Critical Examiner

“I don’t have the time, desire or the need to check every label to see if it contains this one little ingredient.”

High fructose corn syrup (HFCS) has become the latest target in the war against the obesity epidemic.  The very fact that it exists because it is a highly processed corn product makes it ripe for sensationalized headlines like “5 Reasons High Fructose Corn Syrup Will Kill You.”  The name of the product itself makes it sound ominous.  So what is the truth?  Will HFCS kill you and, perhaps, more importantly, is it really anymore dangerous than the thing that it commonly replaces, table sugar?  The short answer is, no.  It is almost exactly the same as regular sugar and is no more harmful than sugar when consumed in amounts that are within or below the recommended dietary guidelines.

This debate was initially sparked by a report released in the early 2000’s that found obesity rates in the US paralleled the rise in HFCS beginning in the 1970’s to the current date.  The author of that paper has since revised his view with the release of a new report stating that both HFCS and sugar play a role in human health, however he could not draw a direct link to HFCS alone because of the lack of quality studies available.  If HFCS is a singular factor for obesity then we would expect other countries to follow the same trend.  However, last year Mexico officially passed the US for the highest obesity rates and yet Mexico uses about 20% less HFCS than the US, after all this is place American’s go to pick up their sugar-sweetened Cokes.  Total sugar and HFCS consumption in Mexico is about 40% less than the US.  Japan uses slightly more HFCS per capita than does Mexico, but Japan isn’t facing an obesity problem anywhere near the scale that the US and Mexico are experiencing.  However, Japan also consumes about 65% less total combined sugar and HFCS than the US.  More recently, a study has drawn a link between HFCS consumption and type II diabetes, but that link starts to look weak if you take a look at the raw data and consider the total amount of sugar use combined in each country.  To me, it appears that both diabetes and obesity are more closely correlated with total sugar consumption.  We shouldn’t selectively pull out single factors to make the story more interesting.

Epidemiological studies certainly have a role in medical science, but we need to be careful with the conclusions that we draw from such studies.  Although its not always possible, we should treat them as a starting point for additional research that can better isolate the event in question, rather than rushing to conclusions and reporting them as hard fact.   This is what shapes public perception and often leads the general public to distrust science upon learning that the reported conclusions were premature.

According to the USDA the use of sugar and other sweeteners has increased by 19% since 1970 in the US, and while cane and beat sugars have been increasingly replaced by corn sugars they are used at a roughly 1:1 ratio today.  In other words HFCS is not outpacing the use of regular table sugar.  The USDA recommended amount of sugar consumed per day is equal to 8 teaspoons and Americans are now getting 30 teaspoons of added sugar per day on average, according to the data gathered up to 2005.  Our caloric intake as Americans has increased from about 2,100 calories a day in 1970 to around 2,800 in 2005, and the added sugar makes up about 477 of those calories.  For reference, one 12 ounce can of Coke would put you over your daily limit at 10 teaspoons of sugar.

Sweetener use in the US per capita

Teaspoons of sugar in cola

To look further into the issue we need to look at a little biochemistry so we can understand how sugars are utilized by the body.  All forms of “sugars” are called carbohydrates, or saccharides.  HFCS is a formulation that consists primarily of two different monosaccharides, which are the simplest forms of carbohydrates as they do not exist in a more basic form on the molecular level.  The two monosaccharides that make up HFCS are fructose and glucose.  HFCS-55 is the most common formulation of HFCS and it is found primarily in soft drinks, but also in other foods where sugar can be replaced, like breads and cereals.  The 55 means that it contains 55% fructose and 42% glucose, the rest is mostly water.  Common table sugar, or sucrose is a disaccharide, meaning it is composed of two monosaccharide units, 50% fructose and 50% glucose, that are linked together by an oxygen atom and this link is called a glycosidic bond.  Fundamentally, those are the only two things that make HFCS different from sucrose; the ratio of fructose to glucose is similar but slightly different, and the glycosidic bond that exists with sucrose but is absent with HFCS.  Biologically, this shouldn’t make a difference.  In fact, the glycosidic bond in sucrose can be broken with heat or in the presence of a weak acid, such as citric acid.  When this happens the sucrose, now in free monosaccharide form, is called invert sugar.  Based on this chemical reaction, it’s very likely that sucrose sweetened beverages that have been stored for long periods of time and have citric acid as an ingredient, now contain invert sugar by the time it reaches the consumer, rather than the disaccharide sucrose, making it nearly indistinguishable from HFCS on a chemical basis.

Ultimately, all monosaccharides are absorbed into the bloodstream at the same area of the intestines.  Succrose, as I mentioned, is a disaccharide.  In order to be digested, the glycolytic bond has to be broken to produce free glucose and fructose and this is accomplished very quickly in the intestines by an enzyme called sucrase.  HFCS bypasses this step since it already exists as free glucose and fructose.  In light of that fact, its thought that the lack of a glycosidic bond might allow fructose to be absorbed more rapidly.  However, this is not the case as shown by the following study that looked at people who consumed HFCS sweetened beverages vs sucrose sweetened beverages and measured various metabolic parameters over a 6 hour period post-treatment.  They found no differences in fructose absorption between the groups, but found a small increase in the bio-availability of glucose, and uric acid with HFCS consumption.  This was a short term study though, so its telling us part of the story but not everything.

Of the claims that dominate the debate between HFCS and sucrose is that fructose is bad for you.  This claim is in part true…for pure fructose.  Glucose and fructose metabolism are different.  Both molecules end up in the liver.  From there, glucose is either stored as glycogen to be used as a source of energy later, or it passes through a series of biochemical reactions called the glycolysis cycle to generate ATP, the unit of energy used by the body, forming citrate and lactate as byproducts.  When energy needs are met, glycolysis is blocked by a negative feedback loop in response to accumulating levels of ATP and citrate.  However, fructose is not responsive to this negative feedback loop.  This is a signal to the cell that says, “we have energy right now and we don’t need to make more,” so any available glucose will instead be stored as glycogen, which can be broken down into energy currency (ATP) when the body needs it.  Although fructose metabolism shares some common intermediates with the glycolysis pathway, it’s more likely to be converted into fat and triglycerides in the liver, which could be a contributor to non-alcoholic fatty liver disease and increased triglyceride levels.  Fructose has also been shown to give rise to insulin resistance and does not increase leptin response, which is the hormone that makes you feel “full” after a meal.  There are conflicting reports, however, on the exact conditions required to increase triglycerides, raise fat production, and promote insulin and leptin resistance.  It should also be noted that small amounts of fructose are safe and may actually provide some benefit for type 2 diabetics.

Glucose and Fructose Metabolism in the Liver. Source

What tends to get lost in the conversation is that pure fructose is used very, very infrequently in foods.  You’ll probably never get enough concentrated fructose from the diet to achieve the levels necessary to cause the adverse health events that are seen in research.  So all the research involving pure fructose or pure glucose does not hold much weight in the HFCS discussion, especially since ingesting glucose and fructose together might have an impact on how fructose is metabolized by virtue of the fact that they share common pathways.  If you want to condemn fructose based on these kinds of experiments, then you must also attack honey which contains roughly 49% fructose and 43% glucose, or agave nectar which by some estimates may contain up to 56% fructose and 20% glucose, a far greater imbalance than what is provided from HFCS.

Even corn syrup wants to distance themselves from HFCS

Unfortunately, the terminology used in the discussion gives plenty of room for deception.  High fructose corn syrup is a term that is being used interchangeably with pure fructose and, as you can see, they are not the same thing.  Many journal articles that I’ve read are feeding mice pure corn syrup (also different from HFCS), fructose, or glucose and then making statements in their reports to the effect of, “So this is why high fructose corn syrup is bad for you…”  Sometimes the experiments are just badly designed, or ask the wrong questions, making it really difficult to tease out whether implications actually exist uniquely for HFCS or for sugars in general.  Still, the sensationalist media will use whatever information they can garner from these studies and form a story that fits their headline, thus shaping public opinion.

The studies that exist comparing real HFCS with table sugar (sucrose), are surprisingly rare.  I found that I most often had to turn to studies that were funded by corn and sugar interests in doing research for this article.

One such study turned out to be one of the more well designed studies on this topic, period.  It did not involve cell culture or animals, or unrealistic amounts of sugars, but used real people and real HFCS and sucrose.  It was a double blind placebo study involving 65 overweight and obese individuals that consumed HFCS or sucrose sweetened low fat milk at 10% or 20% concentration, while maintaining a weight stable diet over the course of the study.  The amount of sweetener used in the study corresponds respectively to twice and four times the amount recommended by the American Heart Association (AHA), corresponding to the amount of sugars that are consumed by 25% and 50% of the American population.  The study found the average weight gain for all participants was about 4.9lbs but there were no significant differences in weight gain between the sucrose and HFCS groups, no differences in blood pressure, and no appreciable changes in cholesterol levels.  There was an increase in measured triglycerides for the HFCS-20% group but these changes were not statistically significant, and were still within the normal range.  I would like to have seen measurements of markers for inflammation as well, but that didn’t happen unfortunately.

An independently funded study using mice fed 8% HFCS in the drinking water with a regular non-fat diet also found that HFCS alone did not contribute to weight gain.  Additionally, mice fed HFCS showed signs of inflammation and insulin resistance.  The frustrating part of this study is that they did not use an experimental group that contained 8% sucrose as a comparison for the HFCS group.  Instead, they used a high fat “western” diet to compare with HFCS, which I’m sure does contain sucrose as a carbohydrate source but the amount is unlisted and the results would be confounded anyway by the differences in fat content.  So unfortunately, this study provides no insight into whether HFCS alone causes these conditions.  It is, however, a good example of a study not asking the right questions, as I mentioned earlier.  Further, the 8% HFCS-water solution is supposed to mimic the amount in soft drinks, but the mice were fed ad libitum, meaning the mice simply drank as much as they wanted throughout the experiment.  There’s no indication in this study of how much HFCS the mice actually consumed throughout the day, and that is not always a common measurement made in these studies, making it difficult to know how the experimental conditions compare to average human HFCS daily intake.

What no one seems to be in disagreement about is that consuming excessive amounts of calories leads to weight gain and obesity, no matter what sweetener source the calories are derived from.  Even the researchers funded by “Big Sugar” admits to this, although they downplay this role for all sugars a bit.  There are a lot of factors that lead to obesity and its difficult to single out one factor, but you can’t downplay the role of sugars when they account for so many extra calories in the average American diet.  If we only focus on HFCS, then we’re ignoring the problem as a whole.  Because if HFCS isn’t being used commonly as a sweetener, then sugar will replace it and prices would just go up for the consumer.  If, after really reading into the topic, you think that you’re being healthier by avoiding HFCS and instead opting to use table sugar or a “natural” sweetener, you’re just being a food snob, plain and simple.

Here is what I’ve done in my life personally.  I’ve cut back on the amount of overall carbohydrates I take in daily by about half.   I’m currently consuming about 200-300 grams daily, more or less depending on the amount of physical activity and energy requirements I need.  Physically I feel much better for it, my lungs are in better shape, I can breathe easier and I can tell that my energy and overall inflammation levels have improved.  However, I love chocolate, soft drinks, and desserts, so I don’t deny myself these things either.  Instead, I might have 100-150 carbs the day before so that I can have that bottle of Mountain Dew or ice cream the next day.  Then, on the same day or the next day, I’ll put to use the energy gained from that into high intensity cardio, running, biking, kickboxing or other physical activity.  The objective is to keep my total caloric intake at a neutral level by the end of the week, based roughly on 2,000-2,200 calories a day.   That’s 14,000 calories a week and in general, I don’t want to be over or under this amount to maintain weight. If you’re goal is to lose weight, then you adjust your diet to be at a net caloric negative from week to week.

I don’t care if my carbs are coming from HFCS, sugar, honey or fruit juices as long as I can maintain a steady caloric intake over a week.  I don’t have the time, desire or the need to check every label to see if it contains this one little ingredient.

There are no real, solid, hard and fast rules regarding carbohydrate intake.  We could survive on about 20-40 carbs a day and be fine.  But remember, sugars are used primarily as an energy source.  If you’re not expending a lot of energy you wont need as many carbs as someone who does expend a lot of energy, like a marathon runner as an extreme example.  As humans, we’re just not designed to consume the amounts of sugars we’re taking in daily with increasing sedentary lifestyle.  We’re supposed to be using that as a source of energy, not storing it up in our bodies.

Let’s just be sensible about overall carbohydrate intake.