Yes, Sugar is Really Bad for You

In a September 19, 2018 article, journalist Jessica Brown acts as a defense attorney for sugar, while recognizing attacks that have been made on sugar. Here is the opening statement:

It’s hard to imagine now, but there was a time when humans only had access to sugar for a few months a year when fruit was in season. Some 80,000 years ago, hunter-gatherers ate fruit sporadically and infrequently, since they were competing with birds.

Now, our sugar hits come all year round, often with less nutritional value and far more easily – by simply opening a soft drink or cereal box. …

But so far, scientists have had a difficult time proving how it affects our health, independent of a diet too high in calories. 

Is it just calories?

One key way to cast doubt on the role of sugar is to say that it is really just total calories. Jessica quotes Luc Tappy:

Luc Tappy, professor of physiology at the University of Lausanne, is one of many scientists who argue that the main cause of diabetes, obesity and high blood pressure is excess calorie intake, and that sugar is simply one component of this.

“More energy intake than energy expenditure will, in the long term, lead to fat deposition, insulin resistance and a fatty liver, whatever the diet composition,” he says. “In people with a high energy output and a matched energy intake, even a high fructose/sugar diet will be well tolerated.”

Tappy points out that athletes, for example, often have higher sugar consumption but lower rates of cardiovascular disease: high fructose intake can be metabolised during exercise to increase performance. 

The trouble with this way of absolving sugar is that a key mechanism through which sugar can cause trouble is by leading people to eat more total calories—both through the insulin mechanism I emphasize in “Obesity Is Always and Everywhere an Insulin Phenomenon” and through making things tasty. So holding calories constant when thinking about the effects of sugar is ignoring one of the primary mechanisms through which eating sugar can cause harm. And to the extent athletes are harmed less by eating sugar, an interesting hypothesis is that exercise might reduce the effect of sugar in making people hungry a little while later.

Is it just correlational, not causal?

Some of the best evidence about the malign effects of sugar comes from data on soft drink and fruit juice consumption. Here Jessica confuses criticism of some studies as being only correlational with the status of research on soft drink and fruit juice as a whole. Indeed, there are some interesting studies that have to be taken with a grain of salt because they are only correlational:

Still, studies have demonstrated other ways in which sugar affects our brains. Matthew Pase, research fellow at Swinburne’s Centre for Human Psychopharmacology in Australia, examined the association between self-reported sugary beverage consumption and markers of brain health determined by MRI scans. Those who drank soft drinks and fruit juices more frequently displayed smaller average brain volumes and poorer memory function. Consuming two sugary drinks per day aged the brain two years compared to those who didn’t drink any at all. But Pase explains that since he only measured fruit juice intake, he can’t be sure that sugar alone is what affects brain health. …

One 15-year study seemed to back this up: it found that people who consumed 25% or more of their daily calories as added sugar were more than twice as likely to die from heart disease than those who consumed less than 10%. Type 2 diabetes also is attributed to added sugar intake. Two large studies in the 1990s found that women who consumed more than one soft drink or fruit juice per day were twice as likely to develop diabetes as those who rarely did so.

But there is a great deal of non-correlational evidence. Jessica writes:

Meanwhile, sugary drinks, which usually use high fructose corn syrup, have been central to research examining the effects of sugar on our health. One meta-analysis of 88 studies found a link between sugary drinks consumption and body weight. In other words, people don’t fully compensate for getting energy from soft drinks by consuming less of other foods – possibly because these drinks increase hunger or decrease satiety.

Following the link through to the meta-analysis, it reports:

… larger effect sizes were observed in studies with stronger methods (longitudinal and experimental vs cross-sectional studies). …

We found 7 studies that examined the connection between soft drink intake and body weight in an experimental or intervention context. Five reported a positive association. In 3 of these studies, participants who were given soft drinks to consume gained weight over the course of the experiment. Two intervention studies aimed at decreasing soft drink consumption among high school students showed that students in the intervention groups essentially maintained their weight over the treatment period, whereas those in the control groups exhibited significant weight gain. Two studies reported no statistically significant effect of soft drink consumption on weight gain. The average effect size for experimental studies was 0.24 (P < .001; Q7 = 24.57, P = .001).

Jessica never pulls this out.

Does sugar sometimes do something good?

There are so hundreds of effects of any one thing; so if one is looking for a good effect—as one might have an incentive to do—one is likely to find a good effect. For sugar, perking up old folks seems may be one:

One recent study found that sugar may even help improve memory and performance in older adults. Researchers gave participants a drink containing a small amount of glucose and asked them to perform various memory tasks. Other participants were given a drink containing artificial sweetener as a control. They measured the participants' levels of engagement, their memory score, and their own perception of how much effort they’d applied.

The results suggested that consuming sugar can make older people more motivated to perform difficult tasks at full capacity – without them feeling as if they tried harder. Increased blood sugar levels also made them feel happier during the task.

And of course, if you wait to eat sugar until your expected remaining life is only a couple of years, it may well be that death will interrupt any serious harm of sugar. It is young people—say anyone with an expected remaining life span of more than two years—who should quit eating sugar.

Is being against sugar crazy or cultlike?

One way to distract from the evidence against sugar is to shift the focus to other, less scientific reasons people might be against sugar. Jessica writes:

There is also a growing argument that demonising a single food is dangerous …

… dietitian Renee McGregor says it’s important to understand that a healthy, balanced diet is different for everyone.

McGregor, whose clients include those with orthorexia, a fixation with eating healthily, says that it isn’t healthy to label foods as ‘good’ or ‘bad’. And turning sugar into a taboo may only make it more tempting. “As soon as you say you can’t have something, you want it,” she says. “That’s why I never say anything is off-limits. I’ll say a food has no nutritional value. But sometimes foods have other values.”

Associate professor at James Madison University Alan Levinovitz studies the relationship between religion and science. He says there’s a simple reason we look at sugar as evil: throughout history, we’ve demonised the things we find hardest to resist (think of sexual pleasure in the Victorian times).

Today, we do this with sugar to gain control over cravings.

“Sugar is intensely pleasurable, so we have to see it as a cardinal sin. When we see things in simple good and evil binaries, it becomes unthinkable that this evil thing can exist in moderation. This is happening with sugar,” he says.

He argues that that seeing food in such extremes can make us anxious about what we’re eating – and add a moral judgment onto something as necessary, and as everyday, as deciding what to eat.

For well-adjusted folks, I think there is a good reason to cut out sugar almost entirely that they don’t give due credit to: after about three weeks off sugar, everything tastes sweeter, and the desire for sugar goes down, so it becomes much easier to avoid sugar. I talk about this in “Letting Go of Sugar.”

Will cutting out sugar lead to eating worse things or cutting out something essential?

One of the weakest arguments in defense of sugar is that cutting it out will lead to other bad dietary adjustments. Give me a break! Because sugar is in almost all processed foods, cutting out sugar leads to avoiding most processed foods—highly likely to be a step in the right direction. (See “The Problem with Processed Food” and the evidence discussed in “Why a Low-Insulin-Index Diet Isn't Exactly a 'Lowcarb' Diet.”)

While Jessica is doing her best to come up with pro-sugar arguments, she is cavalier in assuming that dietary fat is bad and that fruit is so wonderful, that eating fruit sparingly because of its sugar content is a bad thing. She writes:

Taking sugar out of our diets can even be counterproductive: it can mean replacing it with something potentially more calorific, such as if you substitute a fat for a sugar in a recipe.

… we risk confusing those foods and drinks with added sugar that lack other essential nutrients, like soft drinks, with healthy foods that have sugars, like fruit.

On fruit, see the section “The Conundrum of Fruit” in “Forget Calorie Counting; It's the Insulin Index, Stupid.” On dietary fat, see:

Also, see “Faye Flam: The Taboo on Dietary Fat is Grounded More in Puritanism than Science.” Here, as I noted above, “not science” is more important than “yes Puritanism.” But it is worth noting that if there is anything biasing non-scientists’ sense of the virtues and vices of different types of food, the fact that dietary fat uses the same word “fat” as body fat is highly likely to distort some people’s intuitions. (This could be tested by looking at attitudes toward dietary fat in countries where the word for dietary fat is fully distinct from the word for body fat.)

It may be surprising that one has to defend the idea that sugar is very bad, but that is the world we live in. In “The Trouble with Most Psychological Approaches to Weight Loss: They Assume the Biology is Obvious, When It Isn't” I give examples of things people will be saying when the serious harms of sugar really are conventional wisdom. We are not there yet. I am proud to be an anti-apologist for sugar.

Don't miss these other posts on diet and health and on fighting obesity:

Also see the last section of "Five Books That Have Changed My Life" and the podcast "Miles Kimball Explains to Tracy Alloway and Joe Weisenthal Why Losing Weight Is Like Defeating Inflation." If you want to know how I got interested in diet and health and fighting obesity and a little more about my own experience with weight gain and weight loss, see my post "A Barycentric Autobiography."