We are probably well aware that various sugars reside in many of our foods. So when a reader contacted us recently, asking about the sugar content in vegetables, we thought it a good idea to share what we know!
A diet high in a variety of colourful vegetable is something we regularly recommend – for short and long-term health. However some people need to pay close attention to carbohydrate and sugar content of all foods, including vegetables, to manage blood glucose fluctuations.
That is where addressing glycemic index (GI) and glycemic load (GL) come into play.
Unwrapping GI and GL
Vegetables come in glorious wee packages containing different forms of carbohydrates, fibre and phytochemicals. These each impact the way the body receives sugars contained within the vegetables, and therefore the impact on blood glucose.
Foods are given a GI rating out of 100 (equivalent of pure glucose) based on 50g of carbohydrate, and the higher the score, the more dramatic the impact on blood glucose levels – meaning a rapid, sharp blood sugar spike followed by a dramatic dip below baseline blood glucose levels.
The dramatic dip is due to insulin being pumped out in high amounts by the pancreas attempting to remove the mass of glucose from the blood stream. Consequently, we ‘sugar crash’ (complete with sleepiness, shakes and irritability!).
What GI doesn’t account for is whether the carbohydrate content is simple or complex, and what an average serving size of that food would be. That is where GL is a better measure.
The GL takes in total carbohydrate, quantity AND quality in the food. It is the GI times the total carbohydrate in a typical portion of a particular food. A-ha!
Basically, GI and GL are divided into the following and if you are watching total carbohydrate intake, low GI and GL are what you are after:
· Low GI – 55 or less
· Moderate GI – 56-69
· High GI – 70 or more
· Low GL – 10 or less
· Moderate GL – 11-19
· High GL – 20 or more
So, you are watching your sugar and total carbohydrate intake. You notice the humble pumpkin has a GI at 75 (boiled in salted water). Does this mean you must go easy on pumpkin, or that pumpkins are as detrimental as a can of Fanta?
Whilst pumpkin is quite high on the GI scale compared to many of its veg cousins, its overall carbohydrate content is low, with a GL at 3 for an 80gram serve. You would need to eat over 600g of boiled pumpkin to provide the same amount of carbohydrate as 250ml of soft drink (Fanta’s GL is a whopping 23) – and at least pumpkin has fibre to slow the glucose release. Anyway, who is going to eat that much pumpkin in one hit? I think I would explode (or turn orange)!
Factors affecting carbohydrate content
There are a number of factors to consider on how vegetables, and all food and beverage, impact on blood glucose levels by vegetables. These include:
- Starch content
- Processing, cooking and chewing
- Presence of nutrients
- Type of sugar
- Combination eating with protein, fat and fibre, slowing digestion and absorption1
Which veg are best?
So to reiterate, how our body DEALS with glucose and fructose depends on how the food parcel the sugar is delivered in is packaged.
Veg are packed with phytonutrients that can mitigate much damage caused by high blood glucose and diets high in processed foods. So let’s not demonise the veg!
However, here is a list of vegetables that are generally considered high in glycaemic load, and best served with protein and fats to minimise the impact on blood glucose levels:
|Vegetable||GI||GL||Serve size||Carb per serve|
|Potato (boiled, baked, mashed)||82-111||25-33||1 medium||30g|
|Parsnip (boiled)||52||5||½ cup||10g|
|Pumpkin (boiled with salt)||75||3||80 grams||4g|
|Sweet corn (boiled)||60||11||80 grams||18g|
|Sweet potato||61||17||150 grams||28g|
Remember, GI and GL ratings are only a guide. Every person is different, responding uniquely to various foods. Listen to your body – post meal, you want to feel energised and satisfied, and ready to take on the world!
- Hechtman, L 2012, Clinical Naturopathic Medicine, Churchill Livingstone, Chatswood, N.S.W.
- Gropper, SS & Smith, JL 2013, Advanced Nutrition and Human Metabolism, 6th, Wadsworth, Cengage Learning, Belmont CA