Here’s the Research on Sugar and Health | Chris Kresser

Here’s the Research on Sugar and Health

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The research on sugar and health is clear: refined sugars and sweeteners like these can be harmful and addictive.
The research on sugar and health is clear: refined sweeteners, when eaten in excess, can be harmful and addictive. iStock/Diana Taliun

The United States is the top sugar-consuming nation in the world, with the average American taking in an astounding 57 pounds of added sugars per year. (1) What is our out-of-control sugar consumption doing to our health? Read on to learn about the latest research on sugar and health, including the concept of sugar addiction, the health implications of excessive consumption of added sugars, and the evidence for the safety (or lack thereof) of artificial and other non-nutritive sweeteners.

Don’t have time to read it all? Use these links to navigate to each section of the article.

Is Sugar Addiction Real?

For decades, the scientific community was hesitant to describe the human fixation on sugar as an “addiction”; it seemed like an exaggeration to equate the desire for sugar with the desire for a controlled substance such as cocaine or heroin. But now, more and more research on the biochemical and neurobehavioral consequences of sugar consumption has changed the opinions of scientists and health professionals alike. In fact, sugar addiction appears to be a genuine phenomenon that afflicts a significant proportion of our population.

Excess refined sugar can be harmful—and even addictive. Check out this article to find out what the latest research says, and get information on four healthy sweeteners you can use as alternatives. #nutrition #wellness #chriskresser

In a survey of 986 Americans recruited to be nationally representative of the U.S. population, 15 percent of the participants met the criteria for food addiction, as reported by the Yale Food Addiction Scale 2.0. (2) The Yale Food Addiction Scale is a measure for identifying those who are most likely to exhibit compulsive overeating and symptoms of substance dependence (i.e., cravings, bingeing) when exposed to high-fat or high-sugar foods. Importantly, those people who met the criteria for food addiction were of all shapes and sizes, ranging from underweight to obese.

This revealing research suggests that sugar addiction, a subcategory of food addiction, is a real problem affecting a diverse population (including children, as it turns out)—not just those who need to lose weight.

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How Sugar Addiction Works

Substance use disorder is defined as “a behavior pattern in which people continue to use a substance despite having problems caused by its use.” (3) The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) has outlined 11 criteria that characterize substance use disorder, including the following:

  • Taking in a substance in larger amounts or for longer than you’re meant to
  • Wanting to cut down or stop using a substance, but being unable to do so
  • Cravings and urges to use a substance
  • Using substances again and again, even when the substances are harming your body
  • Development of withdrawal symptoms upon ceasing use of the substance

While these behaviors are generally used to diagnose alcohol or drug addiction, they are also consistent with animal and human models of sugar intake! In fact, the scientific literature indicates that there is a striking overlap in neurobiological mechanisms and brain activation patterns between those addicted to controlled or illicit substances and those “addicted” to sugar. (4)

Sugar Activates Brain Reward Pathways

Sugar is a potent activator of the dopamine reward circuit, a biochemical pathway in the brain that mediates the response to rewarding stimuli such as food, sex, social interactions, and drugs. The brain’s reward circuitry is designed to increase an organism’s likelihood of engaging in behaviors that increase its chances of survival; this trait persists in creatures ranging from fruit flies to humans.

When the dopamine reward circuit is stimulated, dopamine is released, producing feelings of pleasure and euphoria that drive an individual to seek out rewarding experiences or substances repeatedly. Activation of the dopamine reward circuit by sugar also initiates anticipation and food seeking behaviors; in other words, the body becomes conditioned to desire and seek out sugary foods. Interestingly, glucose consumption may also stimulate a parallel dopamine reward circuit in the gastrointestinal tract, further stacking the cards against us in our fight against sugar cravings. (5)

Sugar Stimulates Opioid Production

Like many illicit drugs, sugar also exerts addictive properties by stimulating the release of your body’s innate pain-relieving opioids through the endogenous opioid system. (6, 7) Over time, continuously stimulating this system may rewire your neurocircuitry—that is, it will essentially rewire your brain—leading to an addiction.

Evidence of Sugar Addiction in Humans

For many years, our understanding of sugar addiction was limited to animal models. But now we have scientific evidence that supports the existence of sugar addiction in humans. Scientists have found that bariatric surgery patients frequently “transfer” their addiction from high-sugar foods to addictive drugs post-surgery since they are no longer able to eat sugar in large amounts without experiencing gastrointestinal consequences. Transfer of addiction from one substance to another is a hallmark of substance use disorders. (8) Also, obese individuals demonstrate marked dopamine reward circuit dysfunction, including a reduced sensitivity of brain regions to dopamine. (9) These people need to consume a higher level of sugar to achieve “feel-good” levels of dopamine in their brains; this phenomenon is a classic example of tolerance, another key feature of addiction.

Interestingly, sugar addiction has evolutionary, ancestral underpinnings. The human experience of natural reward from sugar is an adaptation intended to help us identify foods with a high caloric density. (For example, our ancestors would have had seasonal access to high-sugar fruits.) The consumption of such foods promoted the storage of body fat, which in turn enabled us to survive periods of famine.

However, in the modern world, very few of us experience hunger. Instead, we have constant access to sugary, processed foods. This mismatch between our evolutionary biology and our modern environment has facilitated our sugar problem and played a fundamental role in the current chronic disease epidemic. (10)

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High-Fructose Corn Syrup: Don’t Drink Your Sugar!

In recent years, “soda taxes” and other public health efforts have been made to curtail our consumption of sugar-sweetened beverages (SSBs) in response to growing evidence of the harmful effects of such drinks. SSB consumption has been linked to childhood obesity and increased risks of adult obesity, diabetes, and cardiovascular disease. (11, 12) Research indicates that people fail to reduce their caloric intake to compensate for the extra calories consumed in SSBs, leading to caloric excess and ensuing weight gain and inflammation. (13) The high-fructose corn syrup used in SSBs and countless other processed foods also poses particular metabolic risks:

  • Excess high-fructose corn syrup (HFCS) consumption promotes insulin resistance, high triglycerides, and visceral fat accumulation, critical features of metabolic syndrome. (Visceral fat, unlike easier-to-lose subcutaneous fat that you can “pinch,” is deposited deep in the abdominal cavity and surrounds internal organs.)  It also alters hepatic lipid metabolism, increasing the risk of non-alcoholic fatty liver disease. (14)
  • Epidemiological research suggests that consuming too much HFCS may promote asthma by dumping large amounts of fructose into the gut lumen, where the sugar is biochemically transformed into inflammatory byproducts that can ultimately induce asthma. (15)
  • Animal studies indicate that excess HFCS alters female reproductive system function. For women, this means it’s possible that HFCS may aggravate polycystic ovary syndrome. (16)
The science is clear: if you want to prevent chronic disease, avoid sugar-sweetened beverages and high-fructose corn syrup.

But what about plain old table sugar? Are added sugars (sucrose) in foods safer to consume than sugar-sweetened beverages or HFCS? Not necessarily. Research indicates that high intake of added sugars poses numerous problems, including an increased risk of gut dysbiosis, decreased immune function, cancer, and neurodegeneration.

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My Roundup of the Research on Sugar and Health

Sugar Promotes Gut Dysbiosis

The bacteria that inhabit our intestines thrive on carbohydrates—both the “good” and the “bad” variety. Complex carbohydrates, such as soluble fiber found in starchy plants like squash or sweet potatoes, feed beneficial gut bacteria, boost anti-inflammatory gut microbiota, and discourage the growth of opportunistic and pathogenic bacteria. (17) The consumption of processed carbohydrates and refined sugar found in less nutritious foods, on the other hand, triggers the growth of harmful gut bacteria and promotes an inflammatory gut microbiota. (18, 19)

Sugar Impairs Immune Function

Refined sugar consumption was first linked to impaired immune function decades ago. (20, 21) While that research is old, more recent studies suggest that the earlier investigators were on to something; the alterations in the gut microbiota induced by refined sugar intake may set off an aberrant immune response, which in turn contributes to impaired immune function and chronic inflammation. (22)

Sugar Can Be Detrimental to Heart Health

The red flags about an unhealthy relationship between sugar intake and cardiovascular disease were first raised by scientists in the 1950s—but because key research was funded by the sugar industry, those warning signs were never publicized. Rather, they were conveniently concealed to protect industry interests. Now we know the truth. A few years ago researchers examined sugar industry internal documents from the 1960s and 1970s which documented research linking sugar consumption with cardiovascular disease. But that story was buried deep in the corporate vaults. Instead, fat and cholesterol were singled out as the dietary causes of cardiovascular disease, a momentous (but erroneous) decision that has had a lasting impact on U.S. dietary policy and public health. (23)

Although the sugar industry tried to conceal the link between sugar and heart disease, the latest research increasingly demonstrates a relationship between the two. Diets high in sugar increase cardiovascular disease risk factors, including insulin resistance, leptin resistance, blood glucose, and triglycerides, while also altering platelet function. Accordingly, diets high in added sugars are associated with a threefold increased risk of cardiovascular disease in adults. (24) Added sugars also contribute to cardiovascular disease in children at intake levels far below current consumption levels. (25)

Sugar Can Harm Your Brain Function

The excessive consumption of refined sugar and carbohydrates also has harmful effects on the brain. Added sugars negatively impact the function of the hippocampus, a brain region responsible for memory, and promote neuroinflammation. (26) The sugary Standard American Diet and diabetes are established risk factors for cognitive decline and dementia. (27) However, you don’t need to have full-blown type 2 diabetes to compromise your brain health; high-normal blood glucose and frequent blood glucose fluctuations also increase the risk of cognitive impairment, decreased brain volume, and reduced cognitive performance. (28, 29)

One mechanism by which a chronically high intake of sugar may harm the brain is through the promotion of brain insulin resistance. Brain insulin resistance is a condition in which cells of the brain become insensitive to insulin and is an established risk factor for neurodegenerative diseases such as Alzheimer’s and Parkinson’s diseases.

More Research Points to a Link between Sugar and Cancer

Knowledge of a connection between sugar and cancer is not new; in fact, evidence pointing to this relationship was inadvertently discovered during sugar industry-funded research nearly 50 years ago! We know about the cover-up of the findings linking sugar and cardiovascular disease, discussed above. In this case, however, the study was simply—and quickly—terminated due to the unfavorable results. When internal documents from the ill-fated research were recently resurrected, they spurred vigorous debate in the scientific community about the role of refined sugar in cancer development. (30)

Despite sugar industry attempts to dismiss any link, a growing body of research indicates that there is an important connection between sugar and cancer. In animal research, table sugar (sucrose) intake at levels comparable to those found in the Standard American Diet has been found to increase tumor growth and metastasis. (31) In humans, high-glycemic index and high-glycemic load diets are associated with an increased risk of colorectal, breast, and endometrial cancers. (32) Furthermore, a large prospective study of over 2,000 individuals found that just a 10 percent increase in ultra-processed food intake (ultra-processed foods are frequently high in added sugars) increased overall cancer risk by 10 percent. (33) These alarming findings suggest that limiting refined sugar and carbohydrate intake and optimizing blood sugar regulation may be important strategies for reducing the risk of cancer.

Why exactly does sugar promote cancer growth? It turns out that cancerous cells rewire their metabolism so that they become very efficient at taking up glucose from the bloodstream for use as fuel. The metabolic adaptation by which malignant cells use glucose to promote growth, survival, and proliferation is known as the Warburg effect. (34) Diets high in refined sugar and other processed carbohydrates supply the body with large amounts of glucose, creating an environment conducive to cancer growth.

Conversely, limiting the amount of glucose in circulation may inhibit cancer growth; studies on the ketogenic diet actively support this notion. The ketogenic diet is a high-fat, moderate protein, very-low-carbohydrate diet that significantly reduces blood sugar and causes the body to rely on ketones, rather than glucose, for energy. The ketogenic diet has proven useful as an adjunct treatment for cancer in a handful of studies. (35) However, for cancer prevention, a real-food diet (such as an ancestral one) that limits refined sugar and processed carbohydrates may be sufficient.

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What the Latest Research Says about Artificial Sweeteners

Concerns about the health effects of added sugars have caused many people to turn to artificial sweeteners to satisfy their sweet tooth. But are artificial sweeteners really a safe alternative? The science, increasingly, suggests otherwise.

In the United States, there are currently six artificial sweeteners approved for consumption:

  • Acesulfame-K (Sweet One)
  • Aspartame and neotame (NutraSweet)
  • Saccharin (Sweet’N Low)
  • Sucralose (Splenda)
  • Advantame

Artificial sweeteners are generally several hundred to several thousand times sweeter than sucrose. (36) The artificial sweetener cyclamate was officially removed from the U.S. and Canadian markets years ago due to its carcinogenic activity; however, the others have remained on the market because there isn’t sufficient evidence of carcinogenic effects.

While current evidence may not support a strong association between artificial sweeteners and cancer, abundant research indicates that artificial sweeteners harm the body in other ways.

Artificial Sweeteners Alter the Gut Microbiota

Artificial sweetener consumption is associated with increased Firmicutes and decreased Bacteroidetes, a bacterial pattern associated with obesity in humans. Artificial sweeteners also can inhibit bacteria from reproducing—both the good, such as commensal gut microbes, as well as the bad, including E. coli and periodontal pathogens that can cause conditions like gum disease. Clearly artificial sweeteners can have a major impact on the gut microbiota, and importantly, even after artificial sweetener use has been discontinued, gut microbial differences persist. These findings suggest that the long-term consumption of artificial sweeteners may have significant implications for gut health. (37)

Artificial Sweeteners Impair Glucose Tolerance

Ironically, artificial sweeteners may cause glucose intolerance by altering the gut microbiota. In one study, rats exposed to eight weeks of aspartame had an altered gut microbiota composition and elevated fasting blood glucose. In another study, the ingestion of saccharin for 11 weeks produced compositional changes in the gut microbiota that preceded glucose intolerance. (38)

Glucose intolerance, in turn, increases the risk of metabolic syndrome, type 2 diabetes, and cardiovascular disease. Interestingly, artificial sweetener consumption is associated with an increased risk of each of these conditions. It’s very possible that people who habitually consume artificial sweeteners are more likely to have chronic health conditions in the first place, but the evidence is still cause for concern and warrants further investigation. (39)

Artificial Sweeteners Alter Hormones

Sucralose and acesulfame-K increase insulin release by activating sweet taste receptors and calcium-sensing receptors. (40) This hormonal response may explain why artificial sweeteners impair glucose tolerance. Artificial sweeteners also fail to reduce ghrelin, an appetite-stimulating hormone that rises during fasting and decreases upon meal ingestion. Lack of ghrelin release promotes increased appetite and food intake, meaning artificial sweetener consumption may initiate a higher, rather than reduced, caloric intake.

Artificial Sweeteners Are Connected with Impaired Neurological Function

The ingestion of artificially sweetened drinks is associated with an increased risk of stroke and dementia. Aspartame is also known to cause neurological symptoms such as headaches, seizures, and migraines. (41, 42) Aspartame induces these effects by causing the production of excess free radicals in the brain and by elevating levels of phenylalanine and aspartic acid, which inhibit the synthesis and release of neurotransmitters. If your goal is to preserve your brain health, you may want to avoid artificial sweeteners.

Despite Claims, Artificial Sweeteners May Not Help with Weight Loss

The research on artificial sweeteners and weight loss is mixed. Studies have found a positive association between the consumption of artificial sweeteners and higher weight, but reverse causality is likely because overweight people are more likely to consume non-caloric artificial sweeteners in an attempt to lose weight. However, in a 2017 meta-analysis, the authors concluded that artificial sweeteners do not necessarily lead to weight loss and, in some cases, appear to cause weight gain. (43)

Pregnant and Nursing Women: Avoid Artificial Sweeteners

Pregnant and nursing women should be wary of artificial sweeteners. Eating artificial sweeteners during pregnancy significantly increases the risk of having a large-for-gestational-age baby, even when maternal BMI and other risk factors are controlled for. Seven years down the road, the children of women who consumed artificial sweeteners during pregnancy are also at an increased risk of being overweight or obese. Maternal consumption of artificial sweetener may promote weight issues in children by causing metabolic changes during a critical developmental window of gestation. (44)

Based on this evidence, I recommend that pregnant and lactating women, children, insulin-resistant individuals and diabetics, and migraine and epilepsy patients avoid artificial sweeteners. (45) If you fit into one of these categories but are trying to moderate your sugar intake, you may want to consider trying a natural non-nutritive sweetener instead, such as those discussed below.

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Four Healthy Options for Sweeteners

If you’re craving something sweet, you do have healthier options. Stevia and monk fruit are two natural, non-nutritive sweeteners that have exploded in popularity in recent years. They are seen as healthier alternatives to artificial sweeteners and may have some unique health benefits. Sugar alcohols are another good option, if you don’t have gastrointestinal issues. And, of course, you can always turn to natural sweeteners found in whole foods to satisfy your craving.

1. Stevia

Stevia comes from the Stevia rebaudiana plant, a perennial herb native to South America. Ounce for ounce, it is 200 to 400 times sweeter than sucrose. Stevia rebaudiana produces compounds called steviol glycosides in its leaves; it is these compounds that have been isolated for use as a non-caloric sweetener.

Stevia may have some health benefits. In animal studies and lab research, it has been found to increase insulin sensitivity and exert antioxidant properties. (46, 47) However, conflicting research suggests there is no difference in glycemic and insulin responses between stevia and glucose. (48) Importantly, stevia has demonstrated antibacterial and endocrine-disrupting effects; it may, therefore, have detrimental effects on the gut microbiota and hormonal balance. (49, 50)

2. Monk Fruit

Monk fruit, also known as luo han guo, comes from the Siraitia grosvenorii plant native to Southeast Asia. Monk fruit contains compounds called mogrosides that are 250 times sweeter than sucrose and have been traditionally used as a natural, non-caloric sweetener.

Compared to stevia, monk fruit has a far more robust body of evidence supporting its beneficial health effects. (51) It is rich in vitamin C and flavonoids. The mogrosides it contains have anti-inflammatory, antibacterial, and anti-cancer effects; decrease blood sugar, total cholesterol, and triglycerides; and improve glucose and fat metabolism. (52, 53, 54, 55, 56, 57) If you are interested in trying monk fruit sweetener, I recommend Lakanto Pure Monkfruit Extract. It’s free of fillers, additives, and artificial flavorings and has a glycemic index of zero.

3. Sugar Alcohols

Sugar alcohols such as xylitol, sorbitol, and erythritol are another popular alternative for those looking to reduce their sugar intake. Compared to artificial sweeteners, there is very little evidence to suggest that sugar alcohols are harmful. In fact, some sugar alcohols may even have health benefits.

Sugar alcohols cause no detectable changes in blood glucose or insulin. This makes them a safe alternative for those with insulin resistance and diabetes. (58) Xylitol has been found to reduce blood sugar levels and improves dental health by inhibiting the growth of oral inflammatory bacteria and by promoting tooth remineralization. (59, 60) Erythritol and xylitol also disrupt undesirable biofilms, which are microorganisms that have banded together and adhered to a surface, such as the oral or gut mucosa. Finally, sugar alcohols also have prebiotic potential, meaning they may feed and support the growth of beneficial gut bacteria.

While sugar alcohols have some unique benefits, I recommend steering clear of them if you have digestive issues. Sugar alcohols are also known as polyols, and polyols are part of the FODMAP group of fermentable carbohydrates that frequently cause gas, bloating, diarrhea, and other digestive issues in people with small intestinal bacterial overgrowth (SIBO) and IBS. Xylitol and sorbitol are more likely to trigger GI issues than erythritol, so if you have some GI issues but are still interested in experimenting with sugar alcohols, erythritol may be your best bet. (61) If you experience mild GI discomfort in response to sugar alcohols, know that the reaction may be temporary; research indicates that the gut microbiota adapts to sugar alcohols over time, resulting in less of a response.

4. Your Best Option: Natural Sugars in Whole, Real Foods

A substantial body of scientific evidence indicates that we should minimize our consumption of refined sugar, high-fructose corn syrup, and artificial sweeteners as much as possible. However, this doesn’t mean we should be afraid of natural sugars in whole, real foods!

The sugars contained in whole fruit or a sweet potato do not have the same effect on your health as a soda or candy bar. The fiber and water in real-food carbohydrates slow the absorption of sugars and promote satiety, preventing the blood-sugar roller coaster associated with the consumption of refined carbohydrates. Real-food carbohydrates also contain an abundance of vitamins, minerals, and phytonutrients that support optimal health. In fact, the phytonutrients in blueberries, strawberries, and cranberries support a healthy glycemic response by improving insulin sensitivity and glucose tolerance. (62, 63)

If you want a concentrated sweetener other than stevia or monk fruit, I recommend using raw honey. In addition to tasting incredible, raw honey has many health benefits. It has antibacterial effects against enteric pathogens such as Salmonella, E. coli, and Shigella, as well as the periodontal pathogen Porphyromonas gingivalis. It is a source of prebiotics that promotes the growth of Lactobacillus and Bifidobacteria. (64, 65) It also offers some cardiovascular benefits because it has antioxidant effects and improves the function of the endothelium, a thin membrane lining the heart and blood vessels.

Finally, while the sugars found in real, whole foods can absolutely have a place in an overall healthy diet, you may want to limit your honey intake and stick to lower-sugar fruits, such as berries, if you have metabolic syndrome, type 2 diabetes, or significant gut dysbiosis. Over time, you may be able to tolerate more natural sugars once you address the underlying causes of gut dysbiosis and metabolic dysfunction.

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