The Best Thing for Your Blood Sugar Levels: Give Up Cereal

September 2, 2011

in Science

By Rob Schick

Was your house one of the ones I envied as a kid? You know, the one where your Mom bought Cap’n Crunch with Crunch Berries? Cocoa Puffs? Fruit Loops? And the house where you could have all the Tang, Hi-C, and Capri-Sun you wanted? If it was, you cannot imagine how much I wanted to live in your house, eat all your sugary cereal, and drink (or eat) Tang till I passed out.

Sugar Cereals

You see my Mom wouldn’t buy us sugar cereal. She relaxed this rule over time, but when I was really young all we got was plain Life, or Cheerios, or maybe Rice Krispies. As we got a bit older, Honey Nut Cheerios were a regular fixture, as was my eventual favorite, Cinnamon Toast Crunch. I ate cereal every day of my childhood and well into my adulthood – even if there was something else like eggs or bacon for breakfast – I would have a “little” bowl of cereal.

I don’t know about you, but I never found Cheerios sweet enough, and I would always dip my tablespoon at least once, and usually twice into the sugar bowl before pouring my milk and tucking in.

I can readily recall that last soupy sludge at the bottom of the bowl with milk and partially dissolved granules of sugar. Yum! (So yummy, in fact, that at least one New York pastry chef is famous for infusing her pastries with cereal-flavored milk.) It’s no wonder I was a chubby kid!

While my weight has been pretty stable as an adult, it faced its most serious challenge when Riki went to pastry school. Mind you I completely supported this idea, but the daily onslaught of delicious French pastries and desserts and ice creams were over the top. So much so that I became a bit of a snob about pastry. “Oh another croissant?” I’d say and turn up my nose. But when the Pithivier came home, or the nougat – oh the nougat – or the divine tarts with apricots soaked in syrup, I couldn’t resist.

And of course, my weight started creeping up. I knew I had to cut back on the sweets, but in no way did I think I’d give them up altogether. I mean we all know that sugar isn’t good for you. I have a mouthful of silver to show for my many mornings of cinnamon toast crunch, and can still viscerally remember the horror of 1970s dentistry. But I figured, it’s not that bad – right? I just have to eat less.

But when we switched up our diet, many of the food blogs I’d been reading said two of the first things you have to give up are sugar and gluten. Gluten was easy enough, if somewhat of a pain, but sugar? Man, sugar was tough. It’s addictive, and the science has shown that it hits the reward centers in our brain just like heroin and cocaine. The blogs (like archevore for example) also said if you want to lose weight, than watch your fruit intake.

So what’s the deal? I mean, no one can argue that Cap’n Crunch is healthy, but fruit? Fruit is good for you.

Well, it turns out that what sugar cereals, fruit, and fruit juice have in common is not just sugar, but specifically, fructose. And fructose, my friends, is baaaaaaad for you.

Most people mistakenly assume that since sugar is natural it’s good for you, or at least we all know it’s better for you than High Fructose Corn Syrup (HFCS). But that’s not quite true. Regular old table sugar, or sucrose, is really composed of two sugar molecules: a glucose ring, and a fructose ring.

Every cell in your body can metabolize glucose, and indeed your brain needs glucose to survive. But the only place in your body that can metabolize fructose is your liver. The mechanics of the biochemistry behind this are pretty complex, but suffice it to say your body can’t handle too much fructose. Your liver treats it as somewhat of a toxin, not too dissimilar from the way it processes ethanol.

There have been two trends in the past 30 years (coinciding with America’s obesity epidemic): fruit available all year round, and highly processed and rewarding food with added sweeteners (either as sugar or HFCS), with the latter being a much more prevalent problem.

Want proof? Take a look at what the USDA says Americans are consuming:

Daily Food Intake

This graphic shows the mean daily intake (in calories) for six different major food types. The symbols are sized and colored to the proportion of total calories, and the numbers to the right of each dot represent the percentage of that item in our diet. It shows, for example, that just 8% of our diet comes from fruit and veggies, while 18 % comes from caloric sweeteners, and 24% comes from flour and cereal products.

So, according to the USDA, we’re eating too much “caloric sweeteners” and not enough fruit and veggies, despite many messages to the contrary. That’s a problem. I would argue, as would many people, that we’re also eating too many refined carbohydrates, but that’s a separate post. If the carbs are refined and processed and include added fats like soybean oil, and added sweeteners like HFCS, than it’s a major problem.

But let’s get back to the fructose and explore why fruit can be bad for you in excess, and why fruit juice really is bad for you.

Dr. Robert Lustig, from the UCSF medical center, has made a career out of studying childhood obesity. While as a society we can (and do) blame obese people for being gluttons and sloths, Lustig argues that we can’t say the same for obese kids. These kids are too young to develop slothful or gluttonous habits; it’s not their fault.

But people are brutal and pick on fat kids. Lustig notes that research shows obese kids report the same feeling of self-confidence that victims of childhood cancer do. In other words, not high.

Why are these young kids getting obese? Though there are many contributing factors to obesity, Lustig argues that one crucial culprit is fructose. Too much fructose overwhelms our liver, which in turn sends messages to the pancreas to secrete insulin to deal with the excess, which in turn causes our body to store the excess energy as fat. In today’s environment (think Big Gulp), this happens over and over again every day.

One additional fallout of this hyperinsulinemia is that over time chronically elevated insulin interferes with our body’s leptin signaling. Leptin is one of the key hormones that mediates the amount of body fat you are carrying around. If it’s working correctly, your brain controls your activity levels and your caloric intake to keep you in balance.

But if it’s not working, then your brain isn’t getting the message from your fat cells that you have enough energy stored for current metabolic needs. So your brain thinks you are starving, and sends a signal to eat even more and conserve energy. This is what happens in obese people with broken leptin signaling. They have more than enough fat, but the brain-body communication system is broken, and so they eat more and move less.

As Gary Taubes has said, people don’t get fat because they are gluttons and sloths, they are gluttons and sloths because they got fat. The brain is in control of this process, not your willpower (which is what I heard over and over again as a kid).

So we want to minimize our intake of fructose, which means minimizing sugar, and it also means eating fruit in moderation. Historically people didn’t eat a ton of fruit, and the fruit we did eat was seasonal. I’m old enough to remember when certain fruits appeared seasonally at the market, or at the farm stands near my hometown. I recall only having watermelon in summer, apples in fall, and citrus in winter. Yet this is no longer the case in America. You can get essentially any fruit at any time of year from anywhere in the world. So eat fruit, but eat it both in season and in moderation. I tend to eat not more than two servings of fruit each day.

But what about fruit juice? We clearly have evolved a taste for sugar. And we’ve evolved an ability to process fructose. Indeed there are times in your life when you want your leptin signaling to get blocked by insulin. Lustig argues that these are puberty and pregnancy, but more about this in a future post. So if our body can process fructose, and it’s “all natural” why would we want to avoid fruit juice?

A whole piece of fruit, i.e. as it came off the bush or tree, contains endogenous fiber. Fruit juice, in contrast, even if it’s “100% unsweetened all natural fruit juice,” contains no fiber but still has all the fructose. Since the fiber plays a key role in slowing down the absorption of fructose into the liver, when you drink fruit juice you overwhelm your liver and its ability to process the fructose. Your insulin rises, and you store the excess energy in your system as fat. Do this over and over again, even several times throughout each day as many American kids do, and you are heading for obesity and metabolic syndrome.

So what’s the takeaway from all this sweet information? Avoid added sugar (“caloric sweeteners”) to the extent that you can, and your body will thank you. Eat fruit and enjoy it, both for its flavor and the micronutrients it contains, but eat it whole, unprocessed and in moderation.

The next time you’re in need of a sweet treat, try the one that’s replaced my late night cereal fix: plain whole-milk Greek yogurt topped with cocoa nibs, toasted unsweetened coconut flakes and a tiny bit of fresh fruit. A shake of bee pollen wouldn’t hurt, either.

Here’s more for you to read, listen and watch:

Previous post:

Next post: