Monday, February 7, 2011

The nutritional value of beets: Part 3 - Glycemic Index and Glycemic Load

Beets are an excellent source of complex carbohydrates and they are high in fibre, making them a valuable addition to a healthy, nutritious diet. But what about their scary GI?

Beets, the GI Cinderella
For the purpose of the Glycemic Index (GI), warnings have been forthcoming that beets are high in sugar and should be avoided. It is true that when we examine the bare facts (provided by the USDA National Nutrient database), the data look scary.

Nutrient value
Percentage of RDA

45 cal
9.56 g
1.61 g
Total fat
0.17 g
0 mg
Dietary fibre
2.8 g
6.76 g

Really? That many calories in 100 grams (about half a cup) of raw beets? That much sugar?

When we examine the data above, we find that the combined totals of dietary fibre and of sugar are equal to the total of carbohydrates. We need to examine what those quantities signify and, when we do, we'll discover that beets have been victims of bad press because the real story is all about good stuff, i.e., complex carbohydrates and dietary fibre, not about sugar.

But first, we need to wrap our heads around two terms: Glycemic Index and Glycemic Load.

(1) Glycemic Index (GI): This is a measure, on a numerical scale, of the rate at which blood sugar level is elevated when a food is consumed. 

There are two types of GI. One, the original, is based upon the consumption of glucose, a simple carbohydrate. The GI value of glucose = 100. The second is based upon the consumption of white bread. Eating this starch, which is another simple carbohydrate and which is made of refined white flour, elevates the blood sugar level even more quickly than does taking glucose. The GI value given to white bread is also 100. 

This makes the GI confusing because one really must know which food is the base measure before the GI value can be meaningful. Frequently, no indication of the base food is given when GI is discussed. For us at this juncture, it is sufficient to know that a food's GI is measured against one of these carbohydrate standards and that the higher the GI is the more quickly blood sugar levels will be elevated.That's the theory, anyway.

Using the GI standard based upon glucose, beets (the roots, raw and fresh) rate a GI of 64. That's scariness of the moderate to high kind.

But there's something else one needs to know before relegating beets to the Off-Limits Fat-Blob No-No Bin along with the chocolate cake, doughnuts, deep-fried chicken, and ice cream, and that is the Glycemic Load.

(2) Glycemic Load (GL): This is the measure, again on a numerical scale, of carbohydrate in a quantity of food. There are three categories of GL: high, medium, and low.

High = 20 or greater
Medium = 11 - 19
Low = 10 or less

While beets have a high GI (64), they have a GL of 5, which is low

Why is this true? It is because, while the carbohydrate value of ½ cup of raw beets is 9.56 g., and that carbohydrate has a high GI, there isn't much of it in beets. Why? Because beets are high in dietary fibre.

When ingesting the bare GI and GL facts, we need to take into account other facts behind these data. And the most telling facts we need to know are:

(a) the more complex the carbohydrate's structure is, the more difficult or impossible it is to digest.
(b)  dietary fibre is carbohydrate composed of sugar attached to other molecules in complex structures that are impossible to digest.

Therefore, although beets are high in sugar, a significant quantity of that sugar cannot be released into our blood system because it is locked into indigestible dietary fibre. 

This makes the health benefits of beets fairly obvious, and it shoos away the scariness of the bad press that beets have received.

See also:


Barry said...

That is quite interesting. Beets would be an excellent food for hiking. Like beet jerky or something similar. I understand potatoes are high glycemic as well, but I don't care because I really like potatoes and life is short. I focus on fibre.

June Adams said...

Barry, I have no idea whether potatoes are rated high on either GI. If I was using a glycemic measure, I'd focus on GL since that tells the most important story. Beet jerky? Ha-ha-ha, that would be a good trick. I suppose it would be possible to make dried beets.

2chickipoos said...

I wonder if you slice beets thinly and lay them on a cookie sheet in the oven witha little olive oil sprayed on the pan & on the beets if they work for the hiking snack. Hmmm...have to give that one a try for skiing.

June said...

That sounds like an interesting experiment. I propose that you try it, document it, and let me know how it works. Then, if you like, you will be able to publish it on my site as a guest blogger. What do you say?