Discover the bitter truth about high-sugar diets, particularly in how they may be triggering ADHD and aggressive behaviors by overactivating the fructose pathway, a mechanism nature may have intended to be used for energy storage and survival.
Yet another research study confirms the link between attention deficit hyperactivity disorder (ADHD), bipolar disorder and aggressive behaviors with sugar intake. This might even have an evolutionary basis, rooted in a foraging response that stimulates risk taking in order to secure food and ensure survival.
The October 2020 study, published in the journal Evolution and Human Behavior, connects fructose -- a component of popular sweeteners sugar and high-fructose corn syrup (HFCS) -- and uric acid, a fructose metabolite, to a heightened risk for these behavioral disorders.
The Fructose Factor
One reason fructose may be associated with behavioral disorders is that it activates an evolutionary-based survival pathway that stimulates foraging behavior as well as the storage of energy as fat.[i]
"We present evidence that fructose, by lowering energy in cells, triggers a foraging response similar to what occurs in starvation," said lead author Dr. Richard Johnson, a professor at the University of Colorado School of Medicine, in a statement.[ii]
Modest fructose consumption may help animals with their fat storage needs, particularly during times of food shortage or starvation. High intake of sugar and HFCS, however, may cause a hyperactive foraging response, which then triggers craving, impulsivity, risk taking and aggression that may increase the risk for ADHD, bipolar disorder and further aggressive behaviors, the researchers proposed.
This means while it's meant for survival, the fructose pathway may have been overactivated due to the high amounts of sugar in the standard Western diet, Johnson said. When the fructose pathway is chronically stimulated, it could desensitize "hedonic responses" and induce depression, the researchers warned.
It's not just fructose, though. High-glycemic carbs and salty food may also contribute to the overdrive since they can be converted to fructose in the body.[iii] The team, however, noted that sugar may be just one contributor and does not negate the importance of other factors -- from genetic to emotional to environmental factors -- in the state of mental health.
The Bitter Truth About Sugar's Impact on Your Body
A number of studies have probed the various ways that a high-sugar diet can affect your body.
Studies have linked fructose consumption to metabolic syndrome, for instance, which is characterized by abdominal obesity, insulin resistance, high blood pressure and hyperlipidemia.[iv] Further:
1. Learning and Memory
Evidence from human and animal studies have established that high-energy diets impair cognitive function. A 2019 study conducted meta-analyses of the results from animal studies and found that a diet that was high-fat, high-sugar or high in both adversely affected performance related to spatial learning and memory.[v]
The largest effect was produced by an exposure to a combined high fat-high sugar diet. Among older adults, excess sugar consumption showed a notable association with poor cognitive functions.[vi]
Cross-sectional analyses on 1,823 preschool children showed that higher consumption of sugar-containing beverages was associated with obesity in the subjects, with packaged juices as the main culprit.[vii]
In a different study, intake of sugar-sweetened drinks at 18 months and 5 years of age was also tied to higher risks of adiposity and being overweight.[viii] Similar results also surfaced in a study on high intakes of free sugars, sucrose and fructose, linking them to long-term weight gain among Japanese men.[ix]
Higher sugar intake has been implicated in increased cancer risk by promoting insulin-glucose dysregulation, oxidative stress, hormonal imbalances and excess adipose tissue.[x]
In a long-term study, diet data were first gathered from 1991 to 1995 using a food frequency questionnaire, documenting intakes of fructose, sucrose, sugary foods and sugary drinks.[xi] The study followed subjects until 2013 to determine cancer incidence, and found 565 diagnosed adiposity-related cancers such as 124 breast cancers, 157 prostate cancers and 68 colorectal cancers.
While total consumption of sugary beverages was not linked with site-specific cancer risk, higher fruit juice intakes were associated with a 58% higher risk of prostate cancer. A 2016 study also showed that dietary sugar intake increased liver tumor incidence in female mice.[xii]
Intake of sugar-laden beverages has been consistently linked to an increased risk of obesity, Type 2 diabetes and cardiovascular disease in different populations.[xiii] The underlying mechanisms include adverse glycemic effects, uric acid production and accumulation of visceral and ectopic fat.
For eight months, rats fed a high-fat diet, high-fructose beverages or both were compared to rats fed a normal diet.[xiv] After two months, the first two diets increased body weight, leptin and oxidative stress in plasma and tissues. After six months, high-fat and high-carb diets induced Type 2 diabetes with widespread effects on tissues.
5. Gut Inflammation
A 2019 study showed that sugar-sweetened beverage and high-fat diet consumption harmfully altered gut microbiota as well as promoted gut inflammation.[xv]
Epidemiological research increasingly points to a dramatic rise in inflammatory bowel disease (IBD) in the Western world, and changes in the gut immune system in response to an altered gut microbiome due to diet are implicated in triggering IBD.