Hello and welcome to the Nutrition Facts podcast. I’m your host, Dr. Michael Greger.
Now, I know I’m known for explaining how not to do certain things (just look at my books, How Not to Die, the one I’m working on right now–How Not to Diet), but what I actually have to share with you is quite positive and boils down to this: What’s the best way to live a healthy life? Here, are some answers.
Today, we look at a topic that has been in the news a lot lately: addiction. There is evidence connecting cravings for foods containing high amounts of sugar and fat with the dopamine-based reward pathways in the brain. In fact, evidence from PET scans suggests brain activity changes associated with the overconsumption of sugar may parallel that of drug addiction. Here’s the story.
People have chewed coca leaves for at least 8,000 years as a mild stimulant without any evidence of addiction. But, when certain components are isolated and concentrated into cocaine, we’ve got a problem. The same may be true of sugar. People don’t tend to binge on bananas. It’s perhaps the reason we’re more likely to supersize soda than sweet potatoes.
“The…overconsumption of sugar-sweetened diets has often been compared to drug addiction, though this parallel was based until very recently more on anecdotal evidence than on solid scientific grounds.” But now, we have PET scans—imaging technology that can measure brain activity. We see the same thing in cocaine addicts and alcoholics. “This would suggest that a reduction in [dopamine] receptors is associated with addictive behavior, irrespective of whether it is due to food,…or to addictive drugs as seen in substance abusers.”
Dopamine is considered the neurotransmitter primarily involved in the pleasure and reward center of our brain, helping to motivate our drive for things like food, water, and sex—all necessary for the perpetuation of our species. It was healthy and adaptive for our primate brains to drive us to eat that banana when there wasn’t much food around. But now that fruit is in Loop form, “this adaptation has become a dangerous liability.” The original Coca-Cola formulation actually included coca leaf, but now, perhaps, its sugar content may be the addictive stand-in.
Those eating calorie-dense diets may have a reduced capacity to enjoy all of life’s pleasures by deadening dopamine pathways in the brain.
The food industry, like the tobacco companies and other drug lords, has been able to come up with products that tap into that same dopamine reward system. Why a picture of a cheeseburger rather than sugary soda pop? Well, now we know fat may have similar effects on the brain as well. You feed some people some yogurt packed with butterfat and within 30 minutes you can start to see the same changes in brain activity you get when you drink sugar water. People who regularly eat ice cream, sugar and fat, have a deadened dopamine response in their brains to drinking a milkshake. It’s like when drug abusers have to use more and more to get the same high. Frequent ice cream consumption is related to a reduction in reward region responsivity in humans—they’re talking about the “pleasure center” in the brain, paralleling the tolerance observed in drug addiction. Once we have so dulled our dopamine response, we may subsequently overeat in an effort to achieve the degree of satisfaction experienced previously, which contributes to unhealthy weight gain.
What do fatty sugary foods have in common? They’re energy-dense foods. It may be less the number of calories than their concentration. Consumption of a calorie-dense diet compared to the same number of calories in a calorie-dilute diet leads to that numbing of the dopamine response. It’s like the difference between cocaine and crack—same stuff chemically, but by smoking crack cocaine we can deliver kind of a higher dose quicker to our brain.
As an aside, I found it interesting that the control drink in these milkshake studies wasn’t just water—they can’t use water because our brain can actually taste water on the tongue. I didn’t know that! So, they had to use artificial saliva. They made people drink a solution designed to mimic the natural taste of saliva. Ewww! Anyway, with this new understanding of the neural correlates of food addiction, there have been calls to include obesity as an official mental disorder. After all, both obesity and addiction share the inability to restrain behavior in spite of an awareness of detrimental health consequences. Now, that’s one of the defining criteria of substance abuse—you keep putting crap in your body, despite the knowledge that you have a problem that is likely caused by the crap. Yet, you can’t stop.
Redefining obesity as an addiction, as a psychiatric disease, would be a boon to drug companies that are already working on a whole bunch of drugs to muck with our brain chemistry. For example, you give people an opiate blocker, like they do for people with heroin overdoses, to block the effects of the drug, and people eat significantly less cheese. It just doesn’t do as much for them anymore when their opiate receptors are blocked. Rather than taking drugs though, we can prevent the deadening of our pleasure center in the first place by sticking to foods that are naturally calorically dilute, like whole plant foods. This can help bring back our dopamine sensitivity, such that we can again derive the same pleasure from the simplest of foods. And, this is not just for people who are obese—yes, when we regularly eat calorie-dense animal and junk foods, like ice cream, we can blunt our pleasure center and overeat to compensate, but when our brain downregulates dopamine receptors to deal with all these jolts of fat and sugar, we may experience less enjoyment from other activities as well. That’s why cocaine addicts may have an impaired neurological capacity to enjoy sex, why smokers also have an impaired ability to respond to positive stimuli. Since these all involve the same dopamine pathways, what we put into our body—what we eat—can affect how we experience all of life’s pleasures. So, to live life to the fullest, what’s the solution?
Well, the food industry, according to some addiction specialists, “should be given incentives to develop low-calorie foods that are more attractive, palatable and affordable so the people can adhere to diet programs for a long time.” No need–Mother Nature beat them all to it.
The evidence clearly indicates that long-term marijuana use can lead to addiction. But, are there negatives consequences? “[A]pproximately 9% of those who experiment with marijuana will become addicted,” and that “number goes up to about 1 in 6 among those who start…marijuana as teenagers and to 25 to 50% among those who smoke marijuana daily.”
By addiction, what they’re talking about is like the colloquial definition: “an acquired, chronic, relapsing disorder that is characterized by a powerful motivation to continually engage in an activity despite persistent negative consequences.” You may want to stop, but when you try, you may suffer withdrawal symptoms that make it hard to quit.
This “withdrawal syndrome…affects around 50% of daily users,” and “typically begins 1 to 2 days after [stopping], peaks at 2 to 6 days.” But the “craving[s], sleep[ing] problems, nightmares, anger, irritability, [unease], and nausea” goes away after one or two weeks.
Marijuana now has this “reputation…as being benign, non–habit-forming”—and that may be true “[f]or most users.” Certainly less addictive than many other drugs, like alcohol, only about half the dependence risk compared to heroin or cocaine, less than a third as habit-forming as tobacco, but 9%, “One in 11 users—1 in 6 for those starting in their early teens—is hardly an inconsequential percentage…”—given that about 20 million Americans actively use the stuff.
“However, not all varieties of cannabis” are equally addictive. “[H]igh potency strains have been associated with a greater severity of dependence,” but that’s the stuff people prefer.
This is not your grandmother’s grass. Based on 38,000 samples of marijuana confiscated by the DEA, the potency has tripled in recent years, from 4% THC up to around 12%, with Denver and California now up around 15%, and Seattle pushing 20%. That’s 15 times more powerful than pot from the ‘70s, so like 15 joints all rolled up into one.
Yeah, but don’t users know this, and “titrate their dose…” accordingly, using “less of the more potent” pot? Yes, but they don’t compensate fully, and so do end up getting higher doses—perhaps reflected in the increase in emergency room visits in Colorado for marijuana intoxication after legalization.
Parallels have been drawn with the tobacco industry intentionally boosting nicotine levels of their products to make them more addictive, but where that analogy breaks down is in the consequences of that addiction. Every year, tobacco kills 25 times more people worldwide than all illicit drugs combined. Alcohol kills about 10 times more, and “cannabis [alone probably] contributes little to [overall] mortality,” at least. So, one has to consider the outcomes of substance dependence.
To see any graphs, charts, graphics, images or studies mentioned here, please go to the Nutrition Facts podcast landing page. There, you’ll find all the detailed information you need – plus links to all of the sources we cite for each of these topics.
Be sure to check out my new How Not to Die Cookbook. It’s beautifully designed, with more than 120 recipes for delicious, plant-based meals, snacks and beverages. All the proceeds from the sales of all my books all go to charity. I just want you to be healthier.
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Thanks for listening to Nutrition Facts. I’m Dr. Michael Greger.
This is just an approximation of the audio content, contributed by Allyson Burnett.