Nutrition 101: The Evils of Sugar

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Posted by: stak
Tags: nutrition
Posted on: 2011-08-06 12:07:32

I've been reading a bunch about proper nutrition lately, and I wanted to write a summary of the main points I've come across. The main reason for this is just so it forces me to think about this better and make sure it all makes sense in my head. A secondary reason is to record what I think about this now, as I'm sure it'll change over time.

Also, a fair number of the statements below are controversial in that there are studies that agree and disagree with them. However, I'm not going to cite any sources for my statements because (1) I'm too lazy and (2) it helps eliminate bias because instead of just following my link and believing me, you're forced to research it for yourself and come to your own conclusions. And I do strongly recommend that you try to research any statement you feel is wrong or that you have a hard time believing, and post your comments below.

Finally, I'm going to try and keep this as simple as possible, to make it readable by the widest audience possible. This means avoiding the use of technical terms as much as possible, even if means sacrificing precision.


Sugars (aka carbs) are generally bad for you. There are a few reasons for this.

1) When your body burns sugar for energy, the chemical reactions produce free radicals. Free radicals cause lots of damage because they destroy other molecules in your body. In particular, they cause proteins in your body to cross-link, which makes the proteins useless. This is why balancing any sugars you eat with antioxidants (which neutralize free radicals) is a good thing.

2) Eating sugar triggers your body's insulin response. The insulin's job is to store the sugar as fat in your body. After it's done putting away the sugar, it still sticks around for a while, until your body stops producing it. This extra insulin leads to cravings/hunger, even though your body doesn't really need food. Overloading your body with sugar will also, over time, decrease the amount of insulin your body produces, resulting in diabetes. This is why people who are diabetic need to take insulin with sugar - this is basically the same as having to take the antidote along with the poison.

(Update 2011-08-08: It was correctly pointed out to me that it's not the amount of insulin production that decreases, but rather your body becomes more resistant to the insulin, so the same amount of insulin has less effect. This insulin resistance is what causes Type 2 diabetes.)

3) Some of the sugar you eat gets stored as glycogen (a quick-burning energy source that your body uses for quick bursts of activity). However, each gram of sugar that gets converted to glycogen also requires 2-3 grams of water. Therefore, this has a dehydrating effect on your body. This water also gets released when the glycogen is burnt, and is the "water weight" that people lose when starting to exercise after a long time.

There are different kinds of sugars that you encounter in everyday foods. Some of these (e.g. glucose) are not as bad because they can be burnt by every cell in the body. Others (e.g. fructose) are really bad because they can only be broken down by the liver. Therefore, eating a particular amount of fructose stresses the liver far more than the same amount of glucose. Note that table sugar (sucrose) is 50% fructose, and pretty much any other sugar additive (e.g. high-fructose corn syrup, agave syrup) is just as bad.

Foods with refined sugars enter your bloodstream much faster, and so the negative effects from eating those foods are much sharper, and stresses your body more. The glycemic index of a food is a measure of how fast the sugar hits your bloodstream; foods with a higher glycemic index are worse. Foods containing a lot of fibre will slow down the sugar, and therefore help your body in dealing with the incoming sugar.

Overall, the amount of sugar you consume should be just enough to replenish your body's stores of glycogen (less than 100 grams per day for most people). You should drink plenty of water with sugar consumption to avoid dehydration when this happens. If you consume more sugar than this, burning it off before the insulin gets a chance to store it as fat is a good idea (unless, of course, you're trying to become obese). Finally, make sure to get enough antioxidants along with your sugar to neutralize those free radicals.

See also: Nutrition 102, Nutrition 103.

Posted by varun at 2011-08-07 13:56:46
If you want to take a look at the book that changed my views on the acceptability of sugar, take a look at Sugar Blues. It's a really fascinating look at how sugar messes with normal human physiology, and also a nice look at the history of why refined white sugar became so prevalent.

I've basically been using agave for quite a while now, and more and more, I notice the almost direct effect having sugar has on my wakefulness and awareness. Message M too, if you'd like - she's been macrobiotic for over two decades.
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Posted by Fai at 2011-08-08 02:57:00
So I think what you say is true about excess sugar, but is not actually true of all sugar. We do need some amount of sugar to live. Agreed that the average western diet now contains way more sugar than we need, but only the excess is wrong, not all sugar.
And I think your comment about diabetes is wrong. Diabetics need to take sugar when their sugar level is dangerously low. And because they can't process it correctly, they must also take insulin with it. But if it was truly unnecessary, you could just skip taking both the sugar and the insulin, but you can't, because our body requires sugar.
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Posted by stak at 2011-08-08 08:38:07
We need sugar *in our blood* to live. We do not need it *in our diet*. Our bodies are capable of producing glucose by breaking down certain amino acids, assuming no incorrect medications/hormonal imbalances that might affect this. Note that although there are essential fatty acids and essential amino acids that our bodies cannot produce from other things, there are no essential carbohydrates. Humans can (and do) survive on diets that contain zero carbohydrates; their bodies just switch to using fats as the preferred energy source, and proteins as a backup.

Diabetics can have low blood sugar (hypoglycemia) if they take too much insulin. When that happens they might need to take sugar, but only because the excess insulin neutralizes the glucose their bodies produce naturally as a response. I guess it's more like balancing two counteracting poisons, rather than a poison and an antidote :)
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Posted by Varun at 2011-08-08 11:08:01
Too true. I've often found that balance in Western diets can be described as "one hand in the freezer, one over the burner".
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