When I was writing for the Opinion section of the Times, I had a number of close advisors. On nutrition matters, I came to rely more and more heavily on David Katz. Later, we became friends and, in 2018, I asked him to sit down and talk with me about how we should be eating, for a Grub Street piece which ran (untruthfully) as “The Last Conversation You’ll Ever Need to Have About Eating Right.”
The response was tremendous, as one of the most-read articles of the year — not just in food; not just for New York Magazine, but online, period.
What we didn’t realize until then, was the degree to which people are looking for guidance on how to eat from people they can trust. And that we qualified.
The net result is our new book, “How to Eat: All Your Food and Diet Questions Answered.” In it, we answer what we gathered and hope are the most pressing questions about diet that confront many readers. We think it’s a useful tool to understand, commit to and maintain a truly healthy diet, and one that will serve as a useful counter to all the bullshit out there. Here’s our second excerpt.
“How to Eat” by Mark Bittman and David L. Katz, M.D., is published by Houghton Mifflin Harcourt and is available here on March 3.
Should I worry about the high sugar content of fruit?
No. Although we understand why you’re asking that, since there’ve been two major fads that renounced fruit in recent years. The first was the glycemic index; the second, fear-mongering about fructose.
What’s the glycemic index?
“The glycemic index is a measure of how much a fixed amount of sugar in various foods raises our blood sugar. High blood sugar, which can lead to diabetes, is a bad and dangerous thing.
And fruit has a high glycemic index?
There’s a relatively high glycemic index for some fruits, and even for some vegetables. The conclusion was that these fruits drive up blood sugar, and the next conclusion was that fruit must increase the risk of diabetes.
That contradicts all your principal ideas about good, plant-based diets including fruits!
Not to mention that the fear over glycemic index also extends to vegetables like carrots.
Well, is the glycemic index a reliable way to judge the healthfulness of a food?
No. The measure has value, but judging a food based only on the glycemic index would be like judging a person’s character based solely on, say, shoe size or bowling average. The glycemic index measures how much blood sugar goes up from the same amount of sugar in different foods. The problem with assigning that measure to fruit or carrots is that to get to the same amount of sugar from carrots and ice cream, you need a very tiny serving of ice cream versus a lot of carrots.
Judging a food based only on the glycemic index would be like judging a person’s character based solely on, say, shoe size or bowling average.
It doesn’t account for the concentration of the sugar. This is the crucial distinction. Imagine, for instance, if we told you one person weighed 100 pounds and another weighed 200 pounds and then we asked you: “Who’s overweight?”
Obviously the 200-pound person.
But what if we now told you that the 100-pound person was a 5-year-old boy, and the 200-pound was a 6-foot-5-inch man. That turns the tables: The man is very lean, while the child is seemingly obese, and thus “heavier” relative to height. Sugar is present in carrots, but it’s pretty dilute. It’s concentrated in ice cream. The glycemic index misses that distinction.
Is there a better way to understand the sugar content of foods?
Yes: the glycemic load. That does account for the concentration of sugar in a food, essentially adjusting for sugar concentration the way the body mass index (BMI) adjusts weight for height.
Does focusing on the glycemic index lead to any positive health effects, like weight loss or lowered blood sugar?
No. Studies have found an association between routine consumption of whole fruit and lower risk of obesity and diabetes. No one becomes obese or diabetic from eating carrots! We are generally making a mistake when we become obsessed with just one measure, any one measure, and think it’s all that matters about a food.
You also mentioned fructose. Is it bad for you?
Our fixation on fructose is a variation of our obsession with the glycemic index. Many people started highlighting the potential harms of fructose. But fructose is fruit sugar. So it’s in apples, bananas, peaches, and every other fruit. And many vegetables as well.
But high-fructose corn syrup is bad, right?
While fructose is a natural sugar found in plants, high-fructose corn syrup is processed in factories by extracting and mixing fructose and glucose from corn. There are different versions, but on average the high-fructose corn syrup in the food supply is about 55 percent fructose, 45 percent glucose. Sucrose, or table sugar, is 50:50. But while there are differences in how they are metabolized, high-fructose corn syrup and table sugar are more alike than they are different in their effects on health.
Then why have we been led to believe that fructose is worse for us than sugar?
The usual: a bit of legitimate science, a lot of hype and distortion. Some particular harms have been associated with fructose relative to glucose — notably, the production and accumulation of lipids in the liver, leading to the condition known as fatty liver. This, combined with the quantity of high-fructose corn syrup in the food supply, led to a backlash against it. That, in turn, got distorted into the idea that all fructose was bad, and that all foods containing fructose were bad, and the next thing we knew, people were renouncing fruit!
What’s the truth about fructose?
The truth about fructose is a lot like the truth about every other nutrient: It’s the food that matters. Fructose on its own is generally found in fruits and vegetables, and those, of course, are almost invariably good for us; they defend against obesity, diabetes, and fatty liver.
High-fructose corn syrup doesn’t occur in any natural food, so it is always a marker of a highly processed food. That food is apt to be bad for you for any number of reasons, the high sugar (fructose) content among them. The same is true of any added sugar, like sucrose, in a processed food: A load of added sugar is going to be bad, and may well be accompanied by other liabilities. But whole fruit is good for us, and the fructose in it does not change that. We don’t extract nutrients from food and live on those; we eat food and then the body processes all the nutrients in them. Eating fruit is not eating fructose; it’s eating fruit.
So fructose is like other sugar?
The person most famously associated with chronicling the particular dangers of fructose, endocrinologist Dr. Robert Lustig, never recommended that people give up whole fruit. His particular concern was high exposure to fructose from added sugar, both high-fructose corn syrup and “regular” sugar.
Is there a good reason to use sugar substitutes?
Well, they’re intended to take sugar out of your diet, take calories out of your diet, and not stimulate an insulin response, therefore — in theory — reducing the risk of weight gain, obesity, and diabetes.
Do they work? Do they do all those things?
It’s not entirely clear. One of the biggest concerns about sugar substitutes is that they do nothing to file down a sweet tooth. If anything, they feed it and help grow it into a sweet “fang.” Because although they may satisfy the craving for sweet, artificial sweeteners are intensely sweet: They range in sweetness intensity from 600 to 1,300 times as sweet as sugar. So even as they satisfy a craving, it might be that they’re cultivating sweetness cravings.
So I’d be better off drinking “real” soda?
The best thing to do would be to not drink any soda, and, for that matter, to not add any sweetener — whether sugar or artificial sweetener — to your coffee or tea.
But my coffee tastes so much better when there’s a little bit of sweetness.
For now it does, but you can retrain your palate. Rather than focusing on how artificial sweeteners are lower in sugar and calories, you might focus on changing your taste buds’ sensitivity for sweetness.
Right, taste bud rehab.
Yup. Artificial sweeteners don’t help with that. We think of artificial sweetener like a Band-Aid. Of course, if you’re bleeding from a cut, a Band-Aid may help. So, we don’t rule it out as valuable. But it’s a temporary solution. For that cut, the long-term solution is for it to heal. For sugar intake, the long-term solution is to “heal” your diet so it’s not loaded up with sugar and other sweeteners. That way, you won’t be eating much sugar and you won’t need to rely on artificial sweeteners to replace what you are already avoiding.
Are there other concerns about artificial sweeteners?
The direct concern is that these artificial sweeteners are exactly that: artificial. They are foreign chemicals that aren’t native nutrient components of food. Studies in animals have shown that artificial sweeteners can disrupt the microbiome.
What does that mean?
Your microbiome is the collection of bacteria that live in your GI tract. With artificial sweeteners, you put a chemical in your food and the bacteria say, “Hey, we don’t recognize this.” They get upset.
How do these disruptions affect my health?
That’s the particularly vexing part. The disruptions of the microbiome that result from artificial sweeteners have been shown in several studies to be directly related to the development of insulin resistance. Insulin resistance is a precursor to diabetes, one of the things that avoiding sugar helps us prevent. So, it’s ironic that chemical substitutes for sugar may contribute to the very problem they are intended to help us dodge. To be fair, the literature is still murky. There are some studies that show that sugar substitute-sweetened beverages and foods do help people reduce sugar and calories in the short term, so there may be some advantage. But longer-term studies show the sugar and calories cut out from one place sneak back in someplace else. And that the sweeteners themselves can do harm in other ways. So, there’s reason to be cautious, and to minimize your reliance on sugar substitutes.
OK, so back to sugar: Is it possible for me to train my palate to become someone who “just isn’t a dessert person” or who “only likes dark chocolate”?
In fact, yes.
If you eat a diet with minimal additions of sugar, you can satisfy your cravings for sweetness with a lot less of the stuff.
Because you become a lot more sensitive to it. The more sugar and sweetness you eat, the more it takes to feel satisfied. The less you eat routinely, the less it takes.
Almost like a drug?
Yeah, sugar has been compared to any other addiction: The more you feed your craving for it, the more it needs. It’s called tolerance.
So it’s possible to be addicted to sugar?
It depends on how one chooses to define “addiction” — those views vary — but for all intents and purposes, yes, because one of the characteristic traits of addiction is tolerance. The more you get, the more you need. You may satisfy your craving for sugar in the moment, but you cultivate the craving over time.
So what do you recommend?
Like we said, taste bud rehab. Learn about all the places sugar is hiding in your diet where you don’t want it in the first place — like marinara sauce and salad dressing — and pick versions of those that don’t have all that added sugar (or make them yourself). Bottled tomato sauce may have more added sugar (relative to calories) than bottled chocolate ice cream topping.
That freaks me out a little. Who would buy that sauce?
A lot of people, because they don’t know the sugar is there — but they like the way it tastes. Ditto for salad dressing, breads, pretzels, chips, and of course breakfast cereal — where sugar is, at times, the main ingredient. It’s safe to say that there’s added sugar in almost every highly processed food. Manufacturers know that because we have that sweet fang, these things appeal to us. You might be eating a variety of processed foods to get the sugar you crave even if you’re using an artificial sweetener in your coffee. Either cook, or look at the ingredient list on products. If there’s added sugar in there, pick something else.
But that still leaves the question: When I do consume sweet foods and drinks, should it be artificial sweetener or the real thing? Diet Coke or regular?
As long as sugar occupies a small place in your diet, we would recommend the real thing; a Coke a week isn’t going to kill you. But think of our mantra, “Instead of what?” You’re really better off with a peach and a glass of water.
Are the new sweeteners like stevia any better?
“Natural” sugar substitutes, like stevia or monk fruit extract, aren’t as intensely sweet as older artificial sweeteners. And in comparison to Splenda (for example), stevia is better because it isn’t a totally foreign chemical that disrupts the microbiome. (It’s even been shown to have an insulin-stabilizing effect.) And since eating less sugar is beneficial, these natural sugar replacements are promising. But the research isn’t conclusive.
Is there any tried-and-true way to lessen my addiction to sugar?
It’s a quantity problem, really. The more you push sugar to the margins of your diet, the better. Focus on the usual: vegetables, nuts, seeds, whole grains, lentils; beans, and fruit. You don’t need any of the sugar that’s in processed foods. Then, if you have an occasional soda or ice cream as a treat, that’s fine, because it no longer matters very much — you’ve already solved the bulk of the problem.
So how much sugar can I eat?
Generally, the recommendation is that at most 10 percent of calories can come from added sugar. But 5 percent, or about five teaspoons a day, would be better. If you’re thinking in terms of 2,000 calories per day, that’s a small soda, or a teaspoon of sugar in each of five cups of coffee, or some ice cream, or sweetened yogurt . . . We’re not saying “don’t eat sugar.” We’re saying “don’t eat a lot of sugar.”