Overview
Commercial foods and beverages have been added with more sugar for the past several decades to encourage mass consumption. This “sweet” trend exists because sugar and sweetened products increase our appetite and make consumers unconsciously stick to a high-sugar diet.
However, little do we know that too much sugar in the body may cause multiple harmful effects that ultimately lead to a condition known as “metabolic syndrome.” Unfortunately, this health problem is the origin of many other serious diseases among adults and children.
This article elucidates the connection between fructose and metabolic syndrome, provides evidence for such an association and offers recent findings in metabolic syndrome treatment and prevention.
RELATED: What Is Metabolic Syndrome & What Are Its Risk Factors and Complications
Fructose in Excessive Amounts May Drive Metabolic Syndrome
What Is Fructose?
Fructose is a sugar found in fruits and other plant-based sources such as honey, sugar cane, and vegetables.
It is the sweetest carbohydrate and does not require insulin for metabolism while having a low impact on blood glucose levels. For natural sweetness, corn syrup usually adds fructose to foods and beverages (containing up to 55 percent of fructose).
Nevertheless, fructose consumption has increased dramatically in the last few decades worldwide due to its commercial use in soft drinks and foods. In the context of the increasing prevalence of diabetes, obesity, and fatty liver disease, the scientific communities have investigated fructose’s role in developing metabolic syndrome.
What Is Metabolic Syndrome?
A common health concern among the senior population is suffering from either high blood pressure or blood sugar. Having only one of such conditions means being closer to age-related chronic diseases, like heart disease or diabetes.
However, there is another, sadly even more concerning, problem. It involves both conditions mentioned above, concurrently causing various systemic health issues.
We call it “metabolic syndrome.”
So, metabolic syndrome is a group of risk factors that co-occur, including:
- High blood pressure
- High blood sugar
- High blood cholesterol
- Excess abdominal and visceral fat
For this reason, a person having more than one condition above has an increased risk of developing:
- Heart disease
- Diabetes
- Obesity
Unfortunately, many people are unaware of their situation as they remain asymptomatic until their metabolic syndrome symptoms become more serious. But you will be astounded if you look at the “mind-blowing” statistics of how widespread the syndrome is.
So, how common is metabolic syndrome?
Metabolic syndrome is becoming more prevalent as 1 in every three adults in the United States develops the condition. People are also more susceptible to metabolic syndrome with age, as the condition affects 40 percent of people in their 60s and 70s.
Sad to say, metabolic syndrome does not exclude anyone. It can be found in men and women, and the incidence rate is 24 percent in men and 22 percent in women.
How Does Fructose Affect Metabolic Syndrome?
Fructose Increases Fat in the Liver
The human body metabolizes fructose and glucose differently, as only a small amount of fructose is released into the circulatory system after intake. In contrast, glucose is the primary sugar found in our blood.
The liver is the main organ where fructose metabolism occurs. This organ metabolizes up to 90 percent of the fructose amount in our body. However, if you consume excessive fructose, the liver metabolizes more sugar than usual and may start storing fructose as fat.
On this account, increased fructose consumption may lead to a fatty liver if the organ is overloaded with sugar. In addition, research suggests that fructose consumption may be a culprit of the metabolic syndrome associated with excess fat accumulation in the liver.
To back this hypothesis, a study on fructose and glucose supplementation in animals showed that the fructose-supplemented diet caused more adverse effects on metabolic responses than glucose despite providing lower caloric intake.
Another study involving daily intake of a fructose-sweetened beverage for six months in overweight human subjects showed significant increases in liver fat without remarkable total fat mass changes.
Such fat accumulation and the weakened oxidation of fatty acid in the liver due to fructose may lead to non-alcoholic fatty liver disease (NAFLD), which is, unfortunately, the origin of various metabolic risk factors.
RELATED: 10 Warning Signs Your Liver is Struggling & What You Can Do About It
Fructose Elevates Uric Acid Level
Uric acid is a byproduct found in our blood. It is formed when the body breaks down foods and drinks. Therefore, the level of uric acid can increase following the consumption of food and beverage products with high-fructose corn syrup.
While most uric acid dissolves in the circulation and is excreted from the body in urine, elevated uric acid level is associated with high cardiovascular risk, including high blood pressure, a condition of metabolic syndrome.
Research shows a positive correlation between fructose intake and uric acid in humans, leading to a hypothesis that excessive fructose may result in an elevation of uric acid.
High uric acid levels may cause an acute constriction of blood vessels by affecting a system called renin-angiotensin. The renin-angiotensin system is a physiological system that regulates blood pressure. Dysregulation of this system narrows and hardens the small arteries and increases blood pressure.
Fructose Alters the Gut Microbiota
Gut microbiota is the microorganism in our digestive tract known as the host. Typically, the gut microbiota can interact with the host and affect the control of energy balance and immune functions.
High fructose intake can negatively affect the interaction between the host and the gut microbiota. As a result, the symbiotic relationship is impaired, possibly causing problems in metabolism and metabolic diseases.
Indeed, the gut microbiota is divergent between healthy people and NAFLD patients. It is because a high-fructose diet harms the gut barrier and the microbiota composition and ultimately causes NAFLD.
Although the underlying mechanisms by which fructose damages the gut have not yet been determined, it is suggested that fructose activates a pathway involving acetic acid generation.
RELATED: 5 Genius Ways to Restore Gut Health
Evidence for the Link Between Fructose and Metabolic Syndrome
In a recent study on dietary fructose and its link with metabolic syndrome in healthy adults, scientists found that those with higher total and added fructose intakes (over 40 grams per day) had higher chances of developing metabolic syndrome.
Specifically, of the 283 study participants, 102 had metabolic syndrome, with a prevalence of 36 percent. In contrast, those consuming lower fructose intake (20 grams per day) were not associated with metabolic syndrome.
The study suggests that some nutrient-specific mechanisms induce the link between fructose and metabolic syndrome. Some of these nutrient-specific mechanisms are unregulated fructose metabolism, which causes fat accumulation in the liver, and elevated uric acid.
The link between high added fructose intake and metabolic syndrome also emphasizes the importance of public health strategies to limit sugar intake from industrialized foods and promote healthier dietary patterns in healthy adults.
Recent Findings in Fructose and Metabolic Syndrome
Long-term High-fructose Diet May Cause Insulin Resistance
Insulin resistance, a common hallmark of diabetes, is one of the adverse outcomes caused by a long-term high-fructose diet.
A study in animals found that a high-fructose high-fat diet after 12 weeks may cause insulin resistance and an imbalance in the gut microbiota, leading to a higher potential of diet-induced metabolic syndrome.
Notably, the increased risk of insulin resistance does not depend on the subject’s body weight. There was no significant difference in this parameter when comparing the animals fed with a high-fructose diet and those consuming average amounts.
The absence of increased weight is consistent with previous research that found that consuming an average number of calories from a high-fructose or high-fat diet induces insulin resistance in animals even without obesity.
Fructose May Cause Metabolic Syndrome Even in Children
Although metabolic syndrome is more common in adults, it has been found that this condition can even be present among children and adolescents.
A study shows that over 85 percent of obese children grow into obese adults, and being obese means being more susceptible to having metabolic syndrome. Furthermore, the prevalence of metabolic syndrome in adolescents in the United States from 1999 to 2004 was 4.5 percent, increasing with age.
On the other hand, a pediatric study on fructose found that early and excessive fructose consumption in children may contribute to the development of various cardiometabolic risk factors, posing a risk for metabolic syndrome.
Specifically, and consistent with the studies above, fructose may play a role in obesity and metabolic alterations due to some nutrient-specific mechanisms and not the amount of energy the nutrient provides.
Metabolic Syndrome Treatment and Prevention
There are no quick fixes for metabolic syndrome. Instead, the best treatment is making slow but steady changes in lifestyle.
Restricting sugar consumption, especially from foods and beverages that contain fructose, is the primary approach to alleviating the impact of metabolic syndrome.
The daily amount of added sugar that a person can consume varies. Men can add up to 36 grams (9 teaspoons) of sugar to their diet per day. This number in women is 25 grams (6 teaspoons) per day. People with diabetes can also consume sugar, with no more than 25 grams daily.
Other strategies for preventing metabolic syndrome include:
- Developing an active lifestyle
- Implementing a healthy diet
- Enhancing physical activity levels
- Managing stress
- Giving up smoking and alcohol
In a recent animal study, researchers have made advances toward developing a drug to treat metabolic syndrome by identifying a receptor that regulates appetite and body weight.
Specifically, the human body has a hormone called asprosin, which stimulates hunger and increases blood glucose levels. Thus, individuals with low blood asprosin levels are less affected by appetite and have lower glucose and insulin levels.
The finding showed that asprosin levels are elevated in metabolic syndrome patients, resulting in weight gain and high blood sugar. On this account, reducing blood asprosin by targeting its receptor called asprosin-Ptprd may lead to protection from metabolic syndrome.
Bottom Line: Sugar Intake Needs to Be Limited
Fructose and other types of sugar are becoming more common in modern dietary patterns. Yet, not many people are aware of the detrimental effects of this ingredient in the development of metabolic diseases. Therefore, awareness of the issue should be raised, especially among those groups of the population that are more vulnerable.
Cutting down on sugar is the primary strategy for preventing metabolic syndrome in the long term. In the United States, an average adult consumes up to 77 grams of sugar daily, three times the recommended amount. In Canada, this number is even higher. Canadian adults’ average total sugar intake is 110 grams per day, equivalent to 26 teaspoons or 21 percent of total energy intake.
Now, this is concerning. Even when we know that sugar does more harm than good, the “sweet” temptation will continue to linger, compelling us to reach more and more of it. The only strategy to reduce sugar intake is to take slow but consistent actions, which may appear more straightforward than you think. These changes include:
- Replacing or removing sugary drinks
- Choosing products with the lowest added sugar
- Adding more fresh or dried fruit
- Cutting the serving back by one-third to one-half
- Using plant-based extracts instead of sugar
References
Feig, D., Kang, D., Johnson, R. (2008). Uric Acid and Cardiovascular Risk. U.S. Department of Health and Human Services.
Maersk, M., Belza, A., Stødkilde-Jørgensen, H., Ringgaard, S., Chabanova, E. et al. (2011). Sucrose-sweetened Beverages Increase Fat Storage in the Liver, Muscle, and Visceral Fat Depot: a 6-mo Randomized Intervention Study. The American Journal of Clinical Nutrition.
Feig, D. (2012). Hyperuricemia and Hypertension. National Kidney Foundation.
Weiss, R., Bremer, A., Lustig, R. (2013). What is Metabolic Syndrome, and Why Are Children Getting It? Annals of the New York Academy of Sciences.
Mouzaki, M., Comelli, E., Arendt, B., Bonengel, J., Fung, S. et al. (2013). Intestinal Microbiota in Patients With Nonalcoholic Fatty Liver Disease. American Association for the Study of Liver Diseases.
Sangüesa, G., Shaligram, S., Akther, F., Roglans, N. Laguna, J. et al. (2017). Type of Supplemented Simple Sugar, Not Merely Calorie Intake, Determines Adverse Effects on Metabolism and Aortic Function in Female Rats. American Journal of Physiology.
Taskinen, M., Packard, C., Borén, J. (2019). Dietary Fructose and Metabolic Syndrome. Nutrients Journal. Multidisciplinary Digital Publishing Institute.
Oh, J., Alexander, L., Pan, M., Attie, A., Walter, J. et al. (2019). Dietary Fructose and Microbiota-derived Short-chain Fatty Acids Promote Bacteriophage Production in the Gut Symbiont Lactobacillus Reuteri. Cell Host & Microbe Journal.
Shi, Y., Liu, Y., Xie, Z., Weiping, J. (2021). Fructose and Metabolic Diseases: Too Much to Be Good. Chinese Medical Journal.
Swarup, S., Goyal, A., Grigorova, Y., Zeltser, R. (2022). Metabolic Syndrome. StatPearls Publishing.
Aoun, R., Chokor, F., Taktouk, M., Nasrallah, M., Ismaeel, H. et al. (2022). Dietary Fructose and Its Association With the Metabolic Syndrome in Lebanese Healthy Adults: a Cross-sectional Study. BioMed Central Journal.
Moughaizel, M., Dagher, E., Jablaoui, A., Thorin, C., Rhimi, M. et al. (2022). Long-term High-fructose High-fat Diet Feeding Elicits Insulin Resistance, Exacerbates Dyslipidemia and Induces Gut Microbiota Dysbiosis in WHHL Rabbits. PLOS ONE Journal.
Giussani, M., Lieti, G., Orlando, A., Parati, G., Genovesi, S. (2022). Fructose Intake, Hypertension and Cardiometabolic Risk Factors in Children and Adolescents: From Pathophysiology to Clinical Aspects. A Narrative Review. Frontiers.
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