Feeding the Machine - Navigating the Maize

In an effort to make these sub-topic posts on nutrition more digestible (ahem, sorry for that), I want to break them down sufficiently enough so that your interest does not wane in the middle of reading one. Any post about carbs and sports could get out of control long if I'm not careful. 

From a performance standpoint, I don't think anyone will argue the fact that we need to ingest carbohydrate to continue to train and race in endurance activities. We've covered this before in these pages. Let's recap the salient points as a segue to this post's topic. First of all, training and racing is supported primarily by glycogen which is stored in a limited capacity in the liver and muscle cells. At race intensity, we can last between 90 and 120 minutes before this supply is exhausted. By ingesting carbohydrate (which is converted to glycogen) during exercise we can stave off exhaustion almost indefinitely. We seem to be able to process about 300 kcal/hour. Yes, I know, fat is part of this energy equation, too, but I want to keep things simple here for the sake of discussion. Some athletes use fat for energy better than others but glycogen and, thus, glucose is still the main player for most of us. Bottom line is carbs are are both good and necessary for athletes.

But what about the rest of the population? Well, that's what I want to talk about here. First of all, let's be clear that glycogen and, thus, glucose, is the staff of life. Even non-athletes need this stuff. Hell, it's the only fuel substrate (aside from ketones... think starvation here) that crosses the blood-brain barrier meaning our brains run on sugar. So, we all need some of it, regardless of our activity. Does that mean the average Joe on the street should be powering down Clifbars and Gatorade to make it through the day? Uh, that would be a resounding NO! The thing is, we can all make glycogen from any of the three macronutrients - carbohydrate, fat and protein. We don't need to eat sugar to get sugar. 

So, what if we do eat a lot of sugar when we really don't need it? We get FAT! In case you haven't noticed, our nation and most of the free world is in the middle of an obesity epidemic of previously unseen proportions. For the first time in history, we have an obesity epidemic in 6 month old babies. WHAT??? Yeah, that's right. We are getting fat really early now. In fact, there are places that are performing bariatric surgical procedures (think stomach stapling) on 10 year olds. That's insane! One of my favorite statistics bandied about today is that the current generation of kids is the first that will experience a shorter lifespan than their parents due exclusively to the impact that obesity will have on their health. 

And what is this impact? It can be summarized in two words - Metabolic Syndrome. To break it down further, metabolic syndrome is characterized by hypertension (high blood pressure), de novo lipogenesis (making fat from sugar), dyslipidemia (elevated triglycerides which lead to heart disease), steatohepatitis (fatty liver), chronic inflammation, hepatic insulin resistance, obesity and central nervous system leptin resistance (this substance is what tells our brains we are full). None of this is good. It's also running rampant through our society. Until 30 years ago or so, we did not see too much of this. What changed?

Glad you asked. Roughly 30 years ago a major shift in nutritional policy took place in this country. No matter that it was based on some of the shittiest science ever to impact government policy but the result was that dietary fat was vilified and we were told to cut it out of our diets to save us all from heart disease. In a future post, I will discuss the fallacy of the "lipid hypothesis" of heart disease but for now I'll just tell you it is complete bullshit. The evidence supporting this contention is substantial. Regardless, a few decades ago our government felt compelled to latch onto some hypothesis so the whole "fat and cholesterol causes heart disease" idea was the one they chose. Great. 

So, we started cutting out the fat from our diet but we needed to replace those calories with something. Well, that something was sugar, namely, high fructose corn syrup (HFCS). This swill came onto the market in 1975 and we started adding it to everything to improve taste and help preserve the product it flavored. The beauty of it was that (is that) it costs about half as much as cane or beet sugar. Now, I don't think I have to get all long-winded on you about HFCS and how it's in everything and how we should be avoiding it. There is already lots of media time spent on both sides of that fence. But what I do want to do is try to wade through the hype and present some of the biochemistry to you so you can understand the truth for yourselves.

First of all, there are some of you that may wish to read no further. I have a friend like this. He avoids these topics because they don't really impact him at all. For those of you who eat similar to the way I discuss in these articles then HFCS is nowhere to be found in your diet so why should you care? For others like me, it's just plain interesting and I feel compelled to educate others. I realize I'm generally preaching to the choir in these pages but, what the hell.  

To start, let's get a little basic chemistry out of the way just so we are all up to speed. I already mentioned glucose earlier. This is what is known as a monosaccharide. More complex sugars go from here. Fructose is also a monosaccharide. Sucrose, which is table sugar, is a disaccharide (di=two) made from one molecule of glucose and one of fructose, 50% of each. Other disaccharides are formed from various combinations of monosaccharides. Chemically join some of these and you get starch and other more complex carbohydrates. HFCS is a disaccharide like sucrose but has 55% fructose and 41% glucose with other sugars rounding out the rest. The difference seems trivial and the corn industry would like you to believe as much. Unfortunately, no increase in fructose in our diet, with only one exception, perhaps, is good. As you will see, it is the accumulation of fructose feedings over time that are poisoning people. 

Why does the food industry like it so much? Like I said earlier, it's half the price of sucrose. Fructose is also 1.7 times sweeter than glucose so food manufactures can use less of it. It acts as a preservative as any sugar would. This is one of the reasons why it's added to EVERYTHING. One other attractive quality of HFCS is that it allows for even browning of baked goods. Nice looking muffins!

Now for some biochemistry. Standard sugar (sucrose) is broken down in the gut and absorbed into the bloodstream from the small intestine. There it is broken down into glucose and fructose. The presence of glucose in the bloodstream causes the pancreas to secret the hormone insulin. Glucose is converted to the storage form of carbohydrate, glycogen, where insulin helps transport it into the liver and muscle cells. When these storage areas are full, the rest is stored as fat. Simple enough, right? Well, things get funky with fructose. You see, fructose does not stimulate insulin release and, thus, can't do much for you when it first hits the blood stream. Fructose metabolism takes place in the liver and this is where things get interesting. The liver sees twice the calories from fructose as it does from any other sugar. This is why adding more fructose to the diet is a problem. 

What's the problem with that, you ask? Fructose metabolism is very complicated and I will spare you the details of the biochemistry. It's important to note that these details have only been fully understood in the last few years. During the course of all these crazy reactions breaking down fructose into something we can use, some scary things happen. In no particular order…

One of the byproducts of fructose metabolism is uric acid which causes both gout and hypertension. A recent study performed on hypertensive obese adolescents involved lowering their blood pressure by giving them allopurinol, the drug normally used to treat gout.

Fructose metabolism leads to increases in a particularly bad type of blood-born fat called "very low density lipoprotein" or VLDL. This is the stuff responsible for creating those heart attack-inducing, coronary artery-blocking plaques and leads to something called dyslipidemia, part of that Metabolic Syndrome I mentioned earlier. Oh yeah, give me some of that! Along those same lines, once liver glycogen stores are full, 30% of the remaining fructose is converted to fat. Worse still, not all of this fat makes it out of the liver, instead causing a lovely sounding problem called Non-Alcoholic Steatohepatitis. This parallels the biochemical chaos caused by chronic ethanol use (alcoholism). Hmm, gets better every minute! In fact, there are 12 recognized disease states seen in alcoholics. With chronic fructose ingestion (that would be your 64 ounce Big Gulp a day scenario), 8 of 12 of these problems develop.

Wow! Anymore bad news? Sure. How about a growing epidemic in obese 6 month olds? Yep, we got that going. One of the biggest predictors of this problem in this age group is how much juice is fed to these kids at home. Oh yeah, another name for fructose? Fruit sugar. Juice is loaded with it. One of our lovely welfare programs, WIC (Women, Infants, Children) provides juice for these kids. Not really doing them any favors. And these are the kids that usually go to bed with a bottle of apple juice in their hands. They're also the kids destined to be last pick for the recess dodge ball game, if you know what I mean. Oh yeah, and that baby formula so many under-informed mothers like to use? 43% corn syrup and 10% sucrose (Isomil). And before they get to that point you should know that sucrose crosses the placenta and it's been demonstrated that the more sweet mom eats the greater the affection for sweets in their off spring. 

Okay, one more. Fructose fails to stimulate the satiety signal in our brain. In fact, kids who are pre-loaded with a fructose meal tend to eat more at the following meal than those given glucose. Fructose leads to over indulgence. In fact, teenagers today eat between 240 and 350 calories more per day than they did 30 years ago. Gee, wonder why that is?

Earlier, I mentioned that the another name for fructose is fruit sugar. I've also been slamming fructose as being pretty awful. You might ask if that means that fruit is bad in the same way. Well, one of my favorite little adages regarding this is that "when god created the poison, he packaged it in the antidote." This simply means that fruit comes with fiber and plenty of micronutrients that significantly alter the metabolism of the sugars within. Much better to eat the fruit than to drink the juice. 

Well, that wasn't as short as I thought it was going to be but hopefully you get it. Oh, I almost forgot. I said earlier that there was one situation where fructose ingestion might be a good thing. This is when an athlete has exhausted most or all of their liver glycogen stores. Since fructose goes right to the liver, it may help replenish these stores more quickly than glucose or sucrose alone. So, using a recovery drink with some fructose content is not necessarily a bad thing. 

In case it isn't clear up there, I pick on fructose a lot but it's important to remember that regular sugar (sucrose) is 50% fructose. Outside of training and racing, you should still be avoiding all forms of refined sweetness for optimal health. During aerobic exercise our insulin requirement for metabolizing carbohydrate goes way down and our ability to utilize these sugars to fuel our efforts is enhanced. This means that eating refined carbohydrate during exercise will not subject you to the same deleterious effects I discussed above. In fact, eating simple carbs while training and racing will surely improve performance. But beyond that, it is best to avoid processed foods containing any sort of corn sweetener and limit your intake of other, so-called "natural" sweeteners like honey and the much-hyped agave nectar. Bon appetite. - Brian

Comments

[Matthew]

Tight and informative. Thanks for letting me off the hook for getting my masters' in sports nutrition. One question: does this mean I have to dump my nightly 2 squares of chocolate??

[brian]

Informative, perhaps, but I'm not sure I would call >2,000 words "tight". What can I do? Glad you liked it. I'm currently wrestling the lipid hypothesis for heart disease down to size. What a beast!

As for your chocolate habit, I'm hoping the fat content and the protein-rich meal that preceeded those two squares will slow their appearance in your blood stream, thereby blunting the insulin spike and saving your life!!