Disease Proof : Disease Proof : Health & Nutrition News & Commentary : Dr. Joel Fuhrman

A recent flurry of news articles have reported on a recent study that showed that treatment of pancreatic cancer cells with fructose increased cell proliferation – uncontrolled proliferation is a hallmark of cancer. This follows on the heels of another study that linked fructose consumption from added sugars to elevated blood pressure. The bad press on fructose is making people question the safety of the ubiquitous commercial sweetener, high fructose corn syrup (HFCS).

Due to the introduction of HFCS, fructose intake has increased dramatically in the U.S. since the 1970s. Between 1970 and 2000, HFCS intake increased by 100-fold, and total fructose intake increased by 30%.¹

Fructose makes up half of the sucrose molecule (with glucose), but may also be present in “free” form. Abosrption of fructose and glucose, and the differences between fructose in natural foods and fructose in HFCS are explained in this post.

These authors investigated whether cancer cells could use fructose for energy, because they are known to use glucose – cancer cells are known to have a greater number of glucose transporters and metabolize glucose more rapidly than normal cells because their rapid proliferation requires greater amounts of energy.²

Although different transport mechanisms are used to get fructose and glucose into cells, their metabolism is thought to be similar once they enter cells. However, these scientists found that in human pancreatic tumor cells, metabolism of fructose and glucose occurs via different pathways, both leading to cell proliferation. Keep in mind that both sugars led to increased cell proliferation at similar rates – that is, this study did not show that fructose is “worse” than glucose, just that they stimulate proliferation by different mechanisms. Glucose was used by the cancer cells for energy production, whereas fructose was used to generate nucleic acids (DNA and RNA). This study was the first to show that cancer cells could differentiate between fructose and glucose, and that they could use fructose as efficiently as glucose to fuel cell growth.^3,4

Sucrose intake, fructose intake, and high glycemic load have all been associated with pancreatic cancer in epidemiological studies, and diabetes also increases risk.^5,6  

The message of this study and others on the negative effects of fructose is that added sugars, abundant in the Western diet, are detrimental to health and should be minimized, but sadly this is not the message that is getting through to the public. 

With the recent media frenzy around HFCS, the conventional wisdom seems to have become that sugar is superior to HFCS because it is more ‘natural’ – prompting many companies to switch from HFCS to sugar for sweetening their products. Meanwhile, the high fructose, low glycemic index sweetener agave nectar, once elevated to health food status, is now being doubted because of the negative press on fructose. 

Comparing sweetener to sweetener is missing the point. All sweeteners have negative health effects, regardless of their relative quantities of fructose, glucose, and sucrose. 

Some sweeteners spike blood glucose, others raise triglycerides and form advanced glycation end products (AGEs), and all provide excess calories and are devoid of nutrients. This is not a question of which sweeteners are healthy and which are unhealthy. None are healthy. All are merely concentrated sugars – contributing to obesity and all its consequences – and therefore should all be minimized or completely avoided in a health-promoting diet.

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The consumption of fructose has increased significantly since the 1970s, when high fructose corn syrup (HFCS) was introduced into the United States food supply. The use of HFCS now exceeds that of sucrose (table sugar) in sweetened foods in the U.S.

Absorption of fructose and glucose:

Sucrose is composed of one fructose molecule and one glucose molecule.   There are differences between fructose and glucose metabolism. Fructose is absorbed in the small intestine, transported to the liver through the portal vein, and then metabolized via the same process that breaks down glucose to make energy – however, fructose is only broken down in the liver, whereas glucose can be used by any cell in the body.  Ingesting glucose raises blood glucose levels, and ingesting fructose does not raise glucose as quickly or as much, but raises triglyceride levels much more.¹

Fructose was once regarded as a “safe” sweetener for diabetics, because of its small effect on blood glucose levels.   However, fructose is a reducing sugar, which means that it contributes to the formation of advanced glycation end products (AGEs), which contribute to diabetes and its complications, Alzheimer’s disease, and cardiovascular disease.² Since fructose consumption also elevates triglycerides and diabetics are already at risk for cardiovascular disease, increasing triglycerides adds to this risk. Added fructose consumption has also been associated with non-alcoholic fatty liver disease, and elevated cholesterol and retinopathy in diabetics.¹

Fructose in natural foods vs. fructose in HFCS:

Fructose makes up half of the sucrose molecule, and HFCS contains similar proportions of fructose and glucose as sucrose does (HFCS is 55% fructose).   Fructose may be found alone (free) or complexed with glucose as sucrose. In most fruits, much of the fructose is bound to glucose. Fructose entry into blood is slowed when it is in sucrose form, because sucrose must be first split by enzymes in intestinal cells. Fructose molecules in HFCS, however, are free, and therefore absorbed more rapidly. It is thought that the enzymes in the liver responsible for breaking down fructose are overwhelmed by the large loads of fructose delivered by HFCS-sweetened beverages, allowing for large quantities of fructose to be released into the blood.¹

Fructose and elevated blood pressure:

The current study examined data from 4528 adults, whose median fructose intake from added sugars was 74 grams per day. As a reference point, 74 grams of fructose is roughly the amount present in 2 ½ twenty-ounce soft drinks or 13 bananas.^1,3 The researchers determined that fructose intake at or above the median 74 grams per day increased the risk of elevated blood pressure. 

Subjects who consumed 74 grams or more of fructose each day in added sugar increased their risk of blood pressure elevated above 135/85 by 26%, above 140/90 by 30%, and above 160/100 by 77%.⁴

Essentially, the average fructose intake in the U.S. is a quantity that increases chronic disease risk – and not just risk of diabetes. Elevated blood pressure contributes to risk of heart attack, stroke, heart failure, and kidney disease.

There are no “safe” sweeteners - whole fruits and root vegetables are the only sweet-tasting foods that are health-promoting.   Added sugar in any form is calorie-dense and deficient in nutrients, and therefore detrimental to health.

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