A sticky question

A Sticky Question:

There has been a lot of talk recently in the news and online about high fructose corn syrup, so to settle my own curiosity I did a little digging.  First some essential background and terminology:

  • Carbohydrates: Carbohydrates are organic compounds (organic meaning made with carbon) that are made from the elements carbon, hydrogen, and oxygen.  Sugars and starches (as well as many other naturally occurring compounds) are all types of carbohydrates.
  • Sugar: A general purpose term for carbohydrates that dissolve in water and generally have a sweet taste.
  • Saccharides: There are many different types of naturally occurring sugars.
  • Monosaccharides are sugars with chemical formula CxH2xO2.  There are monosaccharides with 4, 5, 6, or 7 carbon units, referred to as tetroses, pentoses, hexoses, and heptoses respectively.  For this discussion, we are only really concerned with two specific hexoses: fructose and glucose.  Both have the chemical formula C6H12O6, but they have different chemical structures.
  • Disaccharides are sugars that have been made by the ‘condensation’ of two monosaccharides.  This means they have chemically been combined with the loss of one water molecule (this chemical reaction occurs naturally through the use of enzymes in living plants, or can be done synthetically in the lab).  For our discussion, we’re really only concerned with one disaccharide, sucrose, chemical forumula C12H22O11.  Sucrose is made from the monosaccharides glucose and fructose.

Types of sugars we eat:

  • Sugar: The ‘sugar’ listed on most ingredient lists is the disaccharide sucrose.  It typically is made from either sugar beets or sugar cane.
  • The sugar naturally occuring in fruits and root vegetables: In many cases this is the monosaccharide fructose.
  • Honey: The sweet stuff made by bees is a 1:1 mixture of the monosaccharides fructose and glucose with a bunch of other carbohydrates in the mix.
  • Invert Sugar: Mixture of monosaccharides fructose and glucose, often used in making and sweets.
  • High fructose corn syrup (HFCS): This is similar in composition to honey, as it is made from the monosaccharides fructose and glucose, but in much more pure form.  There are different types of HFCS with different ratios of fructoes to glucose, depending on the desired level of sweetness.  Softdrinks typically use a HFCS with 55% fructose and 45% glucose, while other foods and baked goods use a HFCS with 42% fructose and 58% glucose.  The fructose in HFCS is typically made by taking the monosaccharide glucose (derived from corn) and enzymatically converting it to the monosaccharide fructose.

I was curious about these sweeteners, so I’ll include them too, but I don’t really talk about them any more in this article.

  • Molasses: A byproduct of the production of sucrose from sugar cane, it’s about 60% sucrose, so less sweet than straight table sugar (100% sucrose).
  • Maple Syrup: A sweetener from maple trees, it’s about 60% sucrose, so therefore less sweet than straight table sugar (100% sucrose)
  • Brown Sugar: This is sugar (sucrose) with molasses added for flavor.
  • Powdered Sugar: Sugar (sucrose) that has been finely ground up and then mixed with a small amount of cornstarch to prevent it from clumping.

Phew! OK, so we’ve got all of our definitions – now let’s dig in.

There have been lots of studies and arguments made about the relative ‘healthiness’ of different types of sugars.  My own non-informed opinion coming in to writing this article was based on the following unscientific and personal opinions:

  1. People are fat
  2. People are getting fatter
  3. HFCS is cheaper than sugar
  4. People like sweet foods
  5. Because people like sweet foods, and HFCS is cheaper than sugar, there is lots of HFCS in lots of processed food

From this, I believe that because HFCS is so cheap, it has been contributing to our collective sweet tooth, so we’re all paying the prices around the waistline.  I wasn’t sure though if HFCS was any worse for you than any other sugar, so this is why I set out to learn more.Time for my high horse: People tend to freak out when they hear the term ‘chemical’ or ‘synthetic.’ assuming that anything that is a chemical is bad.  Listen, all of the sugars I discussed above would be considered ‘chemicals’ if I was working with them in the lab.  Just because something is ‘natural’ doesn’t mean it’s safe or good (see Mercury, Radon, Lead, etc etc).  Also, people can make chemicals in the lab that are naturally occuring.  For example, if I made fructose in the lab by enzymatically converting it from glucose, yes indeed the fructose I made is ‘synthetic’ (meaning I made it, not nature).  However, it is chemically identical to the fructose found in fruit, so don’t get all upset about HFCS not being ‘natural’.  It’s made from naturally occuring monosaccharides, so it doesn’t matter if those monosaccharides came from a strawberry or a test tube.

Down to the scientific literature:
I think the whole hubbub may have started around the publication of an article entitled ‘Consumption of HFCS in beverages may play a role in the epidemic of obesity.’ They stated that:

“The digestion, absorption, and metabolism of fructose differ from those of glucose. Hepatic metabolism of fructose favors de novo lipogenesis. In addition, unlike glucose, fructose does not stimulate insulin secretion or enhance leptin production. Because insulin and leptin act as key afferent signals in the regulation of food intake and body weight, this suggests that dietary fructose may contribute to increased energy intake and weight gain. Furthermore, calorically sweetened beverages may enhance caloric overconsumption. Thus, the increase in consumption of HFCS has a temporal relation to the epidemic of obesity, and the overconsumption of HFCS in calorically sweetened beverages may play a role in the epidemic of obesity.”

In my words: fructose (of HFCS) is processed differently in the body than glucose (also of HFCS).  Your body doesn’t respond to fructose with a feeling of ‘fullness’ like it does upon consumption of glucose.  They also talk about people drinking too many sweet drinks (can’t argue with that!).  They then state that people are consuming more HFCS, and people are getting fatter at the same time.  However, they don’t prove that the increase in consumption of HFCS causes the fatness.  They also don’t mention if we are consuming more sugars overall, or if we’re simply consuming more HFCS and less sugar, so our overall sweets consumption hasn’t changed.  If we were consuming the same amount of calories, but more of those calories were coming from HFCS, I would start to get suspicious that HFCS was a potential culprit, but they don’t address this.  I’m not convinced.

Here’s my beef. Depending on the type of HFCS, it is on average a 1:1 mixture of fructose to glucose.  Sucrose is the disaccharide made from glucose and fructose in a 1:1 ratio.  (Here’s where my background in Orgo comes in handy).  If you throw sucrose in an acidic environment (like say, the stomach) it is hydroylzed (water breaks the bond) between the two monosaccharides that formed the disaccharide sucrose to give you: fructose and glucose! Does this mean that in your stomach, sucrose (table sugar) is turned in to fructose and glucose in a 1:1 ratio? If so, that means that eating sucrose and would be no different than eating HFCS in terms of what your stomach ends up seeing.

More fuel for the fire: Another article cited often is entitled ‘Consuming Fructose-sweetened Beverages Increases Body Adiposity in Mice’.  They stated in their results and discussion that:

“We compared the effects of ad libitum access to fructose (15% solution in water), sucrose (10%, popular soft drink), and artificial sweetener (0% calories, popular diet soft drink) on adipogenesis and energy metabolism in mice. Exposure to fructose water increased adiposity, whereas increased fat mass after consumption of soft drinks or diet soft drinks did not reach statistical significance (n = 9 each group). Total intake of energy was unaltered, because mice proportionally reduced their caloric intake from chow. There was a trend toward reduced energy expenditure and increased respiratory quotient, albeit not significant, in the fructose group. Furthermore, fructose produced a hepatic lipid accumulation with a characteristic pericentral pattern….These data are compatible with the conclusion that a high intake of fructose selectively enhances adipogenesis, possibly through a shift of substrate use to lipogenesis.”

In my words: Mice were fed the same amount of calories, but in different forms.  They were fed the monosaccharide fructose, the disaccharide sucrose, or a 0 calories sweetener (plus the same food to make caloric intake the same across all groups).  Those that were fed fructose were lazy, slow, and got fatter than those in other groups.  However, the mice that got lazy, fat, and slow were fed pure fructose, not HFCS (50:50 fructose:glucose), so in the end I don’t think this told us much.  Why didn’t they feed them HFCS to compare to the sucrose (table sugar mice)?

But wait! This article did what I want and they didn’t find any difference between HFCS and sucrose. Titled ‘Twenty-four-hour endocrine and metabolic profiles following consumption of high-fructose corn syrup-, sucrose-, fructose-, and glucose-sweetened beverages with meals.’ they stated in their results that:

“Sucrose and HFCS do not have substantially different short-term endocrine/metabolic effects. In male subjects, short-term consumption of sucrose and HFCS resulted in postprandial TG responses comparable to those induced by fructose.”

In my words: They took men and women, fed them either sucrose, fructose, glucose, or HFCS beverages, and checked their blood for levels of different hormones related to appetite and metabolism.  In general, they didn’t see much of a difference in the levels of leptin (the hormone that makes you feel full) in any of the groups.  So at least in the short term, they didn’t see a difference in being fat/lazy between eating any of the different sugars.  However, this was only a 24 hours study – it would be nice to know what happens over the long term.

There is another study cited by ‘Super Size Me’ (which I thought was a great movie btw) that showed that mice that were feed a diet high in HFCS and fats and not allowed to excercise got fat.  However, there was no control group that was feed a similar diet high in sucrose (table sugar) so I think that study was pretty worthless.  I can’t find the original study publication, so I can’t comment any further than that.

Some researchers did show that high fructose diets can lead to leptin resistance.  Their study was titled “Fructose-induced leptin resistance exacerbates weight gain in response to subsequent high-fat feeding” and they stated that:

“Our data indicate that chronic fructose consumption induces leptin resistance prior to body weight, adiposity, serum leptin, insulin, or glucose increases, and this fructose-induced leptin resistance accelerates high-fat induced obesity.”

In my words: Rats were fed diets where their caloric intake came either from fructose or corn starch (a polymer made from the monosaccharide glucose).  The mice that were fed fructose became resistant to the hormone leptin, which signals your body to feel full. In the long run, the fructose fed mice got fatter than the corn starch fed mice.  Again, I really wish they had fed the mice sucrose instead of corn starch!  I don’t think this contributes to the HFCS vs sugar argument.

Bottom Line: I think the jury is still very much out on this topic – I wasn’t compelled to believe that any of the studies I looked at proved that HFCS is worse than sucrose (table sugar).  I think that a lot of the results of some of these experiments are being used incorrectly – people are saying that mice got fatter eating fructose, but it doesn’t appear that any of them directly compared HFCS to table sugar.  However, even if HFCS is no worse for us than table sugar, let’s all agree that eating less sugar in any form would be a great idea.

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