Fructose: Poison or Pleasure?

Written by: Cassie Vanderwall, MS, RD, LDN, CPT

I can’t do a thing in the morning until I’ve had my juice,” says the young boy in the commercial and judging by the commentary and 87 likes on YouTube, many people also cannot. Juxtapose America’s love for juice against Dr. Robert H. Lustig’s lecture on “The Bitter Truth” about sugar, coining sugar a “toxin” or “poison” and one may be left with a tough decision.

Dietitians, among other health professionals and of course our mom’s have been telling us for years to leave our hands out of the cookie and candy jars and to pick up fruit instead, well what if we’re wrong?
Let’s take a minute and explore the popular sugars in the American diet: Sucrose, Glucose, and Fructose.

  • Sucrose is a di-saccharide because it is made up of two sugars: glucose and fructose. It is our common table sugar. The popular high fructose corn syrup (HFCS) is a mixture of glucose and fructose from corn, but is not considered sucrose because the sugars are separate molecules.

  • Glucose is a simple sugar and the main form of energy for our bodies, including our brains, muscles and organs. It bypasses the liver and is metabolized elsewhere in the body. Glucose uptake is directly regulated by insulin

 

  • Fructose is also a simple sugar found in fruit, vegetables and honey. Commercially, fructose is derived from sugar cane or corn. Fructose’s pathway for absorption is based on whether it’s alone or combined with glucose. If it is combined with glucose, as sucrose, it will be absorbed in the small intestine and begins its journey to the liver where it is metabolized, or broken down. Fructose may soon be stored in the liver as glycogen, sent out to be made into glucose for energy, or become a triglyceride and ultimately fat.


Dr. Lustig has concluded that these sugars are “isocaloric but not isometabolic,” meaning that they all pack 4 Calories per gram, but are metabolized differently and thus have different affects and possibly consequences on the body. Researchers have deemed the short-term physiological effects of these sugars to be equal, however no studies to date have examined the long-term effects.  Despite the lack of causal evidence, there is an abundance of research associating high fructose intake with chronic diseases including obesity, fatty liver disease, gout, insulin resistance, and metabolic syndrome. So, why is fructose a likely culprit?

  • Fructose increases ghrelin, the hunger hormone, often leading to increased appetite following a high fructose meal.
  • Researchers have confirmed that when fructose reaches the liver, it becomes the liver’s top priority and it neglects all else until it is processed. It is associated with fatty liver disease due to its conversion into triglycerides and incorporating into very low density lipoproteins (VLDL), which makes deposits in our fat banks throughout the body, including the liver.
  • Fructose is converted to uric acid, which is the key player in gout.
  • Fructose uptake is not regulated by insulin, but many believe excessive intake of fructose plays a role in insulin resistance.

Now back to the tough decision, do we drink the apple juice or eat the apple? Research tells us that the speed required for metabolism also dictates the reaction. So, if we choose juice, sugar in the liquid form will get to the liver much more quickly than if we ate its equivalent in apples. Therefore, we choose the apple. We also must be cautious of how much we eat because too much of a good thing is still too much.

Two infographics from a New York Times article displays the average Americans intake of sugar in the form of table sugar (sucrose) and HCFS. The amounts are alarming! This same article, points out that adults are eating 40 more grams of sugar per day and adolescents are consuming about 60 more grams of sugar than our earlier counterparts in the mid 1800’s.
I believe that sugar, whether it be sucrose, glucose or fructose is safe to eat, but I also believe that it has the potential to become hazardous in large amounts. Bottom line: Make water your primary beverage, choose 2 to 3 servings of fresh fruit per day and keep sweets as a treat.

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