Glucose and fructose are both simple sugars, but scientists have long suspected there are differences in the way your body processes them.
In a new study, researchers scanned the brains of nine subjects after they got an infusion of equal volumes of glucose, fructose or saline. The brain scans were looking at activity in the hypothalamus, a part of the brain which plays a key role in setting appetite levels and controlling production of metabolic hormones.
According to the Chicago Tribune:
“The researchers ... found that ‘cortical control areas’ -- broad swaths of gray matter that surrounded the hypothalamus -- responded quite differently to the infusion of fructose than they did to glucose. Across the limited regions of the brain they scanned ... glucose significantly raised the level of neural activity for about 20 minutes following the infusion. Fructose had the opposite effect, causing activity in the same areas to drop and stay low for 20 minutes after the infusion.”
People everywhere are finally waking up to the indisputable fact that all simple sugars are not the same when it comes to the physical end results they create. The latest Public Service Announcement warning New Yorkers about the dangers of excessive soda consumption is a powerful illustration of this increasing level of awareness.
When these differences are understood, it's easy to see how and why fructose—mainly in the form of high fructose corn syrup (HFCS)—is in large part responsible for the meteoric rise of obesity and its related health problems.
It's a staple ingredient in a vast majority of sweetened beverages and processed foods of all kinds, from pre-packaged meals to baked goods and condiments. And the number one source of calories in America is soda, in the form of HFCS!
Your Brain Reacts to Fructose and Glucose in Very Different Ways
This latest study is intriguing, as it shows that the difference between fructose and glucose is not just limited to how they're metabolized in your body; your brain also reacts to these two sugars in entirely different ways.
Nine healthy, normal-weight subjects received either glucose, fructose, or saline (as the control). Their brains were then scanned to evaluate activity around the hypothalamus, which is a key player in appetite control and production of metabolic hormones.
Interestingly, the researchers discovered that the "cortical control areas" surrounding the hypothalamus responded very differently to each substance:
- Glucose significantly raised the level of neural activity for about 20 minutes
- Fructose reduced neural activity in the area for about the same amount of time
- Saline had no effect on neural activity
So, what does this mean?
At this point, the implications of these differences are unclear. The Chicago Tribune reported that:
"At this point, said [lead researcher] Purnell in a phone interview, it means nothing more than that the two substances did prompt different responses in the brain--that the brain did not respond to them identically.
Within some of the "cortical control areas" where differences were seen, lie some important neural real estate, including regions where notions of reward and addiction are processed.
As scientists have a closer look in future studies, they should be able to zero in on which specific areas are affected differently by the two forms of sugar."
So, time will tell what these latest findings really mean, but we already know that fructose has a detrimental impact on two hormones involved with satiety and hunger, namely leptin and ghrelin, and that this influence sets in motion a vicious cycle of hunger, increased food intake, and increased fat storage.
Fructose Packs on the Pounds Faster than Any Other Nutrient
Part of what makes HFCS so unhealthy is that it is metabolized to fat in your body far more rapidly than any other sugar. The entire burden of metabolizing fructose falls on your liver, and it promotes a particularly dangerous kind of body fat, namely adipose fat. This is the fat type of fat that collects in your abdominal region and is associated with a greater risk of heart disease.
Additionally, because most fructose is consumed in liquid form (i.e. soda and sweetened beverages of all kinds), its negative metabolic effects are magnified. Because while HFCS has about the same amount of fructose as cane sugar, the fructose in HFCS is in its "free" form and not attached to any other carbs.
The fructose in fruits and in cane sugar is bonded to other sugars which results in a decrease in its metabolic toxicity.
Consuming foods that contain high amounts of fructose—even if it's a natural product—is, to put it bluntly, the fa stest way to trash your health. Among the health problems you invite witha high-fructose diet are:
- Obesity, insulin resistance, metabolic syndrome and type 2 diabetes
- Elevated triglycerides and LDL (bad) cholesterol levels
- Elevated blood pressure
- Liver disease
- Depletion of vitamins and minerals—Unbound fructose, found in large quantities in HFCS, can interfere with your heart's use of minerals such as magnesium, copper and chromium.
- Cardiovascular disease, arthritis, gout, and cancer
Adding insult to injury, HFCS is most often made from genetically modified (GM) corn, which is fraught with its own well documented side effects and health concerns, from an increased risk of developing food allergies to the risk of increased infertility in future generations.
Beware: Mixing Fructose with Glucose Increases Destructive Effect
Fructose consumption clearly causes insulin resistance whereas straight glucose does not. However, it's worth knowing that glucose accelerates fructose absorption! So when you mix glucose and fructose together, you absorb more fructose than if you consumed fructose alone...
This is an important piece of information if you are struggling to control your weight.
Remember, sucrose, or table sugar, is exactly this blend -- fructose plus glucose. So, the key to remember is to not get too nit-picky about the names of the sugars. ALL of these contribute to decreased health:
- Sucrose (table sugar)
- Corn syrup
- High fructose corn syrup (HFCS)
- Crystalline fructose, and any other high-fructose sweetener they may dream up
- Natural fructose in the form of fruits, fruit juices, and natural sweeteners such as honey and agave.
Is Fructose from HFCS Worse than Fructose from Table Sugar?
High fructose corn syrup is about 55 percent fructose while table sugar is about 50 percent. The fructose in the corn syrup is also dissociated from the glucose, unlike table sugar which has it attached. So HFCS is clearly worse than table sugar, but not orders of magnitude. It is only marginally worse.
The MAIN reason why fructose and HFCS are so bad is that in the mid 70s two things happened. Earl Butz changed the US Agriculture policy to massively subsidize corn production in the US, and scientists also figured out how to make HFCS in the lab from corn.
The combination of these two events made fructose VERY cheap. So cheap that it's put in virtually all processed foods because it is virtually free and massively improves the flavor of most foods. So if you are a processed food producer there are virtually no downsides.
So it becomes a QUANTITY issue, and the average person is now consuming 600 percent more than their ancestors did, and some are consuming 1500 percent more. So the massive increase in this toxin is what is causing the problem. If table sugar was as cheap and used as much it would cause virtually identical side effects.
Fructose Metabolism Basics
Without getting into the very complex biochemistry of carbohydrate metabolism, it is important to understand how your body processes glucose versus fructose. Dr. Robert Lustig, Professor of Pediatrics in the Division of Endocrinology at the University of California, has been a pioneer in decoding sugar metabolism. His work has highlighted some major differences in how different sugars are broken down and used.
Here's a summary of the main points:
- After eating fructose, 100 percent of the metabolic burden rests on your liver. With glucose, your liver has to break down only 20 percent.
- Every cell in your body, including your brain, utilizes glucose. Therefore, much of it is "burned up" immediately after you consume it. By contrast, fructose is turned into free fatty acids (FFAs), VLDL (the damaging form of cholesterol), and triglycerides, which get stored as fat.
- The fatty acids created during fructose metabolism accumulate as fat droplets in your liver and skeletal muscle tissues, causing insulin resistance and non-alcoholic fatty liver disease (NAFLD). Insulin resistance progresses to metabolic syndrome and type II diabetes.
- Fructose is the most lipophilic carbohydrate. In other words, fructose converts to activated glycerol (g-3-p), which is directly used to turn FFAs into triglycerides. The more g-3-p you have, the more fat you store. Glucose does not do this.
- When you eat 120 calories of glucose, less than one calorie is stored as fat. 120 calories of fructose results in 40 calories being stored as fat. Consuming fructose is essentially consuming fat!
- The metabolism of fructose by your liver creates a long list of waste products and toxins, including a large amount of uric acid, which drives up blood pressure and causes gout.
- Glucose suppresses the hunger hormone ghrelin and stimulates leptin, which suppresses your appetite. Fructose has no effect on ghrelin and interferes with your brain's communication with leptin, resulting in overeating.
So, if anyone tries to tell you "sugar is sugar," they are way behind the times. As you can see, there are major differences in how your body processes each one. The bottom line is: fructose leads to increased belly fat, insulin resistance and metabolic syndrome -- not to mention the long list of chronic diseases that directly result.
If you, like so many others, have struggled with your weight for years; examined your diet; avoided fat and counted your calories, yet not getting anywhere and wondering what you're doing wrong, please pay very close attention to this issue!
In many cases the primary culprit is an excessive intake of hidden sugar in the form of fructose, whether natural fructose (such as agave syrup or 100 percent fruit juice, for example), or in the form of corn syrup (or high fructose corn syrup), which is a main ingredient in countless beverages and processed, pre-packaged foods.
It's extremely easy to consume high amounts of fructose on a daily basis, especially if most of your foods are processed in any way, or if you drink sodas or any other sweetened beverages such as ice-teas, fruit juices and sports drinks. As previously discussed, even seemingly "health-conscious" beverages like Vitamin Water, Jamba Juice and Odwalla SuperFood contain far more added sugar and/or fructose than many desserts!
So please, understand that it's not dietary fat that's making you fat. It's fructose.
My Recommended Fructose Allowance
As a standard recommendation, I strongly advise keeping your TOTAL fructose consumption below 25 grams per day.
For most people it would also be wise to limit your fructose from fruit to 15 grams or less, as you're virtually guaranteed to consume "hidden" sources of fructose if you drink beverages other than water and eat processed food. Remember, the average 12-ounce can of soda contains 40 grams of sugar, at least half of which is fructose, so one can of soda ALONE would exceed your daily allotment.
Fifteen grams of fructose is not much -- it represents two bananas, one-third cup of raisins, or two Medjool dates. In his book, The Sugar Fix, Dr. Johnson includes detailed tables showing the content of fructose in different foods -- an information base that isn't readily available when you're trying to find out exactly how much fructose is in various foods. I encourage you to pick up a copy of this excellent resource.
Here's a quick reference list of some of the most common fruits that you can use to help you count your fructose grams:
The Way Toward Better Health Begins Here...
There is nothing benign about the fructose consumption inherent in our modern diet. It is literally supercharged with fructose, and we're seeing the consequences of this type of eating in our skyrocketing rates of obesity, diabetes, heart disease, and cases of non-fatty liver disease.
Fortunately, there's plenty of good news here.
There IS a way out of this evil circle, and that is a return to a more holistic diet based on whole foods, along with physical exercise and safe sun exposure to optimize your vitamin D levels.
One of the easiest things you can do to quickly improve your health is to eliminate all soda and sweetened beverages from your life. I say ALL soda, because even though HFCS is clearly something you want to avoid, it is still not as bad as artificial sweeteners, which damage your health even more rapidly than HFCS.
Then, since most processed foods also contain HFCS, avoiding as many processed foods as possible is your next step.
If you want an occasional sweetener, I recommend using:
- The herb stevia
- Dextrose (pure glucose)
I do not recommend agave syrup since it is a highly processed sap that is almost all fructose. It is one of the more seriously mismarketed foods in the natural food world. We actually did an informal study and found the most popular agave brands ranged from 59 to 67 percent pure fructose, far worse than HFCS.
Once you realize the hazards of fructose and begin to avoid it in earnest, your diet will significantly improve, which is an essential factor for a long, healthy life.