Glycemic Load and Glycemic Index: What's the Difference and Why Does it Matter?

A few months ago I wrote about using the glycemic index (GI) ranking to manage weight and diabetes. Another measurement many use for weight and blood sugar management is Glycemic Load (GL). I was confused about the difference between these two systems so I spoke with registered dietitian and certified diabetes educator, Weiner, who straightened me out. This information may help you too.

(Editor's note: People with diabetes should speak to a qualified physician before starting a new diet.)

Q: What is glycemic load in very simple terms?

Susan Weiner: Glycemic load is a ranking system for carbohydrate-rich food that measures the amount of carbohydrates in a serving of food.

Foods with a glycemic load (GL) under 10 are considered low-GL foods and have little impact on your blood sugar; between 10 and 20 moderate-GL foods with moderate impact on blood sugar, and above 20 high-GL foods that tend to cause blood sugar spikes.

Q: How is glycemic load related to glycemic index?

SW: The glycemic index indicates how rapidly a carbohydrate is digested and released as glucose (sugar) into the blood stream. In other words, how quickly foods break down into sugar in your bloodstream. A food with a high GI raises blood sugar more than a food with a medium to low GI.

But the glycemic index does not take into account the amount of carbohydrate in a food. So glycemic load is a better indicator of how a carbohydrate food will affect blood sugar.

Here's a chart with carbohydrate foods' GL and GI

Q: If a food has a high glycemic index and a low glycemic load -- like graham crackers have a GI of 74 and a GL of 8.1 -- how will that affect your blood sugar?

SW: Food ranked high on the GI may represent a huge portion of a food because GI is not based on standard serving sizes. Basically, if a food is ranked high on the glycemic index it has readily available carbohydrate for quick absorption. However, the same food can have a low glycemic load because there may not actually be much total carbohydrate in a given serving of that food. A low GL is the better indicator that a food won't have much impact on blood glucose levels.

Here are two examples: Watermelon has a high GI of 72, yet a low GL of 7.21. The high GI is based on 5 cups of watermelon, not an actual serving size of 1 cup. The low GL means one serving of watermelon doesn't contain much carbohydrate, because it is actually mostly water. The low GL indicates that a serving of watermelon won't have much impact on your blood sugar.

Carrots are another example of a low GL food that many people think will raise their blood sugar a lot -- but it's not true. That's because carrots have a high GI of 71. However, what most people don't know, is that the GL for carrots is only 6. Therefore, unless you're going to eat a pound and a half of carrots in one sitting, an average serving of carrots will have very little impact on blood glucose levels. That said, juicing carrots -- which means consuming more carrots at once -- will have a greater impact on blood glucose.

Q: How can knowing the glycemic load and glycemic index of foods be used to make healthier eating choices?

SW: Everyone can benefit by eating a balanced diet of protein and fat, and foods that are lower on the GL and GI index. Foods with a lower GL and GI typically are high in fiber and nutrients and sustain your energy better throughout the day.

Also, knowing the GL of a food is a better indicator of whether that food will cause your blood sugar to spike. When your blood sugar spikes, the body releases extra insulin to bring down your blood sugar. If your body is asked to release extra insulin on a regular basis, it begins to lead to insulin resistance for many people and diabetes -- especially if diabetes is in your family.

Q: Can knowing the glycemic load of foods help people lose weight?

SW: Yes. Consuming low GL and GI foods keeps us satiated longer because these foods are more slowly broken down for glucose utilization. The result is that you feel fuller for longer.

When you consume high GL and GI foods, blood sugar levels spike which causes a short-term feeling of fullness, but then blood sugars plummet which causes you to crave food again and you ultimately end up consuming excess calories, which contributes to weight gain.

Q: If someone is trying to watch their weight, or has diabetes and wants to keep their blood sugar more stable, can you give us a sample low glycemic load menu?

SW: Here's a sample low GL menu:

Breakfast
2 egg omelet with ½ c. onions
Low-carb bread
1 tbs. almond butter

Snack
1 string cheese
Baby carrots

Lunch
3oz. grilled chicken
1 ½ c. baby spinach
½ c. cucumber
½ c. beets
1 tbs. parmesan cheese
1 small apple

Snack
½ c. broccoli
1 tbs. light ranch dressing

Dinner
3oz. salmon with mango, corn, cilantro salsa
6 spears of asparagus drizzled with extra virgin olive oil
8 oz. seltzer

Dessert
4 oz. sugar-free pudding

Q: How seriously should we take all this?

SW: Some evidence suggests GL and GI diets can benefit overall health -- especially for people with diabetes, although, more conclusive research is needed to know for sure.

People who favor these rankings feel that GL and GI diets can help in the treatment and prevention of chronic diseases. Detractors note that selecting foods only by using GL and GI could cause people to choose bacon rinds over watermelon. I think we each have to decide for ourselves.

Riva is the author of 50 Diabetes Myths That Can Ruin Your Life and the 50 Diabetes Truths That Can Save It and The ABC's Of Loving Yourself With Diabetes. Visit her web site Diabetes Stories.com.

 

 

 

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Comments

[lifeaftercarbs]

08:08 PM on 07/09/2011

If I understand this correctly, glycemic load is just the carb-count of a serving of a given food, expressed as a rank, and has no relationship to glycemic index, which is a measurement of how fast or slow a food affects blood sugar response. Wouldn't there be a multiplier effect if a person piles one low GL food on top of another? It seems more precise to count carbs. But I can see GL rankings being simpler to remember, perhaps.

[Susan Weiner R D]

02:22 PM on 07/12/2011

This article points out the differences, limitations and helpfulness of using GI and GL. GL was developed as researchers realized the limitations of only using GI. Additionally, there is not a glycemic index for all GI foods which also limits the usefulness of only using this tool for daily meal planning and blood sugar control. While most people with diabetes find it more useful to carbohydrate count, it's good to familiarize yourself with GI and GL values. They are another tool for meal planning and can help you better understand foods' impact on blood sugar. That said, then use what works best for you.

[thebigbike]

03:11 PM on 07/07/2011

I appreciate the information and the caveat about relying ONLY on GI, without taking the "load" into account. this would support my intuitive rule of thumb which favors vegetable fibre as a "modifying" influence. Though my experience with watermelon is that it spikes my bloodsugar like a sugary soft drink. Not so with cantaloupe, and in between the two is honeydew melon. Canned orange juice gives me some of that spike, but fresh squeezed, with lots of pulp, seems much more moderated. Of course some of that could be just psychosomatic. As you note, we're all a little different

[Riva Greenberg]

07:22 PM on 07/01/2011

GL and GI are just another tool to use to eat a healthy diet, and they can help avoid blood sugar spikes. One should always take into account one's own circumstances, goals and learn what works for your body.

[Mark Koekemoer]

06:19 AM on 07/01/2011

I don't think a diet following GL can work when you need a lot of calories throughout the day, so for an athlete it seems like it would not be beneficial. But I've seen it often made famous by the Holford diet, and been quite interested, so I guess it's a really good eating plan to lose weight.

[polishlogician]

11:44 PM on 06/30/2011

"Carrots are another example of a low GL food that many people think will raise their blood sugar a lot -- but it's not true."

wow, and for years I labored under the misconception that too much dinner would spoil my carrots for dessert...

[libwingoflibwing]

09:46 PM on 07/04/2011

If carrots are cooked enough to lose their crunchiness, then they are bad for your blood sugar. But if they are raw or only cooked enough to heat them up, such as adding them at the end of a soup or in a stir fry, then they are good for blood sugar control.

[Howard Ahrenberg]

08:45 PM on 06/30/2011

Thats quite a grocery list for 1 day.
Here is my meal guide for 1 day...1 small serving of whatever i can scrape together. ill assume the demographics of your readers is either upper middle class, or baby boomers. if you want to really help us out tell me how to make 52.00 a month in food stamps cover that kind of diet.

[libwingoflibwing]

09:50 PM on 07/04/2011

Start a vegetable garden. If you are in an apartment see if there is a community garden you join. If you can't do that you can still grow some of your own veggies in pots, especially fresh herbs.

Buy dry foods, like beans. That will stretch your food dollars. White rice is not healthy if you're concerned about blood sugars, but long grain rice and wild rice are the best. Buy those too in dry goods, another way to stretch your food dollars.

I hope you have good luck on trying to combine your low food dollar budget and eating healthy. You are in my prayers. Bless you.

[Ranveig Elvebakk]

03:36 PM on 06/30/2011

Same idea, only Glycemic Load makes it more complicated (and is unnecessary) for the patient to learn. Sometimes used as an academic tool.
Most people are well served (so to speak) by understanding high, medium and low Glycemic Index of carbohydrates.

[libwingoflibwing]

09:51 PM on 07/04/2011

Just remember that fresh fruit is good because of the low GL.

[SW84]

08:58 AM on 06/30/2011

GI values have little real world relevance, they were calculated on people in a fasted state using isolated foods.

as for this,

"SW: Yes. Consuming low GL and GI foods keeps us satiated longer because these foods are more slowly broken down for glucose utilization. The result is that you feel fuller for longer. "

maybe the author and dietician should read these studies which do not find that low GI or GL foods are more satiating

Kiens B, Richter EA. Types of carbohydrate in an ordinary diet affect insulin action and muscle substrates in humans. Am J Clin Nutr 1996;63:47-53.

Holt SH, Miller JC. A satiety index of common foods. Eur J Clin Nutr 1995 Sep;49(9):675-90

[laurenmg]

06:55 PM on 06/29/2011

Thanks for clarifying this. I hate when people say that I should avoid watermelon and carrots because they're full of sugar. Get real!