By Dr. Mercola
You may already be aware that fructose – the sugar found in everything from high fructose corn syrup and fruit juice to agave syrup and honey – is harmful when consumed in excess – which is exactly what many (if not most) Americans do.
However, you may be surprised to learn that fructose is, in many ways, very similar to alcohol in the damage that it can do to your body.
So while you may already be exercising caution by not overconsuming alcoholic beverages, it may be time to take a closer look at the equally potentially damaging effects associated with your intake of sodas, fruit juice and other fructose-sweetened foods and drinks as well.
Fructose's Three Major Similarities to Alcohol
Unlike glucose, which can be used by virtually every cell in your body, fructose can only be metabolized by your liver, because your liver is the only organ that has the transporter for it.
Since all fructose gets shuttled to your liver, and, if you eat a typical Western-style diet, you consume high amounts of it, fructose ends up taxing and damaging your liver in the same way alcohol and other toxins do. In fact, fructose is virtually identical to alcohol with regard to the metabolic havoc it wreaks.
According to Dr. Lustig, Professor of Pediatrics in the Division of Endocrinology at the University of California, fructose is a "chronic, dose-dependent liver toxin." And just like alcohol, fructose is metabolized directly into fat – not cellular energy, like glucose.
He discussed this topic in the video above, but after the video was produced his paper on the topic was published in the Journal of the Academy of Nutrition and Dietetics,1 Dr. Lustig explains the three similarities between fructose and its fermentation byproduct, ethanol (alcohol):
- Your liver's metabolism of fructose is similar to alcohol, as they both serve as substrates for converting dietary carbohydrate into fat, which promotes insulin resistance, dyslipidemia (abnormal fat levels in the bloodstream), and fatty liver
- Fructose undergoes the Maillard reaction with proteins, leading to the formation of superoxide free radicals that can result in liver inflammation similar to acetaldehyde, an intermediary metabolite of ethanol
- By "stimulating the 'hedonic pathway' of the brain both directly and indirectly," Dr. Lustig noted, "fructose creates habituation, and possibly dependence; also paralleling ethanol."
Dr. Lustig concluded:
"Thus, fructose induces alterations in both hepatic [liver] metabolism and central nervous system energy signaling, leading to a 'vicious cycle' of excessive consumption and disease consistent with metabolic syndrome. On a societal level, the treatment of fructose as a commodity exhibits market similarities to ethanol. Analogous to ethanol, societal efforts to reduce fructose consumption will likely be necessary to combat the obesity epidemic."
Fructose Versus Alcohol: The Dangerous Metabolic Cascade
After consuming an alcoholic beverage, 10 percent of the ethanol gets broken down by the stomach and intestine as a "first pass" effect, and another 10 percent is metabolized by your brain and other organs. The fact that ethanol is partially metabolized in your brain is the reason you experience that familiar "buzz."
The remaining 80 percent hits your liver, where it must be broken down. This metabolic cascade can be summarized as follows:
- Your liver converts ethanol to aldehydes, which produce free radicals that damage proteins in your liver.
- Some of these aldehydes are converted to glucose, but a large amount of excess citrate is formed in the process, stimulating "junk chemicals" that result in free fatty acids (FFAs), VLDL (smaller, denser LDL (bad cholesterol) particles that stimulate arterial plaque formation) and triglycerides. A 120-calorie intake of ethanol produces VLDL that are transported to your fat cells and contribute to obesity or plaque formation. This is what leads to the dyslipidemia of alcoholism.
- The resulting lipids, together with the ethanol, upregulate enzymes that induce an inflammatory cascade, which in turn causes hepatic insulin resistance, liver inflammation and cirrhosis.
- Fat globules accumulate in your liver as well, which can lead to fatty liver disease.
- Free fatty acids (FFAs) leave your liver and cause your skeletal muscles to become insulin resistant. This is a worse form of insulin resistance than hepatic insulin resistance and can lead to type 2 diabetes.
- After a 120-calorie bolus dose of ethanol, a large fraction (about 40 calories) can contribute to disease.
In nearly every way, fructose is metabolized the same way as ethanol, creating the same cascade of damaging effects in your body. When you consume fructose, 100 percent of it goes directly to your liver to be metabolized. This is why it is a hepatotoxin when consumed excessively – it overloads your liver. Fructose metabolism creates the following adverse effects:
- Fructose is immediately converted by your liver to fructose-1-phosphate (F1P), depleting your liver cells of phosphates.
- The above process produces waste products in the form of uric acid. Uric acid blocks an enzyme that makes nitric oxide. Nitric oxide is your body's natural blood pressure regulator, especially important for the full dilation of the lining of the arteries known as the endothelium. So when it is blocked, your arteries don't fully dilate, creating a greater burden on your heart and raising your blood pressure – leading to chronic hypertension. Elevated uric acid levels can deposit into soft tissues causing painful inflammation, especially gout.
- Almost all of the F1P is turned into pyruvate, ending up as citrate, which results in de novo lipogenesis, the end products of which are FFAs, VLDLs, and triglycerides. The result – hyperlipidemia.
- Fructose stimulates g-3-p (activated glycerol), which is the crucial molecule for turning FFAs into triglycerides within your fat cells. The rate of deposition of fat into fat cells is dependent on the presence of g-3-p. The more g-3-p that is available, the more fat that is deposited. Fructose is the carbohydrate most efficiently converted into g-3-p. In other words, fructose is the most lipophilic (fat-producing) carbohydrate.
- FFAs are exported from your liver and taken up in skeletal muscle, causing skeletal muscle insulin resistance.
- Some of the FFAs stay in your liver, leading to fat droplet accumulation, hepatic insulin resistance and nonalcoholic fatty liver disease (NAFLD).
- Insulin resistance stresses your pancreas, which pumps out more insulin in response to rising blood sugar as your cells are unable to get the sugar out of your bloodstream, and this can progress to type 2 diabetes.
- As with a bolus dose of ethanol, a 120-calorie bolus of fructose results in a large fraction (again, about 40 calories) that directly contributes to disease.
You can see by comparing the metabolism of fructose with the metabolism of ethanol that they are very similar. In fact, when you compare the metabolism of 150 calories of soda with 150 calories of beer (a 12-ounce can of each), about 90 calories reach the liver in either case. Fructose causes most of the same toxic effects as ethanol because both come from sugar fermentation. Both ethanol metabolism and fructose metabolism lead to visceral adiposity (belly fat), insulin resistance and metabolic syndrome.
Health Effects of Too Much Fructose Mirror Those of Too Much Alcohol
Dr. Lustig uses the term "liver toxin" to describe fructose, but he's also careful to note that it's not fructose per se that is toxic. There are instances when your body can use it, e.g. post-workout or fasting-induced glycogen depletion. The problem is that most people consume so much of it that it turns toxic by virtue of the fact that your body cannot use the excess. It simply gets shuttled into your cells and stored as fat. So it's the massive doses you're exposed to that make it dangerous.
When you compare the health outcomes of fructose versus alcohol consumption, you end up seeing a very familiar pattern – the diseases they cause are virtually identical!
|Chronic Ethanol Consumption
||Chronic Fructose Consumption
|Hepatic dysfunction (ASH)
||Hepatic dysfunction (NASH)
|Fetal alcohol syndrome
||Fetal insulin resistance
||Habituation, if not addiction
In reality the scientific literature shows that fructose may be far worse than ethanol in its wide-ranging negative impact on human health. There are at least 70 adverse health conditions that have been linked to fructose consumption beyond those eight listed above.2
Fructose "Buzzes" The Brain Like Other Narcotics
Fructose and ethanol both have immediate, narcotic effects associated with their dopaminergic properties. In the same way that alcohol can lead to the downward spiral of compulsive overconsumption, fructose tends to generate an insatiable and intense sensation of pleasurable sweetness, often driving us to consume far more than our body can handle; even while it damages multiple organ systems, some Americans consume over a pound of the substance a day, seemingly incapable of recognizing how in exchange for its narcotic-like effects it dramatically reduces both the quality and length of the human lifespan.
Perhaps there is a deeper biological reason behind this devastating fructose fixation? Indeed, in addition to fructose's dopamine modulating activity there appears to be a fructose-opiate connection embedded deeply within mammalian biology, and which has been the subject of scientific investigation since the late 80's.
A study published in the European Journal of Pharmacology in 1988 found that both glucose and fructose were capable of antagonizing morphine-induced pain killing effects, likely due to the direct opioid effects of these sugars or their metabolic byproducts on the central nervous system.3 In fact, the researchers found that fructose was more potent than glucose in accomplishing these effects. Could fructose addiction therefore be even stronger than alcohol? For those who are on the fence about this issue, and still consume large amounts daily, perhaps the best way to find out is trying to remove it entirely and seeing if you go through withdrawal symptoms.
Cancer Group Asks U.S. to Study Sugary Drinks, Obesity
The American Cancer Society's advocacy affiliate has asked the U.S. Surgeon General to complete an "unbiased and comprehensive report on the impact of sugar-sweetened beverages…"
Soda, which is loaded with sugar primarily in the form of high fructose corn syrup (HFCS). Around 100 years ago, the average American consumed a mere 15 grams of fructose a day, primarily in the form of fruit. One hundred years later, one-fourth of Americans are consuming more than 135 grams per day, largely in the form of soda.
Fructose consumed at this dose our ancestors did, about 15 grams a day, appears to be harmless (unless you suffer from high uric acid levels). However, at nearly fives times that amount, which is what the average American consumes, it becomes a major contributor to obesity and nearly all chronic degenerative diseases. Instead of consisting of 55 percent fructose and 45 percent glucose, many soda brands, including Coke, Pepsi and Sprite, contain as much as 65 percent fructose, nearly 20 percent higher than originally believed.
According to one study, the mean fructose content of all 23 sodas tested was 59 percent – higher than claimed by the industry.4 And several major brands contained HFCS that is 65% fructose. When you consider that Americans drink up to 57 gallons of soda per year,5 this difference in actual fructose content could make a huge difference in your health.
Either way, the call for an unbiased look into what these drinks are really doing to public health is long overdue, especially considering the research that's already been conducted:
- Dr. David Ludwig of Boston Children's Hospital did a study of the effects of sugar-sweetened drinks on obesity in children. He found that for each additional serving of a sugar-sweetened drink, both body mass index and odds of obesity increased.6
- The Fizzy Drink Study in Christchurch, England explored the effects on obesity when soda machines were removed from schools for one year. In the schools where the machines were removed, obesity stayed constant. In the schools where soda machines remained, obesity rates continued to rise.7
- In a 2009 study, 16 volunteers were fed a controlled diet including high levels of fructose. Ten weeks later, the volunteers had produced new fat cells around their hearts, livers and other digestive organs.8 In addition, their insulin levels increased and insulin sensitivity decreased, which suggests a link to diabetes. A second group of volunteers who were fed a similar diet, but with glucose replacing fructose, did not have these problems.
- Fructose is also a likely culprit behind the millions of U.S. children struggling with non-alcoholic liver disease, which is caused by a pathological build-up of fat within liver cells.
How Much Fructose is Too Much?
When it comes to alcohol, I generally define "moderate" alcohol intake (which is allowed in the beginner phase of my nutrition plan) as a 5-ounce glass of wine, a 12-ounce beer or 1 ounce of hard liquor with a meal, per day. As you progress further, I do recommend eliminating all forms of alcohol.
As for fructose, if you want to shed excess pounds and maintain a healthy weight long-term, and radically reduce (and in many cases virtually eliminate) your risk of diabetes, heart disease and cancer, then start getting serious about restricting your consumption of fructose to no more than 25 grams per day. If you're already overweight, or have any of these diseases or are at high risk of any of them, then you're probably better off cutting that down to 10-15 grams per day.
Fructose is a staple ingredient in the vast majority of sweetened beverages and processed foods of all kinds, from pre-packaged meals to baked goods and condiments. So the easiest way to keep tabs on your fructose consumption is to ditch processed foods from your diet whenever possible. In the event you want an occasional sweetener, do not resort to artificial sweeteners.
Instead, I recommend using:
- The herb stevia (my favorites are the liquid forms that come in flavors like French Vanilla and English Toffee)
- Dextrose (pure glucose) (glucose can be used directly by every cell in your body and as such is far safer than the metabolic poison fructose)
And remember, switching to the following "natural" sweeteners will NOT eliminate any of the risks of fructose consumption, as they all contain HIGH amounts of fructose:
|Brown rice syrup
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What is the Secret Key that Turns Your Fat Switch On or Off?
Humans are genetically programmed to seek energy-dense foods, which served us thousands of years ago when food was scarce. However, this is maladaptive in today's environment of readily available cheap, high-calorie but nutritionally bankrupt foods.
The standard American diet has tripped your "fat switch," as Dr. Johnson discusses in his new book. Contrary to popular belief, it's not the amount of calories and exercise that determine your weight. Once you understand how fructose-rich foods activate your body's "fat switch," you can finally say good-bye to your nagging weight problems.