For years, doctors assumed “a carb is a carb,” that it didn’t matter if it came from an apple or a candy bar, the effects on blood sugar and insulin levels were the same. This didn’t seem right to many doctors so in the 1980s scientists set out to see if some carbohydrates raise blood sugar and insulin levels more or less than others even if they deliver the same amount of sugar into the bloodstream.
JOB 2: REDUCE YOUR GLYCEMIC LOAD
- Stop “Dieting.”
- Stop Worrying About Cholesterol
- “Low Carb” versus Low Glycemic Load
- The Sweet Spot: A Glycemic Load of 500 per Day
- How to Enjoy Sugar
- Intermittent Fasting
- Glycemic Loads of Some Common Foods (From Low to High)
For each food, they measured the amount of carbohydrate that the digestive system breaks down to sugar—the “available” carbohydrate. Then they fed volunteers whatever amount of each food it took to provide 50 grams of available carbohydrate. Sure enough they found that the sugar in some foods raises blood sugar and insulin levels more than the same amount of sugar in others even though the amount that eventually enters the bloodstream is the same. For example, 50 grams of sugar provided by white bread raises blood sugar levels twice as much as 50 grams of sugar delivered by carrots.
How high the blood sugar rises after eating a carbohydrate—whether fruit, vegetables, bread or potatoes– depends on how fast the digestive system breaks it down to sugar. The sugar in fruits and vegetables is surrounded by cell membranes and fiber, which protects it from digestive enzymes. The digestive system eventually overcomes these barriers and sugar enters the bloodstream, but the process takes time. The slower sugar enters the bloodstream, the less it raises blood sugar and insulin levels, again, even though the amount of sugar that ultimately enters the bloodstream is the same.
To compare various foods, scientists developed a measurement called the glycemic index. It reflects how much 50 grams of available carbohydrate in a food raises blood sugar compared with 50 grams of pure glucose.
Here is a list of glycemic indexes and loads of some common foods.
| Food | Glycemic Index | Typical Serving | Glycemic Load |
|---|---|---|---|
| Tomatoes | 15 | 1 Medium Size | less than 15 |
| Carrots | 50 | ! Medium Size | Less than 15 |
| Apple | 56 | 1 Medium Size | 78 |
| Table Sugar | 94 | 1 teaspoon | 35 |
| White Bread | 100 | 1-1 oz Slice | 100 |
While the glycemic index proved its point, it has limited value as a guide to eating. The problem is that the amount of a food it takes to provide 50 grams of sugar bears no relationship to the amounts people actually eat. Whereas two slices of bread will deliver 50 grams of sugar, it takes 7 full-size carrots to do it. Scientists later developed a more useful measurement, the glycemic load, which takes into account amounts of food people typically eat. Here is a more complete list of glycemic loads of common foods.
If you come to understand the difference between glycemic index and glycemic load you may find that you were avoiding a lot of foods you could be enjoying. For example, you might worry about adding a teaspoon of sugar to your coffee. Indeed, table sugar has a glycemic index as high as that of white bread–50 grams of table sugar will raise your blood sugar as much as 50 grams sugar released into your blood from the digestion of white bread. However, a teaspoon of table sugar only weighs 4 grams. You would need to add 12 teaspoons to your coffee to get 50 grams. The glycemic load of a typical serving—1 teaspoon—is less than a tenth of that of a slice of white bread.
You don’t have to worry about a teaspoon of sugar in your coffee, sprinkled on fruit or even in some candies. Sugar is very sweet. If it is not dissolved in water, as in sugar sweetened beverages, or diluted with starch, as in cakes and cookies, it doesn’t take much to make things taste sweet. For example, dark chocolate contains sugar but not much. The glycemic load of two squares of Ghirardelli’s dark chocolate is less than half of that of a slice of white bread.
No matter how sweet something is, as long as you don’t eat more than a few teaspoons of it, it won’t raise your blood sugar as much as, say, a slice of white bread.
Next topic: The latest fad (sometimes it works.): Intermittent Fasting
