T Nation

Truth about Fructose

What’s the real deal with Fruit. The Forbidden Fruit article got me thinking, and seems to be a good carb choice for fat loss on a low carb diet. Then I’ve read Lyle McDonald and others say that it can only be converted into Liver glycogen, and not muscle glyogen, why is this? Some say avoid it b/c sugar is sugar. It’s supposed to be insulin dependent sugar, so there’s supposed to be little insulin response from most fruits. Then I’ve heard that it helps w/ the conversion of T-4 to the active T-3, to stimulate your thyroid. I’m following a diet from a article by Dr. Serrano, similar to the T-dawg. 40%protein, 40%fat and 20% carbs, mainly post-workout and 2-3 oranges a day. I’ve heard people on the Zone eat lost of fruit and lose fat. Poliquin recommends fruit being added eventually even on a fat loss diet. So what’s the truth, anyone know of more research or info? Does it only get stored in the liver? I’m trying to eat as natural as possible, lean beef w/ fish oil, broccoli and fruit. I find it hard to believe God would make fruit so readily available to humans yet it would make us fat.

I’m not an expert, but I did ask Lyle about this recently. He didn’t tell me that it only restored liver glycogen, only that it mostly did. His words were that fructose does a “piss-poor job” of replentishing muscle, so he suggests avoiding it while doing a ketogenic diet (even on carb-up days), but including it during bulking (non-ketogenic) phases because it keeps the liver replentished. so its weakness in one context is a strengt hin another. Now go read the ingredients of Grow! and you’ll find why it’s named Grow! and not Shrink!; even the name indicates the best “phase” for its use.

Diving into my physio book as we speak, but I wish someone would answer this damn fructose issue once and for all.

I know that when I include fructose into my diet it takes me much longer to enter ketosis again as compared to having eaten lots of starchy carbs.

Flex…here’s an excerpt from a newsletter from John Parillo that I just received today:

“Fructose, a simple sugar, is found in fruit. Fructose is used primarily to restore liver glycogen; it’s really not a good re-supplier of
muscle glycogen. Any muscle emptied of glycogen due to exercise is first on the
list to get its quota of glucose. Clearly, one of the keys to effectively restore glycogen is the type of carbohydrate you eat. Natural, complex carbohydrates such as potatoes, yams, whole grains, corn, legumes or
maltodextrin-based drinks like Parrillo Pro-Carb Formula do a better job at this than simple sugars do. If you eat simple sugars like fructose, you’re not going to be able to store as much glycogen. What implications does this have for you as an athlete?
First, you won’t be able to train as hard or as long during your next workout because you will be glycogen-deficient. Second, you’ll
notice less pump while working out, also due to lower glycogen store in the muscle.
Third, fructose is easily converted to body fat. If you want to get leaner and more muscular and build your recuperative powers by
restocking glycogen more efficiently-avoid fruit altogether and choose starchy and
fibrous carbohydrates instead, as the Parrillo Nutrition Manual recommends.”

I’m not implying this is the be-all, end-all solution. It’s just something I happened to come across and saw your post, so I thought I’d share. Parrillo is a pretty knowledgeable and experienced guy, that’s the only reason I decided to share.

#1 You can eat fruit. Just make sure it is below 50 on the glycemic index. Apples, oranges, cherries, grapefruit, etc. Stay away from bananas, mango, apricots, raisins, pineapple and watermelon. #2 fructose is poor at replenishing muscle glucose stores, but excellent at liver replacement. So, it isn’t a good idea on a ketogenic diet, but fine on a regular diet. #3 Following a workout, you want to replenish muscle glycogen fast, so use maltodextrin or dextrose.

I’m glad someone asked this question as I’ve always been somewhat confused on this issue as well. For those of you who consume MRP’s on a reg. basis, have you noticed a difference in fat loss comparing a MRP such as Grow w. a fructose base to the ones w. maltodextrin? I am going to be following the MRP Diet for a few weeks since my schedule makes it hard to get whole food meals in. I just ordered three boxes of Grow, and I should’ve looked closer but I noticed there are 17 g. of sugar (fructose) in each serving. I’m not gonna be real happy if fat loss is going to be slower as I’ve never done a high fructose intake for fat loss. I once read that Dan Duchaine said anything over 50 g. daily of fructose converts to fat. I will likely be consuming at least 4 servings a day if not more.

The Grow! is fine, teddykgb. We used it to test the MRP diet for both fat loss and bulking phases. Read TC’s Atomic Dog in issue 57 if you need further reassurance. Also, I think Cy Willson’s article does a great job explaining why fructose is fine. Or at least why it’s not something that should be feared.

Well, after reading many articles and results of studies dealing with fructose. I’m definitely staying away. I will continue to research but from initial reading fructose doesn’t seem to be healthy or very natural either. I’ve read that it raises triglyceride levels significantly (by 32% in 1 study compared to a group getting energy from another sugar source). It causes glycation, increasing the aging process, free radical damage to tissue cells, etc. I’m sticking with lean beef w/ broccoli and fish oil. Supplementing with protein powder and probably still gonna keep the carbs up post-workout. I know I can’t list links but anyone interested should look up the information themselves. One Dr., I’m not sure how accurate this is, said todays sweet fruits arent even natural and are a hybrid of seeds from trees and shrubs from centuries ago, and a crab apple is the closest thing to todays apple ever created by nature. Anyway, just my $.02.

you have to find out what works for you. i know people who eat lots of fruit (even by itself!) and they are very lean. some people can handle it…some can’t. to each his own! every ‘diet’ works…for someone! the question is-does it work for you?