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Nutrition and type 1 diabetes

Scientific support: Theresa Kössler

People with diabetes do not need a special diabetes diet or special types of food. Diabetes-appropriate nutrition corresponds to an individually tailored, balanced, and wholesome mixed diet.

People with diabetes should organize their mealtimes to fit into their lifestyle. Everyone has different preferences, financial possibilities, or culture. Ideally, people with diabetes should discuss their nutrition in consultation with a physician or a qualified or certified nutritionist.

A nutrition plan can be flexibly designed during intensified insulin therapy. It is important that the amounts of carbohydrates contained in the food can be estimated using nutritional information and tables to correspondingly adjust the required amount of insulin. With practice, this can usually be achieved, meaning the fun and enjoyment of eating is not lost.

How do I eat correctly?

The diet for type 1 diabetes should always be balanced and varied and include nutrient-rich, low-processed foods with high levels of fiber. High-energy foods with added sugar and heavily-processed cereal products, known as refined cereals, should be avoided as far as possible.

Similar to people without diabetes, many diets are suitable for people with diabetes. Alongside a mixed, wholefood diet, primarily comprised of vegetables, fruit, pulses, nuts, seeds, wholewheat products, low-fat milk and meat products and fish, other possible options include low-carbohydrate or low-fat diets, a Mediterranean-style diet, or a vegetarian or vegan diet. It remains unclear if there is a certain type of diet that is especially suited to people with diabetes in the long term.

A balanced diet provides the body with essential energy and nutrients and increases quality of life. Vitamins and minerals help us feel fit and enable many processes in the body to function correctly.

  • For example, secondary plant substances from fruit and vegetables help support the immune system.
  • Fiber helps improve digestion.
  • Some types of fat (e.g., from oily sea fish or linseed) support the functioning of thought-related processes.

A balanced diet can help people with type 1 diabetes achieve good metabolic management. It can also help prevent accompanying illness and complications, including nerve disorders, heart attacks, or diabetic foot syndrome.

Here you can find out more about the complication of type 1 diabetes!

Based on current knowledge, no definitive form of nutrition or diet can be recommended for people with diabetes. Certain types of nutritional concepts are increasingly being mentioned that are said to be suitable for people with diabetes. However, research has been unable to definitively determine whether this is true and what concept offers the most benefits for people with diabetes.

Specialist diabetes associations currently assume that there is no single dietary pattern that is equally suitable for all diabetes suffers. The diet best suited to diabetes appears to vary from person to person. For this reason, individually tailored nutritional counseling for people with diabetes is recommended. In this context, a nutritional concept based on diabetes therapy, personal preferences, and everyday circumstances can be created that can be implemented in everyday life for each individual.

According to current data, a low-carbohydrate diet is most likely to improve sugar metabolism. A diet with reduced carbohydrate consumption can be implemented using various types of dietary patterns. However, the German Diabetes Association points out that you should not only refer to the proportion of essential nutrients – carbohydratefats and proteins. The composition of the nutrients and the properties of the foods also play a significant role. The fat composition, fiber content, and effects of the carbohydrate-containing foods on the blood sugar level should also be taken into consideration for the respective diet.

Special foods for people with diabetes are not necessary. They often contain sugar substitutes, for example, fructose. These substances contain the same energy as normal sugar and therefore provide no benefits. Furthermore, these products can contain high levels of fat and therefore more energy than normal foods. For this reason, since 2012, it has no longer been permitted to sell special foods for people with diabetes in Germany.

Carbohydrates, alongside fats and proteins, are crucial energy sources for the human body. All carbohydrates are made up of sugar building blocks: some contain only 1 or 2 sugar building blocks (e.g., glucose or household sugar), whereas others are made up of long chains of sugar building blocks (for example starch). The body transforms the consumed carbohydrates into glucose (1 sugar building block). Glucose is a source of energy. When glucose enters the bloodstream, the blood sugar level increases. Because type 1 diabetes means there is a dysfunction of the carbohydrate metabolism, those affected should know what foods influence blood sugar levels.

Foods can be classified into four categories based on their effect on the blood sugar level:

  • Carbohydrate-rich foods that cause a high increase in blood sugar levels
    This category includes cereal products, pasta, rice, potato, fruit, juice, certain types of dairy products, and foods and drinks with added sugar. These foods require special consideration when calculating the insulin requirement for a meal.
  • Foods containing carbohydrates that lead to a moderate increase in blood sugar levels
    These include pulses (e.g., beans and lentils), nuts (e.g., peanuts or walnuts), and kernels and seeds (e.g., pumpkin seeds or poppy seeds). Alongside potentially low amounts of carbohydrates, these foods also include high amounts of fiber and fat. These properties ensure that the carbohydrates enter the blood slowly. Therefore, these types of foods often do not need to be included in the insulin requirement calculation.

    However, when eating pulses or large amounts of nuts and seeds, this should be tested out together with the diabetes treatment team because their increased fat content could lead to an increase in blood sugar levels.

Good to know:

If a meal contains high levels of fat and protein, there can be a delayed increase in blood sugar levels.

  • High-protein and high-fat foods that do not increase blood sugar levels or result in a delayed increase
    These include meat, whey, eggs, tofu, butter, mayonnaise, cold meats, and cheese. Foods in this category usually do not have to be included in the insulin requirement calculation. However, professionals have determined that proteins and fats can result in an increase in blood sugar levels. Often the insulin amount calculated for the carbohydrate-rich foods can manage the increase stemming from these foods.

    If a meal contains an excessive amount of fat or protein, then a fat-protein unit can be calculated (for example, for pizza). This is because when a large amount of fat and protein is consumed, the body converts some of it into sugar. This means the blood sugar can increase 3 to 5 hours after the meal. With the help of a diabetes treatment team and using nutritional tables, people with diabetes can learn to calculate a fat-protein unit and to inject the correct amount of insulin.
  • Foods with a high water content that do not cause an increase in blood sugar levels
    These include vegetables, lettuce, and mushrooms. These vegetables contain low amounts of carbohydrates and high amounts of fiber and therefore they have no significant effect on blood sugar. They are also nutrient-rich, low in calories, and contribute to feeling full.

For people with type 1 diabetes, it is essential to correctly estimate the carbohydrate content of foods and drinks. The carbohydrate content is usually described using carbohydrate units, or CU for short. 1 CU unit is equal to 10 grams of carbohydrates.

Sometimes the amount of carbohydrates is given in bread units (BU). One BU is equal to 12 grams of carbohydrates. However, as food manufactures are no longer required to list BUs, calculating using CU may be easier. The listing of the amount of carbohydrates per 100 grams is obligatory on all packaged foods. The CUs can then be calculated using the size of the consumed portion.

People with diabetes can use carbohydrate or nutrient tables to find out how many grams of carbohydrates are included in a type of food. However, the listed figures can differ from one another. This is because fruit has a different sugar content depending on how ripe it is or when other analytic processes are used to determine the sugar content. Therefore, it is recommended to use one table instead of switching between different tables.

The exact insulin dosage required to counteract a CU differs from person to person. All those affected must determine the correct insulin dosage for them with the help of their diabetes treatment team and using blood sugar self-testing.

An example of a CU calculation:

Toast contains 48 g of carbohydrates per 100 g.

One slice weights 20 g.

20 g is 1/5 of 100 g.

48 g / 5 = 9.6 g

One slice of toast contains 9.6 g of carbohydrates. This corresponds to approx. 1 CU.

Scientists have not yet succeeded in determining the ideal amount of carbohydrates as a proportion of the diet. This applies both to people with and without diabetes. The German Diabetes Association states that between 45 and 60 percent of the overall energy needs can be consumed via carbohydrates. However, many studies consider this recommendation to be too high.

The currently available data indicates that a reduced carbohydrate intake can most likely result in an improvement to the sugar metabolism. Depending on the definition, a diet with a moderate reduction in carbohydrates is characterized by a proportion of 26 to 45 percent carbohydrates in the total energy intake.

However, the German Diabetes Association does not recommend specifically restricting the intake of one main nutrient in the diet in the long term. They also stress that the composition of the nutrients, i.e., the properties of the foods, for example, the fatty acid pattern or proportion of fiber, are more important than their intake as an overall percentage.

People with diabetes should eat carbohydrates from vegetables, pulses and wholewheat products. Among other things, these products all have high levels of fiber, which causes blood sugar levels to increase more slowly. People with diabetes should eat 40 grams of fiber per day. This corresponds to 5 portions of fruit and vegetables (1 apple, 1 bowl of raspberries, lettuce, tomatoes, lentils), and 2 to 3 slices of wholewheat bread.

Good to know:

More important than the quantity are the properties of carbohydrate-rich foods.

Apart from this, fewer white flour products and free sugars should be consumed. These types of foods cause a rapid increase in blood sugar levels. Specialist associations recommend no more than 50 grams of free sugars per day. This corresponds to approx. 12 teaspoons per day. Free sugar refers to all sugars added to foods and drinks and sugar naturally contained in honey, syrup, fruit juices, and fruit juice concentrates.
Take note: Processed food often contains a lot of sugar even though it tastes salty.

There are alternatives to conventional sugar for the sweetening of foods. These alternatives can be categorized into two groups:

Sweeteners are produced artificially. They provide no energy and have no effect on blood sugar levels. According to specialist associations, sweeteners can help achieve or maintain a healthy body weight when their use leads to a reduction in the consumption of energy-rich foods with added sugar.

However, care should be taken not to exceed the acceptable daily maximum amount. These amounts are determined by the European Union (EU). All food producers in the EU must adhere to these maximum levels when processing sweeteners in food, meaning these products should be safe. Examples of sweeteners are

  • cyclamate,
  • saccharine,
  • acesulfame K,
  • aspartame, or
  • stevia.

Sweeteners do not require the injection of insulin.

Sugar substitutes
Sugar substitutes are usually of natural origin and have no effect on blood sugar levels. Because the majority of sugar substitutes contain calories, they should not be consumed in large amounts. Consuming large amounts of sugar substitutes can lead to stomach pain or diarrhea. Examples of sugar substitutes are

  • sorbitol,
  • xylitol,
  • isomalt,
  • maltitol, or
  • lactitol.

Sugar substitutes do not require the injection of insulin.

Take note: However, food packaging declares sugar replacement substances as carbohydrates. People with type 1 diabetes should look closely to see if these are carbohydrates that affect blood sugar levels or not. If the product contains a sugar substitute, then this should be subtracted during the calculation of the insulin dosage.

The glycemic index (GI) illustrates the effect of foods containing carbohydrates on the blood sugar level. It predicts how fast and how much the blood sugar will increase after eating a certain type of food.

The 100% reference value is the blood sugar level after the intake of 50 grams of dextrose. When comparing to other foods, the exact amount of the respective food that also contains 50 grams of carbohydrates is used. For example, that would be 100 grams of lentils or 60 grams of cornflakes. Foods containing carbohydrates that have a high GI (e.g., white bread, cornflakes, or French fries) cause a large and rapid increase in blood sugar levels. In contrast, foods containing carbohydrates that have a low GI (e.g., pulses, vegetables, and wholewheat products) enter the bloodstream more slowly, resulting in a more moderate increase in blood sugar levels.

To estimate the effects of a food containing carbohydrates on the blood sugar level in relation to the amount of carbohydrates consumed, the glycemic load (GL) is also often calculated. GL provides an indication of the blood sugar response to a portion of a food containing carbohydrates. The GL is the product of the GI and the net carbohydrates (in grams) per food portion divided by 100.

Good to know:

Formula to calculate the glycemic load (GL):

GL = GI x consumed net carbohydrates [g] / 100

For example, a baguette and carrots have a similar GI. With a higher proportion of fiber and the corresponding lower proportion of net carbohydrates, the GL of carrots is significantly lower in comparison to the GL of a baguette.

Foods with large amounts of complex carbohydrates and fiber generally have a low GI. But also the method of preparation can influence the GI. For example, cooked carrots have a higher GI than raw carrots. In addition, the side dishes on a meal can influence how rapidly the carbohydrates are transferred into the bloodstream.

Carbohydrate-rich foods with a low GI are a suitable choice, provided the other ingredients of the respective food are also beneficial to health.

Small amounts of alcohol are permitted for adults with diabetes. However, alcohol causes the liver to no longer release sugar into the bloodstream, resulting in a drop in blood sugar levels. This increases the risk of low blood sugar. Therefore, alcohol should be consumed together with meals containing carbohydrates. Special care must be taken with alcohol after exercise or additional physical activity, as it can result in low blood sugar levels.

Furthermore, attention must be paid to the fact that alcohol has a high energy density and regular consumption can lead to weight gain.

The daily alcohol limit for women is 10 grams per day and for men it is 20 grams per day. 20 grams corresponds to approx. 1 bottle of beer (0.5 liter) or a glass of wine (0.2 liter). However, these threshold levels should not be understood as an invitation to consume alcohol on a daily basis. According to the German Center for Addiction Issues, the low-risk consumption of alcohol requires at least 2 alcohol-free days per week.

Most people with type 1 diabetes prefer intensified insulin therapy because it grants them more flexibility regarding eating and drinking. With the help of learned insulin self-adjustment, it is possible to vary mealtimes and insulin administration times as required without causing serious blood sugar level fluctuations. For selected mealtimes and carbohydrate amounts, the rapid-acting insulin is adapted in such to ensure blood sugar remains at normal levels.

Intensified insulin therapy makes it possible to accept a spontaneous invitation to dinner, afternoon coffee, or a birthday party. It is also possible to eat a smaller meal than normal when less hungry or to eat breakfast on weekends later than during the week.

Find out more here about intensified insulin therapy!

People with a body mass index above 25 kg/m² are considered overweight. A body mass of 30 kg/m²  and above is considered obese (adipose). Being overweight or obese reduces quality of life and causes many accompanying illnesses and complications.

To help with weight loss, overweight people should consume less energy than they burn. This can be achieved by eating less energy-rich foods, which contain unhealthy fats and free sugars (e.g., soft drinks, convenience foods, fatty and sweet baked goods, and meat products). Additionally, if possible, avoid the consumption of alcohol.

Along with weight loss, it is crucial to maintain the new healthier weight. To achieve this, alongside a healthy diet, physical activity is particularly important.

Find out more here about being overweight and obesity!

Find out more here about physical activity and type 1 diabetes here! 

All people with diabetes should take part in training programs. Nutritional counseling dealing with individual questions and needs should be a component of the training and medical care. In these programs, people with diabetes learn how and why foods and meals affect blood sugar levels. The treating physician can help find a suitable program.

Good to know:

Nutritional counseling is part of every training program for people with diabetes.


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As of: 09.03.2020