I was just going to write a brief reply, but ended up with the following novel. Sorry about this... I can't help it..
Dr. Oz is an idiot who no one should pay attention to. I just cited that because I thought it was funny...
But let's take a serious look at this issue.
The glycemic index of agave nectar is low compared to glucose because it contains more fructose than glucose:
Agave nectar (
https://en.wikipedia.org/wiki/Agave_nectar ):
56% fructose,
20% glucose
Compare this with the most commonly used grade of HFCS in sugary drinks, HFCS 55:
HFCS 55 (
http://www.sugar-and-sweetener-guide.com/hfcs-55.html ):
55% fructose,
40% glucose
Also compare with normal "table sugar", sucrose, which consists of a fructose molecule stuck to a glucose molecule:
Table sugar:
50% fructose,
50% glucose
Fructose has to be metabolized into glucose in the liver in order to raise blood sugar, whereas glucose IS blood sugar, so the latter causes levels to spike more quickly, and since it is absorbed quicker, the spike of maximum concentration is higher. But about half of the fructose you consume is converted to glucose (see
https://en.wikipedia.org/wiki/Fructolysis ); the rest is converted to lactate and glycogen, which eventually leads to triglyceride production.
So, what about the health claims that fructose is either better, worse, or equally bad for you compared to glucose or sucrose? This question is pretty controversial. On the "fructose is evil and will kill you" side, we have Robert Lustig:
"Yes, fructose has a low glycaemic index of 19, because it doesn't increase blood glucose. It's fructose, for goodness sake. It increases blood fructose, which is way worse. Fructose causes seven times as much cell damage as does glucose, because it binds to cellular proteins seven times faster; and it releases 100 times the number of oxygen radicals (such as hydrogen peroxide, which kills everything in sight). Indeed, a 20oz soda results in a serum fructose concentration of six micromolar, enough to do major arterial and pancreatic damage. Glycaemic index is a canard; and fructose makes it so. Because fructose's poisonous effects have nothing to do with glycaemic index; they are beyond glycaemic index."
https://www.theguardian.com/commentisfree/2013/oct/21/fructose-poison-sugar-industry-pseudoscience
Here is a summary of some scientific findings which raise concerns about fructose, with a less alarmist tone than Lustig:
"Why is fructose of concern? First, it is sweeter than either glucose or sucrose. In fruit, it serves as a marker for foods that are nutritionally rich. However, in soft drinks and other “sweets,” fructose serves to reward sweet taste that provides “calories,” often without much else in the way of nutrition. Second, the intake of soft drinks containing high-fructose corn syrup (HFCS) or sucrose has risen in parallel with the epidemic of obesity, which suggests a relation (2). Third, the article in this issue of the Journal (1) and another article published elsewhere last year (3) implicate dietary fructose as a potential risk factor for cardiovascular disease. "
http://ajcn.nutrition.org/content/86/4/895.full
On the pro-fructose side, there is industry-funded propaganda like this:
"Misinformation about fructose recently appeared in the media. This misinformation alleges obesity and negative health consequences from the consumption of HFCS and fructose. .... Low glycemic carbohydrate foods may be of benefit to people with diabetes, as they can help to prevent surges in blood glucose. ...", etc... it goes on cite studies showing fructose doesn't cause people to gain more weight in the short term, and to defend HFCS as well as fructose...
https://caloriecontrol.org/fructose/
And this seemingly reasonable article in a scientific journal, which basically tries to debunk all the bad things that have been said about fructose and HFCS, and concludes fructose and HFCS are not harmful, or at least no more harmful than table sugar:
"At present, we believe that the following conclusions are warranted. First, there is no unique relationship between HFCS and obesity. Second, there is broad scientific consensus that there are no significant metabolic or endocrine response differences or differences in health-related effects between HFCS and sucrose. Third, the metabolism and health effects of both HFCS and sucrose are different from those observed in studies that compare pure fructose with pure glucose, neither of which is consumed to any appreciable degree in the human diet. Fourth, recent randomized clinical trials have suggested that there are no adverse effects on total cholesterol, LDL cholesterol or HDL cholesterol at amounts ranging up to the 90th percentile level of fructose consumption, although other investigators have shown increases in cholesterol and/or LDL cholesterol in subjects consuming either sucrose or HFCS (66, 68–70), so further research studies are needed to clarify this issue. There is, however, a reliable increase in triglycerides from consumption of elevated levels of carbohydrates (particularly simple sugars), which merits further exploration. ..."
http://advances.nutrition.org/content/4/2/236.full.html
But wait, who paid for the above reasearch?
"Author disclosures: J. M. Rippe, consulting fees from ConAgra Foods, PepsiCo International, Kraft Foods, the Corn Refiners Association, and Weight Watchers International. T. J. Angelopoulos, no conflicts of interest."
Oh. Ok, well the fact that the research was paid for in part by the HCFS industry doesn't
necessarily mean it's bogus...
Specifically regarding agave nectar, here is a popular article that seems reasonable, saying it's bad for you:
Here's Dr. Weil, who is a celebrity doctor, but one who I have more respect for than Dr. Oz, on agave:
"I’ve stopped using agave myself and no longer recommend it as a healthy sweetener. The reason agave ranks relatively low on the glycemic index is because it has a high content of fructose. Fructose does not readily raise blood sugar (glucose) levels because the body doesn’t metabolize it well. New research suggests that excessive fructose consumption deranges liver function and promotes obesity. The less fructose you consume, the better."
https://www.drweil.com/diet-nutrition/nutrition/whats-wrong-with-agave-nectar/
So given all of the above, what is my own non-expert opinion? I think Dr. Lustig is a bit extreme. I don't think--
in moderation--agave nectar, or any form of sugar, will kill you. But I don't think it is very good for you, simply because, in general, it's best to keep simple sugars and carbs to a minimum. IMO, when it comes to any form of sugar/carbohydrates, moderation is the key.
