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Have you ever heard (or read) that certain fruits or vegetables, like watermelon, should be avoided because of their sugar content? Perhaps your source said these foods were unhealthy because of their high glycemic index. Maybe they mentioned these foods might “spike your blood sugar”, or cause an insulin response. But what do these terms mean, why does glycemic load matter (even for those of us without diabetes), and what are the five factors that change a food’s effect on blood sugar?
Read on, and find out.
Let’s start with what happens inside your body when you eat something high in simple carbohydrates, like a donut.
If the incoming food is made up of simple carbohydrates or is particularly starchy, its breakdown in your stomach will result in sugars going into your bloodstream fairly quickly. That rapid rise in blood glucose (sugar) leads to an alarm going off in the pancreas. This alarm sends insulin, a hormone, out into the blood. There, it “orders” fat cells, muscle cells, and other cells to take sugar in from the blood for energy or storage, reducing sugar in the blood to a normal level.
So what happens if you skip a meal, and your blood sugar is low?
The pancreas is again alerted, and this time it sends out glucagon. This hormone marches out to the liver and commands it to release glucose into the blood to reach a normal level.
How can these natural (and necessary!) responses lead to health problems?
- Insulin resistance & pre-diabetes: Occur when you cells stop responding to insulin properly. May occur in part because of excess consumption of simple carbohydrates (high glycemic foods). Other factors include excess abdominal/visceral fat and physical inactivity.
- Having high insulin levels for an extended about of time is associated with a multitude of negative things including high blood pressure, high cholesterol, and inflammation.
So, how can you measure this response?
In all of these cases, the measurement of this response takes the form of a number. The number represents how quickly a given carbohydrate source breaks down into sugars. The lower the number, the better.
Glycemic Index (GI):
- The most “classic” of indices
- Based on how quickly a given carb-based food breaks down into sugar
- Not always indicative of the insulin response
- Portion size is not accounted for, as the amount consumed is different depending on how much of the food is made up of digestible carbohydrates
- Low (good) = 0-55, medium = 56-69, and high = 70+
Glycemic Load (GL):
- A more realistic measurement, as GL considers each food’s portion size
- Uses GI numbers, but factors in each food’s carbohydrate content
- If given the GI of a food, you can calculate it yourself by multiplying the GI by the number of carbs in a serving, then dividing by 100
- Low = 0-10, Medium = 11-19, High = 20+
- Here’s an extraordinarily thorough table with both GI and GL for many foods. This means watermelon, which has a high GI at 76, ends up with a low GL of 5 after accounting for serving size.
Note, ALL of these numbers are subject to change, based on either the ripeness of the fruit, the amount eaten, or the nutritional characteristics of the food it is paired with.
Five Factors for Better Blood Sugar Control
Generally, the more ripe an item of produce, the higher the sugar content, as its starchier components are broken into smaller pieces (sugars). There’s a reason banana bread recipes call for overripe bananas and not green ones (you’ll end up with sweeter bread).
How much you eat of a given food matters. Eat an entire watermelon, and you’ll get a much larger insulin response than you would get from munching on a single slice.
While complex carbohydrates minimize an insulin response by breaking down into sugars more slowly, pairing simpler carbs with fat or protein can slow the entry of natural sugars into your blood. Pairing an apple with peanut butter, for example, is a prime way to enjoy the fruit’s sweetness without the blood sugar swing.
Cooked carrots produce a much higher insulin response than raw ones. Al dente pasta breaks into sugars more slowly than overcooked pasta.
Your genetics, lifestyle, and dietary choices all play into your insulin responses.
Hopefully knowing these five factors (in combination with GL calculations) can help you harness the benefits of a low glycemic eating style.