Carbohydrates and Diabetes: What’s the Link?

If you have diabetes, it’s important to know how carbs can affect your blood glucose levels. If you eat too many carbohydrates, especially the types of carbohydrates which your body processes rapidly, your blood glucose levels will fluctuate dramatically, posing health risks. Even if you don’t have diabetes, it’s good to know the ins and outs of carbs and how they affect your body.

So how do you learn to moderate your carb intake effectively? You need a good understanding of two things: carbohydrate distribution and carbohydrate quality. Carbohydrate distribution refers to when and the amount of carbohydrates you eat. Carbohydrate quality refers to the types of carbohydrates you eat, and can be moderated using the glycemic index or load. If you familiarise yourself with both aspects of carbohydrate intake and make any necessary changes to your diet, you’ll be well on your way to effectively managing your blood glucose levels.

Carbohydrate distribution

Carbohydrate distribution refers to when you eat and the amount of carbohydrates you eat.

If you have diabetes, eating regular meals with an even distribution of carbohydrates throughout the day is important for good control of your blood sugar levels. If you eat large quantities of carbohydrates at main meals, and little or none between meals, you risk excessive fluctuations in your blood sugar levels. It’s better to eat smaller amounts of food more frequently, as this results in steadier, more even blood glucose levels. In general, the recommended daily eating pattern for good blood glucose control suggests:

  • Three meals and three snacks for people with Type 1 diabetes and normal blood glucose variations
  • Three meals (and 1-2 snacks as needed) for those with Type 2 diabetes

If you’re diabetic, your doctor or dietitian can advise you on the level of calories and carbohydrates most appropriate for your weight, medications and activity level. You should also check your blood glucose regularly for feedback on how your carbohydrate intake is affecting your blood glucose levels.

Whether or not you have diabetes, a rough rule-of-thumb for carbohydrate intake is to aim for 13g of carbohydrate per 100 calories; this is equivalent to about 50% of your total calories. Variations on this rule are shown in the Carbohydrate Intake table below.

Daily Total Calories Daily Total Carbohydrates Percentage of Carbohydrate Calories Each Main Meal (3) Between Meals (3)
1200 calories 120g 40% 30g 10g
1500 calories 170g 45% 40g 15g
2000 calories 250g 50% 60g 25g
2500 calories 345g 55% 70g 45g
3000 calories 450g 60% 90g 60g

From Allan Borushek’s Pocket Calorie, Fat & Carbohydrate Counter, 2005 edition.

Carbohydrate quality

When choosing carbohydrates, it’s best to choose complex carbohydrates that are rich in fiber and low in sugar, such as brown or basmati rice over white rice.

Moderating your carbohydrate intake involves more than just eating the right amounts of carbohydrate at the right times. You also need to choose the right kinds of carbohydrates.

Various forms of carbohydrates affect blood glucose levels in different ways. The same amount of carbohydrates obtained from different foods may affect blood glucose differently. For example, white and brown rice contain approximately the same amount of carbohydrates, but white rice will cause your blood glucose levels to rise faster than brown rice.

The aim is to choose carbohydrate foods which cause a slow, steady release of glucose into the bloodstream. These tips can help you achieve this goal:

  • Choose carbohydrates containing soluble fibre, as these can help slow the release of glucose into your bloodstream. The best sources of soluble fibre are fruits, vegetables, oat bran, barley, dried beans and peas.
  • The physical form of the carbohydrate food (whether it is solid, puree, or liquid), can influence the rate of glucose release. Choose solid forms of food, rather than liquid – for example, choose oranges instead of orange juice. In general, the more refined or processed the food substance, the quicker the release of glucose into the bloodstream.
  • Choose raw carbohydrate foods rather than cooked ones, and whole foods rather than processed foods. These are generally more slowly absorbed, even though the carbohydrate content is often the same.
  • Avoid carbohydrate foods high in simple sugars, such as white bread, biscuits and lollies, as these will speed up the release of glucose.

Using the glycemic index and glycemic load

The glycemic index can be used as a tool to determine what carbohydrate foods you should opt for.

Originally developed as research tools, the glycemic index (GI) and glycemic load (GL) can also be used to help predict how different types of carbohydrate foods will affect your blood glucose levels. The term “glycemic” means “sugar in the blood”. The GI and GL rank carbohydrates on a scale from 0 to 100, based on their immediate effect on the “sugar in the blood” after eating. This is called the glycemic response.

Foods with a high GI/GL are those which are rapidly digested and absorbed, resulting in marked fluctuations in your blood sugar levels. Low GI or GL foods produce gradual rises in blood sugar and insulin levels, and have proven benefits for your health. However keep in mind, for diabetes and weight control, portion size is also vital, regardless of a food’s GI/GL rating.

To stabilise your blood glucose levels, the bulk of your carbohydrates should come from low GI/GL sources. Mostly this means eating less sugars and refined grains and more vegetables and unrefined grains, however there are a few exceptions… Some complex carbohydrates behave more like simple sugars, leading to a quick release of glucose. For example, white potatoes, French fries and many breakfast cereals, such as cornflakes, all have a high GI/GL.

Although GI/GL can be helpful for understanding how carbohydrates affect your body, research has not yet proven that a low GI/GL diet will prevent diabetes. The GI/GL should by no means be used in isolation, but can be a helpful tool for managing diabetes.

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