recovery: a randomised double-blind trial. Psychopharmacology. 190(1): 81-89
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Vitamin C Reduces Stress Response

Stress is particularly damaging to the body because it causes detrimental changes to normal homeostatic function. When stress is acute, hormonal and nervous activity occurs that restores normal function after a period of rest and adaptation. Exercise is a form of stress and following exercise the body undergoes a period of disruption whereby restoratorative processes occur and this leads to an improved resilience to further stress. However, if the stress is chronic or severe, detrimental health effects occur. Vitamin C may be able to improve the adaptive process to stress by modulating the stress response following exercise. For example, in one study researchers observed significant attenuation of the stress response in ultramarathon runners who consumed 1500 mg per day of vitamin C, but not in those who took 500 mg per day. This took the form of a significant reduction in circulating cortisol and adrenaline. In addition, the vitamin C group also had significant reductions in inflammation through lower cytokine release. 

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Peters, E. M., Anderson, R., Nieman, D. C., Fickl, H. and Jogessar, V. 2001. Vitamin C supplementation attenuates the increases in circulating cortisol, adrenaline and anti-inflammatory polypeptides following ultramarathon running. International Journal of Sports Medicine. 22(7): 537-543
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