Brief post on Sugar
Sugar, a demonized item in western culture. But is sugar bad, or simply misunderstood? In this week’s blog, I’ll attempt to put some fact behind the fear, and tell you the real story of sugar, how it’s processed in the body, the kinds of sugar out there, and what you really need to function properly.
First let’s define sugar. Sugar is a molecule; for humans, it’s a primary energy source, but the term sugar is a ubiquitous term encompassing many different molecules that all have similar properties. The “sugar” that we are all familiar with is sucrose, a disaccharide that has a very sweet taste and is used as a flavor enhancer in many foods. It’s naturally occurring and common in plant based organisms. Besides sucrose, there are many other saccharides out there that occur in nature. Monosaccharides such as glucose, fructose, and galactose are basic energy sources for the human body, glucose being the chosen type of fuel that cells can use in its energy cycle. Fructose and galactose must be converted in the liver to glucose before being used. Disaccharides, such as sucrose and lactose must be first broken down into their component parts before being used. Lastly, in technical terms, all carbohydrates are sugars. The type and quality of the sugar with regards to the human metabolic process defines whether we classify it as a true “sugar” in the dietary sense, or a complex carbohydrate, the difference being simply the process by which the body breaks down that carbohydrate, and what other nutrients it holds in its structure. The other part of sugars that should be understood is that some polysaccharides are fibers, or sugars that are structurally indigestible to humans, fiber also plays an important role as a cleaner of the digestive tract, and also as a tool the body uses to absorb excess water and lock down nutrients for slower absorption.
OK so you know that sugar comes in many forms. But what is the process the body uses to break it down? Depending on the type of sugar, our body will attempt to absorb it in different places. Sucrose is digested in the stomach into its component monosaccharides (fructose and glucose) in a 1 to 1 ratio, the fructose continues on and is absorbed in the intestines whereas glucose is absorbed directly from the stomach into the blood and carried to the cells that need energy. Fructose absorption in the liver carries the fructose molecule to the liver where it is acted upon by fructokinase and converted into glucose (and eventually glycogen) or pyruvate for energy production. Lactose, in a similar process to fructose (but using different pathways) is cleaved into glucose and galactose (galactose is another monosaccharide) where the galactose is acted upon in the intestines similar to fructose. There are other, less common reactions in the body for numerous other sugars, but these are the most common main forms that we think of when we think of sugar and most result in glucose and another monosaccharide being produced.
Knowing the above information, we can begin to have an understanding of what happens when we eat foods rich in a specific sugar type, and what it does to our bodies. Sucrose (commonly known as table sugar) enters the body and is broken down quickly, sending a surge of glucose from the stomach, directly into our blood stream, since there’s no conversion necessary for glucose to start feeding our cells, our blood sugar spikes and our bodies recognize this and send out the appropriate enzymes to utilize this. Insulin is a hormone created in the pancreas. It triggers the opening of cell receptors that fit the molecular pattern of glucose and allow absorption of glucose into the cell. When we flood our bodies with glucose, our insulin levels rise, and we receive as much energy as we can handle, the problem with this is twofold, first is that these rising blood sugar levels also trigger fat storage, which nobody wants, second, if this reaction is common and long term, our bodies can build up resistance to insulin levels, which can lead to type two diabetes. Of course along with the long term side effects is the “crash” we receive after, when the body receives a massive amount of energy all at once, it does it’s best to remove that extra as quickly as possible, when the glucose levels in the blood drop, the body is still looking for energy (it takes a while for insulin levels to fall) and since there is relatively low levels now, the body reduces its metabolic rate to compensate, making you feel sluggish and tired.
Fructose is a different matter, because the body cannot use fructose as a direct cellular energy source, the rise in blood sugar is governed by the body’s ability to convert it to glycogen in the liver, the path that leads from ingestion of fructose to usable energy is much longer, and slower than it is for sucrose. This means that the amount of usable energy being release into the blood at any one time is far slower and more controlled. This doesn’t mean that blood sugar levels won’t rise, and stay higher, it just means it won’t spike and crash as it would with sucrose. Consuming foods with large amounts of fructose can still lead to fat storage, especially when the products in question contain High Fructose Corn Syrup (HFCS) which also contains a high percentage of glucose in it (and now you can see how bad that would be). If we were to consume lactose in levels similar to HFCS, we would, most likely, see similar results, but lactose is less common naturally and thus generally not the cause of common sugar related problems.
Some side notes to consider.
When we consume sugars, no matter which type they are, much of the focus should be around the form the food takes when we consume it, this is almost as important as what type of sugar it is. When a sugar is locked up in indigestible or very dense material, the absorption rate is slowed, as the enzymes in the digestive tract can only act upon surface material, so when you eat “whole grains” and foods that are less milled such as fruits and vegetables, your body must “work around” the other material, either breaking it down, or digesting it first (depending on what material it is), this has a governing effect on blood sugar levels. so when someone says you should eat fiber rich foods, not only do they mean to help you clean your digestive tract, but also to help regulate energy absorption.
This leads directly to the concept of liquids and sugars. Liquids, by necessity, have a faster absorption rate for all nutrients than solids. This means that when you drink your sugars, you’ll inevitably be absorbing the sugars at a faster rate, this is the main reason why fruit juice is far less beneficial than solid fruits, despite the amounts of micronutrients in it (vitamins and minerals). So thinking that you’re being healthy by drinking that 16 oz glass of orange juice is not necessarily correct. Yes you receive high doses of some vitamins, but you’re also consuming large volumes of sugar (fructose and sucrose), which can be bad. It’s best to temper your fruit juice consumption to low levels (around 6 to 10 oz. per day and during times where activity will be higher soon after).
What should you take away from this:
Sugar is vital to almost all life, from bacteria to humans. But it can be a detriment as well. To be healthy, you should be cognizant of not only the amount of sugars you eat, but also the types of sugars, and the forms they take. Keeping sugar levels relatively low per meal, and trying to make your carbohydrate food sources complex (few simple and disaccharides) is a good way to keep your energy levels from spiking and crashing, it also allows your body to deliver the correct energy amounts for longer periods, reducing the “mood swings” associated with sugar fluctuations in the body.
When reading labels, look for how much sugar something has. But also look at the fiber levels, and search labels for “added fiber” which is not as effective as naturally occurring fiber simply because it is not bound to the existing sugars and thus easier to separate in the body.
Other key words to guard against with regards to sugars:
Processed flour (bleached, enriched), processed sugar (bleached, enriched), High Fructose Corn Syrup, added sugars, and any time a label says “enriched, or enhanced”.
key words that are GOOD to look for:
natural fiber (as opposed to added fiber), whole grain.
there are many more, consult a Registered Dietitian if you have more questions on this topic.