IRA FLATOW, HOST:
This is SCIENCE FRIDAY. I'm Ira Flatow. How much soda, you know, pop do you drink a day? A can? More? Well, to put things in perspective: The average American drinks 57 gallons of soda a year, about 600 cans, and some of that, of course, is diet soda, it's sugar-free, but over half is not. And that's one reason there is so much added sugar in the American diet.
According to my next guest, Americans consume 450 calories of added sugar every day, and that is not counting fruit. He says all that extra sugar, especially fructose, can be toxic and hard on your liver, just like alcohol. In fact, in a commentary in the journal Nature, he proposes a solution: regulating and taxing sugary food and drink just as we do with alcohol.
What do you think? Is a sugar tax a good idea? Do you think education is enough? Is sugar really the enemy? Is it fat? We're going to talk about all these things with Robert Lustig, professor of pediatrics in the Division of Endocrinology, University of California, San Francisco. He's also head of the Weight Assessment for Teen and Child Health Program there. He joins us from KQED. Welcome to SCIENCE FRIDAY.
DR. ROBERT LUSTIG: Thank you so much, Ira, my pleasure.
FLATOW: You're welcome, and I want to let our listeners know they can join in. Our number is 1-800-989-8255. You can tweet us @scifri, @-S-C-I-F-R-I, go to our website at sciencefriday.com. That's a lot of sugar you're saying we're consuming, and you're saying it's really - is all sugar equal? Let's start with that question.
LUSTIG: All right, let's define what we're talking about. All food is inherently good. There is no bad food. God wouldn't do that to us. It's what we do to the food that's a problem. And what we do to the food, unfortunately, is a big problem. And it's not just the addition of sugar, that's a primary issue, but it's also the removal of fiber.
And the reason why fiber is so important is because it actually delays the absorption of sugar so that your liver has a chance to catch up. So it's both a dose phenomenon and a flux phenomenon. Both are going on at the same time.
The goal is to keep your liver healthy because when your liver is healthy, that means you're healthy. When your liver is healthy, your pancreas doesn't have to make as much insulin in order to make the liver do its job. That lowers levels of insulin throughout the body. And for the most part, that has been the single biggest problem that we have seen in not just nutrition science but endocrinology.
This phenomenon call metabolic syndrome is hyperinsulinemia, high insulin levels, insulin resistance, driving all of these chronic metabolic diseases that we know about: Type 2 diabetes, obesity, hypertension, lipid problems, heart disease, fatty liver disease, polycystic ovarian disease and likely early data suggests cancer and dementia, as well.
All of these are diseases of energy balance that are a problem at the level of the liver. So keeping your liver healthy is important.
FLATOW: And that's where the alcohol connection is, I'm thinking, because that's what alcohol attacks is your liver also, right?
LUSTIG: Exactly. Here's the way to look at it. Where do you get alcohol from? Fermentation of sugar. It's called wine. We do it here in Napa and Sonoma every day. The big difference between alcohol and sugar in terms of how your body deals with it is that for the alcohol, the yeast does the first step of metabolism, which in science is called glycolysis.
For sugar, we do our own glycolysis, but ultimately after that, the substrate, the product of that metabolism, is delivered to an area of the cell called the mitochondria. The mitochondria is the part of the cell that burns energy and creates chemical energy for your body to use.
If you overload your mitochondria, and it doesn't matter what the substrate was that got you there, you're going to end up having that mitochondria convert that to liver fat, and when your liver converts it to fat, it starts getting sick, and that is what we have seen.
People think this is about obesity; it's not because 40 percent of normal-weight people have the same metabolic defects as the obese do. This is a problem that extends way beyond your waistline.
FLATOW: And so - and you're also pointing out that it's fructose that is the real culprit here.
LUSTIG: So let's talk about, you know, the definition of sugar. So when you see sugar on the side of a package, that could be one of six different things. It could be glucose or dextrose, which is - for lack of a better comparison what you would find in Karo syrup. You don't see people going around chugging Karo syrup. It's not even that sweet.
It could be gallactose, which is a component of milk sugar, which is converted to glucose in the liver almost immediately. It could be fructose, which is the sweet aspect of sugar, the thing that actually makes us go seeking it. And that's the one that's metabolized completely differently. Or it could be a combination of glucose and glucose - that's called maltose, that's what you find in beer.
It could be glucose and gallactose, that's lactose, that's milk sugar. Or it could be glucose and fructose, and that's called sucrose, and that's cane table sugar, the stuff you put in your coffee.
Every one of those is recorded in that total sugars that's on the nutrition label, and you're not allowed to know which it is because the Food and Drug Administration allowed the food industry to basically combine them all together in an effort to basically confuse the public.
FLATOW: So are you saying then that we should regulate fructose?
LUSTIG: What I'm saying is that our current food supply is so glutted with fructose, that is added sugar, sugar that was put there very specifically for the food industry's purposes, both for palatability and for shelf life, that it has now created a toxic - basically a toxic side effect in our livers, driving all of these chronic metabolic diseases.
And the only thing that can reverse this is reduction in consumption. The question is how does one do that when, number one, the food industry is making money hand over fist because of this; number two, the federal government supports this because we export sugar all over the world. Six percent of all our exports are food, and they certainly don't want to admit to the rest of the world that there's a problem with added sugars in food because, you know, we'll stand to lose quite a bit of money.
There is no other method to deal with this. There's no drug target. Once you supply that much sugar to your mitochondria, bad things happen, and there's no way around it. So how do we get societal consumption of sugar to go down? One of the bigger problems is that sugar is also potential for abuse, that is dependency, for lack of a better word, addiction.
Numerous studies, both in animals and humans, show that the area of the brain, the reward center, is affected by sugar the same way it is by tobacco, alcohol, nicotine, cocaine, heroin, and therefore it fosters continued consumption.
So how do you regulate, how do you reduce the amount of consumption of a substance that is abused and toxic at the same time? We have not had any success with educational efforts alone. All of our success with any one of those substances of abuse have come through regulation. We're proposing that sugar be looked at in the same vein.
FLATOW: Why is it, then, that we evolved for eating fruits and honey and things that do contain sugar like that?
LUSTIG: That's a great question, and I can't tell you the absolute answer, but let me give you a little piece of evolutionary interest. We as human beings really only had sugar available to us one month a year, it's called harvest time. And the fruit would fall to the ground, we'd gorge on it, consume it like crazy. That would increase our adiposity, it would increase our fat stores very specifically.
And then what would come after that? Four months of winter, no food at all. And so putting on those extra pounds in advance of a four-month famine was actually adaptive and actually let us make it through winter so that we could repeat the cycle all over again. It was actually metabolically and evolutionary adaptive.
The problem is that we now have a maladaptive situation because sugar is available 24/7, 365 in amounts that has never been known to man previously. How do we know this is true? Because the orangutans in Papua New Guinea have what are known as masting fruit orgies every January when harvest time comes, and the food falls to the ground, and they do exactly the same thing. We assume that this must be the reason sugar was put here for us in the first place.
FLATOW: 1-800-989-8255. To the phones, to - let's go to Caroline(ph) in Murray, Kentucky. Hi.
CAROLINE: Hello.
FLATOW: Hi there. Go ahead.
CAROLINE: Well, I was (unintelligible). I know we - it's on the nutrition label, but sometimes it's hard to read. But I see cereal boxes that say now contains three grams of fiber per serving. Maybe it also needs to say also contains 26 grams of sugar.
FLATOW: Well, they have it on the box. That's on the box.
CAROLINE: So that it's right out there on the front of the box instead of the side of the box.
FLATOW: I got you.
LUSTIG: Well, here's the problem. The Nutritional Labeling and Education Act of 1990...
FLATOW: Thanks for the call.
LUSTIG: ...basically allows for the labeling of total sugars, not added sugars. It's the added sugars that we care about because the sugar that's in fruit is not a problem. You don't see a nutrition label on a pineapple. It's got plenty of sugar, but we don't need one because all food is inherently good. It's what you do to the food afterward that's the problem. And so when you add sugar and remove fiber, that's called processed food, and that's where the problem is. That's what we're really talking about. Sugar is just one manifestation of food processing.
We do it specifically for palatability, especially with the directive to decrease the fat in the diet, which it makes no sense at all when you understand the science of it. The point is that we could actually change the food label if we wanted to. We could, instead of saying what's in the food, we could say what was done to the food. And that would actually be way smarter.
FLATOW: So you think then that sugar, not fat, is to blame for the obesity epidemic?
LUSTIG: Look, we've had a reduction in percent consumption of fat from 40 to 30 percent over the past 30 years. And in the process, our obesity and metabolic syndrome prevalence has gone through the absolute roof. Now, in 1977, the McGovern commission dietary guidelines for Americans basically told us that we needed to reduce our consumption of fat. The question is: Where did that come from? Where did that directive come from? Very simple, in the early 1970s, we learned about this thing in our blood called LDL, low-density lipoproteins.
In the mid-1970s, we learned that dietary fat raised our LDL, which is true. And we also then learned in the late 1970s that LDL levels in populations correlated with cardiovascular disease. So the thought was if dietary fat raises your LDL and LDL raises your risk for cardiovascular disease, let's get rid of dietary fat, therefore cardiovascular disease would go down. That was the thought process. And the AHA, the AMA and the USDA all bought into this, and that is what was done, and the food industry went along with it.
They retooled. They reengineered all their recipes. That's how we got Entenmann's fat-free cakes. That's how we got Snackwell's. They're still with us. Bottom line, not only has it not worked, but it's actually made things way worse. Now, the question is: Was that logic rational? And I would pose to you that that logic was completely off base. Why? Well, number one, dietary fat does raise your LDL - that's true - but there are two LDLs, not one. There's one called large buoyant, and there's one called small dense.
When you measure your LDL levels in your blood, you measure both at the same time. It turns out the large buoyant has nothing to do with cardiovascular disease. They float. They go along inside your blood vessels. They're too large to get under the surface of the cells that line the arterial wall. They don't cause anything. The small dense ones, though, those are the ones that are driven up by carbohydrate, and they are small enough to get under the surface of endothelial cells.
They're the ones that start the foam cell process. They're the ones that start atherogenesis, and they're the ones that have gone through the roof, because when we took the fat out, the food tasted like cardboard. We had to substitute something. We substituted carbohydrate. So, yes, our percent fat went down, and our percent carbohydrate went up astronomically, and that drove hyperinsulinemia, drove liver fat, drove all the processes I've mentioned before, and that's how we got into this mess. We have to get out of it.
FLATOW: I'm Ira Flatow. This is SCIENCE FRIDAY from NPR. Talking with Dr. Robert Lustig, who is co-author of a paper in Nature that proposes a solution to this and that is regulating, taxing sugar and then drinks that have in there. Do you think this is practical or just something that you think is nice to think about but it's never going to ever happen?
LUSTIG: Well, look, here's the deal. We didn't think that a $12 pack of cigarettes would fly either, and that's what we have in New York City today. Ultimately, when the public recognizes what's going on, they're going to call for changes. And whether taxing sugar is the right way to do it or not is sort of not the issue. What we offer in the Nature comment is a panoply of societal interventions and changes that could ultimately lead to reduced consumption.
Obviously, people have picked on taxation because, number one, the question of a soda tax is currently on the table in many states. Anyway, it - obviously, it generates a huge visceral response, so the media love to harp on it. Ultimately, my issue is how do we get the added sugar out of the food that was put there very specifically for the food industry's purposes, not ours? And I'll be happy to consider any alternatives that ultimately lead to that ultimate goal.
FLATOW: You sound like - you sound very much like Michael Pollan. When people say, you know...
LUSTIG: Well...
FLATOW: ...eat like your grandmother did, you know?
LUSTIG: Well, very, very simple. Doc - I'm sorry. Mr. Pollan, who actually is a personal friend, has seven words. He said very clearly in The New York Times Magazine article: Eat food, not too much, mostly plants. I'm going to make it even easier for your listeners, Ira. Three words: eat real food. Because all food is inherently good, whether it's meat, whether it's fat, even whether it's carbohydrate because carbohydrate comes with its inherent fiber. And that's what ultimately mitigates the negative effects of carbohydrate.
It's refined carbohydrate, the processed carbohydrate that's the problem. The fat that occurs naturally, even saturated fat, does - it raises your LDL, but it raises the LDL that doesn't matter. It's the trans fat that causes significant cardiovascular disease. That's synthetic. That's added. In other words, if you ate what came out of the ground or you ate the animals that ate what came out of the ground, you would be fine. It's when you deviate from that, which is what our entire food industry has done for profitability and also for shelf life, that's where we get into trouble.
FLATOW: One quick question: Is honey a good sugar substitute or is that...
LUSTIG: Honey is exactly the same as cane sugar, beet sugar. It makes absolutely no difference, gram for gram, calorie for calorie, exactly the same. It is sucrose. The difference with honey is that because it has its own unique flavor and because it's relatively expensive people tend to use less of it. And anything that causes you to use less of it that's a good thing. But if you, you know, stacked it up and did a study where you gave somebody an equal amount of carbohydrate as honey and an equal amount of carbohydrate as refined sugar, basically it would do the same thing to your liver, and it would do the same thing to your brain.
FLATOW: All right. Dr. Robert Lustig, professor of pediatrics in the Division of Endocrinology, University of California, San Francisco, also head of the Weight Assessment for Teen and Child Health Program there. You can read his commentary in the journal Nature about what's wrong with our food system. Stay with us. Thank you, Doctor. We'll be right back after this break.
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FLATOW: I'm Ira Flatow. This is SCIENCE FRIDAY from NPR. Transcript provided by NPR, Copyright NPR.