Fructose

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One of the greatest sources of Fructose is soft drinks.

Fructose can be good or bad for an athlete depending on when it's consumed. Fructose can help athletic performance when taken as a fuel source during exercise, but at other times excessive fructose can create health issues. Fructose is found in sugar (sucrose), High Fructose Corn Syrup, Honey and Agave. Excessive fructose intake has been described as "an environmental toxin with major health implications"[1]. High Fructose Corn Syrup may be slightly worse for health than sugar, and may be a source of toxic mercury.

1 What is Fructose?

Fructose is a common simple sugar that along with glucose makes up ordinary table sugar (sucrose), and High Fructose Corn Syrup (HFCS). In table sugar, one molecule of fructose is combined with one molecule of glucose. In High Fructose Corn Syrup the fructose and glucose are not linked together, but mixed in various ratios, generally close to 50:50 (55% and 42% is common[2], with 55% being used in drinks and 42% being used in foods[3]). Fructose is sometimes called "fruit sugar" because it is commonly found in fruit. Some fruit, such as apples and pears contain twice as much fructose as glucose[4].

2 Health risks of Fructose

The effect of fructose is very different from glucose, with different pathways in the body being used[5]. Fructose tends to result in the production of fat, influences hormones that control appetite, energy balance, and the storage of body fat, as well as tending to create insulin resistance[6][7]. It has been proposed that intakes of >50g per day of fructose may be a cause of type II diabetes[8]. Fructose is also believed to be a risk factor for hypertension, elevated triglycerides, obesity, preeclampsia, chronic kidney disease, stroke, cardiovascular disease, and mortality[9][10], as well as causing liver disease similar to that seen in alcoholics[11][12][13][14]. Also, there may be a link between fructose and dementia[15] and reduced aerobic capacity[16]. Both Fructose and Glucose tend to result in increased body fat, Fructose can produce a greater increase in visceral (internal) fat[17][18], which is a risk factor for heart disease[19] and diabetes[20]. Between 1977 and 2001 Americans increased the percentage of their daily calories from soft drinks from 2.8% to 7.0% and from fruit juice from 1.1% to 2.2%[21].

2.1 Fructose and Fruit

The health risks of high fructose consumption and not generally seen with high intakes of whole fruit[2]. While fruit does contain fructose, it's not easy to consume significant quantities of fructose from whole fruit. For instance, an Apple contains about 10g of fructose, and a 16 ounce soft drink contains about 26g of fructose. The Apple is generally much slower to consume than a soft drink, and in addition, the Apple contains Fiber which will slow absorption. However, the health benefits of whole fruit do not seem to apply to fruit juice[22]. There does not appear to be any evidence that fruit juice has a lower health risk than soft drinks.

2.2 Sugar and High Fructose Corn Syrup

Corn syrup does not naturally contain any fructose, but it can be processed so that some of the glucose is converted to fructose, hence the term High Fructose Corn Syrup. Typically high fructose corn syrup has a similar amount of fructose as ordinary table sugar (sucrose) which is 50:50 fructose and glucose. With table sugar, the fructose and glucose are linked together, but they are separate in High Fructose Corn Syrup, as well as honey[23], and cooking sugar with and an acid (such as jam making) separates the fructose and glucose[24]. The consensus of research indicates that High Fructose Corn Syrup has a similar effect to ordinary table sugar[25][3][26][27][28][29][30][31][32][33]. There are a few studies which indicate differences between the separate fructose/glucose which is found in High Fructose Corn Syrup or honey and table sugar. Rats fed 40% of calories from fructose/glucose had impaired fasting glucose and were less active than with equivalent amounts of sugar[34], and higher triglycerides (60% of calories)[35]. Fructose metabolism is different for different species so animal studies, especially concerning triglycerides, may not be applicable to humans[36]. I found two studies that showed a difference in humans. Carbohydrate sensitive men had a greater insulin response to a large dose of separate fructose/glucose after a 9 hour fast compared with table sugar, though not a greater blood sugar level[37]. Another study[38] showed higher triglyceride levels from separate fructose/glucose than table sugar in 8 healthy men. A more significant concern is mercury contamination of HFCS which a study found in half of the samples analyzed[39]. Overall, I would conclude that high fructose corn syrup is slightly worse than sugar, which combined with the risk of mercury contamination indicates it may be worth avoiding.

3 Fructose and Obesity

Studies have shown that drinking soft drinks results in an increase in energy intake and body weight in both overweight[40] and normal weight[41] subjects. This weight gain has also been shown in animal studies[42][43], and a study of diabetics[44]. One mechanism may be that fructose does not stimulate the hormone leptin that reduces appetite[45]. One study showed that drinking artificially sweetened (aspartame) soda actually caused a reduction in energy intake compared with no soda and some also lost body weight[41].

4 Fructose for Athletes

As noted in Nutrient Timing, the human body responds to nutrition differently when exercising. This is also true for fructose, which can be a beneficial addition to a sports drink. Combined carbohydrate types, such as fructose, glucose or Maltodextrin are absorbed more easily than when taken in isolation[46], and the combination of fructose and glucose provides more carbohydrate fuel than glucose alone[47][48]. While fructose alone does not improve performance in the way that glucose does[49], the combination of fructose and glucose improves performance more than glucose alone[50]. The combination of fructose and glucose also results in better fluid absorption than either alone[2]. Also, some of the health issues of fructose are mitigated by exercise[51]. Fructose on its own can cause digestive upsets, but the combining glucose with fructose either as sugar (sucrose) or separately dramatically improves fructose absorption[52]. Therefore a good sports drink should contain some fructose along with glucose and/or Maltodextrin. See Fellrnr's Go Juice.

5 References

  1. ↑ The effect of fructose on renal biology and... [J Am Soc Nephrol. 2010] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/21115612
  2. ↑ 2.0 2.1 2.2 Fructose, exercise, and health. [Curr Sports Med Rep. 2010 Jul-Aug] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/20622544
  3. ↑ 3.0 3.1 Effects of glucose-to-fructose ratios in solutions on subjective satiety, food intake, and satiety hormones in young men http://www.ajcn.org/content/86/5/1354.full
  4. ↑ NDL/FNIC Food Composition Database Home Page http://ndb.nal.usda.gov/
  5. ↑ Fructolysis - Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/Fructolysis
  6. ↑ Dietary fructose: implications for dysregulation of... [Nutr Rev. 2005] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/15971409
  7. ↑ ARS | Publication request: Consumption of fructose-sweetened beverages for 10 weeks reduces net fat oxidation and energy expenditure in overweight/obese men and women http://www.ars.usda.gov/research/publications/publications.htm?seq_no_115=247054
  8. ↑ Hypothesis: Could Excessive Fructose Intake and Uric Acid Cause Type 2 Diabetes? http://edrv.endojournals.org/content/30/1/96.full
  9. ↑ Potential role of sugar (fructose) in the epidemic of hypertension, obesity and the metabolic syndrome, diabetes, kidney disease, and cardiovascular disease http://www.ajcn.org/content/86/4/899.full
  10. ↑ Sugar-sweetened beverages and risk of obesity ... [Physiol Behav. 2010] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/20138901
  11. ↑ Soft drink consumption linked with fatty... [Can J Gastroenterol. 2008] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/18925303
  12. ↑ Fructose consumption as a risk factor for non-alco... [J Hepatol. 2008] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/18395287
  13. ↑ Diabetes of the liver: the link betw... [Obesity (Silver Spring). 2009] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/19282820
  14. ↑ Soft drinks consumption and nonalcohol... [World J Gastroenterol. 2010] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/20518077
  15. ↑ Increased fructose intake as a... [J Gerontol A Biol Sci Med Sci. 2010] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/20504892
  16. ↑ Fructose consumption leads to reduced aero... [Lipids Health Dis. 2012] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/22713601
  17. ↑ JCI - Consuming fructose-sweetened, not glucose-sweetened, beverages increases visceral adiposity and lipids and decreases insulin sensitivity in overweight/obese humans http://www.jci.org/articles/view/37385
  18. ↑ High-fructose corn syrup causes char... [Pharmacol Biochem Behav. 2010] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/20219526
  19. ↑ Effect of potentially modifiable risk factors associated with myocardial infarction in 52 countries (the INTERHEART study): case-control study : The Lancet http://www.thelancet.com/journals/lancet/article/PIIS0140-6736%2804%2917018-9/fulltext
  20. ↑ The perils of portliness: causes and consequences o... [Diabetes. 2000] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/10866038
  21. ↑ Changes in beverage intake between 1977 and 2001. [Am J Prev Med. 2004] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/15450632
  22. ↑ Excess fruit juice consumption by preschool-aged ... [Pediatrics. 1997] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/8989331
  23. ↑ National Honey Board. "Carbohydrates and the Sweetness of Honey" http://www.honey.com/images/downloads/carb.pdf
  24. ↑ Inverted sugar syrup - Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/Inverted_sugar_syrup
  25. ↑ High-fructose corn syrup, energy intake, and appetite regulation http://www.ajcn.org/content/88/6/1738S.full
  26. ↑ Sugars and satiety: does the type of sweetener make a difference? http://www.ajcn.org/content/86/1/116.short
  27. ↑ Fructose and Satiety http://jn.nutrition.org/content/early/2009/04/29/jn.108.097956
  28. ↑ No differences in satiety or energy intake after high-fructose corn syrup, sucrose, or milk preloads http://www.ajcn.org/content/86/6/1586.full
  29. ↑ Effects of high-fructose corn syrup and sucrose co... [Nutrition. 2007] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/17234503
  30. ↑ Endocrine and metabolic effects of consuming beverages sweetened with fructose, glucose, sucrose, or high-fructose corn syrup http://www.ajcn.org/content/88/6/1733S.full
  31. ↑ Dietary fructose and glucose differentially affect li... [J Nutr. 2009] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/19403705
  32. ↑ Fructose and metabolic diseases: new findi... [Nutrition. 2010 Nov-Dec] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/20471804
  33. ↑ The Effects of High Fructose Syrup http://www.jacn.org/content/28/6/619.long
  34. ↑ Metabolic and behavioural effects of sucrose and ... [Eur J Nutr. 2012] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/21800086
  35. ↑ Comparison of free fructose and glucose to sucrose in the ability to cause fatty liver http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2805058/
  36. ↑ Fructose and Cardiometabolic Disorders: The Controversy Will, and Must, Continue http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2910863/
  37. ↑ Blood insulin, glucose, fructose and gastric inhibito... [J Nutr. 1983] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/6350543
  38. ↑ Triglyceride concentrations: the disaccharide effect http://www.sciencemag.org/content/206/4420/838
  39. ↑ Mercury from chlor-alkali plants: measured co... [Environ Health. 2009] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/19171026
  40. ↑ Sucrose in soft drinks is fattening - Faculty of Life Sciences - University of Copenhagen http://curis.ku.dk/portal-life/en/publications/sucrose-in-soft-drinks-is-fattening%2894de5d20-a1bb-11dd-b6ae-000ea68e967b%29.html
  41. ↑ 41.0 41.1 Effect of drinking soda sweetened with aspartame or high-fructose corn syrup on food intake and body weight. http://www.ajcn.org/content/51/6/963.abstract?ijkey=9ecb2a9daf19fcdbe03490e78a64def1c95019d6&keytype2=tf_ipsecsha
  42. ↑ Differential Effects of Sucrose, Fructose and Glucose on Carbohydrate-Induced Obesity in Rats http://jn.nutrition.org/content/112/8/1546.short
  43. ↑ Effects of chronic dietary fructose with and witho... [Br J Nutr. 1993] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/8399102?dopt=Abstract
  44. ↑ Metabolic Effects of Fructose Supplementation in Diabetic Individuals http://care.diabetesjournals.org/content/12/5/337.abstract?ijkey=a483f995454dcd72f638bb91b226ad8886b2f7ea&keytype2=tf_ipsecsha
  45. ↑ Fructose, weight gain, and the insulin resistance syndrome http://www.ajcn.org/content/76/5/911.long
  46. ↑ Effects of carbohydrate type and concen... [Med Sci Sports Exerc. 1995] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/8614315
  47. ↑ Oxidation of combined ingestion of glucose and sucrose during exercise http://www.metabolismjournal.com/article/S0026-0495%2805%2900004-1/abstract
  48. ↑ Effect of graded fructose coingestion with maltodextrin on exogenous 14C-fructose and 13C-glucose oxidation efficiency and high-intensity cycling performance http://jap.physiology.org/content/104/6/1709.full
  49. ↑ Influence of glucose and fructose ingestion on ... [Clin Physiol. 1984] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/6542834
  50. ↑ Substrate utilization during exercise with gl... [J Appl Physiol. 2001] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/11181599
  51. ↑ Exercise counteracts fatty liver disease i... [Lipids Health Dis. 2010] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/20946638
  52. ↑ Absorption capacity of fructose in healthy adults. Comparison with sucrose and its constituent monosaccharides. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1433856/
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