You’ve probably read that the new No. 1 food villain isn’t fat or cholesterol. It’s sugar.
In fact, you’ve probably read it right here in one of my previous columns.
You might also be reading – not here, but elsewhere – that bread is just as bad for you as sugar. That the body can’t distinguish between the two and digests both the same way.
Not true, according to Robert Lustig, a pediatric endocrinologist at the University of California, San Francisco, and author of “Fat Chance: Beating the Odds Against Sugar, Processed Food, Obesity, and Disease.” Neither sugar nor most bread is all that good for you when consumed in more than moderate quantities. But they are metabolized differently by the digestive system.
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I asked Lustig to walk me through the chemistry, and, fortunately, you don’t have to be Walter White to understand it.
Sugar, Lustig explained, is made up of one glucose molecule bound to one fructose molecule. Enzymes in the gut cleave the bond so the glucose can be absorbed into the bloodstream. This triggers the release of insulin, which shuttles the glucose into the cells where it’s used for energy. Eat too much sugar, though, and the body will convert the excess glucose into “love handles” for your gut or extra padding for your butt.
In other words, you get fat.
Meanwhile, the newly liberated fructose is sent to the liver to be metabolized. Too much sugar and the excess fructose can overwhelm the liver’s ability to handle it.
The excess fructose is converted into fat, which either is released into the bloodstream as triglycerides, leading to obesity and heart disease, or stays in the liver, leading to the appropriately named fatty liver disease, which can cause diabetes and heart disease.
Meanwhile, bread (along with other starchy foods like rice, pasta and potatoes) is made up of long strings of glucose molecules. As with table sugar, if you eat too much bread, the excess glucose is converted into fat, which can lead to obesity and all its inherent problems (heart disease, high blood pressure, diabetes, etc.)
So what’s a bread lover to do?
Lustig said bread isn’t inherently bad. The problem is the processed flour used to make most bread is bone-white because all the good-for-you fiber has been stripped away.
But don’t assume whole wheat bread’s the answer. What you want instead is whole grain bread.
Think of a kernel of wheat as an egg. The kernel’s tough outer shell, called the bran, is where you find the wheat fiber. Inside the bran is both the endosperm which, like the egg white, contains carbohydrates and protein, and the germ, rich in nutrients like an egg yolk.
Whole wheat bread contains all three parts, but they've been pulverized and mixed together.
Whole grain bread, as the name suggests, is made with the complete, intact grain. Because the bran remains unbroken, it takes longer for the digestive system to break it down.
This is a good thing for several reasons. First, whole grain bread will keep you feeling fuller longer. Second, that slower absorption minimizes spikes in blood sugar and insulin levels.
And third (and coolest of all), that slow absorption rate means whole grain bread travels further down the intestine, where you’ll find the good gut bacteria we’re increasingly realizing are vital to health.
(According to one study, these bacteria outnumber the cells in the human body by 10 to 1. Who’s living off whom?)
Anyway, these bugs have to eat, and they thrive on the kind of carbs found in bread.
So not only will they keep you healthy, but the more they eat, the less you’ll absorb, which might also lower your risk of gaining weight.
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