Fructose is one of the most controversial forms of sugar available and contributes to obesity, diabetes, heart disease and liver problems, leading many to call for it to be banned or restricted in some parts of the world. According to Merriam-Webster, the official fructose definition is “a crystalline sugar that is sweeter and more soluble than glucose.” Fructose, also known as levulose or D-fructose, is found on its own in many food sources (especially processed foods), or paired with other simple sugars in some ingredients. For instance, glucose plus fructose equals sucrose, also known as table sugar.
Like glucose, fructose sugar is a type of simple sugar, or monosaccharide, which means it can act as a reducing sugar. And similar to other simple sugars, the fructose structure is made up of a linear carbon chain with hydroxyl and carbonyl groups. Despite the similarities between fructose and glucose, however, the two are metabolized very differently in the body. In fact, when consumed in high amounts, some research suggests it could contribute to insulin resistance, liver disease and high cholesterol.
Compared to glucose, fructose is metabolized and used differently by the body. Glucose is the main source of energy for the body, and it’s used directly by the cells for fuel. Fructose, on the other hand, must be metabolized first by the liver. Eating high amounts can overload the liver, impairing its function and causing it to turn excess amounts into fat. Because of the issues associated with fructose metabolism, studies show that going overboard on this simple sugar can increase the risk of non-alcoholic fatty liver disease as well as other health problems like insulin resistance and high cholesterol levels.
Regular consumption can also negatively impact several other aspects of health. For example, it can increase the production of uric acid, which may increase blood pressure and trigger symptoms of gout. It could also cause leptin resistance, which can contribute to overeating and weight gain.
Fructose malabsorption, also known as fructose intolerance, is another issue that occurs when your body is unable to break down the sugar efficiently. Caused by a number of different factors including stress, irritable bowel syndrome or chronic inflammation, malabsorption can trigger digestive issues like nausea, bloating, gas and stomach pain.
Compelling evidence shows that processed fructose is a primary driver for both obesity and type 2 diabetes. The average American consumes one-third of a pound of sugar per day, half of which is processed fructose, which is the most damaging of all. The majority of all this sugar is hidden in processed foods and beverages, so to address obesity and/or diabetes, ridding your diet of processed fare is key for success.
Dr. Robert Lustig, Professor of Pediatrics in the Division of Endocrinology at the University of California, has been a pioneer in decoding sugar metabolism. He was one of the first to bring attention to the fact that processed fructose is far worse, from a metabolic standpoint, than other sugars, including refined sugar.
Fructose is actually broken down very much like alcohol, damaging your liver and causing mitochondrial and metabolic dysfunction in the same way as ethanol and other toxins. It also causes more severe metabolic dysfunction because it’s more readily metabolized into fat than any other sugar.
Other researchers are now backing up these claims. Most recently, a meta-review published in the Mayo Clinic Proceedings2 confirms that all calories are not equal, which is precisely what Dr. Lustig has been telling us. The dogmatic belief that “a calorie is a calorie” has significantly contributed to the ever-worsening health of the Western world. It’s one of the first things dieticians learn in school, and it’s completely false. In reality, the source of the calories makes all the difference in the world when it comes to health.
In the featured review3,4,5 the researchers looked at how calories from the following types of carbohydrates—which include both naturally-occurring and added sugars—affected health:
- Starch
- Pure glucose
- Lactose (natural sugar found in dairy)
- Sucrose (table sugar)
- Fructose, found both in fruit and in processed high-fructose corn syrup
As reported by Time Magazine:6
“What they found was that the added sugars were significantly more harmful. Fructose was linked to worsening insulin levels and worsening glucose tolerance, which is a driver for pre-diabetes.
It caused harmful fat storage—visceral fat on the abdomen—and promoted several markers for poor health like inflammation and high blood pressure.
‘We clearly showed that sugar is the principal driver of diabetes,’ says lead study author James J. DiNicolantonio, a cardiovascular research scientist at Saint Luke’s Mid America Heart Institute. ‘A sugar calorie is much more harmful.'”
US Dietary Guidelines Promote Unhealthy Amounts of Sugar
The researchers warn that current dietary guidelines in the US are harmful, as they promote unhealthy amounts of sugar consumption. According to the Institute of Medicine, as much as 25 percent of your total daily calories can come from added sugars and still be considered healthy.
Similarly, the 2010 US Dietary Guidelines allows up to 19 percent of calories to come from added sugars. Remarkably, the American Diabetes Association does not recommend restricting fructose-containing added sugars to any specific level at all…
In sharp contrast to such liberal recommendations, the American Heart Association suggests limiting sugar to six teaspoons of sugar per day for women and nine teaspoons for men. The World Health Organization suggests limiting added sugar to a maximum of five percent of your daily calories.
As a standard recommendation, I strongly advise keeping your total fructose consumption below 25 grams per day, which is about six teaspoons. If you have signs of insulin resistance, such as hypertension, obesity, or heart disease, you’d be wise to limit your total fructose consumption to 15 grams or less until your weight and other health conditions have normalized.
According to the featured review, the research clearly shows that once you reach 18 percent of your daily calories from sugar, there’s a two-fold increase in metabolic harm that promote prediabetes and diabetes, so current dietary guidelines are definitely a recipe for chronic disease.
Lead author DiNicolantonio told Time Magazine:7
“We need to understand that it isn’t the overconsuming of calories that leads to obesity and leads to diabetes. We need to totally change that around. It’s refined carbs and added sugars that lead to insulin resistance and diabetes, which leads to high insulin levels, which drives obesity.”
DiNicolantonio and his team advise significant governmental changes to address the situation, including ending subsidies of corn, and adding subsidies for healthy whole foods. Most people eat processed foods because they’re cheaper than whole foods, and switching agricultural subsidies around could change that.
Such changes are likely to take time however, so in the meantime, you would be wise to reconsider your own dietary habits. Remember, while you may need to spend a little more now in order to make sure you’re eating healthy, it could save you a ton of money in the long run.
Over the past two decades, the cost of managing type 2 diabetes has doubled, and diabetics spend an average of $2,600 more on health care each year compared to non-diabetics.8 Wouldn’t you rather spend that money on healthier foods, and circumvent the hassles and added health risks associated with diabetes altogether?
Other Recent Research Supports Fructose-Diabetes Link
Other recent research9,10 from the University of Utah also confirms that fructose is more harmful than table sugar. Here, corn syrup was found to have an adverse effect on animals’ rate of reproduction, and caused premature death. According to senior author Wayne Potts,11 “this is the most robust study showing there is a difference between high-fructose corn syrup and table sugar at human-relevant doses.”
Female mice fed a diet in which 25 percent of calories came from corn syrup had nearly double the death rate compared to mice fed a diet in which 25 percent of calories came from sucrose. Corn syrup-fed mice also produced 26.4 percent fewer offspring than those fed table sugar. As reported by Reuters:12
“The study suggests humans, especially women, could face adverse health effects tied to consuming too much corn syrup, which is found in many processed food products… Between 13 and 25 percent of Americans are estimated to eat diets containing 25 percent or more of calories from added sugars, according to the paper.”
According to the authors of this paper, 42 percent of the added sugar found in the US diet comes from corn syrup; 44 percent comes from sucrose. The remaining 14 percent of added sugars are in the form of natural sweeteners such as honey, molasses, and fruit. The evidence clearly shows that processed fructose is the worst in terms of promoting adverse insulin and leptin reactions, which underlie diabetes and a wide variety of other chronic disease states. That said, all sugars contribute to insulin resistance to some degree—including whole grains, which are touted as having heart-health benefits—so to really safeguard your health, you need to pay attention to sugar in all its forms.
Processed Foods Is the Primary Source of Sugar
Doctors and health officials alike are still trying to convince you that you can have your cake and eat it too, as long as it’s “in moderation.” The problem with that is that if you eat a diet consisting primarily of processed foods, moderation goes out the window because virtually all processed food items contain some form of added sugar. Oftentimes, just ONE food item can contain an entire day’s worth of sugar. When you add all the processed foods you eat in a day together, the total amount of sugar can be quite staggering. One recent study has linked the proliferation of restaurants and warehouse clubs like Costco and/or super-centers like Walmart to the rapid rise in obesity—all of which sell primarily processed foods.
As reported by The Atlantic:13
“In 1990, no state had an obesity prevalence of 15 percent or more. By 2010, no state was less than 20 percent obese… Charles Courtemanche, an assistant professor of economics at Georgia State University, analyzed a number of… theories [explaining rising obesity rates] for a recent study,14 Courtemanche realized that a lot of past studies came to conclusions like, ‘the increasing popularity of driving to work is correlated with the rise of obesity.’ But he wasn’t sure what, specifically, was having the greatest effect on obesity’s rise. He gathered 27 things he thought might be contributing to obesity… and put them in what he calls a ‘statistical horserace’…
Only two of the factors ended up being meaningful drivers of obesity: 1) the proliferation of restaurants and 2) the rise of warehouse clubs, like Costco, and super-centers, like those Walmarts that have grocery stores in them… [B]oth restaurants and super-centers saw a remarkable growth since 1990, and together they explain about half the rise in class II and class III obesity—the worst varieties. Interestingly, regular supermarkets actually had a slight negative effect on obesity rates, so it’s not just that food has become more accessible. Instead, Courtemanche said, it’s that it’s become much, much cheaper.”
Although not specified, the food he’s talking about is processed food. Sweetened beverages may be among the worst culprits, and in most places a can of soda is far less expensive than a bottle of water. When bought in bulk, it’s usually even less expensive. So sure, places like Costco may be adding to the problem by providing health-harming foods at even lower prices, but the fact remains that it is the processed food that is the real problem, not just the fact that food is made available at inexpensive prices… If fresh produce was the least expensive food around, more people would probably buy more of it, but they wouldn’t gain a ton of weight as a result.
Gut Bacteria Implicated in Both Type 1 and Type 2 Diabetes
Type 1 diabetes—known as insulin-dependent diabetes—is actually an autoimmune disease that occurs because your immune system mistakenly attacks the cells in your pancreas that produce insulin. Like other autoimmune diseases such as lupus and multiple sclerosis, type 1 diabetes occurs because of a malfunctioning in your body’s defense system, or your immune system. According to recent research, onset of type 1 diabetes in young children tends to be preceded by a change in gut bacteria. Involving just 33 children with genetic predispositions, it’s a small study, but previous research has also found that certain microbes can help prevent the disease, suggesting your gut flora may be a predisposing factor for this condition.
“[O]ne hope is that the results will lead to an early diagnostic test for type 1 diabetes, said researcher Aleksandar Kostic, a postdoctoral fellow at the Broad Institute of MIT and Harvard,” WebMD15 writes. “There is also the possibility of developing new therapies for type 1 that would target the ‘ecosystem’ of the gut, he said.”
Research also suggests there’s a connection between certain types of bacteria and body fat that produces a heightened inflammatory response that contributes to metabolic dysfunction. Superantigens—toxic molecules produced by pathogenic bacteria such as staph—may actually play a role in the development of type 2 diabetes through their effect on fat cells. Preliminary research16 presented in 2010 revealed that transplanting fecal matter from healthy thin people into obese people with metabolic syndrome led to an improvement in insulin sensitivity. More recent research suggests that your diet alone can dramatically alter your microbial balance.
According to Jeffrey Gordon, director of the Center for Genome Sciences and Systems Biology at Washington University in St. Louis,17 a diet high in saturated fat, and low in fruits and vegetables allows microbes that promote leanness to overtake colonies of microbes that promote obesity. Speaking of obesity and gut bacteria, it’s important to remember that when you take an antibiotic, or regularly consume foods contaminated with antibiotics (such as CAFO beef, courtesy of their use as a growth promoter in livestock), you decimate the beneficial bacteria in your GI tract. This may have a notable impact on your weight and metabolism.18
Optimizing Your Gut Flora May Be One of Your Most Important Disease Prevention Strategies
Optimizing your gut flora may be one of the most important things you can do for your health. Not only could it help normalize your weight and ward off diabetes, but it’s also a critical component for a well-functioning immune system, which is your primary defense against all sorts of disease. Reseeding your gut with beneficial bacteria is key for preventing pathogenic microbes and fungi from taking over. To optimize your gut bacteria, keep these recommendations in mind:
- Eat plenty of fermented foods. Traditionally fermented and cultured foods are the best route to optimal digestive health. Healthy choices include lassi, fermented grass-fed organic milk such as kefir, various pickled fermentations of cabbage, turnips, eggplant, cucumbers, onions, squash and carrots, and natto (fermented soy). Fermented vegetables, are an excellent way to supply beneficial bacteria back into our gut. And, unlike some other fermented foods, they tend to be palatable, if not downright delicious, to most people. As an added bonus, they can also a great source of vitamin K2 if you ferment your own using the proper starter culture.
- Take a probiotic supplement. Although I’m not a major proponent of taking many supplements (as I believe the majority of your nutrients need to come from food), probiotics is an exception if you don’t eat fermented foods on a regular basis.
In addition to knowing what to add to your diet and lifestyle, it’s equally important to know what to avoid, and these include:
Top 10 Sources and Types
Check out these 10 common sources that might be sitting on your shelves.
- Fruit – Most of the natural sugar in fruit is actually fructose. However, this type of fruit sugar is not actually harmful, and fruit can typically be enjoyed in moderation as part of a healthy, well-rounded diet. This is because fruit is also rich in fiber, plus other vitamins, minerals and antioxidants that your body needs. Additionally, compared to processed foods with added sugars, you would also have to consume quite a bit of fruit to reach unsafe levels of fructose in the body.
- Soda – Soda is often pumped full of high fructose corn syrup (HFCS), along with many other additives and artificial flavorings. This common sweetener is made from corn syrup, and it contains varying amounts of both glucose and fructose. One key difference between HFCS versus sugar is that the glucose and fructose molecules are bound together in sucrose but not in HFCS. Like other forms of added sugar, some research suggests HFCS may contribute to metabolic syndrome and obesity, along with several other serious health problems.
- Juice – It’s no secret most fruit juice is already high in sugar. However, many food manufacturers take it a step further and add extra high fructose corn syrup to help dial up the sweetness and flavor. Making your own juice at home or switching to low-sugar alternatives like infused water, herbal tea or kombucha is a great way to skip the simple sugars.
- Convenience Meals – Frozen meals and boxed dinners have become a staple ingredient in many households across the country. What most people don’t realize, however, is that many of these foods are loaded with additives, preservatives and, yes, even added sugar.
- Condiments – Besides what you put on your plate, what you put on your food can also impact your intake of this simple sugar. This is because certain condiments are actually jam-packed with fructose, typically in the form of high fructose corn syrup. In particular, ketchup, barbecue sauce, relish, jams and jellies are all usually high in added sugars and HFCS.
- Diet Products – Many products advertised as “low-fat” or “low-calorie” are actually pumped full of this form of simple sugar. In fact, manufacturers often add extra sugar in low-fat foods to enhance the flavor and produce a more palatable product. Some also use sugar alternatives like crystalline fructose, which help boost the sweetness while also reducing the amount of sugar in a product. Low-fat dairy products, salad dressings and baked goods are a few of the most common sources of hidden fructose, so keep an eye out and check the label carefully.
- Granola Bars – Despite being marketed as a “healthy” snack, most store-bought granola bars are loaded with added sugar. The solution? Try making your own granola at home using nutrient-rich ingredients like nuts, seeds and oats! Check out this recipe for homemade granola bars for an idea to help get you started.
- Candy – Candy and candy bars are two of the most common HFCS foods on the market. Most contain high amounts of fructose, which is why it can often be spotted among the first few ingredients on the label.
- Canned Fruit – Not only does fruit naturally contain fructose, but many fruit cocktails are also canned in syrup and sweetened with HFCS to add extra flavor. For this reason, filling up on fresh fruit is a much better option to keep added sugar consumption in check.
- Breakfast Cereal – It may seem like a healthy way to kick off your morning, but did you know most breakfast cereals are packed with more added sugars than some desserts? Next time you’re shopping for cereal, check the label and look for a brand with minimal amounts of added sugar. Alternatively, give oatmeal a try.
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