Ask a biochemist. page

[Molecular Grokologist]

I've enjoyed answering a number of other questions about biochemistry in other threads, so I thought that I'd offer my modest expertise in biochemistry to anybody who has a question. I may know the answer to your question, but if I don't, I'll check the literature to see if anybody does. If nobody knows, I'll speculate wildly! A good time for all, to be sure.


So be my guest, is there something YOU'VE been wondering? I'll do my best to keep answers simple (even at some slight cost to strict accuracy), but you're always welcome to ask me for details if I'm overly vague.


Have at thee, MDA forumites!

[TenYearStorm]

Very glad to have you here!

I read your last thread. How do you think that fructose is messing up insulin sensitivity and causes diabetes whereas, according to you and others, glucose isn't what messes it up in the first place...? Ingesting glucose makes a person secrete insulin whereas fructose doesn't. I know fructose causes glycation and all that nonsense but how does it make you fat and insulin resistant? Why do you say that small amounts of it are okay (I have heard this from Dr. Eades, too)?

[Molecular Grokologist]

How does fructose mess up insulin sensitivity? It's a tough question, but I'll provide a couple of the popular explanations since it's not yet entirely clear.


First, fructose metabolism (as opposed to glucose metabolism) bypasses some important feedback regulation mechanisms which would otherwise make sure that the buildup of downstream products would slow down the processing of the reactant (fructose) upstream. This leads to a load of a variety of compounds whose net effect is "make lots of trigs". Some of the fatty acids, however, aren't properly assembled because they've built up to levels that your enzymes can't keep up with, so fatty deposits accumulate in your liver, interfering with function.


Another problem is that fructose consumption changes the expression of a number of proteins (most notably GLUT5) which regulate normal glucose metabolism, altering your body's capacity to respond to otherwise harmless boluses of glucose.


Yet another is that high levels of fructose promote polyol (highly polymerizeable alcohols) and AGE formation, causing both "gumming up" of important proteins and chronic inflammation.


Once the liver ("grand central station" of the body as Stephan Guyenet so aptly put it) is screwed up, none of the various systems in the body are talking to each other properly. If the liver ain't happy, ain't nobody happy. Voila, insulin resistance.


By contrast, although glucose certainly causes insulin secretion, in the absence of damage, this simply causes storage of the glucose as fat and insulin levels quickly return to baseline, allowing the stored fat to be drawn upon for energy. No problem there. Of course, there are things which sometimes hitch a ride with gluten like some gluten peptide fractions which can cause all sorts of problems, but glucose itself (at least in my opinion, which is worth what you paid for it) isn't necessarily the originator of the issue.


Small amounts of fructose intake essentially act as mild stressors for the regulatory systems in your liver and elsewhere, causing the body to compensate by increasing it's sensitivity to and capacity to properly dispose of glucose. Too much, and you overwhelm your ability to beneficially over-compensate and you just kick the crap out of your liver.


There's a lot more to it, of course, but I don't think I've done the subject too great an injustice.

[Darthash]

I would like to know in detail what caffiene does to your body? like i have read that it produces cortisol.

[andrewc]

I've a couple of problems that I've been struggling to explain:


I've been strength training (very high weights, low reps(max of 5) with 3-5 minutes rest between sets) for a number of years and have read many comments suggesting that carbohydrate intake is unnecessary provided you are eating sufficient protein (and fat) and allowing at least 48 hours to replenish glycogen from protein.


In my experience there appears to be a wide variation in individual response to the above diet, whilst following a genuinely very demanding strength based routine. Some seem to flourish, others like me, are forced to resort to carbohydrates (losts of leafy veg and some starchy carbs to increase the carb intake).


After trying even high protein intake ( >3 gm/lb LBM )

I've been unable to recover between workouts and have gradually increased carb consumption to around 150gms/day, whilst maintaining high protein and majority of kcals from fat.


This forum frequently has people expressing support for both approaches.

Are these different dietary responses simply because I (and others) have failed to adapt to a high fat/protein diet ?


2nd question:

I've had a number of conversations with strength trainees who eat extremely high carb and protein (and negligible fat). One in particular is differentiates between carbohydrate and sugar, explaining that his high carb diet (think > 1000 gms carb day - thats carb content of food, not the weight of the food itself) does not promote body fat gain in the absence of dietary fat.


I thought all carbs were eventually processed as sugar (accepting the differences between glucose and fructose) ?


Is he correct re a v high carb diet not being fat promoting in the absence of fat, provided you're in an approximate energy balance ?


Thanks for any insight you can offer.

[Brewtality]

How beneficial are probiotics to a normal primal person, and how do they help?

[OnTheBayou]

I about choked seeing the word "polyol" as an unwanted product of fructose consumption.


Polyol is a synthetic lubricant for car air conditioning systems!

[BarbeyGirl]

What a gracious and exciting offer. Thanks, MG! The nerds are grateful.


We've discussed this question here before, but to no definitive end:


Is it better to eat carbs alone, or with fat/protein?


It's my understanding from the Eades (Protein Power) and others that a combination causes a greater insulin spike than carbs alone. However, we're often advised to slow the absorption of carbs by eating them with fat/protein (butter on the sweet potato, nuts with the apple, etc.)


So which is it? Does it even matter in a person who has a healthy metabolism and is eating 50-100g carbs per day, mostly as veggies?


ETA -- Just read your fructose explanation above. Very helpful, thanks!

[Stabby]

Why is it that when somoneone switches from eating little fat to lots of fat, they tend to feel sick? I remember reading something about compromised bile production, is this the case?

[NorthernMonkeyGirl]

Oooo goody goody!


1- What are your thoughts on vitamin D (if that's not too vague)? As in, do high level supplements help the body, or are high plasma levels of vitamin D merely a marker for a healthy system? In which case, adding extra vitamin D into the system may unbalance and upset things?


2- Oxalates. Having just read a WAPF article here http://www.westonaprice.org/The-Role...Disorders.html is there any role for oxalates in health / weight loss? Maybe that's phrased wrong. It boils down to "Do I need to watch intake?" - I eat a fair amount of high oxalate food according to that list.


3- What is the biochemical equivalent of a boot up the arse so I stop succumbing to my sugar addiction...?

(If you can answer that then you deserve a Nobel!)


Thank you very much