Lectures by science professors don't usually become Internet sensations.
But a 90-minute talk by Robert Lustig, M.D. – titled “Sugar: The Bitter Truth
” – went viral in 2009 and remains widely viewed.
Professor Lustig is a pediatric neuro-endocrinologist at the University of California who became disturbed by the weight and metabolic problems he saw in more and more children.
He's now waging a war against added sugars, and goes so far as to say that sugar is toxic when it's consumed at the rate typical of American diets: one-quarter of a pound per day or 90 lbs per year.
More controversially, he calls sugar an addictive substance, with brain effects similar to those exerted by cocaine, heroin, and prescription painkillers.
But European researchers just published an evidence review that takes issue with Dr. Lustig's idea.
The answer to this question seems critical, so we took a look at the evidence on both sides of the debate.
First, let's quickly review the story of sugar as a food to be feared.
The sugar wars
Jeremiads against sugar date back 34 years, starting with William Dufty's 1975 book, Sugar Blues.
Dufty's tract presaged today's anti-sugar crusades … but was short on hard evidence (scarce at the time) and long on anecdotes and oddball assertions.
We now have much more evidence that Dufty was right to call added sugars – not dietary fat and cholesterol – the most serious risk to heart and overall health.
A large and fast-growing body of evidence shows that added sugars harm us in myriad ways.
There's compelling evidence that added sugars far exceed saturated fats or cholesterol as threats to heart health ... and that added sugars are key factors in the epidemic of obesity and diabetes, or “diabesity”.
Excess sugar promotes unhealthful blood-fat profiles, accelerates pro-aging processes (inflammation and glycation) … and feeds cancer growth (Cantley LC 2013).
Dr. Lustig focuses his fire on fructose, because added fructose – not the small amounts people can get from eating whole fruits – is uniquely damaging to metabolic health.
However, Lustig says that demonization of high-fructose corn syrup (HFCS) is a distraction.
This is because it's nearly identical (half glucose and half fructose) to cane sugar … which he finds equally bad for health, along with natural sugars like honey and maple or agave syrup.
We should note that while wheat contains almost no fructose, white flour and whole wheat bread alike raise blood sugar (glucose) levels in the body about as much and as rapidly as added sugars do.
Sugar as an addictive food
Dr. Lustig and others make a stronger claim … that sugar acts like an addictive drug because it triggers the same reward/pleasure response in the brain.
And he notes that limited research suggests that the more sugar you eat, the more sugar you need to get the same mood lift.
He cites research by Dr. Eric Stice of Oregon Health Sciences University who fed people milkshakes of varying fat and sugar content while they were in an MRI scanner.
(Drs. Stice and Lustig were featured in a 2103 episode of CBS-TV's 60 Minutes, titled “Is Sugar Toxic?
Fatty milkshakes stimulated the brain region that creates a food's “mouth-feel” … but sugar did more to stimulate the brain's reward center, which releases opioids and the feel-good chemical dopamine.
Importantly, the Oregon MRI study found that adding more fat to the shake didn't increase the sugar-related reward response in the brain.
In other words, according to Dr. Lustig, this MRI study showed that “we want sugar way more than we want fat”.
Because dietary sugar lights up the same reward section of the brain stimulated by cocaine and other drugs, Dr. Lustig and others consider sugar an additive substance.
Nora Volkow, M.D. – director of the National Institute of Drug Abuse – endorses the idea, but the scientific community has resisted it.
A study published by an EU task force lends support to opponents of the idea that sugar is an addictive substance.
Let's scrutinize that evidence, and see whether it really undermines the position taken by Drs. Lustig and Volkow.
EU team finds little evidence of fat or sugar addiction
The new findings come from the NeuroFAST consortium – an EU-funded project studying eating behavior, addiction and stress.
A team of university scientists from Scotland, Germany, and Spain found no strong evidence that people become addicted to sugars or fats like they become addicted to drugs (Hebebrand J et al. 2014).
Instead, they concluded that people can become compulsive about and virtually addicted to eating ... but found no hard evidence that people truly become addicted to sugar or fat.
Despite the milkshakes-MRI study from Oregon, the EU-based team concluded that the brain does not respond to sugar and fat like it does to drugs such as heroin, nicotine, or cocaine.
They noted that rats given unlimited access to sugar will eat more of it, but reduce their calorie intake from other sources and maintain a stable body weight (Avena et al.,
This suggests that sugar addiction in humans – which the EU team finds an unproven idea – may not be a driving cause of obesity.
(Instead, they cite evidence that high-fat diets induce behaviors in rats that look more like a true addiction.)
The EU researchers found people can develop a compulsion to eat, driven by the positive feelings that the brain associates with eating.
They say that this compulsion to eat is a behavioral disorder, and resembles conditions such as gambling addiction.
And they say that efforts to tackle obesity should focus on people's relationship with eating, rather than arguments over the reality of addiction to foods high in fat, salt, added sugars, solo or in combination.
The accepted diagnostic manual for mental disorders (DSM-5) does not contain a diagnosis of “eating addiction”, but the EU team acknowledged that future research might support its inclusion … and the reality of addiction to sugar and/or fat.
(“Internet gambling disorder” is the only mental condition that the DSM-5 categorizes as a “non-substance-related addictive disorder”.)
According to NeuroFAST project coordinator Suzanne Dickson from Sweden's University of Gothenburg, “There is currently very little evidence to support the idea that any ingredient, food item, additive or combination of ingredients has addictive properties.” (UA 2014)
Dr John Menzies from the University of Edinburgh, put their conclusions this way:
“More avenues for treatment may open up if we think about this condition as a behavioral addiction rather than a substance-based addiction.” (UA 2014)
Professor Julian Mercer of the University of Aberdeen took a notably dismissive stance:
“… most individuals with a weight problem … put on weight rather slowly … and … it is almost certainly completely inappropriate to suggest that food addiction or eating addiction has any role to play.” (UA 2014)
We beg to differ.
Did the EU team draw a meaningless distinction?
The NeuroFAST consortium's conclusion seems to rest on a distinction without a difference.
It's obvious that sugar doesn't impact the brain exactly like cocaine, nicotine, or opioid drugs like heroin, oxycodone, vicodin, hydrocodone, and oxycontin.
But in rats and humans alike, eating sugar stimulates the release of internally produced opioids, as well as dopamine: a pleasure/reward brain chemical.
We fail to see why, if Internet gambling disorder is now categorized as an addictive disorder, the same diagnosis wouldn't apply to compulsions to eat sugary foods.
We think that Drs. Lusting and Volkow and others are on the right track when they identify sugar as an addictive substance, even if its effects aren't identical to those of cocaine, nicotine, or heroin.
As Dr. Stice and colleagues wrote last year, “… [overeating] leading to obesity is associated with substantial neurochemical changes in the brain.
These findings verify the relevance of reward pathways for promoting consumption of palatable, calorically dense [high-sugar and/or high-fat] foods …” (Stice E et al. 2013).
They went on to say that these findings “… lead to the important question of whether changes in [the brain's] reward circuitry in response to intake of such foods serve a causal role in the development and maintenance of some cases of obesity.”
Three years ago, the authors of an insightful evidence review suggested several possible factors in the obesity epidemic (Berthoud HR et al. 2011):
- Diet-driven differences in the early development of children's reward responses.
- A mutually reinforcing relationship between high-sugar/high-fat foods and overeating.
- Gradual de-sensitization to high-sugar/high-fat foods, as seen in drug and alcohol addiction.
- Changes to the brain's reward functions cause by key metabolic effects of being overweight: increased inflammation, oxidative (free radical) stress, and more.
This nuanced view sounds right, and places the role of sugar “addiction” in context, as an important factor in the obesity epidemic … if not the sole or primary explanation.
It seems like a no-brainer to give your body – and brain – a break by cutting back on added sugars of all kinds.
- Berthoud HR, Lenard NR, Shin AC. Food reward, hyperphagia, and obesity. Am J Physiol Regul Integr Comp Physiol. 2011 Jun;300(6):R1266-77. doi: 10.1152/ajpregu.00028.2011. Epub 2011 Mar 16. Review.
- Cantley LC. Cancer, metabolism, fructose, artificial sweeteners, and going cold turkey on sugar. BMC Biol. 2013 Jan 31;12:8. doi: 10.1186/1741-7007-12-8.
- Hebebrand J, Albayrak O, Adan R, Antel J, Dieguez C, de Jong J, Leng G, Menzies J, Mercer JG, Murphy M, van der Plasse G, Dickson SL. "Eating addiction", rather than "food addiction", better captures addictive-like eating behavior. Neurosci Biobehav Rev. 2014 Sep 6. pii: S0149-7634(14)00214-0. doi: 10.1016/j.neubiorev.2014.08.016. [Epub ahead of print] Review.
- Sinha R, Jastreboff AM. Stress as a common risk factor for obesity and addiction. Biol Psychiatry. 2013 May 1;73(9):827-35. doi: 10.1016/j.biopsych.2013.01.032. Epub 2013 Mar 26. Review.
- Smith DG, Robbins TW. The neurobiological underpinnings of obesity and binge eating: a rationale for adopting the food addiction model. Biol Psychiatry. 2013 May 1;73(9):804-10. doi: 10.1016/j.biopsych.2012.08.026. Epub 2012 Oct 23. Review.
- Stice E, Figlewicz DP, Gosnell BA, Levine AS, Pratt WE. The contribution of brain reward circuits to the obesity epidemic. Neurosci Biobehav Rev. 2013 Nov;37(9 Pt A):2047-58. doi: 10.1016/j.neubiorev.2012.12.001. Epub 2012 Dec 10. Review.
- Strom S. / The New York Times. U.S. Cuts Estimate of Sugar Intake. Accessed at http://www.nytimes.com/2012/10/27/business/us-cuts-estimate-of-sugar-intake-of-typical-american.html
- University of Aberdeen (UA). Eating is addictive but sugar and fat are not like drugs, study says. September 9, 2014. Accessed at http://www.abdn.ac.uk/ne