Glycemic Index Versus Glycemic Load: Can Green Smoothies Cause High Blood Sugar Levels?

One of the questions I most often get is “Are green smoothies good for diabetics?”

The main concern is, of course, the high fruit content of the smoothie – and the resulting sweetness of the drink causing blood sugar problems.

This is an important topic, so I’m going to address it in a series of posts, providing you with the information that I have on this topic, as well as giving you some low-fruit or no-fruit recipes. But first, I want to talk about two important concepts for people with blood sugar problems, the glycemic index of foods versus glycemic load.

There is a widespread misconception that all foods that have a high glycemic index should be eliminated from the diet because of their ability to cause a rapid spike in blood glucose levels. Common theory supposes that a low glycemic index makes a food good for you, and a high glycemic index makes a food unhealthy. Many over-zealous anti-carbers have turned fruit and starchy vegetables into demon foods to be avoided at all costs.

This causes many people to avoid eating fruits & many of the sweeter/starchier vegetables.

This is a mistake.

The glycemic index (GI) ranks foods based on how fast they break down during digestion and thus how quickly their sugars enter the blood. So, in other words, the glycemic index tells you how fast carbohydrates turn into blood sugar. What the GI does not tell you is how much of that carbohydrate is in a serving of any food. Having both pieces of information is critical to correctly assess a food’s effect on blood sugar levels.

That is where the concept of “Glycemic Load” (GL) comes in.

Glycemic Index Versus Glycemic Load

While the Glycemic Index is most commonly known as an indicator to how healthy or unhealthy a food is, it is actually the Glycemic Load that you should pay attention to, not just the GI.

The Glycemic Index measures the speed at which a certain food raises blood sugar in relation to a control food. Glycemic Index uses a scale of 0 to 100, with higher values given to foods that cause the most rapid rise in blood sugar. Pure glucose serves as a reference point, and is given a Glycemic Index (GI) of 100. GI’s of 55 or below are considered low, and 70 or above are considered high.  However, GI alone is NOT an accurate measure of how much of a certain food raises blood sugar.

The Glycemic Load, on the other hand, ranks foods based on portion size and grams of carbohydrates per portion. This gives a much more accurate view of how foods might affect blood sugar. To calculate the Glycemic Load of a food, take the number of grams of carbohydrates in a serving, multiply it by it’s Glycemic Index, then divide it by 100. GL’s of 10 or below are considered low, GL of 11 to 19 inclusive is medium, and 20 or above are considered high. Foods that have a low GL almost always have a low GI. Foods with an intermediate or high GL range from very low to very high GI.

The glycemic load is a relatively new way to assess the impact of carbohydrate consumption, giving a fuller picture than glycemic index alone. A GI value tells you only how rapidly a particular carbohydrate turns into sugar. It doesn’t tell you how much of that carbohydrate is in a serving of a particular food. You need to know both things to understand a food’s effect on blood sugar levels.

To give you an example, the carbohydrate in watermelon has a high glycemic index, but there isn’t a lot of it, so watermelon’s glycemic load is extremely low.

Glycemic Index and Glycemic Load of Fruits

FRUITS Serving size (grams) Glycemic index (glucose = 100) Glycemic load per serving
Apple, average

38±2

120

6

Banana, ripe

51

120

13

Dates, dried

103±21

60

42

Grapefruit

25

120

3

Grapes, average

46±3

120

8

Orange, average

42±3

120

5

Peach, average

42±14

120

5

Peach, canned in light syrup

52

120

9

Pear, average

38±2

120

4

Pear, canned in pear juice

44

120

5

Prunes, pitted

29±4

60

10

Raisins

64±11

60

28

Watermelon

72±13

120

4

Via http://www.health.harvard.edu/

This table demonstrates that all fruit has a low glycemic load, except dried dates and raisins. It is best to eat fruit fresh, as drying and dehydrating concentrate fruit sugars to an unnatural level that the body is not designed to handle well. It is also important to eat fruit whole, not juiced, as the fiber in fruit slows sugar absorption to its natural speed.

When you eat fruit whole and raw, it is hard to get excess sugar from fruit. Fruit isn’t in the same category of foods as table sugar, high fructose corn syrup, maple syrup or candy. Fruit contains vitamins, minerals and antioxidants that counter-balance the potential harmful effects of the sugars in fruit. The fiber in fruit slows down the release of sugars, reducing the speed at which fruit may raise your blood sugar.

Glycemic Load of Vegetables

All vegetables are super-low on the glycemic load scale. They are basically glycemic-free (and guilt-free) foods!

The numbers are the grams of available carbohydrate (that is, carbohydrate minus dietary fiber) in 100 grams of the portion of the food):
low glycemic index foods
VEGETABLES:
Alfalfa seeds, sprouted 1.28
Arugula 2.05low glycemic index foods
Asparagus, cooked 2.63
Bamboo shoots, cooked 0.92
Beans, green, cooked 4.69
Beans, snap, green, cooked 4.68
Beet greens, cooked 2.56
Broccoli, cooked 2.16
Brussels sprouts, cooked 4.5
Cabbage, cooked 2.16
Cauliflower, cooked 1.41
Celeriac (celery root), cooked 4.7
Celery 1.95low glycemic index foods
Chard, swiss, cooked 2.04
Collards, cooked 2.1
Cucumber 1.8
Dandelion greens, cooked 3.5
Eggplant, cooked 4.14
Endive 0.25
Fennel, bulb 4.19
Green onions, young, tops only 3.94
Hearts of palm, canned 2.22
Jicama 3.92
Kale 3.63
Lettuce, butterhead 1.32
Lettuce, cos or romaine 0.67
Lettuce, iceberg 0.69
Mustard greens, cooked 0.1
Mushrooms 2.94-3.57 (except shitake)
Nopales, cooked 1.27
Okra, cooked 4.71
Olives, canned ripe 3.06
Parsley 3.03
Peppers, serano 3.00
Peppers, jalapeno 3.11
Peppers, sweet green 4.63
Peppers, sweet red 4.43
Purslane 3.43
Radicchio 3.58
Radishes 1.99
Rhubarb 2.74
Sauerkraut 1.78
Scallions (green onions) 4.74
Spinach, cooked 1.35
Squash, zucchini, cooked 2.53
Tomatillos 3.93
Tomatoes 3.54
Tomato juice 3.83
Turnips, cooked 2.9
Turnip greens, cooked 0.86
Watercress 0.79

Source: http://www.mendosa.com/freefoods.htm

Glycemic Load of Green Smoothies

The bottom line is that even if you include fruits in the smoothie, the overall Glycemic Load of the smoothie will still remain VERY LOW thanks to the low glycemic index of fruits and super-low (almost negligible) glycemic load of raw vegetables and greens.

For non-diabetic people, it is not needed to restrict consumption of fruit or green smoothies in order to prevent the disease, as there is no evidence that drinking green smoothies, or increasing fruit intake causes diabetes.

Limitations of the Glycemic Index and the Glycemic Load

Some proponents of the Glycemic Index (including many diet books authors) would like you to believe that GI and GL are all that matters when selecting which foods to eat. In reality, diet is a more complex issue than that.

Many other factors influence individual glycemic response, including preparation method, combination with other foods, as well as individual differences in glycemic response.

How the Glycemic Index can lead to overeating

Using the Glycemic Index and Glycemic Load can be misleading and lead to overeating.

Apples have a GI of 38, and a medium-size apple, contains about 18 grams of net carbohydrates and provides a Glycemic Load of 5. This is a low GL, and most would consider the apple to be a very appropriate snack. But now look at peanuts. A 4-oz serving not only weighs less than the apple, but has a much lower GI (14), and provides an even lower GL of 2. Based on Glycemic Load alone, you would have to believe that the peanuts were a better dietary choice than the apple. But if you take a look at the total Calories contained in these two foods, you’ll see that the apple contains approximately 77 Calories, while the peanuts contain more than 500! Those 400+ extra Calories are NOT going to help you lose weight.

The Conclusion?

Eat your fruits and vegetables! All of them! Any kind you like! And do it without guilt.

Instead of worrying about glycemic index of foods, make sure you consume lots of unprocessed, preferably raw plant foods: leafy greens, celery, cucumbers, tomatoes, peppers, etc., as well as raw fruits.

It would really be a major challenge to overeat vegetables and fruits. The average woman who needs at least 1500 calories per day would likely find it very difficult to eat 15 large potatoes or bananas. In general, vegetables and fruits fill you up long before you can eat enough to fill you out.

If you’re really worried about blood sugar levels or trying to lose weight, you may want to lay off the bananas, starchier tubers and root vegetables to speed up the process. But from a strict maintenance or health point of view, you should embrace all the vegetables and fruits you feel like eating.

The American Diabetes Association (ADA) says, “Therefore, the use of added fructose as a sweetening agent is not recommended; however, there is no reason to recommend that people with diabetes avoid naturally occurring fructose in fruits, vegetables, and other foods.”

Questions? Comments? Suggestions?

If you have a favorite recipe, why not submit it here in the comment section of this smoothie recipes blog for others to enjoy too!

I also welcome any comments, questions and suggestions. Thanks!


3 Comments

  1. Thanks for the post!

    I searched the web looking to see if green smoothies could potentially spike blood sugar enough to cause fat storage. Unbeknownst to me would I stumble upon the GI and GL tables for my answer.

    Usually, both an apple and an orange fill my blender everyday as the base of my smoothies. Sometimes I’ll throw in a lemon, lime, or other fruit as well. It’s when this third fruit is added I become concerned about too much sugar. But, you’ve quashed my worries with the informative write-up!

  2. Thank you so much for your info. My husband is borderline diabetic, both of his parents and all grandparents, aunts and uncles are also. We were told that he has a 95% chance of becoming diabetic simply because of heredity.
    I have been very concious of everything we eat, and bought a healthmaster to aid with eating more raw fruits and vegetables, and he has been enjoying them, but I also was wary of using too many fruits.
    We grow our own organic strawberrries, raspberries, and blueberries, along with a small vegetable garden, so we use quite a lot of fresh fruits, and am glad to see that this is not detrimental.
    Thank you again for taking the time to educate us, and keep us a little healthier!

  3. Normally, your blood glucose levels increase slightly after you eat. This increase causes your pancreas to release insulin so that your blood glucose levels do not get too high. Blood glucose levels that remain high over time can damage your eyes, kidneys, nerves, and blood vessels..,-:

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