The High Fructose Corn Syrup Debate

On an episode of Oprah, I watched in disbelief as Dr. Oz dipped his hand into a beaker of amber-colored liquid as thick as molasses. As he pulled his hand out of the thick syrup-like goo, he stated quite confidently that ‘it’ was responsible for the increasing rates of obesity and diabetes – he was, of course, talking about high fructose corn syrup (HFCS).

Sensationalism at its Best

While it’s true that North Americans are consuming more HFCS than ever before, can the rates of obesity and diabetes be blamed on this marvel of modern food technology? The answer is hotly debated.

So, What the Heck is HFCS? The Technical Stuff

It starts with the extraction of glucose from corn starch to produce a pure glucose syrup [starch is the stored form of glucose in grains and root vegetables]. Growing up, we used to have a bright yellow bottle of corn sugar, a.k.a. pure glucose, or ‘dextrose’, that we’d pour on ice cream for a sweet treat (I know, makes my teeth ache!). This syrup is then enzymatically converted to fructose, to which more glucose syrup is added making HFCS; a blend of two monosaccharides or single sugars. HFCS was called such to distinguish itself from the original corn sugar, which was/is pure glucose [dextrose].

‘High’ Fructose in HFCS is Therefore a Relative Term.

HFCS is used as HFCS-55 [55% fructose, 45% glucose] and is used primarily in beverages or as HFCS-42 [42% fructose, 58% glucose] which used in solid foods. Sucrose or table sugar is a disaccharide containing 50% fructose and 50% glucose. Of note, honey also contains the two single sugars (like HFCS), fructose and glucose but in equal amounts like sucrose. The take home point is that these sweeteners virtually all have the same amount of fructose for all practical purposes.

So Why the Hate-on for HFCS?

Unless you’ve been living under a rock for the past couple of years, you’ve no doubt come across loads of overly simplistic, uninspired, and for the most part, uninformed rehashed messages on Twitter, blogs and Facebook that include something like: 1) the introduction of HFCS is responsible for, and has lead to an overall increased consumption of fructose, 2) because HFCS is a blend of two single sugars, haters of HFCS say that it is absorbed more quickly unlike table sugar, 3) unlike glucose, fructose lacks the satiety properties which can lead to over-eating, and 4) the fructose in HFCS is metabolized in a similar manner like alcohol leading possibly leading to insulin resistance and lipogenesis (both in the liver and belly).

A depressing list of potential problems to say the least.

As always, we ask ourselves – what is the evidence?

Fortunately there is no shortage of quality data on these topics, much too much to go into in one blog entry, or two for that matter. Refer to links throughout and at the end for further reading.

Has HFCS as a sweetener lead to an increase in total fructose consumption?

In the December 2007 issue of the American Journal of Clinical Nutrition, G. Harvey Anderson (PhD), from the Department of Nutritional Sciences, University of Toronto, Ontario, reports that while it’s true that the use of HFCS as a caloric sweetener has increased from zero in 1970 to 40% in 1997, there has been a subsequent decrease use of sucrose from 80% in 1970 to 40% in 1997. HFCS has been used as a substitute for, and therefore has displaced, sucrose as a caloric sweetener rather than an addition to sucrose.

As a result the ratio of fructose to glucose in the food supply has not changed. There’s no denying we’re eating more total added sugars, including fructose, and that other sources (fruit juices, sweetened beverages and other caloric sweeteners) have increased our overall intake of fructose, but it’s overly simplistic and uninformed to single out HFCS as the sole perpetrator.

How much are we eating?

It’s hard to put an absolute number on it. Best estimates are between 80 to 100g per day, up from 20g or so at the turn of the century, to about 50g by the 1950-60s.

Does HFCS make us eat more?

Regarding the claim that HFCS leads to overeating because it does not result in a sense of satiety (e.g. our brain doesn’t say ‘enough is enough’) by not stimulating insulin and leptin secretion, the debate gets messy. The anti-fructose camp tends to rely on rat studies (and a few human studies) where researchers give fructose in excessive amounts, as a single sugar; not surprisingly, it’s easy to find metabolic problems. Here’s the problem. Fructose, both in commercial and natural foods, also comes with glucose: HFCS, sucrose (table sugar), honey, maple syrup, brown sugar, fruit, and root vegetables all have glucose packaged nicely along with the fructose. Interestingly, agave syrup, the darling of raw foodists and many vegetarians is 90% fructose!

A review looking at fructose’s effect on satiety did not find sufficient evidence that it is less satiating than glucose or that HFCS is less satiating than sucrose. Also studies found that a ‘preload’ of fructose led to less eating compared to a glucose preload. One study that did find an increase in appetite after fructose consumption used a ridiculous and improbable amount of free fructose, 135 grams, or the amount in about 6-7 regular sodas.

HFCS vs. sucrose. Singles are worse than pairs?

It has also been suggested that HFCS, with its two single sugars glucose & fructose, is worse on all fronts, than sucrose. Sugars are primarily digested in the small intestine by both amylase from the pancreas & enzymes along the surface of the gastrointestinal tract. There is no credible evidence that it matters whether or not a sugar is worse if it's a dissacharide like sucrose or two monosaccharides like HFCS, or honey. We humans are funny. Honey is more similar to HFCS in its biochemical structure than is sucrose, but everyone gets warm fuzzy feelings from honey, no doubt due its praise by hippies in the 70s, and because it's 'natural'…huh.

How much is too much?

Because the problem of excess fructose consumption does exists, the question of ‘how much is too much?’ is hotly debated. Because fructose is metabolized in the liver in a similar manner to alcohol, some have tried to estimate a safe amount of fructose consumption based on an alcohol equivalence. For men, the general recommendation is about 20g of ethanol per day [two standard drinks], for women, 10g [one standard drink]. From this, a daily maximum of 20g or so of fructose has been suggested. Fortunately others have taken a more scientific approach to the question. Several meta-analysis here, and here have put the number between 50-60g per day.

How much food is that?

For a list of the fructose content of foods, try here [foods listed on this site are in ‘mg’ not ‘g’ so 26000mg is 26g]. Two large pieces of fruit can have 15-20g of fructose, so you can see what little wiggle room there is for foods naturally high in fructose or for the very modest use of added sugars if 50-60g of fructose per day is your goal!

What does this all mean in the real world?

Weight gain, overeating, metabolic syndrome and obesity are multifactorial. Appetite regulation is influenced by complex signaling and environmental cues. While it may be true, in an experimental setting, that consuming large amounts of pure fructose can have a detrimental effect on blood lipids, blood glucose and the like, it’s imperative not to make the (gigantic) leap and apply results from these kinds of feeding studies to how fructose is consumed in food whether its HFCS, or other sources of fructose be they natural or otherwise.

In terms of overall consumption, the best evidence to date points to the fact that the ratio of fructose to glucose in the diets of North Americans is the same since the introduction of HFCS as a substitute for sucrose as a caloric sweetener, and has not led to a some kind of frenzied out-of-control amount of fructose in the food supply. Don't get me wrong, North Americans DO eat far too much added sugar (and therefore fructose too). An estimated figure for those in the US is some 135 lbs or 61kg of sugar per year!

Any potential negative effects from fructose are due to its overall increased total intake, whether that’s from sucrose, agave, brown sugar, fruit juice or HFCS, as people are eating more and more added sugar from processed foods. Although it's tempting (and very easy) to be able to point the finger on a single cause, like HFCS, the reality is that there's a larger interaction of many variables.

The best advice is to reduce the intake of sugars by eating fewer foods with added sugars, cutting back on, and eating smaller portions, of baked goods, fruit juice & sweetened beverages by focusing on wholesome foods.

Image: Troy B. Thompson

Sources:

http://www.ncbi.nlm.nih.gov/pubmed/20047139

http://www.ncbi.nlm.nih.gov/pubmed/20086073

http://www.ncbi.nlm.nih.gov/pubmed/18996880

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2910863/

http://www.ncbi.nlm.nih.gov/pubmed/19592634