Nutrition Diva

Do sweetened breakfast cereals lead to obesity?

Episode Summary

Sweetened cereals are aggressively fortified. But do the benefits outweigh the potential risks?

Episode Notes

Giving kids sweetened breakfast cereals must increase their future risk of obesity and Type 2 diabetes, right? Actually, maybe not.

Nutrition Diva is hosted by Monica Reinagel. A transcript is available at Simplecast.

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Episode Transcription

Hello and welcome to the Nutrition Diva podcast. I’m your host Monica Reinagel and today I want to tell you about an exchange I recently had with a Nutrition Diva listener—because I learned a lot from it.

The nominal subject of our conversation was sweetened breakfast cereals and their effect on children’s nutrition and health. But for me, it was equally about the perils of making assumptions—and we ALL do this, myself included.

Some beliefs just seem so obvious that it doesn’t occur to us to check whether the evidence supports our beliefs. We just assume that it does. Perhaps that’s what we mean when we say something is self-evident: It requires no corroboration. Furthermore, if we go looking for evidence to support something we already believe to be true, we can easily misinterpret the evidence we find in order to make it line up with our assumptions.

This conversation was triggered by an episode I did recently on fortified foods and the role they play in meeting our nutritional needs. Ready-to-eat breakfast cereals are among the most aggressively fortified foods. And in my previous episode, I cited some data showing that fortified cereals (including sweetened ones) play an important role in meeting the nutritional needs of millions of children.

In a nutshell, people who eat ready-to-eat cereal have higher intakes of several key nutrients (due in part to fortification) and are more likely to meet nutrient recommendations than non-cereal eaters. The positive impact of cereal on overall nutrition is even more pronounced in children from lower-income households.

In response to that episode, I got an incredulous email from a listener. He couldn’t believe that I had failed to mention all the research that’s been done on the long-term consequences of feeding kids sweetened breakfast cereals, specifically obesity and Type 2 diabetes.

I asked him to please share with me the research he’d seen connecting the consumption of sweetened breakfast cereal with an increased risk of obesity or Type 2 diabetes. It certainly seemed possible to me that there could be such a connection. But I was having trouble finding any evidence of it.

A few days later, he sent me some research that he had found to prove his point. Upon closer examination, however, the studies he sent did not actually say what he thought they did.

“Here's a study linking high sugar cereal to childhood obesity,” he wrote.

The study he cited was looking at data on children’s exposure to television ads that market sweetened breakfast cereals. The authors speculated that this marketing is “likely” to contribute to childhood obesity. But they offer no data to support that assertion.

In fact, a 2013 randomized controlled trial found that children who frequently consumed ready-to-eat cereals "had significantly lower BMI over a 3-year period." They also had greater intakes of essential nutrients.

That study specifically focused on lower-income kids, but a 14-year prospective study of 367,442 individuals in the broader population also found that "consumption of ready-to-eat cereal was associated with reduced risk of…mortality from specific diseases such as CVD, diabetes, and cancer."

These data do not support the hypothesis that the consumption of sweetened breakfast cereals contributes to childhood obesity or an increased risk of obesity and Type 2 diabetes later in life. (Whether TV marketing to children should be better regulated is an entirely different question.)

But, to be fair, most of the large studies looking at links between cereal intake and health and nutrition do not distinguish between sweetened and unsweetened breakfast cereals. They are all lumped together. If we looked just at the sweetened cereals, perhaps the link between them and increased disease risk would be clear.

My listener found another study that he was convinced showed just that. He even highlighted what he thought to be the salient section for me, which read:

"An analysis of all child-targeted foods sold in Canadian supermarkets… showed that 93% of breakfast cereals derived over 20% of their calories from sugar. Higher sugar intake by children (and particularly sugar-sweetened beverages) has been shown… to be associated with a higher risk of obesity."

There it is: Breakfast cereals are high in sugar and higher sugar intake is linked to higher obesity risk.

But did you catch the logical fallacy?

Take a closer look (or listen): The authors first share some stats about the sugar content of breakfast cereals, that a large percentage get over 20% of their calories from sugar. What they say next, however, is not about cereal. They say that higher sugar intake in kids—particularly from sugar-sweetened beverages—is linked to increased risk.

This study does not show that eating sweetened cereal is linked to increased risk of obesity—although they certain do imply that. It does not even show that kids who eat these cereals have higher sugar intakes. In fact, it turns out that kids who regularly eat ready-to-eat cereal don’t eat any more sugar than kids who don’t.

That actually surprised me. But maybe it shouldn’t have.

Here are two facts followed by an assumption:

Fact #1: According to the CDC, the average daily intake of added sugars is 17 teaspoons for children and young adults—significantly higher than the recommended limit.

Fact #2: Sweetened breakfast cereals contain a significant amount of sugar; 3-4 teaspoons per serving is not unusual. 

Assumption: Sweetened breakfast cereals are contributing too much sugar to kids’ diets.

But that’s not where most of the sugar in kids’ diets is coming from. Sweetened beverages are the #1 source of added sugar in the American diet, followed by desserts, sweet snacks, candy and actual table sugar. Cereal and bars (together) account for only 7% of the added sugar in the typical diet… the same percentage as comes from sandwiches.

Why is limiting added sugar important?

Most people assume that it is because sugar—in and of itself—uniquely promotes obesity and Type 2 diabetes. It’s another one of those things that might just seem obvious or self-evident. But the reality is a little more complex. An analysis of the data from the Women’s Health Study, which involves almost 40,000 women, found no correlation between sugar intake and Type 2 diabetes risk.

Sugar intake does appear to be correlated with an increased risk of obesity. But even there, it’s not quite as cut-and-dried as it might seem. If you control for total calorie intake, that link fades. Sugar intake is linked to weight gain mostly because people who are eating a lot of sugar also tend to be taking in too many calories. If you reduce your sugar intake but not calories, it’s not going to solve the problem. (Added sugar consumption in Australia, for example, has gone way down in recent years, while obesity rates have continued to climb.)

But if we are looking to cut calories, it certainly makes sense to start with the empty ones—foods that aren’t contributing any nutritional value to the diet. That would certainly include sweetened beverages and candy—but probably not cereal and sandwiches. Not only are cereal and sandwiches contributing far less sugar to the diet overall, but at least they are providing some valuable nutrients along with the sugar.

To be honest, I find it a bit awkward to be in the position of defending foods that I myself don’t eat very often and would not regularly feed to my children (if I had any). When I eat sweetened cereals, I consider them more of a dessert. And I personally do not care to start my day with dessert. If I’m eating cereal for breakfast, I choose a low- or no-sugar option.

Furthermore, I still think that reducing added sugar intake (from all foods) to no more than 10% of calories is a great goal. If you can get it down to 5% of calories, even better. Why? Because it gives you more calories to spend on foods that help fulfill your nutritional needs—without exceeding your calorie budget.

So, if you can get your kids to eat low or no sugar cereals for breakfast, I think that’s better for them than a highly sweetened one. But if you (or your kids) want to spend your added sugar allowance on Lucky Charms or Frosted Flakes, that’s your prerogative. (I’m more of a Honey Nut Cheerio gal myself.)

This deep dive into the evidence on sugar and kids and cereal turned up some results that I didn’t expect—and challenged some of my assumptions. And that’s one of the reasons I wanted to devote an episode to this.

It’s so important for all of us to be open to information that conflicts with what we believe to be true. Those areas where we simply assume that science and research support our beliefs. Those biases that are so ingrained (or systemic) that we don't even recognize them as biases.

My new rule is going to be this: When something seems self-evident to me, that’s a sign that I need to check my facts. Not only to see if I can find evidence to support my beliefs. I need to actually look just as hard for evidence that disproves my beliefs—as uncomfortable as that may be.

So keep those emails and questions coming. I don’t mind if you disagree with me—in fact, I welcome it. As long as you’re willing to keep an open mind and to follow the evidence wherever it leads.

Nutrition Diva is a Quick and Dirty Tips podcast. It's audio-engineered by Nathan Semmes with script editing by Adam Cecil. Thanks also to Morgan Christianson, Holly Hutchings, Davina Tomlin, and a special welcome to our new intern, Kamryn Lacy.