Comment by montecarl | Hacker News Reader

Comment by montecarl | Hacker News Reader

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> People enzymatically convert corn sugar to match what comes out of sugar cane. Straight-up corn sugar is harmless, "high-fructose" is deadly.

Corn sugar is the monosaccharide glucose (more specifically its a specific stereoisomer of glucose called dextrose or D-glucose).[1] Cane sugar is sucrose, which is a disaccharide of composed of glucose and fructose.[2]

There is no way to enzymatically convert a monosaccharide to a disaccharide, you would need to be joining the glucose together with a fructose, which, as we are not fruit don't just have naturally occurring in our body.

When you eat sucrose, the enzyme sucrase-isomaltase located in the small intestine catalyzes its hydrolysis into fructose and glucose.[3,4] High-fructose corn syrup is a mixture of glucose and fructose which is exactly what you get when your body enzymatically breaks down sucrose.[5]

So corn sugar is glucose. Sugar can is sucrose. And high-fructose corn syrup is a mixture of "pre-digested" sucrose. I think that high-fructose corn syrup is probably bad in that its in everything and cheap, but I can't see how its any worse than regular sugar. And corn sugar is not the same as regular sugar, it lacks fructose entirely.

[1] https://en.wikipedia.org/wiki/Corn_sugar

[2] https://en.wikipedia.org/wiki/Sugarcane

[3] https://en.wikipedia.org/wiki/Sucrase

[4] https://en.wikipedia.org/wiki/Sucrase-isomaltase

[5] https://en.wikipedia.org/wiki/High-fructose_corn_syrup

Yet, millions of tons of corn sugar is, in fact, made via industrial enzymatic process into "high-fructose corn sugar", mainly because it is sweeter when cold than straight glucose, and doesn't absorb water from air as readily. Cane sugar in beverages has typically already separated into glucose and fructose, no sucrase needed.

Fructose is a problem because it is processed as a toxin, in the liver. Fructose was invented by flowering plants in the early Cretaceous because, erg for erg, it tasted sweeter to insects. Our evolutionary ancestors never had need to evolve means to process much of it. The liver makes it into fat, wraps it in cholesterol, and ships it off to the fat cells to store, emitting lots of uric acid as waste. Too much uric acid causes lots of problems.

If production of cholesterol is inadequate, worse things happen.

Fructose is a minor problem if consumed along with enough fiber, because enough fiber delays absorption long enough for your intestinal bacteria to get a crack at it first. (They can eat fructose all day long.) But modern industrial "food" processing is all about eliminating fiber, and delivering the straight-up stuff. The only actual fruit without enough fiber is, oddly, grapes.

Again, worth pointing out that none of this fructose stuff is really operable, because there isn't a mainstream "low-fructose" sugar that anyone uses as a sweetener†. As you acknowledged across the thread: HFCS is (if not chemically identical) bioavailably the same thing as cane sugar.

† Other sugars get used for functional reasons other than sweetening, of course.

You can buy straight glucose, sold as "corn sugar", from brewery suppliers. In the US they would like to sell you a 50-pound bag for $100, but a 10-pound bag for $20 should last you a long time. It all comes, ultimately, from Tate and Lyle. It may also be labeled "dextrose"; same stuff. They will let you pay as much as you like. (Some claim to offer "organic", but there is really no way to tell and, by the evidence, they are probably just re-bagging it with a new label, and lying. Enforcement is nonexistent.)

There are other sugars, maltose, maltodextrin, [not lactose] with varying numbers of glucose molecules stitched end on end, collectively amyloses. With enough, it becomes starch.

There is also left-handed enantiomeric glucose, zero calories, expensive, and racemic glucose, 50% calories. The latter is made from raw chemicals. Guessing they make the former by feeding the latter to bugs and selling what is left over, although there are crystallization tricks.

I bake with corn sugar, and it works fine. I have found that hot chocolate made with it is unsatisfying without a half-teaspoon of table sugar added. Or a marshmallow.

>lactose, etc. Those are just varying numbers of glucose molecules stitched end on end.

Not so: lactose is a glucose stitched to a galactose molecule.

I am corrected. Chemistry offers a limitless supply of complications.

> Our evolutionary ancestors never had need to evolve means to process much of it.

That's not true because about half of the carbs in fruits and vegetables is fructose. (Cherries have the lowest ratio I know about at about 30%; apples and pears have the highest at around 70%; most fruits and vegetable are almost exactly half fructose and half glucose.)

Also, if you eat a spaghetti meal or a lot of potatoes (which rapidly become glucose and get absorbed) your body will convert a decent amount of the glucose into fructose according to researcher Robert Lustig MD.

(I don't disagree with your overall point that most affluent people consume too much fructose. In the ancestral environment however calories were scarce enough that people should have and did eat almost all the fructose they could find.)

Prehistorically, fructose without intermixed fiber was found mainly in honeycombs, i.e. rarely. Beverages are the way most people get the most concentrated blasts of fructose nowadays. With enough fiber, intestinal bacteria get first crack at it. (Keep your intestinal bacteria well-fed; hungry bacteria will eat you instead.)

Your body has processes to produce fructose, which is then processed by the liver to fat for storage, when preparing for lean times seems indicated.

It is hard to research, but it seems like mangoes have the highest proportion of fructose. Honey has more fructose than glucose, and agave syrup is mostly fructose.

Worth keeping in mind that Lustig is a crank who says a lot of things that are beyond what is supported by the science and most likely untrue. I don't know if that particular statement is true or not, but I am less likely to believe it with Lustig's name attached than without it.

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