I finally had time to look at the youtube video and found it very interesting. Dr. Lustig is a wonderful lecturer (aside from his frequent use of the work "ok"), and I found myself drawn in and actually watched the whole video. I agree completely with his general conclusions about the cause of the "metabolic syndrome" and the evils of excessive consumption of sucrose or corn syrup. He explained the mechanism of how the metabolism of fructose leads to obesity and cardiovascular disease beautifully.
As for my impressions of the content, I think his presentation is a bit alarmist in calling fructose a "toxin". As a chemist, I noticed he oversimplified the biochemistry of metabolism quite a bit.
1. Fructose can be metabolized by muscle and kidney cells using the same enzyme (hexokinase) that starts glucose metabolism. Hexokinase binds glucose much better than fructose (the rate constant for glucose metabolism is 100 time larger than that of fructose), so the majority of fructose does reach the liver, but it is not the "only" metabolic pathway for fructose.
2. The claim that fructose is toxic to the liver for the same reason that alcohol is toxic is not really true. Even small amounts of alcohol can damage the liver because ethanol is broken down into acetaldehyde by alcohol dehydrogenase. This aldehyde is harmful since it is not rapidly metabolized (as opposed to glyceraldehyde produced in the breakdown of fructose), and aldehydes are reactive with proteins, potentially damaging them. Furthermore, reactive oxygen species are not produced in the metabolism of fructose. However it is true that an excess of fructose can lead to hepatitis and fatty deposits in the liver by the same mechanisms as the breakdown of alcohol. The issue in both cases is one of volume overload.
3. For someone battling cancer, the lack of a rapid glycemic response to fructose is very significant, since high levels of insulin lead to higher concentrations of free insulin growth factor (IGF) which stimulates cell division and tumor growth. Thus even if the overall glycemic load of a given number of grams of sucrose and pure glucose is the same, the slower absorption of sucrose (due to the fructose in it) leads to a lower insulin spike. In a recent article on the benefit of exercise to avoid recurrence in colorectal cancer, the authors speculate that the mechanism of the benefit is likely the increased sensitivity of the body to insulin due to exercise, which lowers the level of insulin in the body and therefore IGF. See J. Meyerhardt et al., Arch. Intern Med., Vol. 169, page 2102, 2009
4. Small amounts of fructose consumption is not harmful, and using fructose-based sweeteners is modest amounts (in coffee etc.) is not a worry. Fructose tastes "sweeter", and should be used in smaller amounts than sucrose or glucose. However, as Dr. Lustig points out, care should be taken to avoid large amounts of corn syrup as this overloads the liver into producing fatty acids and fat deposits.
Thanks for posting the link! I found it very informative.
This is just my 2 cents.
Colon cancer dx Feb. 24, 2009, T3/N2/M0
Right Hemicolectomy Feb. 26, 2009
Stage 3C: 4/19 positive nodes
High grade adenocarcinoma with tumor budding
FOLFOX6 April 15 - Oct. 1, 2009
Elective sub-total colectomy July 3, 2012 due to 2 DALMs