By Dr. Mercola
In the video above, part two of the excellent series "The Skinny on Obesity," Dr. Robert Lustig, Professor of Pediatrics in the Division of Endocrinology, and Elissa Epel with the Center for Obesity Assessment, Study and Treatment at the University of California, continue the discussion about the impact of sugar on disease rates around the world.
If you missed part 1, you can view it here.
While total calorie consumption has contributed to increases in diabetes rates around the world, they don't explain the whole story. In 1985, the year I finished my residency and started in private practice, the average number of calories consumed per day for the global population was 2,655.
At the time, 0.62 percent of the global population had diabetes.
By 2010, the average daily caloric intake had risen to 2,866—an eight percent increase—but surprisingly, the diabetes rate rose by a whopping 727 percent, to 5.13 percent of the total global population.
When scientists dug deeper to determine what it is that people are eating that's contributing most to the global crisis in obesity and obesity-related diseases, they discovered that a calorie isn't just a calorie.
The source of the calories you consume makes all the difference in the world. They discovered that it's the increase in total fats and carbohydrates specifically that's causing the massive weight gain in people around the world. What's more, there's just ONE food on Earth that, because of its unique composition, metabolizes in your body as both fat and carbohydrate—and that product is sugar.
Sugar is Both a Fat and a Carb, and this Combo Drives World-Wide Obesity-Related Disease Rates
Sugar is the only calorie source that correlates with the increase in diabetes. In 1985, when the world-wide sugar consumption was 98 million tons, diabetes affected 30 million people. By 2010, sugar consumption had risen to 160 million tons, and global diabetes prevalence reached 346 million people. Overall, sugar is 50 times more potent than calories, in terms of causing diabetes. But why does it have this extraordinarily potent effect?
The answer lies in its unique structure. As just mentioned, it metabolizes as both fat and carbohydrate, and the reason for this is because it contains both glucose and fructose. These two sugars are not interchangeable, and your body processes each of them differently.
Sucrose (table sugar) is 50 percent glucose and 50 percent fructose. High fructose corn syrup (HFCS) is anywhere from 42 to 55 percent fructose depending on which type is used. Glucose is the form of energy your body is designed to run on. Every cell in your body uses glucose for energy, and it's metabolized in every organ of your body; about 20 percent of glucose is metabolized in your liver. Fructose, on the other hand, 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 regards to the metabolic havoc it wreaks. According to Dr. Lustig, fructose is a "chronic, dose-dependent liver toxin." And just like alcohol, fructose is metabolized directly into fat—not cellular energy, like glucose. So eating fructose is really like eating fat—it just gets stored in your fat cells, which leads to mitochondrial malfunction.
Not even fatty fruits like avocado or coconut have this effect, because your body treats them as either a fat or a carb—not both. Sugar is the only food that functions as both a fat and a carb simultaneously, and it is this combination of fat and carb that causes metabolic derangements and, subsequently, disease. So, please, don't be fooled: when it comes to sugar, the claim you hear on TV, that "sugar is sugar" no matter what form it's in, is a misstatement that can, quite literally, kill you—albeit slowly.
Carbohydrate Biochemistry 101
To further explain the differences between glucose and fructose, and the similarities between fructose and ethanol (alcohol), let's review how each is metabolized in your body.
Glucose Metabolism: Glucose is a product of photosynthesis and is found in rice, corn and other grains. Once you take in glucose from a meal, 80 percent of it is used by all of the organs of your body; 20 percent goes to your liver to be metabolized and stored. The following is what happens to that 20 percent, once it reaches your liver (this is normal, and how your body was designed to operate):
- Whatever glucose your body doesn't need immediately gets converted into glycogen for storage in your liver. Glycogen can be easily converted to energy when you need it. Your liver has no limit to how much glycogen it can store without detrimental effects.
- A small amount of pyruvate is produced, which ends up being converted to ATP (the chemical storage form of energy) and carbon dioxide.
- Insulin is released by your pancreas in response to the rise in blood glucose (i.e., blood sugar), which helps the glucose get into your cells. Without insulin, your cells would not be able to process the glucose and therefore would have no energy for movement, growth, repair, or other functions. Insulin is key to unlocking the door of the cell to allow the glucose to be transferred from the bloodstream into the cell.
- When you consume 120 calories of glucose, less than ONE calorie contributes to adverse metabolic outcomes.
Fructose Metabolism: 100 percent of the fructose you consume goes directly to your liver. Fructose metabolism creates a number of adverse effects, including:
- Fructose is immediately converted to fructose-1-phosphate (F1P), depleting your liver cells of phosphates. This process produces waste products in the form of uric acid. Uric acid blocks an enzyme that makes nitric oxide, which is your body's natural blood pressure regulator. Hence your blood pressure rises, leading to hypertension. Elevated uric acid levels can also cause 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 free fatty acids (FFAs), very low-density lipoproteins (VLDLs are smaller, denser LDLs that get stuck beneath your epithelial cells and stimulate plaque formation), and triglycerides. The end result is hyperlipidemia.
- Fructose stimulates g-3-p (activated glycerol), which is the crucial molecule for creating triglycerides within fat cells. The more g-3-p that is available, the more fat is deposited.
- FFAs are exported from your liver and taken up in skeletal muscle, causing skeletal muscle insulin resistance. Some of the FFAs also stay in your liver, leading to fat 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.
- When you consume 120 calories of fructose, about 40 calories contribute to adverse metabolic outcomes.
Ethanol Metabolism: After consuming an alcoholic beverage, 10 percent of the ethanol gets broken down by your 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 is broken down by your liver, causing the following metabolic cascade:
- Your liver converts ethanol to aldehydes, which produce free radicals that damage proteins in your liver. Excess citrate is formed in the process, stimulating the production of FFAs, VLDL and triglycerides.
- The resulting lipids, together with the ethanol, create a cascade of inflammation, causing hepatic insulin resistance, liver inflammation and cirrhosis. Fat accumulation in your liver can also lead to fatty liver disease.
- FFAs 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.
- When you consume 120 calories of ethanol, about 40 calories contribute to adverse metabolic outcomes—the same amount as fructose.
Liver Toxins Cause Identical Diseases
As you can see, in nearly every way, fructose is metabolized the same way as ethanol, creating the same toxic effects in your body. However, while Dr. Lustig uses the term "liver toxin" to describe fructose, 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. The problem is that people consume so MUCH of it that it turns toxic by virtue of the fact your body cannot use it. 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! According to the chart included in the video above, these include:
Chronic Ethanol Consumption Chronic Fructose Consumption Hypertension Hypertension Cardiomyopathy Myocardial infarction Dyslipidemia Dyslipidemia Pancreatitis Pancreatitis Obesity Obesity Hepatic dysfunction (ASH) Hepatic dysfunction (NASH) Fetal alcohol syndrome Fetal insulin resistance Addiction Habituation, if not addiction
How Much Fructose is Safe to Eat?
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.
I've also included a chart below of fructose levels in fruit to give you an idea of what 25 grams a day looks like. Just remember fruit is only one source, as 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.
In the past many have objected to my position on limiting fruit intake and I am fine with that, BUT if you are convinced, for whatever reason, that you can have unlimited fruits than I would strongly encourage you to have a blood uric acid level drawn. High uric acid is a potent marker for fructose toxicity, so if your levels are above:
- 4 mg/dl for men
- 3.5 mg/dl for women
... then you would be wise to avoid all forms of fructose until your levels have normalized—just as you would with high insulin levels. Here's a quick reference list of some of the most common fruits that you can use to help you count your fructose grams:
Fruit Serving Size Grams of Fructose Limes 1 medium 0
Date (Deglet Noor style)
1/8 of med. melon
(3.5" x .75")
Grapefruit, pink or red
Fruit Serving Size Grams of Fructose Boysenberries 1 cup 4.6
1/8 of med. melon
1/16 med. melon
Grapes, seedless (green or red)
What Can You Use to Sweeten Your Food if You Don't Eat Sugar? (Hint: NOT Artificial Sweeteners)
It's important to realize that when we talk about "sugar," ALL sugars are included. So when you're evaluating your sugar consumption, you can't stop counting once you've accounted for the number of spoons of table sugar you've added to foods and beverages. You must also include all other types of sweeteners, such as HFCS, honey and agave.
But please do not resort to using artificial sweeteners to sweeten your food once you limit sugar. There's little doubt in my mind that artificial sweeteners can be even worse than sugar and fructose, and there is scientific evidence to back up that conclusion. I've compiled a long list of scientific studies into the health effects of aspartame, and it covers a range of concerns, from behavioral and mood changes, to brain damage, weight gain, pre-term delivery, and cancer.
Splenda is another artificial sweetener that is touting their "improved" versions as a smart and healthy way to sweeten your food, but please do not be misled. Splenda is likely to push your health in the wrong direction, and there's nothing smart about that …
Consuming artificial sweeteners can cause distortions in your biochemistry, and if you drink diet soda in an attempt to lose weight, it won't help you. Instead, most studies looking at this show very clearly that diet soft drinks actually increase your obesity risk by stimulating your appetite, increasing carbohydrate cravings, and stimulating fat storage!
So please, do your homework on this, and do not be swayed by sweet-talking dietitians, doctors, or any other health professional that tells you artificial sweeteners have gotten the 'green light' and are safe to use. There's simply too much evidence pointing in the other direction. So, what can you use if you want an occasional sweetener? 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 cane sugar, honey, date sugar, coconut sugar, brown rice syrup, fruit juice, molasses, maple syrup, sucanat, sorghum, turbinado or agave syrup will NOT ameliorate any of the risks of sugar consumption, as they all contain HIGH amounts of fructose.
The Low-Fat Craze Adds to Metabolic Disease
If you're in the habit of reading labels, you've no doubt realized it's difficult to find any kind of processed, packaged food that does not contain some form of added sugar or high fructose corn syrup. And low-fat or "diet" foods tend to be the worst of the bunch. The reason for this is that when fat is removed, most of the flavor goes with it. To compensate, sugars are added.
In short, most processed, packaged foods are toxic for your metabolism and lead to mitochondrial damage and disease. Considering the fact that many eat virtually nothing BUT processed foods, it's no wonder obesity-related diseases are peaking.
The answer, of course, is to return to a more natural diet, meaning a diet of whole, preferably organic, foods, cooked from scratch, without added sugars and other chemicals. Ideally, you would eat as much of your food raw as possible, as cooking destroys many valuable nutrients.
Like many people, I have very little "free time" in my life, but still I am committed to preparing over 95 percent of my meals in order to preserve my health. A major leap in the right direction would be to strive for a diet of 90 percent non-processed food and only 10 percent from other sources. To help you get started, I've created a complete nutritional program that is freely available online. It's divided into beginner, intermediate, and advanced, to help you progress at your own pace.