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[[File:Soft drink shelf.JPG|right|thumb|500px|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 [http://en.wikipedia.org/wiki/Agave_nectar Agave]. Excessive fructose intake has been described as "an environmental toxin with major health implications"<ref name="FructoseMajorHealth"/>. High Fructose Corn Syrup may be slightly worse for health than sugar, and may be a source of toxic mercury.
=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<ref name="FructoseExerciseHealth"/>, with 55% being used in drinks and 42% being used in foods<ref name="FructoseHFCS2"/>). 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<ref name="FructoseNutrientDatabase"/>.
=Health risks of Fructose=
The effect of fructose is very different from glucose, with different pathways in the body being used<ref name="FructoseFructolysis"/>. 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<ref name="FructoseHavel"/><ref name="FructoseFatOxidationCox-2012"/>. It has been proposed that intakes of >50g per day of fructose may be a cause of type II diabetes<ref name="FructoseUricT2Diabetes"/>. Fructose is also believed to be a risk factor for hypertension, elevated triglycerides, obesity, preeclampsia, chronic kidney disease, stroke, cardiovascular disease, and mortality<ref name="FructoseEpiRole"/><ref name="FructoseSSB"/>, arthritis<ref name="DeChristopherUribarri2016"/>, asthma<ref name="DeChristopher-2016"/>, and chronic bronchitis<ref name="DeChristopher-2015"/>, as well as causing [http://en.wikipedia.org/wiki/Non-alcoholic_fatty_liver_disease liver disease] similar to that seen in alcoholics<ref name="FructoseLiverAssy"/><ref name="FructoseLiverOuyang"/><ref name="FructoseLiverCollison"/><ref name="FructoseSDNAFLD"/>. Also, there may be a link between fructose and dementia<ref name="FructoseDementia"/> and reduced aerobic capacity<ref name="FructoseAerobic"/>. Both Fructose and Glucose tend to result in increased body fat, Fructose can produce a greater increase in visceral (internal) fat<ref name="FructoseVisceralFat"/><ref name="FructoseAbdominal"/>, which is a risk factor for heart disease<ref name="FructoseVisceralFatHeart"/> and diabetes<ref name="FructoseVisceralDiabetesMontague-2000"/>. 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%<ref name="FructoseIntake"/>.
==Fructose and Fruit==
The health risks of high fructose consumption and not generally seen with high intakes of whole fruit<ref name="FructoseExerciseHealth"/>. 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 couple slow absorption. However, the health benefits of whole fruit do not seem to apply to fruit juice<ref name="FructoseJuiceKids"/>. There does not appear to be any evidence that fruit juice has a lower health risk than soft drinks.
==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<ref name="FructoseHoney"/>, and cooking sugar with and an acid (such as jam making) separates the fructose and glucose<ref name="FructoseInvertedSugar"/>. The consensus of research indicates that High Fructose Corn Syrup has a similar effect to ordinary table sugar<ref name="FructoseHFCSMeta1"/><ref name="FructoseHFCS2"/><ref name="FructoseHFCS3"/><ref name="FructoseHFCS4"/><ref name="FructoseHFCS5"/><ref name="FructoseHFCS6"/><ref name="FructoseHFCS7"/><ref name="FructoseHFCS8"/><ref name="FructoseTappy"/><ref name="FructoseHFCSJacn"/>. 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<ref name="FructoseGFDiffRat"/>, and higher triglycerides (60% of calories)<ref name="FructoseDiffTG"/>. Fructose metabolism is different for different species so animal studies, especially concerning triglycerides, may not be applicable to humans<ref name="FructoseHFCSSpecies"/>. 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<ref name="FructoseHFCSCarbSens"/>. Another study<ref name="FructoseHFCSHumanTG"/> 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<ref name="FructoseHFCSMercury"/>. 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.
=Fructose and Obesity=
Studies have shown that drinking soft drinks results in an increase in energy intake and body weight in both overweight<ref name="FructoseWeight1"/> and normal weight<ref name="FructoseWeight2"/> subjects. This weight gain has also been shown in animal studies<ref name="FructoseWeightAnimal1"/><ref name="FructoseWeightAnimal2"/>, and a study of diabetics<ref name="FructoseWeightDiabetics"/>. One mechanism may be that fructose does not stimulate the hormone leptin that reduces appetite<ref name="FructoseWeightLeptin"/>. 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<ref name="FructoseWeight2"/>.
=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<ref name="FructoseExCombMix"/>, and the combination of fructose and glucose provides more carbohydrate fuel than glucose alone<ref name="FructoseExCombRoy"/><ref name="FructoseExCombRowlands"/>. While fructose alone does not improve performance in the way that glucose does<ref name="FructoseExFrucOrGluc1"/>, the combination of fructose and glucose improves performance more than glucose alone<ref name="FructoseExFrucAndGlucBoys"/>. The combination of fructose and glucose also results in better fluid absorption than either alone<ref name="FructoseExerciseHealth"/>. Also, some of the health issues of fructose are mitigated by exercise<ref name="FructoseFLDExcRat"/>. Fructose on its own can cause digestive upsets, but the combining glucose with fructose either as sugar (sucrose) or separately dramatically improves fructose absorption<ref name="FructoseAbsorbtion"/>. Therefore a good sports drink should contain some fructose along with glucose and/or [[Maltodextrin]]. See [[Fellrnr's Go Juice]].
=References=
<references>
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<ref name="FructoseWeightLeptin">Fructose, weight gain, and the insulin resistance syndrome http://www.ajcn.org/content/76/5/911.long </ref>
<ref name="FructoseWeightAnimal2">SW. Rizkalla, J. Boillot, V. Tricottet, AM. Fontvieille, J. Luo, JL. Salzman, JP. Camilleri, G. Slama, Effects of chronic dietary fructose with and witho.without copper supplementation on glycaemic control, adiposity, insulin binding to adipocytes and glomerular basement membrane thickness in normal rats.. [, Br J Nutr. , volume 70, issue 1, pages 199-209, Jul 1993] - PubMed - NCBI , PMID [http://www.ncbi.nlm.nih.gov/pubmed/8399102?dopt=Abstract 8399102]</ref>
<ref name="FructoseWeightAnimal1">Differential Effects of Sucrose, Fructose and Glucose on Carbohydrate-Induced Obesity in Rats http://jn.nutrition.org/content/112/8/1546.short </ref>
<ref name="FructoseWeight2">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 </ref>
<ref name="FructoseWeightDiabetics">Metabolic Effects of Fructose Supplementation in Diabetic Individuals http://care.diabetesjournals.org/content/12/5/337.abstract?ijkey=a483f995454dcd72f638bb91b226ad8886b2f7ea&keytype2=tf_ipsecsha </ref>
<ref name="FructoseWeight1">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 </ref>
<ref name="FructoseExCombMix">X. Shi, RW. Summers, HP. Schedl, SW. Flanagan, R. Chang, CV. Gisolfi, Effects of carbohydrate type and concen..concentration and solution osmolality on water absorption. [, Med Sci Sports Exerc. , volume 27, issue 12, pages 1607-15, Dec 1995] - PubMed - NCBI , PMID [http://www.ncbi.nlm.nih.gov/pubmed/8614315 8614315]</ref>
<ref name="FructoseExCombRowlands">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 </ref>
<ref name="FructoseExCombRoy">Oxidation of combined ingestion of glucose and sucrose during exercise http://www.metabolismjournal.com/article/S0026-0495%2805%2900004-1/abstract </ref>
<ref name="FructoseHFCS4">Fructose and Satiety http://jn.nutrition.org/content/early/2009/04/29/jn.108.097956 </ref>
<ref name="FructoseHFCS3">Sugars and satiety: does the type of sweetener make a difference? http://www.ajcn.org/content/86/1/116.short </ref>
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<ref name="FructoseNutrientDatabase">NDL/FNIC Food Composition Database Home Page http://ndb.nal.usda.gov/ </ref>
<ref name="FructoseFructolysis">Fructolysis - Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/Fructolysis </ref>
<ref name="FructoseUricT2Diabetes">RJ. Johnson, SE. Perez-Pozo, YY. Sautin, J. Manitius, LG. Sanchez-Lozada, DI. Feig, M. Shafiu, M. Segal, RJ. Glassock, Hypothesis: Could Excessive Fructose Intake could excessive fructose intake and Uric Acid Cause Type uric acid cause type 2 Diabetesdiabetes? , Endocr Rev, volume 30, issue 1, pages 96-116, Feb 2009, doi [http://edrvdx.endojournalsdoi.org/content10.1210/30er.2008-0033 10.1210/er.2008-0033], PMID [http:/1/96www.ncbi.nlm.nih.full gov/pubmed/19151107 19151107]</ref><ref name="FructoseEpiRole">RJ. Johnson, MS. Segal, Y. Sautin, T. Nakagawa, DI. Feig, DH. Kang, MS. Gersch, S. Benner, LG. Sánchez-Lozada, Potential role of sugar (fructose) in the epidemic of hypertension, obesity and the metabolic syndrome, diabetes, kidney disease, and cardiovascular disease ., Am J Clin Nutr, volume 86, issue 4, pages 899-906, Oct 2007, PMID [http://www.ajcnncbi.nlm.orgnih.gov/contentpubmed/86/4/899.full 17921363 17921363]</ref><ref name="FructoseJuiceKids">BA. Dennison, HL. Rockwell, SL. Baker, Excess fruit juice consumption by preschool-aged children is associated with short stature and obesity... [, Pediatrics. , volume 99, issue 1, pages 15-22, Jan 1997] - PubMed - NCBI , PMID [http://www.ncbi.nlm.nih.gov/pubmed/8989331 8989331]</ref><ref name="FructoseLiverAssy">N. Assy, G. Nasser, I. Kamayse, W. Nseir, Z. Beniashvili, A. Djibre, M. Grosovski, Soft drink consumption linked with fattyliver in the absence of traditional risk factors... [, Can J Gastroenterol. , volume 22, issue 10, pages 811-6, Oct 2008] - PubMed - NCBI , PMID [http://www.ncbi.nlm.nih.gov/pubmed/18925303 18925303]</ref><ref name="FructoseLiverOuyang">X. Ouyang, P. Cirillo, Y. Sautin, S. McCall, JL. Bruchette, AM. Diehl, RJ. Johnson, MF. Abdelmalek, Fructose consumption as a risk factor for non-alcoalcoholic fatty liver disease., J Hepatol, volume 48, issue 6, pages 993-9, Jun 2008, doi [http://dx.doi. [J Hepatolorg/10.1016/j.jhep.2008.02.011 10.1016/j.jhep. 2008.02.011] - PubMed - NCBI , PMID [http://www.ncbi.nlm.nih.gov/pubmed/18395287 18395287]</ref><ref name="FructoseMajorHealth">RJ. Johnson, LG. Sanchez-Lozada, T. Nakagawa, The effect of fructose on renal biology anddisease... [, J Am Soc Nephrol, volume 21, issue 12, pages 2036-9, Dec 2010, doi [http://dx.doi. 2010org/10.1681/ASN.2010050506 10.1681/ASN.2010050506] - PubMed - NCBI , PMID [http://www.ncbi.nlm.nih.gov/pubmed/21115612 21115612]</ref><ref name="FructoseVisceralFat">JCI - KL. Stanhope, JM. Schwarz, NL. Keim, SC. Griffen, AA. Bremer, JL. Graham, B. Hatcher, CL. Cox, A. Dyachenko, Consuming fructose-sweetened, not glucose-sweetened, beverages increases visceral adiposity and lipids and decreases insulin sensitivity in overweight/obese humans ., J Clin Invest, volume 119, issue 5, pages 1322-34, May 2009, doi [http://wwwdx.jcidoi.org/articles10.1172/viewJCI37385 10.1172/37385 JCI37385], PMID [http://www.ncbi.nlm.nih.gov/pubmed/19381015 19381015]</ref><ref name="FructoseVisceralFatHeart">S. Yusuf, S. Hawken, S. Ounpuu, T. Dans, A. Avezum, F. Lanas, M. McQueen, A. Budaj, P. Pais, Effect of potentially modifiable risk factors associated with myocardial infarction in 52 countries (the INTERHEART study): case-control study : The ., Lancet , volume 364, issue 9438, pages 937-52, doi [http://wwwdx.thelancetdoi.comorg/journals10.1016/lancet/articleS0140-6736(04)17018-9 10.1016/PIIS0140S0140-6736%2804%2917018(04)17018-9], PMID [http://fulltext www.ncbi.nlm.nih.gov/pubmed/15364185 15364185]</ref><ref name="FructoseVisceralDiabetesMontague-2000">CT. Montague, S. O'Rahilly, The perils of portliness: causes and consequences oof visceral adiposity... [, Diabetes. , volume 49, issue 6, pages 883-8, Jun 2000] - PubMed - NCBI , PMID [http://www.ncbi.nlm.nih.gov/pubmed/10866038 10866038]</ref><ref name="FructoseFatOxidationCox-2012">ARS | Publication request: CL. Cox, KL. Stanhope, JM. Schwarz, JL. Graham, B. Hatcher, SC. Griffen, AA. Bremer, L. Berglund, JP. McGahan, Consumption of fructose-sweetened beverages for 10 weeks reduces net fat oxidation and energy expenditure in overweight/obese men and women ., Eur J Clin Nutr, volume 66, issue 2, pages 201-8, Feb 2012, doi [http://dx.doi.org/10.1038/ejcn.2011.159 10.1038/ejcn.2011.159], PMID [http://www.arsncbi.usdanlm.nih.gov/researchpubmed/publications/publications.htm?seq_no_115=247054 21952692 21952692]</ref>
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<ref name="FructoseAerobicDeChristopherUribarri2016">Fructose consumption leads to reduced aeroL R DeChristopher, J Uribarri, K L Tucker, Intake of high-fructose corn syrup sweetened soft drinks, fruit drinks and apple juice is associated with prevalent arthritis in US adults, aged 20–30 years, Nutrition & Diabetes, volume 6, issue 3, 2016, pages e199, ISSN [http://www.worldcat.org/issn/2044-4052 2044-4052], doi [http://dx.doi.org/10.1038/nutd.2016.7 10.1038/nutd.2016.7]</ref><ref name="DeChristopher-2016">LR. DeChristopher, J. Uribarri, KL. Tucker, Intakes of apple juice, fruit drinks and soda are associated with prevalent asthma in US children aged 2-9 years., Public Health Nutr, volume 19, issue 1, pages 123-30, Jan 2016, doi [http://dx.doi.org/10.1017/S1368980015000865 10. 1017/S1368980015000865], PMID [Lipids Health Dishttp://www.ncbi.nlm.nih. 2012gov/pubmed/25857343 25857343] </ref><ref name="DeChristopher- PubMed 2015">LR. DeChristopher, J. Uribarri, KL. Tucker, Intake of high fructose corn syrup sweetened soft drinks is associated with prevalent chronic bronchitis in U.S. Adults, ages 20- NCBI 55 y., Nutr J, volume 14, pages 107, 2015, doi [http://dx.doi.org/10.1186/s12937-015-0097-x 10.1186/s12937-015-0097-x], PMID [http://www.ncbi.nlm.nih.gov/pubmed/22713601 26474970 26474970]</ref>
</references>
