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Fructose is a monosaccharide, or single sugar, that has the same chemical formula as glucose but a different molecular structure.
By Dr. Justin Marchegiani
Most people aren’t aware that too much fruit can be bad for you due to it’s excess levels of fructose. Unfortunately, it seems that fructose is in everything today. It can damage the liver and increase the presence of free radicals in the bloodstream. We see it in unhealthy processed and refined foods, foods that are mistakenly thought to be healthy, and of course, in whole fruits. The key is knowing what to look for when decreasing and managing your fructose consumption.
What Is Fructose?
Fructose is the primary sugar in fruit. Glucose and fructose compose table sugar. Table sugar is sucrose (50% glucose and 50% fructose).
In high fructose corn syrup, these percentages are modified (typically, 55% fructose and 45% glucose). However, there is a wide variation (42%–90%) in the percentage of fructose in HFCS. Fructose consumption continues to increase with higher and higher percentages being manufactured and consumed.
High fructose corn syrup also goes by other names, so you won’t always see “high fructose” on labels. “Isolated fructose” is another name showing up on labels. Do your research and know how to find HFCS on labels.
You might have heard that agave is healthy (after all, it comes from a cactus), but it’s actually 90% fructose, so stay away.
What’s Different about Fructose?
Don’t let fructose’s lower glycemic index fool you. The problem with fructose is it’s metabolized much differently from other sugars. While glucose goes to the muscles and other parts of the body to be metabolized and used for fuel, fructose is primarily metabolized in the liver. When the body takes in more fructose than the liver can metabolize, this creates a number of problems.
The liver only holds about 60 grams, so fructose will either be converted to glycogen (the energy storage form of glucose) or, if we’ve exceeded our capacity of 60 grams, be converted to fat.
Over time that fat (fatty acids) will seep into the bloodstream. The major cause of a fatty liver is the consumption of extra sugar or fructose. Nonalcoholic steatohepatitis (NASH), inflammation of the liver, can occur as the fructose converts into fat. This can cause a number of issues:
Foam Cells—Fatty acid particles are small and dense, so small they can fit into the endothelial fissures in the arteries. Once in the artery, fatty acids create foam cells, which cause inflammation in that artery that can lead to a blockage and decreased blood flow.
Insulin Resistance—Because one of the liver’s major roles is to stabilize blood sugar in the body, if we create insulin resistance at the site of the liver, that means the body has to pump more insulin for the liver to work. More insulin creates more fat, which leads to more inflammation.
Fructose Malabsorption—With all of the fructose consumption, we tend to have fructose malabsorption. Gut bacteria loves to feed on fructose, and a lot of that bacteria is going to gobble up that fructose and create more dysbiosis and malabsorption of various nutrients. It may even leak various toxins into the bloodstream, like lithocholic acid and endotoxins.
Metabolic Syndrome—The following symptoms encapsulate metabolic syndrome:
- Lipogenesis, a high amount of fat, is a result of fructose getting converted by the liver.
- Insulin resistance is a result of our liver becoming more numb to insulin, so our body needs more.
- Dysglycemia, abnormal blood sugar, is a natural result of an abnormality in our insulin.
- High blood pressure is the result of an increased amount of uric acid, another byproduct created as the liver metabolizes fructose, and it can be inflammatory. Uric acid decreases endothelial synathase, the molecules that vasodilate blood vessels. When we decrease our vasodilator, we naturally constrict the blood vessel. Higher uric acid results in higher blood pressure.
- Obesity is a result of the abnormalities in our blood sugar and insulin, our primary fat-storage hormone.
Don’t Sugarcoat Your Proteins (High Fructose Foods)
Fructose glycates, which means that it sugarcoats your proteins. Have you ever ordered crème brûlée at a restaurant and watched as a blowtorch burns that crisp coating on the top? That coating is like the coating fructose creates on your proteins as it travels through your bloodstream.
Glycation is a magnet for free radicals, which come in and chip off pieces of your DNA and cause the following:
- Additional damage and accelerated aging
- Cross-linking of proteins, which causes wrinkles, aging, and other skin issues
- Cell adhesion, which increases the risk of cardiovascular conditions, stroke, etc.
Normal Fructose Consumption
For thousands of years, people consumed 16–24 grams of fructose per day, primarily in the form of whole fruits and honey. Today, we consume closer to 80 grams per day, and much of that is in unhealthy processed foods that contain high fructose corn syrup.
Consuming fructose in whole fruit is far better for you, even at the higher end (24 grams) of the scale, because fruit contains pectin, soluble fibers, that binds the fructose. The fiber slows the process and lessens the effect of the fructose.
Unfortunately, we are consuming far too much free fructose, meaning it’s not bound to fiber. We’re going to see that primarily in high fructose corn syrup.
Fructose-heavy diets are causing obesity, gut dysbiosis, rapid aging, and diseases associated with cell adhesion. However, fruit doesn’t have to be bad for you if eaten in moderation. The best course of action is to replace high-fructose items in your diet with small amounts (16 to 24 grams of fructose) of whole fruits.