We've spent two months doing something called The Sugar Files, which was mostly in praise of sugar.
In praise of sugar?

Yes, but I didn't praise it. I kicked it off with a depressing history of sugar, and my last contribution is talking to you about sugar and how it affects our lives and our health. It's often compared to drugs—do you think sugar is an addictive drug?
It's certainly not for everyone. Just as some people can drink in moderation, other people can't. And some people can smoke in moderation, and other people can't. I was someone who couldn't. I think clearly some people find it easier to consume no sugar at all, no added sugar, than to try to consume it in moderation. And because I'm one of those people, I guess I think everyone should experiment with no sugar and see how they feel. I got an email from a guy today who said he'd given up sugar now for months and he's still having what he considers to be a post-sugar rush. I'm probably going to steal that.

But there was that study with lab rats where they chose sugar water over cocaine and heroin.
Yeah but those are lab rats. Is it addictive to us? If you have children I don't think you need carefully done scientific research to tell you that this substance has some unique effect that no other substances do. But is it classically addictive? This is how it differs from other drugs.

With sugar, it’s sort of out of sight out of mind. If you don’t see it, if you're not around it, you’re not likely to crave it. Whereas with cigarettes, and I assume this is certainly true of heroin and cocaine and alcohol for alcoholics, if you make the attempt to give it up, your brain is definitely crying out from dysfunction. While quitting smoking there’s a three-week period where your brain doesn’t function right without nicotine doing whatever it does to the nerve endings, and clearly it's the same case for other addictive drugs. I've had people tell me that they go through cravings like that when giving up sugar, but they seem to be rare. Whereas I think for most of us, if it’s not around, you don’t really think about it. And even with my children, if it’s not around, they really don't think about it. It’s only when they’re confronted with it that they go ahead and eat it.

Most people don't realize or think about how prevalent sugar is in their daily lives, but it's everywhere. How did it become so prevalent?
That's why the first chapter is called Drug or Food? As you see sugar saturate diets, and it does, populations will consume as much sugar as they can afford, up to or even beyond the point where they become obese and diabetic. The question is does that happen because it's an inexpensive, useful nutrient that also happens to taste so good, or does it happen because it's a drug? It clearly has psychoactive properties, and it clearly influences that part of our brain that other drugs of abuse do, the reward center of our brain.

We forget that just 200 years ago, our average weekly sugar intake would have been the equivalent of the amount of sugar in a 12-ounce can of Coca-Cola. A number of the foods that are now the standard purveyors of sugar in our diets didn’t exist. Soft drinks didn’t exist, candy didn’t exist, chocolate bars didn’t exist. Ice cream was such an unbelievable luxury that if anybody had it, it would be written up in the newspaper.

All of this is the product of the industrial revolution. It all begins from 1840 onward, and it goes as long as sugar prices plummeted both because of endless improvements in harvesting and refining sugar, and the founding of the beet sugar and high fructose corn syrup industries.

Sugar used to be something that your system would have to deal with once a week. Pre-agriculture, you would get significant sugar from eating fruit seasonally, say one or two months a year. By the 1960s I think most Americans wouldn’t go three hours without a sugar dose. It’s that daily dosing of sugar that our bodies can’t cope with, and the result is obesity and diabetes. Not just because of the calories in that sugar, but because of the harmful effects of those calories. They’re not empty calories, they’re harmful calories.

Sugar is in virtually every processed food. In American white bread, up to 12 percent of the calories are from sugar, whereas in European white bread it’s closer to 2 percent. I found that interesting because I’m often asked, “Well if you think bread is so fattening, how do you explain French women eating it a bunch?” Part of it is that I think French women of a certain age don’t eat a lot of bread because they’re aware that it’s fattening. But their bread also has a much lower sugar content.

The last chapter of your book is called "How Little is Too Much?" But there isn't a definitive answer to that question. Do you think the best thing to do is completely avoid sugar?
There are two issues here. One is if you make the decision, which not everyone does, to eat the healthiest possible diet, can that diet contain some sugar, however we define 'some?' The answer probably very much differs by your health status. If you're predisposed to obesity and/or diabetes, or you're already obese or diabetic, I would argue that you're probably healthier with a diet that would not include sugar. If you're a 20-year-old marathoner and your parents lived to be 95 and are healthy, then go for it.

But I would still say you could do an enormous amount of good by avoiding sugary beverages, sweets, pastries, ice creams, all the things you feel guilty eating and drinking. You obviously feel guilty for a reason. You know they’re not good for you.

All the things that people consider treats.
I was a smoker. When you're a cigarette smoker, you can't imagine deriving pleasure from your life without cigarettes. Cigarettes completely saturate your day, just like sweets have, in the sense that you wake up looking forward to your first cup of coffee and your first cigarette, then you walk to work and smoke a cigarette, then you get to work and you're looking forward to your next cigarette. You have cigarettes after sex, you have cigarettes when you're angry, you have cigarettes when you're happy. They just modulate every emotional experience.

When you quit, the first three weeks you feel overwhelmed by cravings, it’s a constant struggle. You get past the first three weeks and the first three months and you’re just kind of angry and depressed and unhappy. In the first year you’re generally unhappy and there’s no real source of joy in life. Then by year two and three, you get to the point where you can’t imagine you ever smoked. The idea that at some point in my life I needed cigarettes to be happy is almost incomprehensible to me now, and I think the same thing is true of sugar.

It seems like there's so much evidence, and very clear evidence, against sugar. How does the industry get around that and deny that it's bad for us?
Up until recently our dominant dietary philosophy and public health policy was to get Americans to eat a low-fat diet. The way the food industry did that was to remove the fat from products and replace it with sugar or high fructose corn syrup and advertise them as health foods. So all the sugar industry had to do was let the nutrition and public health communities pursue their anti-fat campaign. It was good for sugar because sugar was something you could put in low-fat foods to make them taste good.

The other thing was “a calorie is a calorie according to our nutrition and obesity experts.” All the industry had to do was say “there’s no such thing as a fattening or fat-reducing food. A calorie is a calorie.” With that logic sugar is benign; it’s no more likely to cause obesity or diabetes than quinoa or kale. The key, they’d say, is not to eat it in excess.

Sugar is always at the scene of the crime in populations whenever dietary epidemics happen. The problem is you could make an argument that sugar has the gun necessary to commit the crime, but what you can’t do is find the smoking gun. You don’t have definitive evidence. If your standard of evidence is innocent until proven guilty, then I say, and I make this argument in the prologue, that we should rethink our relationship with sugar until somebody bothers to prove it innocent, if such a thing can be done. And arguably, that’s virtually impossible also.

Is it actually impossible to prove it guilty?
If you wanted to really demonstrate that sugar was the cause of obesity, diabetes, and heart disease, you'd want to do extensive studies. We did these studies with dietary fat and they didn't support the idea that dietary fat was the cause of heart disease. You'd want to take, say, 50,000 Americans, and 25,000 of them go on the Mediterranean diet with sugar and 25,000 of them go on it without sugar. You need to give them advice on how to do the diet, and then you've got to follow them for long enough that you would expect a significant number to get obese or lean, or to get diabetic, or for a significant amount of heart attacks to manifest themselves.

Since both groups are now eating healthy diets, or certainly healthier than they used to be eating, you might have to keep them on the diet for 10 years, which is excruciatingly hard to do because during those 10 years, they might end up reading articles about sugar being bad for you. So those on the diet with sugar might stop eating sugar. But let’s say you can keep everyone on their diets, and then at the end of 10 years you can see whether everyone on the diet without sugar is healthier than everyone on the diet with it. That’s how you’d definitively do it.

You could do other studies shorter term, what are called better-controlled studies, where you really watch what the people are eating so they don’t have a choice but to eat exactly what you’re giving them and exactly how much you’re giving them. You could swap out the calories of sugar from one diet with calories from something else in another diet, and you could probably demonstrate that sugar causes a lot of the symptoms of insulin resistance including fat accumulation in the liver, but you wouldn’t be able to demonstrate that people didn’t adjust to it with time.

This wouldn’t demonstrate that they actually get heart disease and diabetes or obesity from eating sugar; it would just demonstrate that you could just give them the risk factors, increase the risk of getting heart disease and diabetes over the course of, say, three months, which is about the longest you can do those studies.

It’s really hard to do, but if people thought it through, and if the government made a concerted effort, you could probably do all of this for a billion dollars. That’s about a day’s worth of costs to the healthcare system due to these diet-related illnesses. It’s hard to argue it’s not worth it.