Dietary management of type 2 diabetes

The basics

Insulin is the hormone that allows the glucose from food to enter the body’s cells so that it can be used for energy.

Glucose is obtained from carbohydrate-containing foods such as breads, cereals and fruits.

In the case of patients with type 2 diabetes — the most common form of diabetes — the glucose accumulates in the blood because the body is resisting the insulin, and the pancreas is unable to secrete more insulin in response.¹

It is important to control diabetes, as it can lead to long-term complications such as heart and kidney problems.²

Why does diet come into the picture?

There is no one special diet for managing diabetes. However, the amount and, more importantly, the type of carbohydrate consumed influence the blood glucose levels in people with diabetes.

In addition, the overall food choices a person makes — such as the saturated fat in the diet — influence calories, energy balance and therefore body weight.³ Particularly, weight concentrated around the abdomen is a predisposition to diabetes.

A possible explanation to this is that adipose tissue is metabolically active and releases inflammatory chemicals in the blood, which are said to cause insulin resistance.²

How is a dietitian involved?

Dietitians provide nutrition education to diabetic patients on concepts like healthy food choices and low GI carbohydrate choices.

Dietitians assist patients in making dietary changes that not only help with blood sugar control, but also help manage their weight.

As previously mentioned, weight is a major factor in the progression of diabetes. However, even a modest weight loss of 5% has shown to improve glycaemic control and may even avoid the need for glucose-lowering medications.

In fact, in the pre-diabetic stage, a 5–10% weight loss can prevent diabetes altogether.

The pre-diabetic stage is characterised by abnormally high blood glucose levels, but it is not at a stage where it can be diagnosed as diabetes.⁴

Which is the right type of carbohydrate?

Carbohydrates are important as they are our main source of energy. However, one should choose low GI carbohydrates.

GI refers to the glycaemic index, which is a way of ranking carbohydrate-containing foods (from 0–100) based on whether they raise blood sugar levels a lot, moderately or a little.

Low GI carbohydrate foods get digested slowly in the blood and hence prevent ‘spikes’ in blood sugar levels.

In addition, because they get absorbed slowly, they keep you full for longer and therefore control your appetite. Examples of low GI carbohydrates include wholegrain breads and cereals, oats and fruits.

On the other hand, foods with a high GI value get absorbed very quickly and cause an instant rise in blood sugar levels.

Examples of high GI carbohydrates refer to refined foods such as white bread, cakes, pastries and fruit juice.⁵

What does dietary management of diabetes involve?^3,6

1. Eating regular meals and spreading low GI carbohydrates across the day.
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2. Consuming low GI carbohydrates. Choosing the type of carbohydrate is a more sustainable method of diabetes management, for example, swapping corn flakes with traditional porridge, choosing wholegrain bread instead of wholemeal bread, choosing basmati rice over jasmine rice.
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3. Amount of carbohydrates: the general advice is to have about 2–3 servings of carbohydrates at main meals and one serve at snacks. However, this needs to be individualised and can be worked out with the help of an Accredited Practising Dietitian. One serving of a carbohydrate is 15 g and can, for example, be one slice of bread or half a cup of cooked pasta or rice.
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4. Portion control includes filling half a plate with vegetables, a quarter with grain and starchy vegetables and another quarter with meat or alternative.
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5. Choosing healthy fats — such as olive oil, nuts, avocado and oily fish like salmon and tuna — which are protective against heart disease, is important since diabetes is strongly associated with risk of heart disease.

Foods to avoid ⁶

Foods that should be limited for people with type 2 diabetes include:

• sweet foods and foods with added sugars, such as fruit juice and sugar-sweetened beverages
• salt
• alcohol
• saturated fats, including full-fat dairy products, processed meat like bacon and salami, and snack foods like chips and baked goods.

General macronutrient distribution

The carbohydrate intake should be about 45–60% of the diet and it should consist of predominantly high-fibre, low-GI carbohydrates.

The fat intake should be about 20–35% of total kilojoules, with less than 10% saturated fats. Trans fats should be limited as much as possible.

Protein should be about 15–20% intake.

The alcohol intake should be moderate (1–2 standard drinks per day) and the sodium level should be below 2300 mg/day.³

Importance of carbohydrate intake

If the carbohydrate intake is higher than usual and physical activity isn’t increased, blood glucose levels can rise too high — this is known as hyperglycaemia.

Hypoglycaemia is when the blood glucose level drops too low, which can happen when food intake is inadequate or a meal is skipped.

Hypoglycaemia is of particular concern when a patient is on medications that cause hypos and/or insulin.⁷

Evidence regarding low carbohydrate diets

There is no target carbohydrate intake. There is evidence to suggest that a calorie-controlled, low carbohydrate diet, high in unsaturated fat and lower in saturated fat, as part of a lifestyle modification program, along with regular exercise can:

• achieve considerable weight loss
• control glucose better
• reduce the need for diabetes medication.

However, the benefits may be attributed to the weight loss, which can be achieved through reduction in overall calories and does not require a reduction in carbohydrates.⁷

What about the ketogenic diet?

This is a diet that allows very small amounts of carbohydrates (less than 50g of carbohydrates in a day) which causes the body to move from its preferred fuel — glucose obtained from carbohydrates — to fats, resulting in fat loss. This process is known as ketosis.

Although the ketogenic diet can achieve weight loss through the metabolism of fatty acids, suppression of hunger, and reduction in Hba1c because of lowered carbohydrate intake, it is important to note that there are side effects.

There is a hypoglycaemia risk for patients on insulin or medicines that can lead to hypoglycaemia.

The inadequate fibre intake on the ketogenic diet in the long term can lead to constipation and even cancer of the colon.⁸

Summary

Whilst there are general dietary guidelines for people living with diabetes, there is no ‘special diet’ for diabetes management. However, calorie intake and diet quality do impact the management of the disease.

The dietary advice must be individualised — one cannot use a ‘one-size-fits-all’ approach.

Accredited Practising Dietitians have the formal training and evidenced-based knowledge to provide advice about food, diet and nutrition. They can also help develop realistic SMART goals and monitor progress.

To find a local APD, search ‘Find an Accredited Practising Dietitian’ at daa.asn.au or free call 1800 812 942.

Juhi Bhambhaney B. Food Science. M. Nutrition and Dietetics | Accredited Practising Dietitian | Ent Clinic, Royal Randwick Shopping Centre

References

1. Furukawa S, Fujita T, Shimabukuro M, Iwaki M, Yamada Y, Nakajima Y, et al. Increased oxidative stress in obesity and its impact on metabolic syndrome. The Journal of Clinical Investigation. 2017;114(12):1752-61.
2. Diabetes Australia. Managing Type 2. At: https://www.diabetesaustralia.com.au/managing-type-2
3. Dyson PA, Twenefour D, Breen C, Duncan A, Elvin E, Goff L, et al. Diabetes UK evidence-based nutrition guidelines for the prevention and management of diabetes. Diabetic medicine: a journal of the British Diabetic Association. 2018;35(5):541-7.
4. Wylie-Rosett J, Delahanty L. An integral role of the dietitian: implications of the Diabetes Prevention Program. Journal of the American Dietetic Association. 2002;102(8):1065-8.
5. Baker Heart & Diabetes Institute. Carbohydrates and glycaemic index (GI). At: https://www.baker.edu.au/-/media/documents/fact-sheets/Baker-Institute-factsheet-carbohydrates-and-glycaemic-index.pdf
6. Evert AB, Boucher JL, Cypress M, Dunbar SA, Franz MJ, Mayer-Davis EJ, et al. Nutrition therapy recommendations for the management of adults with diabetes. Diabetes care. 2014;37 Suppl 1: S120-43.
7. Tay J, Luscombe-Marsh ND, Thompson CH, Noakes M, Buckley JD, Wittert GA, et al. Comparison of low- and high-carbohydrate diets for type 2 diabetes management: a randomized trial. The American journal of clinical nutrition. 2015;102(4):780-90.
8. Yancy WS, Foy M, Chalecki AM, Vernon MC, Westman ECJN, Metabolism. A low-carbohydrate, ketogenic diet to treat type 2 diabetes. 2005;2(1):34.