It's not that simple. Biological enzymes tend to be highly or exclusively stereo-selective.
See the following two references which detail differential or unique biological effects dependent on the chirality (left or right-handedness) of L-Fructose.

http://pubs.acs.org/doi/abs/10.1021/ja01209a027
This article (click on text to enlarge) describes isolation of L-fructose by feeding a mix of D and L to yeast, who ate all the D-Fructose leaving only L-Fructose.

http://books.google.ie/books?id=Ggl...result&resnum=8
This link also says there ten different isomers of Fructose.

there seems to be a whole lot of confusion on the web about the naming of fructose isomers. Partly I think because the common form, Levulose or D_fructose, is actually Levorotatory, tempting some people to think it is called L-Fructose. This error occurs in the Weston Price article quoted above. Be very wary of naming accuracy unless it's from a hard-core glycobiology student.

For a picture of the four most discussed isomers see the graphics one third way down in http://www.edinformatics.com/math_s...ng/fructose.htm

There has been some mention of the ease of conversion between fructose isomers. My understanding is that this refers mostly to the conversion between alpha-D-Fructose and Beta-D-Fructose. Doing the D to L flip seems to be a lot more difficult,. Most higher animals can't do it. Some bacteria seem to have figured it out.

I have seriously uncomplicated my life by avoiding anything that ends in "ose". Problem solved!

Agree with Nancy's last point, but the argument of whether "natural fructose" is better or the same for you as the HFCS variety needs a bigger picture perspective.

It seems the debate has taken a "nutritionism" approach and is taken out of the context of real-world nutrition.

A couple of brief points;

a) HFCS is not especially obesigenic compared with other sugars - at least not in a hypocaloric diet.
b) calling all sugars "poisons" is a little alarmist.
c) does anybody really believe that eating an apple has the same physiological impact as eating an equivalent amount of HFCS?
d) while we may not have studies demonstrating the differences in "natural" vs. "unnatural" fructose intake, there are studies that show higher vs. lower fruit diets show no difference in weight loss (hypocaloric diets). Rodriguez had 2 groups - 1 high fruit, one low fruit (4% of calories from fructose vs. 13+%). Over 8 weeks, both groups lost weight and fat, with no differences between the 2. Interestingly though, the higher fruit group lost more belly fat.
e) Crujeiras et. al had similar findings. Again no difference in weight loss b/w the 2 groups, however the higher fruit group showed better defense against oxidative stress.

Bottom line, no need to skip fruit because of the "fructose"

Darn it, I recall reading something over the past couple months where I believe they at least had different sources in the study and cited results that way... I don't recall whether that had any impact on results, however. Haven't re-located it in a PubMed and Medline search today.

I did run across this, which doesn't talk about different sources for the fructose, but had kind of an interesting anomaly mentioned at the end (TG=triglyceride):

"Unexpectedly, the effects of short-term consumption of HFCS and sucrose on postprandial TG levels were not intermediate to those of fructose and glucose but comparable to fructose alone. Studies to determine whether these high postprandial TG levels are sustained during long-term consumption of sucrose and HFCS are needed. Additional studies in women and in subjects with and without components of the metabolic syndrome, as well as dose-response studies, are needed to more fully understand the metabolic effects of fructose-containing sugars."

That's from:
Twenty-four-hour endocrine and metabolic profiles following consumption of high-fructose corn syrup-, sucrose-, fructose-, and glucose-sweetened beverages with meals
http://www.ajcn.org/cgi/content/full/87/5/1194

And just now I did see this, which I think is a particularly interesting point in light of what Scars just mentioned:

"High fructose diets can have a hypertriglyceridemic and pro-oxidant effect, and fructose fed rats have shown less protection from lipid peroxidation. Replacing the fructose in these diets with a more natural source of high fructose, honey, reduces this susceptibility and lowers plasma nitrite and nitrate levels [109]." ...
"Recent findings have also shown that the hyperlipidemic and pro-oxidant effect induced by a high fructose diet can be decreased by oligofructose consumption. Oligofructose administered to fructose fed rats did not alter insulin concentrations, and lowered plasma leptin by 50% compared to control groups. Oligofructose prevented TG changes induced by fructose feeding, and decreased hepatic TG accumulation. The peroxidation effect of fructose was also decreased by oligofructose, and had beneficial protective effects [110]."

Those are from:
Fructose, insulin resistance, and metabolic dyslipidemia
http://www.pubmedcentral.nih.gov/ar...entrez#id762126

This argument sounds A LOT like the whole grain vs refined grain argument.

Thank you, amergin - that was an EXTREMELY illuminating post! I was so confused. Why the heck is it called D-Fructose anyway? Is that consistent with other isomers, like D-Glucose or L-Glutamine?

As for what to eat, I'm with Wifezilla.

Well that is interesting because you would expect that the more fructose taken in the higher the triglycerides, since that is part of the expected action from the liver in response to Fructose. There was also something I posted earlier about how glucose actually makes fructose be taken up better, so if that's true then pure fructose would be better for you than sugar or say and apple with a mixture of fructose, sucrose and glucose. Still, I'm talking in relative terms here. The difference in absorption would be minute (like 10% of a small number).

http://en.wikipedia.org/wiki/Fructooligosaccharide

I think Oligofructose isn't actually fructose. It's like an alternative sweetener.

Sounds like a fructose polymer like inulin. It's still a FODMAP in that case.

But no one should be blind to the fact that high fructose corn syrup MAY and indeed probably is, laced with mercury because of the way it is manufactured.
Not So Sweet: Missing Mercury and High Fructose Corn Syrup If anyone here thinks that having a sweetener laced with mercury is worth risking then God Help them.

I really don't think it is reasonable to equate the fructose in a portion of fruit to the same quantity of fructose laced with mercury in HFCS.

I also think we have to consider the time scale and quantity of natural fructose available to a paleo hunter gatherer and compare that to the intake of fructose and time scale available now.

Maybe if we limited fructose consumption to the amount we could personally gather and consume regularly and in season it would produce a reasonable limit however even that would be significantly higher than our ancestors given the increase in fructose selective breeding has introduced.

However tasty a fruit based smoothie may be I think we are kidding ourselves if we equate this with the intake available to our paleo HG ancestors.

You Betcha! All we need is meat (sung to the tune of "all we need is love")

Do we need any grains at all? I love the "we don't have a crop" argument. Birds have a crop and can digest grains- HUMANS do not.

-ose= bad.

See http://en.wikipedia.org/wiki/Dextrorotatory

"The prefixes "(+)-", "(-)-", "d-", "l-", "D-", and "L-"

A dextrorotary compound is often prefixed "(+)-" or "d-". Likewise, a levorotary compound is often prefixed "(-)-" or "l-". These "d-" and "l-" prefixes should not be confused with the "D-" and "L-" prefixes based on the actual configuration of each enantiomer, with the version synthesized from naturally occurring (+)-glyceraldehyde being considered the D- form. For example, nine of the nineteen L-amino acids commonly found in proteins are dextrorotatory (at a wavelength of 589 nm), and D-fructose is also referred to as levulose because it is levorotatory. See the article: Chirality (chemistry)."


I can't promise it will make things any less confusing though. With Lines like "These "d-" and "l-" prefixes should not be confused with the "D-" and "L-" prefixes...."
it can't be any other than confusing.

I'm also with Wifezilla on the all-important, and undeferrable, question of "what to eat?".

In my mind it means that there's some part of the molecular structure that is put together exactly opposite of the other form. Not sure if it's the entire thing or just a fragment of it. I kind of got the impression it could be a fragment. In other words, if they were a chain of letters A - B - B - A - C is fructose then A- B -C -A -B might be L-fructose, just the ending B A C is reversed.

Ok, so Levulose is fructose of the right-handed variety (D-Fructose). So corn syrup wouldn't be considered Levulose. A little confusing becausing I was thinking the L in levulose might stand for left.

So it sounds like if you want to know if Levulose (naturally occurring fructose) is as bad as L-fructose then that'd probably be what to search for. And no, I'm not including any contamination with mecury in my estimation of what I think about Fructose. That's just extra badness.

My stance is: All fructose is bad except in amounts consumed by humans like 10,000 years ago, i.e. not much. That means that sugar is bad, honey is bad and corn syrup is extremely bad and lets lump agave syrup right in there with corn syrup. It is all processed by the liver and can lead to NAFLD, diabetes and so on, if consumed in large quantities. Corn syrup is worse because it may have other things that cause additional problems, such as mercury contamination, etc.

Also, glucose increases the uptake of fructose so it might actually be worse in sugar.

If tomorrow they threw out all the corn syrup based fructose and replaced it with apple fructose, it'd probably be nearly as bad.

Healthy low carbers probably don't eat more fructose than their body can handle, generally, YMMV of course. Diabetic ones or people with high triglycerides might want to be more cautious.

Table sugar is not a whole, healthy or natural food. Go look up the sort of processing they do on sugar.

Anyway, that's my opinion.

I don't think anyone has any idea how long it takes to collect a cup of wild strawberries. True wild strawberries are about the size of your pinkie nail. You have to lay on your belly to see them unless you want to kill your back stooping.


Nope. Well, unless you are chewing on a piece of raw sugar cane that is

The Masai people hunted down beehives by following a species of birds that eat bees.
http://en.wikipedia.org/wiki/Honeyguide