Health & Fitness
Sugar is Sugar?
Simple introduction to the the Glycemic Index - what is it & what's it used for!
Sugar is sugar is sugar, right? Not exactly...
If you're diabetic, Paleo, or following any popular diet plan, you are told to watch your sugar intake. While it is true that all sugar (glucose, sucrose, dextrose…) has the same type of effect on your body, the intensity and duration of that effect depends on type of food you eat. This is what people are talking about when they refer to Glycemic Index.
What is the Glycemic Index?
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Very simply, the Glycemic Index (GI) is a chart that compares the time it takes your body to break down different types of food into glucose. How? By measuring blood glucose (sugar) levels before and after each type of food is consumed.
The Glycemic Index was developed in 1981 by Dr. David Jenkins from the University of Toronto. He was researching why diabetic patients were having trouble controlling their blood sugar, even though they were following the prescribed diabetic diet at the time. Dr. Jenkins found that different types of carbohydrates have a different effect on glucose levels. For example, patients who ate pretzels had a higher glucose reading than patients who ate peanut butter.
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The Glycemic Index runs from 0 (no effect) to 100 (pure glucose). The higher the GI value, the more rapidly a food is digested and converted into glucose in the body. A high GI level indicates a fast conversion, which leads to a “spike” in blood sugar levels. It causes that sugar “rush and crash” we experience after eating a candy bar. A low GI value means a slower release of glucose. This is important because the body is always trying to maintain a steady state of chemicals in the blood. If glucose rises to a certain level, the body generates insulin to process it. If it can’t handle the amount of sugar in the bloodstream, the body converts it to fat. For diabetics, the insulin system is already disrupted, so the body works overtime to process any sugar consumed.
I Love Lucy…but not that much!
Do you remember the I Love Lucy episode in which Lucy and Ethel worked in a candy factory? The conveyer belt was running so fast that our heroines couldn’t keep up. Some candy made it into the boxes but mostly it fell on the floor, they stuffed it in their mouths, and crammed more in their shirts! What a mess! Now imagine your blood stream as the conveyor belt – it runs wild every time you eat a high GI food.
If you’re diabetic, like my husband, high GI foods spell trouble! He controls his Type 2 Diabetes by diet (not too tough, living with a Paleo wife!). But on vacation a few weeks ago, he had more than his share of pizza, ice cream, and Coca Cola! Each day his blood glucose levels were elevated...at first not bad…then a bit worse…pretty bad…and BANG! 55 points higher than he’s ever registered! (196, if you’re curious).
There was one day in particular he was exhausted, feeling crappy, and not hungry…but craving sugar and caffeine. Guess which day? You know the answer: he felt terrible the day his glucose shot up! All that extra sugar in his diet caught up with his body. When you work all year for a week in the sunshine, is it worth even a single day you’re too tired to enjoy it?
My husband found out the hard way: he’d rather exchange that ice cream in the park for the energy to run around with his kids the next day.
So what can I eat?
The GI Index is helpful when you’re deciding on a bagel vs. eggs for breakfast…or whether to have that soda vs. an iced coffee. A plain bagel has a GI rating of 72, while an egg has 0 (it’s a protein – no glucose in protein or fat). What about an apple for snack or graham crackers? 39 vs. 74. Want a banana instead? Its GI is 62 – better than graham crackers, but your best bet is that apple!
It’s tough to remember the GI for every food you eat. But there are many lists available on the Internet. Harvard has a nice chart of 100 common foods:
http://www.health.harvard.edu/newsweek/Glycemic_index_and_glycemic_load_for_100_foods.htm
One simple rule of thumb is this: grains, starches and sugars cause sugar highs and leave you craving more in an hour. Protein and fat keep your blood sugar even and you from falling asleep at 2 p.m. because your blood sugar dropped!
Ever wonder why some mornings you’re so hungry your stomach feels like it’s turned inside out? Think about what you had to eat the night before. Chances are, it was a high GI food (dessert, anyone?). When my last meal at night was dinner (salmon and asparagus, not pasta and Italian bread), even if it was early, I’m hungry the next morning but not ravenous. I can wait a bit to eat a healthy breakfast. I don’t need to stop for a donut on my way to work!
I’m hearing about something called the Glycemic Load – what’s that all about?
The Glycemic Load (GL) is another way to measure the effect of glucose on your blood sugar…if you love math! The GL looks at the grams of carbohydrates in a serving of food, whereas the Glycemic Index uses100g of carbohydrates in a food, regardless of portion.
Lets look at a banana vs. watermelon. A banana has a Glycemic Index of 53. It’s pretty dense, with not a lot of water content (~20% carbs by weight). Its Glycemic Load is 10.5. Compare that to watermelon, which has a GI of 72 – higher than the banana. But it’s full of water (only 5% carbs by weight), so a serving of watermelon has a Glycemic Load of 3.6 – much lower than the banana!
It makes sense – you don’t eat 100g of “watermelon carbohydrates”, you eat a cup of watermelon! But here’s the catch: the Glycemic Load is calculated based on the food’s available carbohydrate, times the food's Glycemic Index value, divided by 100 (AvCarb x GI / 100). You need to know the Glycemic Index value in order to calculate the Glycemic Load.
So even though the GL is rated by serving size, most people find Glycemic Index lists more available and just as effective to guide their food choices. But the Glycemic Load definitely has its place if you are focused on portion and serving size.
What about plain old…sugar?
Sometimes we want sugar in our coffee…or maple syrup on our pancakes. What does this do to our glucose levels? White table sugar has a Glycemic Index rating of 64, the highest of common sweeteners, but it is actually lower than some non-sweet items like rice (89) and wheat bread (71). Sweet taste and glucose impact aren’t related - it is how quickly the food is broken down into sugar!
Coconut sugar (sometimes called “coconut crystals”) is the lowest of the natural sweeteners. Coconut sugar is made from the sap of coconut flowers and is lower on the Glycemic Index than white table sugar, so it is a good alternative. It looks and tastes a bit like brown sugar, so don’t worry about your baked goods tasting like coconut!
The more you know…
This is just a taste (pun intended!) of the science behind the Glycemic Index. For more information on GI, GL, and sugars, here are some informative websites and articles:
http://www.fitsugar.com/Glycemic-Index-Where-Do-Sweeteners-Fall-3031565
For a look at the original article (with charts!), please visit us at:
Amy Buttiglieri
2014-03
