Dear Science,

I have a friend who's really into healthy eating but subject to occasional sugar cravings. He claims that if you eat some meat prior to eating high-glycemic foods like rice, white bread, candy, and such, then the meat proteins slow the conversion of the sugars into glucose. True?

Sugar Skeptic

It probably makes sense that if you drink a huge tub of sugary soda, your blood-sugar levels will soon skyrocket. How high the blood-sugar levels reach after a meal is a function of how sugary the food is, how easily the sugar in the meal is digested, and how good an individual's body is at dealing with the absorbed sugar. The digestibility of the sugar in a food can be measured, and it can be turned into a measure—the food's glycemic index. The higher the glycemic index, the more quickly the sugar is absorbed.

You and your friend already know something that surprisingly few know: Many foods that do not look sugary and do not taste sweet are quickly and efficiently converted into sugar shortly after entering our lips. Starches—like those found in white bread, rice, and other simple grains—are chemically composed of sugar molecules chained together. Our bodies contain enzymes that can break down these sugar polymers into individual molecules. You can test one—amylase—by putting a morsel of plain white bread in your mouth and chewing but not swallowing for a minute or so. The amylase in your saliva will make the bread taste sweet, revealing the vast amount of sugar contained within even a bite of bread. Simple, starchy, "white" foods have high glycemic indices, shooting blood sugar skyward.

As to your friend's claim, several studies have been completed. A recent study in the British Journal of Nutrition by K. A. Hätönen and L. M. Valsta and others compared the spike in blood sugar after a meal of mashed potatoes to a meal of mashed potatoes with oil, chicken breast, salad, and combinations of those four items. As you'd expect, a meal solely of potatoes (near pure starch) spiked blood sugar about as much as drinking a pure glucose solution. Mashed potatoes eaten with oil or chicken dramatically lowered the spike in blood sugar, and thus the effective glycemic index of the meal. Salad, in contrast, did little to reduce the rise in blood sugar from the potatoes. Similar studies have been completed showing that eating nuts, fish, and other forms of protein with starchy meals can reduce the overall glycemic index of the meal.

Of course, wheat and rice come naturally with protein and fat to balance out the starch. It's only after all the processing—typical only in modern food making—that the pure starch is left behind.

Your friend is right: Some of the consequences from giving in to a sweet tooth can be helped with a bit of protein or fat.

Sweetly Yours,


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