What are the best low GI foods? That might not be a question you ask yourself currently. Maybe you don’t give Glycaemic Index a second thought? You’d probably should, though. You’d be able to improve your health if you did.
What is the Glycaemic Index (GI)? And why is it important? We look at those questions and give you our perspective.
Why should you care? Because GI has lots of implications for your health, as do the food choices you make.
Let’s take a closer look
What is the Glycaemic Index?
The Glycaemic Index is a scale that goes from 0 to 100, measuring how much blood sugar rises in response to a food.
Foods are given a score on the index as follows:
- 0-55: Low GI score, producing a slow rise in blood sugar
- 55-70: Medium GI score, creating a moderately quick rise in blood sugar.
- 70-100: High GI score, generating a rapid rise in blood sugar.
Note that only single foods appear on the index, rather than meals. The GI of a meal may be very different to the GI of a particular food within the meal.
What are the implications of GI?
It might seem like a bit of a detail, the rate at which blood sugar rises. But it has many implications for health and is implicated in several health conditions. To understand why, we’ll go into a little more detail.
A rise in blood sugar will cause a release of insulin. You can think of insulin as a ‘storage’ hormone. Insulin receptors in cells all over the body facilitate the uptake of nutrients into those cells. Those nutrients will be bundled into their stored form and tucked away for safekeeping. For example, muscle cells will synthesise proteins, the liver and muscles will store glycogen (the body’s way of storing carbohydrate), and fat cells will construct and store fat.
The nutrients getting stored come from the bloodstream. The result of all this storage of nutrients, especially of carbohydrate, is the lowering of blood sugar back to previous levels. So, in summary, you eat a meal, blood sugar rises, insulin is released, nutrients from the meal get stored, blood sugar is lowered.
Blood sugar will rise quickly if a food is absorbed easily and rapidly from the gut. This will be the case with high GI foods. Initially, the rate at which you clear sugar from the bloodstream does not match the rate at which it is entering the bloodstream, and so blood sugar rises. The subsequent insulin response is large and rapid. If a food is absorbed slowly from the gut, clearance of blood sugar will better keep pace with the rate it is entering the bloodstream, and so blood sugar will not rise nearly as much. The subsequent insulin response is much more moderate.
So, high GI gives rise to a large insulin spike; low GI gives rise to moderate insulin response.
The implications of high insulin levels
Why is a large insulin response a problem? After all, insulin has evolved to help us tuck away nutrients for storage, and it works well! There are two main issues I’d like to highlight.
It encourages poor eating behaviours
A large insulin spike is going to clear blood sugar pretty quickly. You may still have high insulin once you have absorbed all the food, and the nutrients have passed into the bloodstream. In this case, insulin can drive down blood sugar to levels that are too low. One of the symptoms of low blood sugar is hunger. Or even craving. So, here’s the pattern: you eat fast-digesting carbohydrate; your blood sugar rises quickly; you get a large insulin spike; your blood sugar is lowered and goes too low; you get sugar cravings; you eat more fast-digesting carbohydrate.
This pattern was useful when food was scarce because it encouraged us to make the most of any food bounty we came across. These days, of course, high-calorie food is plentiful, and we’re not working off the calories by hunting and gathering like we used to.
It turns off fat burning.
Insulin suppresses the utilisation of fat as a fuel in a dose-dependent manner. The higher insulin levels, the more fat usage is suppressed. If you’ve developed poor eating behaviours, then it’s likely insulin is high for most of the day and fat utilisation is suppressed for most of the day.
Researchers have shown that people who consume high GI diets have lower fat utilisation compared to those on a low GI diet. The more you can use fat as a fuel, the more you will spare your carbohydrate stores. That will improve energy levels, stamina and muscle retention, as well as helping improve body composition.
You may be thinking this wouldn’t matter: as long as you were in a calorie deficit, you’d still be able to lose weight. Yes, you would, but then you almost certainly wouldn’t have high insulin levels. All-day high insulin (hyperinsulinaemia) is associated with poor eating behaviours, overeating and weight gain. The suppression of fat burning is one of a collection of physiological changes that lead to ill health.
As you’ll see in the next section, there are several well-established health concerns relating to high glycaemic diets.
The health issues associated with high GI diets
High GI diets are associated with a number of physiological dysfunctions:
- High blood glucose (hyperglycaemia)
- Insulin resistance and hyperinsulinaemia
- Increased blood fatty acid levels
- Endothelial dysfunction (heart surface artery constriction).
These are all risk factors for cardiovascular disease, and they are a collection of issues known as metabolic syndrome. They are more prevalent in people with a sedentary lifestyle. If you have insulin resistance and metabolic syndrome, you’re at much higher risk of developing type 2 diabetes.
For a great read about the latest science on diabetes, I’d suggest reading the diabetes chapter in this book.
If you’d like to understand more about GI and health, have a look at this summary of the health risks of high GI diets and the beneficial effects of a low GI diet.
How to decrease the GI of your meals
There’s a rather obvious implication of the previous two sections: eating a low GI diet is better for your health and will encourage healthy eating patterns. And because low GI foods help you feel fuller for longer, they will help with weight loss too.
So what are the factors that determine the GI of a food? Here’s the checklist:
The structure of the carbohydrate
If it’s a complex carbohydrate, a starch, consisting of large molecules that require breakdown, that’s better than simple sugars. Of the two polysaccharides in starch, amylose is harder to break down than amylopectin. That means starches higher in amylose tend to be lower GI.
The type of sugar in the carbohydrate
At the simplest level, after breakdown, some sugars digest quicker than others. Glucose is high GI; fructose is low GI. Interestingly, ordinary table sugar, which we might typically think of when we use the word ‘sugar’, has a GI of around 67. So it’s officially ‘moderate GI’. That’s because it is a disaccharide consisting of one glucose and one fructose molecule. Fruits contain a mixture of both glucose and fructose but, because they also provide a lot of fibre, they tend to be quite low GI. Here’s a useful list of GI values for common sugars and sweeteners.
Anything that slows gastric emptying
Protein, fat, vinegar or other acids will all serve to slow the digestion and lower the GI of a meal.
The fibre content
Fibre, particularly soluble fibre, will help trap sugars and slow their ultimate breakdown and absorption. That means whole grains, pulses, fruits and vegetables are usually excellent choices.
The degree of breakdown
The stomach has to churn food and physically break it down to release nutrients. If your food is finely milled, then a lot of that breakdown is done for you before you eat it, and it will tend to have a high GI.
Bread, cakes, biscuits and breakfast cereals all fit into this category. Unprocessed food will contain more fibre and take longer to break down, so lowering the GI. Similarly, cooking will break down starches and make them more digestible. So, if a food is palatable when raw, that’ll usually give you a lower GI.
Our top 10 low GI foods
Now that you know the factors associated with the GI of a food, see if you can identify all the factors in our top 10 low GI foods list. If you look up the GI of a food, you’ll find different values. That’s because GI is determined by experiment, and different researchers will obtain different results. We’ve picked a representative number but, by all means, look up foods for yourself. You’ll find there is no definitive source, but there usually is good agreement between different sources. If you’d like to have a browse through different foods to get a feel for it, take a look at this comprehensive list of GI values.
You could easily construct hundreds of lists that would be perfectly valid, but here are our picks of the best low GI foods:
Loaded with goodness, super tasty and the lowest GI fruit.
You’ll find some variety among GI values for lentils, but they’re all in the low category. Lentils are great for weight loss, and we’ve written about them before.
The nation’s favourite vegetable. Packed with goodness, keep it al dente for the most health benefits and lowest GI.
Pearl barley: 25
A lot of whole grains are low GI, but some are closer to the moderate boundary of 55. Barley isn’t though. It’s the lowest GI wholegrain we could find which is great, because we love this versatile grain. Great in stews and slow cooker recipes.
Very popular and very convenient. And of course, packed with goodness. You know what they say about apples and doctors?
You may have noticed chickpeas have features on our social posts. And we’ve even written an article about them. Versatile, tasty, great texture and super healthy.
Plain Greek yoghurt is full of protein and very low GI – have it with cherries for the perfect low GI snack.
Raw carrots: 16
Carrots have been given a bad rap in the past, with claims of high GI. More recent studies seem to suggest it is a low GI vegetable. We particularly love them raw as part of a great snack. They’re packed with goodies too.
We’ve written about beans before. They are a nutritional powerhouse and should be in everyone’s diet. There are loads of varieties, so you can keep your recipes varied. Another favourite for the slow cooker.
No food list would be complete without a berry of some sort. Raspberries are packed with vitamins, minerals and antioxidants.
Notice that nearly all the entries have good amounts of fibre and are unprocessed? There’s a clue! Manufacturing or processing rarely makes food healthier or slower to digest.
Always try to eat a diet that is as low GI as possible. The resulting moderate blood sugar response is better for your health and your weight goals. Low GI foods also tend to be very healthy. In fact, there’s such a thing as ‘the GI diet’, and you’ll find lots of books on it, including a ‘for Dummies’ guide.
You may need to search for the GI of various foods to be sure but, in general, stick to unprocessed vegetables, fruits, whole grains, pulses and low-fat dairy. Sound familiar? That’s because it’s the foundation of many diets such as the DASH diet and the government’s Eatwell guide.
It’s also the kind of diet we have advocated from the start. Remember, we don’t just do training, our programmes are holistic: training, nutrition, lifestyle. Give us a call if you’d like to know more about GI or our programmes.