Why You Should Avoid High Fructose Corn Syrup


Today’s “Ask the Nutrition Consultant” comes from Tasha! 

Q: Why is high fructose corn syrup so terrible for us? 

A: Great question Tasha! High fructose corn syrup (HFCS) is a sweetener derived from corn which is usually genetically modified. The corn is first milled to produce corn starch, which is then further processed to create corn syrup. Corn syrup consists mostly of glucose. To make it sweeter and closer in taste to regular table sugar (sucrose) some of the glucose is converted to fructose using enzymes.  

Gram for gram, HFCS has slightly higher levels of fructose than regular table sugar and the fructose and glucose in HFCS are not bound together like they are in table sugar (they are “free” or unbound and can be absorbed more easily). Fructose and glucose are also metabolized differently by the body. When we consume glucose the liver is initially bypassed and the glucose reaches systemic circulation to be used by our body tissues (brain, muscles). Any excess glucose consumed will first be stored as glycogen, and secondarily as body fat. Fructose on the other hand is exclusively metabolized by the liver with the help of a particular enzyme called fructokinase. Fructose metabolism lacks many of the cellular controls that are present in glucose metabolism in the body, and while some fructose is processed and stored as liver glycogen most fructose has a tendency to go down a pathway of hepatic de novo lipogenesis, or “new fat formation.” When we consume large quantities of unbound fructose like what is found in HFCS, the liver gets overloaded and starts turning the fructose into fat.  

Eating a lot of fructose, especially from HFCS can raise levels of LDL cholesterol and triglyceriedes, increase blood levels of uric acid leading to gout and high blood pressure, cause deposits of fat in the liver (non-alcoholic fatty liver disease), cause insulin resistance and lead to obesity and type II diabetes, and promote overeating and leptin resistance.  

It’s important to note that the fructose naturally found in fruits and vegetables does not impact the body in the same way as concentrated HFCS because fruits contain lots of fiber and digest more slowly.  


Hyman, M. (2022, October 7). Why fatty liver is so common and how to heal it. The Doctor’s Farmacy with Mark Hyman, M.D. Podcast. Podcast retrieved from https://drhyman.com/blog/2022/10/06/podcast-ep611/

George A Bray, How bad is fructose?, The American Journal of Clinical Nutrition, Volume 86, Issue 4, October 2007, Pages 895–896, https://doi.org/10.1093/ajcn/86.4.895

Gunnars, K. (2018). Is fructose bad for you? The surprising truth. Retrieved from https://www.healthline.com/…/why-is-fructose-bad-for-you

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