How Fructose Intake Affects Metabolic Health: What You Need to Know

Fructose, a simple sugar found in many foods and drinks, has become a topic of debate in the health community. With research showing the metabolic effects of fructose in the diet, it’s important to understand what fructose is and its implications for our health and well-being.

What is Fructose?

Fructose is a simple sugar, or monosaccharide, naturally occurring in fruits and honey. It’s often referred to as fruit sugar and is found in apples, dates, pears, prunes, figs, to name a few. When consumed as fruit, fructose is considered a “free” sugar and is part of a healthy diet. It was originally believed to be indistinguishable from glucose, another monosaccharide, but more recent evidence suggests it may be more detrimental to health in high quantities, especially in the form of high fructose corn syrup.

In the 1960’s manufacturers started making high fructose corn syrup from corn starch to put into many foods and drinks as a sweetener. Now, many Americans get their fructose predominantly from high fructose corn syrup and it’s still a common ingredient in many processed foods and beverages like sweetened fruit juices, soda, and sports drinks. 

In the 1970’s high fructose corn syrup accounted for <1% of caloric sweeteners. By 2000, that number jumped to 42%! The same trend can be seen for sugar intake, with added sugar intake reaching 69 kg per person each year by 1999. Since then, intake has declined slightly but continues to be above the recommended 5% to 10% daily energy intake. This trend has corresponded with a significant increase in metabolic and chronic diseases like obesity, fatty liver disease, diabetes, and cardiovascular disease.  While fructose is likely not to be entirely blamed for all of the previous, it certainly may be contributory.

Interestingly, high fructose corn syrup is banned in some countries but still accounts for about 40% of sweeteners in America. With the correlation between high fructose intake and many chronic diseases, being aware of the impact high fructose corn syrup has on the body is imperative to making choices that support health and well-being. 

High Fructose Foods

Foods high in fructose include:

• Fruits
• Fruit juices
• Honey
• Agave syrup
• Molasses
• Processed foods with added sugars, often in the form of high fructose corn syrup
• Soda and sweetened beverages
• Candy and packaged sweets or pastries
• Fast food
• Condiments and sauces

Fructose found naturally in whole foods can be part of a healthy diet. Processed foods sweetened with high fructose corn syrup, on the other hand, are the predominant issue, and universally considered to have detrimental health effects. .

Fructose Metabolism and the Body

Fructose was originally believed only to be metabolized by the liver, but recent evidence suggests the small intestine also metabolizes it. This can lead to deterioration of the intestinal lining, as we’ll talk about below. 

Health Effects of Fructose

Because excessive sugar intake is believed to play a role in obesity, metabolic disorders, diabetes, cancer, depression, and cardiovascular disease, high fructose intake is now being researched to further our understanding.

When consumed in large amounts as high fructose corn syrup, fructose can lead to increased fat production (lipogenesis), contributing to fatty liver disease, abnormal lipid levels, and insulin resistance. This, in turn, can lead to conditions like obesity, type 2 diabetes, and heart disease. Not only that, but a high fructose diet can also result in a disrupted gut barrier and altered gut microbiota.

Non-Alcoholic Fatty Liver Disease

Among the various diseases associated with fructose intake, non-alcoholic fatty liver disease is the most prevalent. It’s diagnosed when liver cells have lipid infiltration and inflammation independent of infection, metabolic disease, or alcohol consumption. Interestingly, fructose intake is associated with fatty liver disease in a dose-dependent manner, so reducing fructose intake decreases lipid infiltration in the liver cells. This is especially true for liquid processed forms of fructose, such as soda or high-sugar fruit juices.

Insulin Sensitivity, Pre-Diabetes, and Diabetes

Lipid accumulation in the liver may also contribute to insulin resistance, which occurs when the cells don’t respond to insulin as they should to regulate blood sugar properly. This is often a precursor for further metabolic dysfunction and diabetes.

Studies have shown that high fructose consumption accelerates cellular dysfunction, inflammation, and oxidative stress within the pancreas. The majority of research has found a positive correlation between high sugar intake and increased risk for type 2 diabetes. In adolescents specifically, a study found that drinking 350mL of a high fructose corn syrup beverage caused insulin resistance and visceral adipose tissue accumulation. Additionally, in countries with high availability of high fructose corn syrup, type 2 diabetes occurs 20% more. Many of these studies are often completed long-term, looking at the effects of fructose intake over 10 years or more – showing the chronic health effects of high fructose intake over time. 

Cardiovascular Disease

Human studies have shown that high fructose consumption increases cardiovascular disease risk by 26% – even after other unhealthy lifestyle and dietary behaviors were accounted for. There is mounting evidence that higher fructose consumption impacts lipid metabolism and contributes to high cholesterol and triglycerides, hypertension, inflammation, white adipose tissue accumulation, and coronary artery disease. 

Compared to glucose, fructose is a more potent inducer of lipogenesis, converting excess carbon into lipids.  It’s also believed that added sugars may have other systemic effects that can be observed in the short term, before the development of chronic diseases like type 2 diabetes and cardiovascular disease. 

Cancer

Evidence also supports high fructose intake being a tumor promoter, with pancreatic cancer and high fructose intake having the strongest correlation. Studies also have seen it associated with lung, colon, and breast cancers.

Cognition

Excessive fructose intake may also impact cognition, with some studies pointing to cognitive impairment and an increased risk of dementia with high intake. Other aspects of cognition can also be affected, including memory, concentration, and mood. 

Gut Health

Significant changes occur to the gut microbiome with increased fructose consumption. High fructose diets impair the lining of the gut wall and reduce protective microbiota in the gut. This results in increased inflammation, a disrupted gut barrier, and altered gut microbiota causing decreased microbial diversity – not to mention the subsequent effects of gut microbiome disruption like obesity, insulin resistance, and fatty liver disease. Two specific strains of beneficial microbes that have anti-inflammatory properties that work to improve gut health are especially affected – Eubacterium eligens and Streptococcus thermophilus. Many studies also show these changes occurring independent of caloric intake or body weight. Fructose can also induce issues like a leaky gut by facilitating the transition of toxins to various other organs in the body.

A study looking at short-term fructose consumption found that a high intake of high fructose corn syrup caused a reduction of beneficial gut microbes, but fructose intake from fruit helped positively modulate the gut microbiota to support digestive health. This supports the belief that fructose from natural sources like fruit are part of a healthy diet, while consumption of high fructose corn syrup is the issue.

Fructose: The Real Truth

Fructose can be a part of a healthy, nutrient dense diet when consumed in the form of fruit. But when consumed as high fructose corn syrup, problems can arise. Understanding fructose’s role in chronic disease, especially metabolic disease, is essential when considering its role in your diet or making dietary changes. By recognizing the health effects of fructose and its impact on the gut microbiota, the gut barrier, and systemic inflammation, you can make more informed choices about what you put in your body. 

If you’re already struggling with chronic disease and want to talk with a professional to improve your health by getting to the root of your symptoms, functional medicine may be right for you. Functional medicine providers look at the whole picture – your diet, lifestyle, health history, medications, and more to create a plan to optimize your health. At Arizona Wellness Medicine, we do just that – support you in creating lasting lifestyle changes to promote your health and well-being. Learn how functional medicine can help here.

Resources:

1. The Impact of Free Sugar on Human Health—A Narrative Review
2. “Sweet death”: Fructose as a metabolic toxin that targets the gut-liver axis
3. Sugar consumption, metabolic disease and obesity: The state of the controversy
4. Dietary Fructose and Fructose-Induced Pathologies
5. High Fructose Intake and Adipogenesis
6. Fructose-Induced Intestinal Microbiota Shift Following Two Types of Short-Term High-Fructose Dietary Phases