Yeah, the Pop Tart things is dumb, but it's hardly central to the issue. What I believe he was trying to suggest (and I could be wrong, since I'm not a telepath) is that while it is misleading to say that "a calorie is a calorie", it is to a first-order approximation true that "a carbohydrate is a carbohydrate" because the metabolic effects of glucose, fructose, sucrose, maltose, maltodextrins, or starch are a lot more similar than they are different.
Feinman is not anywhere claiming that fructose and ethanol do not share a metabolic pathway. He is saying that the mere existence of a pathway tells us nothing about how much that pathway is used. Just because it is possible for me to throw money in the trash with used paper towels does not mean that I treat money the same way I treat used paper towels.
The reason fructose isn't as bad for us as alcohol is because we have evolved a special mechanism, the hepatic portal, to shunt fructose directly to the liver and avoid exposing the rest of the body to it. Lustig ignores this, but Feinman ignores that it's necessary for our well being.
Every metabolic pathway is a "special mechanism" that we evolved. And I don't know what you mean when you say that "Feinman ignores that it's necessary for our well being". Are you saying that Feinman is not explicitly pointing out that without the hepatic portal we would have a lot of trouble safely metabolizing fructose? Well, sure, if we exclude any metabolic pathway, we're not going to metabolize stuff as well. That's not news, it's a tautology. I'm not going to criticize him for not explicitly reminding us that metabolism is good for metabolism.
Finally, "he's a doctor, not a scientist" is hardly sufficient excuse for saying that ethanol is a carbohydrate. If my general practitioner ever said something that dumb I'd find a new doctor pronto, and she's not holding herself out as an expert on metabolism. I'm not expecting that every pediatrician be able to recite the entire Krebs cycle from memory, but I do expect that a doctor took introductory organic chemistry and knows what a carbohydrate is.
no subject
Feinman is not anywhere claiming that fructose and ethanol do not share a metabolic pathway. He is saying that the mere existence of a pathway tells us nothing about how much that pathway is used. Just because it is possible for me to throw money in the trash with used paper towels does not mean that I treat money the same way I treat used paper towels.
The reason fructose isn't as bad for us as alcohol is because we have evolved a special mechanism, the hepatic portal, to shunt fructose directly to the liver and avoid exposing the rest of the body to it. Lustig ignores this, but Feinman ignores that it's necessary for our well being.
Every metabolic pathway is a "special mechanism" that we evolved. And I don't know what you mean when you say that "Feinman ignores that it's necessary for our well being". Are you saying that Feinman is not explicitly pointing out that without the hepatic portal we would have a lot of trouble safely metabolizing fructose? Well, sure, if we exclude any metabolic pathway, we're not going to metabolize stuff as well. That's not news, it's a tautology. I'm not going to criticize him for not explicitly reminding us that metabolism is good for metabolism.
Finally, "he's a doctor, not a scientist" is hardly sufficient excuse for saying that ethanol is a carbohydrate. If my general practitioner ever said something that dumb I'd find a new doctor pronto, and she's not holding herself out as an expert on metabolism. I'm not expecting that every pediatrician be able to recite the entire Krebs cycle from memory, but I do expect that a doctor took introductory organic chemistry and knows what a carbohydrate is.