Why Drinking Diet Soda Makes You Crave Sugar

Recommendations on limiting sugar consumption vary around the world, with guidelines ranging from “[l]imit sweet desserts to one every other day” to “[k]eep sugar consumption to 4 or less occasions per day.” In the United States, the American Heart Association is leading the charge, “proposing dramatic reductions in the consumption of soft drinks and other sweetened products” and recommending fewer than about 5 percent of calories a day from added sugars, which may not even allow for a single can of soda.

Why is the American Heart Association so concerned about sugar? “Overconsumption of added sugars has long been associated with an increased risk of cardiovascular disease,” meaning heart disease and strokes. We used to think added sugars were just a marker for an unhealthy diet. At fast-food restaurants, for example, people may be more likely to order a cheeseburger with their super-sized soda than a salad. However, the new thinking is that the added sugars in processed foods and drinks may be independent risk factors in and of themselves. Indeed, worse than just empty calories, they may be actively disease-promoting calories, which I discuss in my video Does Diet Soda Increase Stroke Risk as Much as Regular Soda?.

At 1:14 in my video, you can see a chart of how much added sugar the American public is consuming. The data show that only about 1 percent meet the American Heart Association recommendation to keep added sugar intake down to 5 or 6 percent of daily caloric intake. Most people are up around 15 percent, which is where cardiovascular disease risk starts to take off. There is a doubling of risk at about 25 percent of calories and a quadrupling of risk for those getting one-third of their daily caloric intake from added sugar.

Two hundred years ago, we ate an estimated 7 pounds of sugar annually. Today, we may consume dozens of pounds of sugar a year. We’re hardwired to like sweet foods because we evolved surrounded by fruit, not Froot Loops, but this adaptation is “terribly misused and abused” today, “hijacked” by the food industry for our pleasure and their profits. “Why are we consuming so much sugar despite knowing too much can harm us?” Yes, it may have an addictive quality and there’s the hardwiring, but the processed food industry isn’t helping. Seventy five percent of packaged foods and beverages in the United States contain added sweeteners, mostly coming from sugar-sweetened beverages like soda, which are thought responsible for more than a 100,000 deaths worldwide and millions of years of healthy life lost. Given this, can we just switch to diet sodas? By choosing diet drinks, can’t we get that sweet taste we crave without any of the downsides? Unfortunately, studies indicate that “[r]outine consumption of diet soft drinks is linked to increases in the same risks that many seek to avoid by using artificial sweeteners—namely type 2 diabetes, metabolic syndrome heart disease, and stroke.” At 3:15 in my video, you can see data showing the increased risks of cardiovascular disease associated with regular soft drinks and also diet soda. They aren’t that dissimilar.

“In other words, the belief that artificially sweetened diet beverages reduce long-term health risks is not supported by scientific evidence, and instead, scientific data indicate that diet soft drink consumption may contribute to the very health risks people have been seeking to avoid.” But, why? It makes sense that drinking all that sugar in a regular soft drink might increase stroke risk, due to the extra inflammation and triglycerides, but why does a can of diet soda appear to increase stroke risk the same amount? It’s possible that the caramel coloring in brown sodas like colas plays a role, but another possibility is that “artificial sweeteners may increase the desire for sugar-sweetened, energy-dense beverages/foods.”

The problem with artificial sweeteners “is that a disconnect ultimately develops between the amount of sweetness the brain tastes and how much glucose [blood sugar] ends up coming to the brain.” The brain feels cheated and “figures you have to eat more and more and more sweetness in order to get any calories out of it.” So, “[a]s a consequence, at the end of the day, your brain says, ‘OK, at some point I need some glucose [blood sugar] here.’ And then you eat an entire cake, because nobody can hold out in the end.”

If people are given Sprite, Sprite Zero (a zero-calorie soda), or unsweetened, carbonated, lemon-lime water, but aren’t told which drink they’re getting or what the study is about, when they’re later offered a choice of M&M’s, spring water, or sugar-free gum, who do you think picks the M&M’s? Those who drank the artificially sweetened soda were nearly three times more likely to take the candy than those who consumed either the sugar-sweetened or unsweetened drinks. So, it wasn’t a matter of sweet versus non-sweet or calories versus no-calories. There’s something about non-caloric sweeteners that somehow tricks the brain.

The researchers did another study in which everyone was given Oreos and were then asked how satisfied the cookies made them feel. Once again, those who drank the artificially sweetened Sprite Zero reported feeling less satisfied than those who drank the regular Sprite or the sparkling water. “These results are consistent with recent [brain imaging] studies demonstrating that regular consumption of [artificial sweeteners] can alter the neural pathways responsible for the hedonic [or pleasure] response to food.”

Indeed, “[t]he only way really to prevent this problem—to break the addiction—is to go completely cold turkey and go off all sweeteners—artificial as well as fructose [table sugar and high fructose corn syrup]. Eventually, the brain resets itself and you don’t crave it as much.”

We’ve always assumed the “[c]onsumption of both sugar and artificial sweeteners may be changing our palates or taste preferences over time, increasing our desire for sweet foods. Unfortunately, the data on this [were] lacking”…until now. Twenty people agreed to cut out all added sugars and artificial sweeteners for two weeks. Afterwards, 95 percent “found that sweet foods and drinks tasted sweeter or too sweet” and “said moving forward they would use less or even no sugar.” What’s more, most stopped craving sugar within the first week—after only six days. This suggests a two-week sugar challenge, or even a one-week challenge, may “help to reset taste preferences and make consuming less or no sugar easier.” Perhaps we should be recommending it to our patients. “Eating fewer processed foods and choosing more real, whole, and plant-based foods make it easy to consume less sugar.”

Speaking of stroke, did you see my Chocolate and Stroke Risk video?

For more on added sugars, see:

You may also be interested in my videos on artificial and low-calorie sweeteners:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations:

How Healthy is the Mediterranean Diet?

The heart of a traditional Mediterranean diet is mainly vegetarian—much lower in meat and dairy than a standard Western diet—and uses fruit for dessert! So, it’s no surprise that those eating that way had very low heart disease rates compared to those eating standard Western diets. My video Mediterranean Diet & Atherosclerosis gives the lowdown on the link between the fats we eat and the health of our arteries.

A landmark study has been cited to suggest that all types of fat—whether animal or vegetable—are associated with the appearance of new atherosclerotic lesions in our coronary arteries, which feed our hearts. About 100 men were given angiograms at baseline and then again two years later, looking for the development of coronary lesions, all while monitoring their diets every year. Only about 1 in 20 eating lower fat diets had new lesions, compared to about 8 in 20 on more typical American diets of around 33% or more fat. But, when the researchers drilled down, only three types of fat appeared to increase significantly the likelihood of the appearance of new lesions: lauric, oleic, and linoleic. Lauric acid is a saturated fat found in coconut oil and palm kernel oil, which can be found in such junk foods as whipped cream and candy bars. Oleic comes from the Latin word oleum, for olive oil, but that’s not where the subjects of this study were getting their oleic acid: The top sources for Americans are cake, chicken, and pork, and linoleic comes mostly from chicken. So, the study really just showed that people eating lots of junk, chicken, and pork tended to close off their coronary arteries.

To see if major sources of plant fats like olive oil or nuts help or hurt, ideally we’d do a multi-year, randomized study where we’d take thousands of people, have one-third eat more nuts, another third eat more olive oil, and the final third do essentially nothing, and then see who does better. And that’s exactly what researchers did. The PREDIMED study took thousands of people in Spain who were at high risk for heart disease and were already eating a Mediterranean-ish diet, and randomized them into three groups for a couple of years—one group with added extra virgin olive oil, a second with added nuts, and a third group that was told to cut down on fat, but actually didn’t, so basically ended up as a no-dietary-changes control group. What happened to the amount of plaque in their arteries over time?

Whereas there was significant worsening of carotid artery thickening and plaque in the no-dietary-changes control group, those in the added-nuts group showed a significant reversal in thickening and an arrest in plaque progression. There were no significant changes in the added olive oil group.

“The richness of the plant-based MedDiet [Mediterranean diet] in potentially beneficial foods, such as fruit, vegetables, legumes, nuts, cereals, and olive oil, is believed to explain its cardioprotective effects.” However, these results suggest nuts are a preferable source of fat compared to olive oil and may “delay the progression of atherosclerosis, the harbinger of future cardiovascular events” such as stroke. Adding nuts appeared to cut the risk of stroke in half.

Note, though, they were still having strokes, albeit half as many. So, the nuts appeared to be helping. However, they were still eating a diet conducive to strokes and heart attacks. All three groups had basically the same heart attack rates, the same overall death rates. That’s what Dr. Ornish, a proponent of a mostly whole foods, plant-based diet, noted when he commented on the study: “There was no significant reduction in the rates of heart attack, death from cardiovascular causes, or death from any cause,” only that stroke benefit. But, hey, that’s not nothing. A Mediterranean diet is certainly better than what most people are consuming, but a diet based on whole plant foods may be even better, since it’s shown to reverse heart disease, not contribute to it. The authors of the study replied that they didn’t wish to detract from Ornish’s work, noting that Mediterranean and plant-based diets actually share a great number of foods in common. Yes, Ornish’s diet can reverse heart disease. The major problem with the Ornish diet, argued proponents of the Mediterranean diet, is that it doesn’t taste good, so hardly anyone sticks to it.

If you’d like to learn more, I bring up the Ornish back-and-forth in my 2015 annual live review, Food as Medicine: Preventing and Treating Our Most Dreaded Diseases with Diet, and directly address the accusation that plant-based diets are marked by poor compliance for disease prevention and reversal. For a shorter overview on heart disease, check out How Not to Die from Heart Disease.

For more on the famous PREDIMED trial and the body of evidence surrounding Mediterranean diets, I’ve got a bunch of good videos for you:

What might happen to the arteries of someone who goes on a low-carb diet? You don’t want to know. (But, if you’re really curious, see: Low Carb Diets and Coronary Blood Flow.)

What we eat doesn’t only have an impact on the structure of our arteries over the long-term (i.e., the thickening and narrowing described in the video), but the function of our arteries within hours of consumption. To see what your breakfast may have done to your arteries, check out:

Note, though, the benefits of plant-based nutrition can be undermined by vitamin B12 deficiency if you don’t include a regular reliable source in your diet. See Vitamin B12 Necessary for Arterial Health.

In health,

Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations: