The low glycemic (GI) diet is based around the glycemic index – a ranking system used to measure food’s impact on blood sugar levels. Simply put, the lower the GI rating, the more steady the impact on blood sugar.
Research has shown that a low GI diet can offer a number of health benefits; including lower blood sugar levels and a reduced risk of heart disease and type 2 diabetes.
However, experts warn against relying on the GI value of foods alone as other factors, such as cooking method and nutrient content, also affect the health value of food.
Here, we’ll discuss the glycemic index in more detail, what a low GI diet is, and cover some of the benefits and downsides.
What is the glycemic index (GI)?
Carbohydrates are an essential part of any healthy diet.
When we eat carbohydrates (found in bread, cereals, dairy products, fruits, and vegetables), our digestive system breaks them down into simple sugar, which then enters the bloodstream. However, different carbohydrates have different effects on blood sugar.
The glycemic index (GI) is a system used to rank foods containing carbohydrates according to how quickly they affect blood sugar levels. The lower a food’s GI rating, the more stable its impact on blood sugar levels.
To determine a food’s GI rating, experts look at how quickly it’s broken down and absorbed into the blood compared with 50g of pure glucose (sugar) – which has a GI value of 100.
The three GI ratings are…
- Low GI: 55 or lower
- Medium GI: 56-69
- High GI: 70 or higher
Food with a low GI value is digested and absorbed more slowly, which causes smaller, steadier rises in blood sugar levels. High GI foods, on the other hand, are digested and absorbed quickly, causing rapid spikes and drops in blood sugar levels.
Low GI foods can be preferable for health as blood sugar spikes can lead to fatigue and lethargy, and in the long-term, increase the risk of conditions like type 2 diabetes.
However, it’s important to note that only carbohydrate-containing foods are given a GI value, so not all food groups are covered.
What are some examples of high GI and low GI foods?
The low GI diet essentially involves swapping high GI foods for low GI alternatives.
There are plenty of low GI foods to choose from, such as…
- Whole grain, rye, multigrain, or sourdough bread
- Fruits including strawberries, apples, peaches, apricots, plums, kiwi, and tomatoes
- Vegetables including broccoli, carrots, cauliflower, zucchini, and celery
- Starchy vegetables like sweet potatoes, butternut squash, and corn
- Breakfast cereals such as bran flakes and steel-cut oats
- Legumes including chickpeas, lentils, butter beans, baked beans, and kidney beans
- Long grain, basmati, and brown rice
- Grains like barley, quinoa, and buckwheat
- Dairy products like milk, cheese, and yoghurt
- Dairy replacement products like soy, coconut, and almond milk
Other foods that contain little or no carbohydrates and so don’t have a GI value can also be included in the low GI diet. Some examples include…
- Fish and seafood such as salmon, tuna, trout, and sardines
- Nuts like almonds, cashews, walnuts, and pistachios
- Fats and oil like avocado and olive oil
- Herbs and spices such as garlic, dill, basil, salt, and pepper
Meanwhile, high GI foods that are avoided in a low GI diet include sugary foods and drinks, white bread, potatoes, and white rice.
For more in-depth guidance on what foods can be eaten on a low GI diet, check out this guide from Low GI Health.
What are the health benefits of the low GI diet?
Some of the health benefits of the low GI diet include…
1. The low GI diet can be beneficial for diabetes
Diabetes is a condition where the body is unable to process sugars effectively – making it difficult to maintain healthy blood sugar levels.
Experts suggest that following a low GI diet can be an effective way to manage carbohydrate intake and help to delay or prevent potential complications from type 2 diabetes.
For example, this scientific review revealed that in people with prediabetes or diabetes, a low GI diet promoted healthy blood sugar control and weight loss.
In contrast, research has linked high GI diets with an increased risk of developing type 2 diabetes.
2. Low GI diets may reduce the risk of heart disease
Research has revealed a strong link between high GI diets and an increased risk of heart disease; while low GI diets are associated with a reduced risk.
This study found that low GI diets reduced total cholesterol by 9.6% and LDL (bad) cholesterol by 8.6%. Having high cholesterol is a risk factor for heart disease and, as a result, another study (which followed 138,000 people for 9.5 years) found that those who ate a low GI diet were less likely to suffer from heart disease and stroke.
3. Low GI diets may promote healthy weight loss
Some research has suggested that low GI diets may promote healthy weight loss.
For example, this study looked at the potential benefits of low GI diets on body mass index (BMI), waist circumference, and waist-to-hip ratio in patients with heart disease.
During the study, one group ate low GI foods and excluded high GI foods, but continued eating fat and protein. The other group followed a diet recommended for those with coronary heart disease which limited fat, fried foods, and some proteins.
After three months, all body measurements within both groups had decreased, but the changes were only significant in the low GI group.
These results can partially be explained by the fact that, because low GI foods take longer to be broken down and absorbed, they can help you to feel fuller for longer. Many people find that this helps to encourage portion control and avoid overeating.
In fact, one study found that having a low GI breakfast resulted in eating 285 less calories at lunchtime.
4. Low GI diets may boost energy and mood
Low GI foods can have a positive impact on energy levels because they release sugar into the bloodstream gradually – providing the body with a sustained, longer-lasting source of energy.
For example, white bread releases four times as much sugar into the bloodstream as hummus, despite containing the same amount of carbohydrates.
The GI value of foods has been found to impact mood too. As shown in this study, which tracked overweight and moderate-weight people, eating a high GI diet resulted in a 38% higher score of depressive symptoms and a 26% higher score for fatigue and lack of motivation.
5. Low GI diets may reduce the risk of cancer
There’s evidence to suggest that people who eat more high GI foods have a greater risk of developing various types of cancer.
For example, this study found that amongst patients with colon cancer, those who ate the most GI foods were nearly twice as likely to see their cancer return after chemotherapy. High GI diets have also been shown to increase levels of insulin-related growths, which are risk factors for breast cancer.
Meanwhile, low GI diets have been linked with a reduced risk of breast, ovarian, colorectal, and endometrial cancers.
Though, it’s worth noting that many high GI foods, (such as biscuits, brioches, and ice cream) also contain other ingredients that are known to increase cancer risk – including saturated fats.
What are some disadvantages of the low GI diet?
The main issue with this diet is that it’s not accurate to assume that all low GI foods are healthy and all high GI foods are unhealthy. For example, watermelon and parsnips are generally classed as high GI foods, while chocolate cake has a lower GI value.
Other factors, such as how refined foods are, the type of sugar they contain, the amount of carbs you eat in one sitting, and the ripeness of fruit and vegetables, can also influence GI value. For example, research shows that an unripe banana has a GI of 30, while an overripe banana has a GI of 48.
Plus, research tells us that when foods contain protein and fat, or are cooked with it, it slows down the absorption of carbohydrates – therefore lowering the GI value. For example, crisps (which are cooked in fat) have a lower GI value than potatoes, which aren’t. But, because crisps are high in fat, they wouldn’t be considered the healthier option.
These factors mean that while GI rankings can be useful for promoting healthy choices, they shouldn’t necessarily be relied on as the sole basis or guidance for a healthy diet.
Final thoughts…
As research shows, eating a low GI diet offers a number of potential health benefits – including blood sugar regulation, healthy weight loss, and improved mood.
That said, there are also a number of drawbacks that should be considered. Therefore, low GI food ratings can be a useful tool but shouldn’t necessarily steer the direction of everything you eat.
It’s important to speak to your doctor before starting any new diet.
For more healthy diet tips, head over to the diet and nutrition section of our website. Here you’ll find everything from essential vitamin and mineral guides to ideas for healthy food swaps.
Have you tried the low GI diet? Are you making any lifestyle changes to boost your health? We’d be interested to hear from you in the comments below.
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