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  • Does a Very Low Carbohydrate Diet affect Exercise Performance?

    Carbohydrates have been known to be the universal fuel for physical activity and a necessity to prevent lean mass reduction. Recent studies have been tackling this subject and have shown that a Very Low Carbohydrate Diet (VLCD) can still preserve lean body mass or increase it in case of exercise and in fact has no detrimental effect on athletic performance. (1)
    Numerous studies have taken elite athletes and put them under the test of VLCD or ketogenic diets to explore their outcomes.
    A study published last year in the Sports Science for Health Journal, put 6 master endurance athletes on a 4 week low carbohydrate diet and found there was no change in time trial performances. (2) Another study published just earlier this year, found that a carbohydrate restricted diet followed by a strength training athlete had no effect on their strength and power levels despite a reduction in their body mass. (3) Regarding their athletic performance stats, athletes were not affected.
    The endocrinology department at Boston University compared the effects of a normal diet versus a low carbohydrate diet on 55 subjects for a 12 week period. The results showed that Low Carbohydrate diets may be more beneficial to cardiovascular health and inflammation than a diet with a regular amount of carbohydrates. The scientist found lowered levels of inflammatory markers including C-reactive protein, and an elevated health promoting markers such as serum adiponectin and high density lipoprotein-cholesterol. (4)
    More in depth investigations have been done by Volek and his team in the department of kinesiology at the University of Connecticut. This team of scientist assessed the body composition and hormonal responses in a comparative study between 20 subjects. Those that followed the carbohydrate restricted diet showed no significant changes in glucagon, total or free testosterone, sex hormone binding globulin (SHBG), insulin-like growth factor-I (IGF-I), cortisol, or triodothyronine (T3) uptake, nor were there significant changes in body composition or hormones in the restricted carbohydrate group. (5)
    However it's not all good news, a study published in the American Journal of Kidney Disease concluded that the consumption of a low carbohydrate diet delivers a marked acid load to the kidney, increases the risk for stone formation, decreases estimated calcium balance, and may increase the risk for bone loss with healthy subjects. (6)

    After reviewing the available publications up till now, the concept of the sole reliance on carbohydrates as a fuel for exercise is slowly changing. Yet, the metabolic effects of such dietary restriction needs more investigation at least within the athletic community since the influence of exercise is important on human physiology.

    References:
    1) Manninen, Anssi H. "Metabolic effects of the very-low-carbohydrate diets: misunderstood "villains" of human metabolism." J Int Soc Sports Nutr 1.2 (2004): 7-11.

    2) Piacentini, Maria Francesca, et al. "No changes in time trial performance of master endurance athletes after 4 weeks on a low carbohydrate diet." Sport Sciences for Health 8.1 (2012): 51-58.

    3) Sawyer, Jason C., et al. "EFFECTS OF A SHORT-TERMCARBOHYDRATE RESTRICTED DIET ON STRENGTH AND POWER PERFORMANCE." Journal of strength and conditioning research/National Strength & Conditioning Association (2013).

    4) Ruth, Megan R., et al. "Consuming a hypocaloric high fat low carbohydrate diet for 12weeks lowers C-reactive protein, and raises serum adiponectin and high density lipoprotein-cholesterol in obese subjects." Metabolism (2013).

    5) Volek, Jeff S., et al. "Body composition and hormonal responses to a carbohydrate-restricted diet." Metabolism 51.7 (2002): 864-870.

    6) Reddy, Shalini T., et al. "Effect of low-carbohydrate high-protein diets on acid-base balance, stone-forming propensity, and calcium metabolism." American Journal of Kidney Diseases 40.2 (2002): 265-274.

  • All you need to know about Citrulline

    What is Citrulline?
    L-Citrulline is an amino acid, naturally produced in human body and first isolated in lab from watermelon by Koga and Odake in 1914. L-Citrulline is one of the main components of the urea cycle, and is readily absorbed into intestinal mucosa and converted into L-Arginine. Bioavailability of L-Citrulline in form of L-Arginine into the bloodstream is greater than L-Arginine supplement that taken directly. Therefore, in more recent years, L-Citrulline has become a popular sports supplement for improving sports performance [1] and maintenance of cardiovascular health. [2, 3]

    Effects of Citrulline on insulin, growth hormone, IGF-1
    Citrulline has no direct effect on insulin, but it is converted into Arginine, which is an insulin secretagogue (an agent that stimulates secretion). Therefore, Citrulline indirectly affects insulin levels. Citrulline may have a positive influence on growth hormone during exercises or physical efforts. However this positive influence is short lived and ultimately the effect is decreased subsequently when you return to rest. In a study published in 2010 in the European Journal of Applied Physiology, Citrulline supplementation was shown to cause an increase in growth hormone immediately after a bout of endurance cycling. However, the effect on growth hormone declined some 3 hours after ceasing the exercise bout by up to 72%, so the total growth hormone effect remained around 28%.[4]
    In another study, there was no significant effect observed on IGF-1 concentrations after subjects were given 0.18g/kg dose of citrulline for 7 days consecutively and did not partake in any exercise. [5] Therefore, Citrulline does not directly stimulate secretion of growth hormone alone, as it requires the coupling with exercise.

    Effects of Citrulline on skeletal muscle
    Citrulline increases the efficiency of skeletal muscles by similar mechanism as observed with supplementation with arginine and nitrate based supplements. However, the exact mechanisms of this ergogenic benefit are largely unknown suggesting further research is required on the effects of citrulline on skeletal muscle. [6]

    How to take citrulline
    Dosage of L-citrulline depends on several varying factors such as age, health, exercise regime, and other health conditions. However, in general terms 1.5 g is an appropriate dose of citrulline. At present there is not enough research data to determine the perfect dosage of citrulline. Therefore, it would be wise to consult with a healthcare practitioner or expert in the field before for deciding an appropriate dosage.
    Citrulline is well tolerable in rats in dose of 3 g per kg weight. [7,8] Yet, there are no side effects reported in human. However, it is consider safer than arginine and ornithine, as these compounds cause intestinal upsets if dose exceeds from 10 g, but in the case of citrulline, it is well tolerated in dose of 15 g. [9]

    Summary
    L-citrulline is a non-essential amino acid, which is converted into L-arginine after absorption. It is a great sports supplement for heart, blood vessels and muscle health. The main health benefits of L-citrulline is that it stimulates the production of nitric oxide and doubles the amount of L-arginine in the body, which helps to relax arteries, improves physical stamina and blood circulation throughout the body. Therefore, it is widely used as a core ingredient in pre workout supplements to help improve physical performance during exercise.

    References
    1] Bendahan D, et al. Citrulline/malate promotes aerobic energy production in human exercising muscle. Br J Sports Med. (2002)

    2] Orozco-GutiƩrrez JJ, et al. Effect of L-arginine or L-citrulline oral supplementation on blood pressure and right ventricular function in heart failure patients with preserved ejection fraction. Cardiol J. (2010)

    3] Orea-Tejeda A, et al. The effect of L-arginine and citrulline on endothelial function in patients in heart failure with preserved ejection fraction. Cardiol J. (2010)

    4] Sureda A, et al. L-citrulline-malate influence over branched chain amino acid utilization during exercise. Eur J Appl Physiol. (2010)

    5] Thibault R, et al. Oral citrulline does not affect whole body protein metabolism in healthy human volunteers: results of a prospective, randomized, double-blind, cross-over study. Clin Nutr. (2011)

    6] Brown GC. Nitric oxide and mitochondrial respiration. Biochim Biophys Acta. (1999)

    7] Giannesini B, et al. Citrulline malate supplementation increases muscle efficiency in rat skeletal muscle. Eur J Pharmacol. (2011)

    8] Takeda K, et al. Effects of citrulline supplementation on fatigue and exercise performance in mice. J Nutr Sci Vitaminol (Tokyo). (2011)

    9] Moinard C, et al. Dose-ranging effects of citrulline administration on plasma amino acids and hormonal patterns in healthy subjects: the

    10] Citrudose pharmacokinetic study. Br J Nutr. (2008)

  • Does Glycemic Index affect Exercise Performance?

    Carbohydrates have a significant positive influence on exercise performance, largely due to their role as a major energy source. The ingestion of carbohydrates prior to exercise has also been shown to have a positive influence on both metabolic responses and exercise performance. (1) Carbohydrate feeding provides greater muscle glucose uptake and reduced hepatic glucose output during exercise in addition to sparing muscle glycogen stores and preventing muscle glycogen depletion. (2,3)

    Glycemic index ranks foods based upon their effects on blood glucose level increases. . Foods with a high glycemic index are said to be digested quickly and provide a rapid spike in blood glucose levels, whilst low glycemic index foods are considered to be the opposite having a minor impact on blood glucose levels and slowly digesting. Theoretically it would make sense to suggest that high glycemic foods would provide a quick burst of energy and therefore have a positive effect on exercise performance, however this is not the case. Exercise performance has been shown to remain unaffected by high glycemic foods in several studies. (4,5) In a study published in the Journal Medicine and Science in Sports and Exercise, scientist showed that a pre exercise low glycemic index feeding maintained higher plasma glucose levels at the end of a 2 hour exercise bout. (6) Additionally, subjects reported lower ratings of perceived exertion indicating low glycemic foods may also assist with reducing fatigue levels. It is believed that low glycemic foods enhance glucose availability during exercise.

    However, despite there being evidence to suggest that low glycemic foods have a positive influence on exercise performance, there is also equal evidence to suggest there is no influence what so ever by the glycemic index of a pre exercise meal. In a study published in the Journal of the International Society of Sports Nutrition in 2011, scientist showed ingestion of different glycemic index foods of the same quantity did not result in a difference to exercise performance. (7)

    The actual answer to this question is not all that easy to answer, particularly given the conflicting evidence provided by both sides of the argument. This is the great thing about science is that it constantly evolves and the more research that is done, the more we begin to learn and the more confident we can be in the findings. For now though, further research is required into the effects of glycemic foods on exercise performance. Despite there being no clear opinion on the influence of differing glycemic index pre exercise foods, we do know one thing for sure - a carbohydrate rich source of food is the most optimal pre exercise food that can positively influence exercise performance.

    References
    1) Hargreaves M. Pre-exercise nutritional strategies: effects on metabolism and performance. Can J Appl Physiol. 2001. 26:S64-70.

    2) Marmy-Conus N, Fabris S, Proietto J, Hargreaves M. Preexercise glucose ingestion and glucose kinetics during exercise. J Appl Physiol. 1996. 81:853-857.

    3) Tsintzas K, Williams C. Human muscle glycogen metabolism during exercise. Effect of carbohydrate supplementation. Sports Med. 1998. 25:7-23.

    4) Earnest CP, Lancaster SL, Rasmussen CJ, Kerksick CM, et. al. Low vs. high glycemic index carbohydrate gel ingestion during simulated 64-km cycling time trial performance. J Strength Cond Res. 2004. 18:466-472.

    5) Febbraio MA, Keenan J, Angus DJ, Campbell SE, Granham AP. Preexercise carbohydrate ingestion, glucose kinetics, and muscle glycogen use: effect of the glycemic index. J Appl Physiol. 2000. 89:1845-1851.

    6) DeMarco HM, Sucher KP, Cisar CJ, Butterfield GE. Pre-exercise carbohydrate meals: application of glycemic index. 1999. 31(1):164-170.

    7) Jamurtas AZ, Tofas T, Fatouros I, Nikolaidis MG, et. al. The effects of low and high glycemic index foods on exercise performance and beta-endorphin responses. J Int Soc Sports Nutr. 2011. 8:15.

  • Creatine and Kidney Function

    Some people argue that creatine supplementation results in adverse health effects particularly kidney damage. Media reports and several websites play an active role in spreading such erroneous information. While this may appear to be true to the eyes of the public, the truth is actually quite the opposite. This article will present the benefits of creatine supplementation and the effects of its chronic use to human health from a scientific standpoint.

    Overview on Creatine
    Creatine is a protein substance naturally found in the human body. Because creatine is mostly found in muscles, it is believed that creatine plays a dynamic role in generating muscular energy. Today, it is one of the most talked-about dietary supplements that helps to develop and increase muscle strength. Due to the supplements' hailed benefits, creatine appears to be one of the most used supplements among athletes which some scientist have raised concern about. They contend that chronic use of creatine supplements lead to reduced kidney function.

    Use of Creatine Supplements
    Creatine supplements are widely used among professional athletes and "gym junkies". Consumption of the supplement is not illegal nor restricted in any country. One case in point is the International Olympic Committee and National Collegiate Athletic Association which permit their students to take creatine supplements and further reveal that no plans have been set in prohibiting its use in colleges and universities.

    Other than building muscle strength, creatine supplements are used in treating the following conditions:
    Depression
    Eye problems
    Parkinson's disease
    High cholesterol
    Arthritis
    Congestive heart failure
    Muscular disorders such as muscle dystrophy

    Creatine Supplementation Damages Kidney: Fact or Fallacy?
    In spite of many claims stating that creatine monohydrate supplements decrease renal function, this has been proven otherwise. In a study conducted in the Journal of the International Society of Sports Nutrition this year showed that 3 months of supplementation with creatine monohydrate and a high protein diet had no significant impact on kidney function including Glomerular Filtration Rate or Cr-EDTA clearance. (1) in which subjects were individuals attending resistance training routines while taking high-protein diet.

    In another study published in the American Journal of Kidney Disorders, scientist gave a subject with only one kidney a high dose (20g/d for 5 days and then 5g/d for the next 30 days) of creatine monohydrate each day and found that there was no negative changes to Glomerular Filtration Rate nor Cr-EDTA clearance, again showing creatine supplementation does not impair kidney function. (2)

    To date, no long term clinical studies have shown adverse effects from the use of creatine mononhydrate in various populations including athletes, infants or adults. (3,4,5)

    Summary
    Long-term use of creatine monohydrate supplements is considered safe as medically backed by studies referenced in this article. This has led the International Society of Sports Nutrition to publish a position stance on the use of Creatine. It is the position of the International Society of Sports Nutrition that the use of creatine as a nutritional supplement within established guidelines is safe, effective, and ethical. (6)

    References
    1) Lugaresi R, Leme M, De Salles V, Murai I, Roschel H, et al. Doe long-term creatine supplementation impair kidney function in resistance-trained individuals consuming a high protein diet? JISSN. 2013;10(26).

    2) Gualano B, et al. Effect of short-term high-dose creatine supplementation on measured GFR in a young man with a single kidney. Am J Kidney Dis. 2010.

    3) Kreider RB, Melton C, Rasmussen CJ, Greenwood M, Lancaster S, Cantler EC, Milnor P, Almada AL: Long-term creatine supplementation does not significantly affect clinical markers of health in athletes. Mol Cell Biochem 2003, 244:95-104.

    4) Poortmans JR, Francaux M: Long-term oral creatine supplementation does not impair renal function in healthy athletes. Med Sci Sports Exerc 1999, 31:1108-1110.

    5) Robinson TM, Sewell DA, Casey A, Steenge G, Greenhaff PL: Dietary creatine supplementation does not affect some haematological indices, or indices of muscle damage and hepatic and renal function. Br J Sports Med 2000, 34:284-8.

    6) Buford TW, Kreider RB, Stout JR, Greenwood M, Campbell B, Spano M, Ziegenfuss T, Lopez H, Landis J, Antonio J: International Society of Sports Nutrition position stand: creatine supplementation and exercise. J Int Soc Sports Nutr 2007, 4:6.

  • What's the real deal on High Fructose Corn Syrup (HFCS)?

    The habitual use of high fructose corn syrup nowadays is widely associated with the ballooning cases of chronic diseases including obesity and type 2 diabetes. But is HFCS really to blame for the rise in these metabolic conditions? More recently HFCS appears to be taking the brunt of the blame game whilst table sugar goes almost unnoticed.

    What is High Fructose Corn Syrup?
    High Fructose Corn Syrup, abbreviated as HFCS, is a special form sweetener that is made up of 55% fructose and 42% glucose. Although commonly related to the United States of America, high fructose corn syrup was actually first introduced in Japan in the 1970s when they convert cornstarch into a special form of sweetener.

    High fructose corn syrup works by developing a sweeter sugar taste similar to that of cane sugar. It is relatively cheap, thus more and more manufacturers are now using it in place of cane sugar.

    How does High Fructose Corn Syrup Differs from Sugar?
    HFCS is a blend of both glucose and fructose molecules. The fructose component of the syrup can vary between 40-55% depending on its intended purpose. There is only a minor subtle difference between HFCS and sugar (sucrose) particularly at a molecular levels. Sucrose is an equal 1:1 ratio of both sucrose and fructose making it 50% fructose and 50% sucrose. The molecular difference between HFCS and table sugar is negligible at best.

    What does science tell us about HFCS?
    There has been mostly negative media exposure surrounding HFCS particularly accusations that it is a significant contributing factor the rise in chronic diseases such as obesity and diabetes. However from a scientific stand point, the effects of HFCS to satiety, weight loss and hormonal responses have found no significant difference between HFCS and table sugar. In a study published in 2007, scientist investigated the effects of HFCS consumption and fasting blood glucose, insulin, leptin and ghrelin levels in a group of female subjects. (1) The results showed that there were no significant differences between the effects of HFCS and table sugar on fasting blood glucose, insulin, leptin and ghrelin levels. This was again confirmed in a study published in the American Journal of Clinical Nutrition in 2008 where table sugar and HFCS did not have substantially different short-term endocrine/metabolic effects. (2)

    Summary
    HFCS frequently cops a bad wrap by the media. This point of this article is not to suggest HFCS is good for us, but to merely highlight that often what you may hear in the media may not always be exactly right. Yes HFCS is bad for our health in high intakes, however so to is table sugar. And as this article points out (with scientific reasoning) both HFCS and table sugar have the same negative metabolic and endocrine effects. To be on the safe side, I'd recommend you avoid the pair of these sugars as there is no denying that they contribute to metabolic conditions such as obesity and type 2 diabetes in the long term.

    References
    1) Melanson KJ, Zukley L, Lowndes J, Nguyen V, et al. Effects of high-fructose corn syrup and sucrose consumption on circulating glucose, insulin, leptin, and ghrelin and on appetite in normal-weight women. Nutrition. 2007;23(2):103-112.
    2) Stanhope KL, Griffen SC, Bair BR, Swarbrick MM, et al. Twenty-four-hour endocrine and metabolic profiles following consumption of high-fructose corn syrup-,sucrose-,fructose-, and glucose-sweetened beverages with meals.

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