Insulin resistance

What is it, what causes it and how can you overcome it?

First of all, let’s discuss what insulin is.  Insulin is a hormone produced by the pancreas, a small organ that sits just under your stomach. Insulin is responsible for keeping your blood sugar (glucose) levels down.

When you eat food, it gets digested and broken down into its basic units. Carbohydrate for instance, is digested in the stomach and broken down into glucose. Glucose leaves the stomach and enters the small intestine. From there the glucose is absorbed into your blood stream. In order to use the glucose as energy it needs to leave the blood stream and enter your cells (e.g. muscle cells, lung cells, brain cells) where it gets burned for energy.

In order for the glucose to enter your cells you need insulin. Insulin acts a bit like a key to a door. Insulin unlocks the cell door so that glucose can move out of your blood into your cells.

People with Type 1 diabetes do not make any insulin. Insulin is therefore the main treatment for people with Type 1 diabetes. A person with Type 1 diabetes cannot live without taking insulin. There is currently no cure for Type 1 diabetes.

Some people make insulin but not enough to manage their blood sugar levels (as in the case of SOME people with Type 2 diabetes, gestational diabetes and people with secondary diabetes).  Lifestyle changes, weight loss and changes to your diet can help to lower blood sugars but due to the nature of their individual diabetes they may end up needing medication or insulin to help support their body in managing their blood glucose.

Most people with Type 2 diabetes however do produce enough insulin but the inulin is not able to do what it is supposed to do. Remember, I said that insulin is a bit like a key that unlocks the cell door so that glucose can move out of your blood into your cells? If the cell door is blocked, then insulin cannot open the door and glucose cannot move into the cell resulting in high blood sugars. This is referred to as insulin resistance. Although insulin resistance is present in most people with Type 2 diabetes it can also be present in people with other types of diabetes including Type 1 diabetes.

So, what causes insulin resistance?

1.       Excess body weight

When we carry excess body weight, then the excess body fat blocks the cell “key hole”. The insulin cannot open the cell door resulting in high blood sugars. This is more likely the case in people with Type 2 and gestational diabetes but if you have Type 1 diabetes and carry excess weight then you can also become insulin resistant. You may have noticed that your insulin requirements increase when you have gained weight. Losing excess weight can help to overcome insulin resistance.

2.       High fat food.

Fatty meals, especially meals high in saturated fat, increase insulin resistance. When we eat fat the body breaks it down into fatty acids. High levels of these fatty acids build-up in the cells resulting in the insulin being unable to unlock the cell door. This may lead to a rise in your blood sugars several hours after a high fat meal…think fish and chips or pizza!

3.       Protein

Studies suggest that consuming a high protein diet in the long term, especially animal protein, increases your risk of developing insulin resistance. In the short term, eating excess protein can also increase your blood sugars several hours after a meal. Many people think that protein has no effect on blood sugars. However, when we digest protein, we break it down into amino acids (the building blocks of protein). The body uses the amino acids to build and repair muscle and other cells. However, any excess protein that the body does not use for build and repair will be converted into glucose. You may thus find that after a meal high in protein your blood sugar can start to rise 2-3 hours post meal.

4.       Hormones

Hormones can play havoc with our blood sugars. Hormones generally increase our insulin resistance making insulin less effective. Women may find that the week before their period their blood sugars are higher than normal. Also going through menopause will increase your insulin resistance.

5.       Emotional and physical stress

Emotional stress and physical stress such as trauma, illness, headaches and injury causes a release of stress hormones such as cortisol, adrenaline and noradrenaline. These stress hormones make us more insulin resistant resulting in higher blood sugars.

6.       Exercise

Most people associate exercise with hypo’s but some types of exercise may actually increase your blood sugars. Think weight training, competitive sport, sprints and HIIT exercise. You can blame your stress hormones for this again!

Can we do anything to reduce insulin resistance?

Yes! There is a lot we can do to reduce insulin resistance almost immediately.

1.       Aim for a low-fat diet in particular try to reduce your intake of saturated fat and trans fats.

2.       Reduce your protein intake especially protein from animals and processed meats.

3.       Increase your fibre intake. Aim for 30g fibre every day. Fibre is great for lowering insulin resistance.

4.       Reduce your intake of highly processed foods. Processed foods are typically low in fibre and nutrients and can be high in fat.

5.       Adopt a whole food plant based (WFPB) diet.  WFPB diets by their nature are low in fat, low in animal protein and high in fibre. WFBP diets have shown to be effective in reducing insulin resistance.  

6.       Try to do regular, moderate intensity exercise at least every 2-3 days to maintain insulin sensitivity.

7.       Make time to relax or to do some relaxation exercises every day e.g., yoga.

8.       If you have type 1 diabetes, then you may have to alter how you take your quick acting insulin to match your insulin with the delayed rise caused by fat and protein.

9.       If you carry excess weight, then try to lose some weight.

Summary

Insulin resistance causes high blood sugars however it is possible to overcome insulin resistance and achieve your target blood sugars by making changes to your diet and lifestyle.

References

Wendy et al. (2016)  Impact of Diet Composition on Blood Glucose Regulation, Critical Reviews in Food Science and Nutrition, 56:4, 541-590.  

Kirstine et al. (2015). Impact of Fat, Protein, and Glycaemic Index on Postprandial Glucose Control in Type 1 Diabetes: Implications for Intensive Diabetes Management in the Continuous Glucose Monitoring Era. Diabetes Care 38 (6): 1008–1015

Roden. (2004) How Free Fatty Acids Inhibit Glucose Utilization in Human Skeletal Muscle, Physiology 19:3, 92-96

Orlich et al. (2014) Vegetarian diets in the Adventist Health Study 2: a review of initial published findings. Am J Clin Nutr. 100(1): 353S–358S

Can people with diabetes Eat Fruit?

Can people with diabetes eat fruit?

I often hear from my clients that they have been advised not to eat fruit because fruit contains sugar and the sugar will cause their blood glucose (blood sugar) levels to go up. The truth is that some of the sugar if fruit does not increase blood glucose levels. Fruit is low in sugar compared to starchy foods and fruit has a low glycaemic index. Some fruits are even associated with a lower risk of getting diabetes.

First of all, what is sugar?

Sugar is a carbohydrate. Starch is also a carbohydrate. When you look at a food label you will notice that the nutritional label usually states “total carbohydrate… of which sugar is….The difference between the total carbohydrate and the sugar is the starch. Both sugar and starch affects blood sugars.

Not all sugars are equal!

When most people think of sugar, they think of table sugar however, sugar can be divided into different types of sugar. Monosaccharides are single sugars that cannot be divided or digested into smaller units. Fructose, glucose and galactose are monosaccharides. Disaccharides are a sugar containing two monosaccharides and through digestion can be broken down further into monosaccharides. For example sucrose (table sugar) is a fructose + glucose molecule, lactose (milk sugar) is a glucose + galactose molecule and maltose (malt sugar) is two glucose molecules.  Starch present in starchy foods is called polysaccharides. Polysaccharides are made up of a chain of glucose molecules.

Glycaemic index

Some sugars (and starch) affect blood glucose levels quicker than others. This is referred to as the glycaemic index (GI). The glycaemic index is a ranking of food between 1-100 based on how quickly food affect blood glucose levels. Food can be divided into low, medium, and high GI foods.

Low GI foods as a GI of between 0-55

Medium GI food has a GI of between 56-69

High GI food as  GI of 70 and higher

Food with a high GI causes a rapid rise in blood close levels and best not to eat too often when trying for good blood glucose control. On the other hand, a low GI diet has shown to be effective on lowering HbA1C.

Glucose affects blood glucose the quickest and has a GI of 100. Fructose has the lowest GI 23. 

Some fruit are higher in fructose than glucose and therefore have a lower GI. Fruit also contains a lot of fibre which helps lower the GI of most fruit

Low GI fruit

Apple, Avocados, Blackberries, Blueberries, Cherries (fresh), Clementines, Cranberries, Fresh Damsons, Fresh fig, Fresh gooseberries, Grapefruit, Grapes, Guava, Kiwi, Lemon, Fresh lychees, Mandarin, Mango, Nectarines, Oranges, Fresh passionfruit, Peach, pear, pineapple, plums, raspberries, rhubarb, satsumas, strawberries, tangerines.

Medium GI fruit

Fresh apricots, underripe banana, Fresh melon, papaya

High GI fruit

Watermelon

Glycaemic load (GL)

GI is only part of the story. It does not reflect the total amount of carbohydrate (sugar and starch) per typically portion size. The total amount of carbohydrate per portion will also affect blood glucose. This is referred to as the carbohydrate load (GL).  The GL (or total amount of carbohydrate per meal) has a bigger impact on blood glucose than the GI.

The GL of a food can be worked out by using this equation:

GL (g) = GI ÷ 100 x available carbohydrate(g) per serving.

The higher the GL of a food the bigger the effect on blood glucose.

Food with a high glycaemic load has a GL of 20 or more.

Food with a medium glycaemic load has a GL of between 11-19.

Food with a low glycaemic load has a GL of 10 or less.

Now let’s look at watermelon again.

Watermelon has a high GI (80) but a typical portion of watermelon (80g) only contains 6g is sugar.

Glycaemic load of watermelon is 80(GI) ÷ 100 X 6g = 4.8

Therefore, even though watermelon has a high GI because the GL is so low the effect on your blood glucose will be small.

What about grapes?

A typical portion of grapes (80g) provides 12g carbohydrate.

GI of grapes =53

GL = 53÷100 x 12 = 6

An 80g portion of grapes have a small glycaemic load and therefore the effect on your blood glucose will be small.

Compared that to a slice of bread

GI of wholegrain bread = 51

A slice of bread provides roughly 18 g carbohydrate

GL = 51÷100 x 18 = 9.

Although a slice of bread still has a low glycaemic load, it is higher than both a portion of watermelon or grapes.

The total carbohydrate per meal is important

Fruit contains less total carbohydrate (sugar and starch) per portion than starchy foods.  For example, a medium size banana provides around 15 g carbohydrate, an apple 10g carbohydrate, 10 grapes provides 10g carbohydrate and a small orange only 8g carbohydrate. A typical sandwich provides 35-45g of carbohydrate and a typical portion of pasta or rice is 45 g of carbohydrate or more. A digestive biscuit is 10g carbohydrate, a small chocolate bar can be 12g carbohydrate an individual bag of crisps can be anything between 12-25g carbohydrate per bag.

Including fruit into your diet

People with Type 1 diabetes can adjust the amount of insulin they take based on the total amount of carbohydrate in a meal. This is called carbohydrate counting. Therefore, the amount of carbohydrate from fruit can be included to the total amount of carbohydrate in a meal.

Similarly, people with Type 2 diabetes can include fruit to their diet as part of a healthy balanced diet. People with type 2 diabetes who are on set amounts of insulin can achieve more stable blood glucose when aiming to have the same amount of carbohydrate at every meal time. This is called carbohydrate consistency. Fruit can be part of the total amount of carbohydrate aimed for at every mealtime.

Benefits of eating fruit.

Studies have shown that some fruit such as blueberries, grapes and apples are associated with a lower risk of getting Type 2 .diabetes. Cherries and other dark fruits such as blueberries, black currants, cranberries, red cabbage and eggplant contains anthocyanins (flavonoids). Studies have suggested that anthocyanins increase insulin sensitivity and increases insulin secretion.

Furthermore flavonoids have beneficial anti-inflammatory effects reducing the risk of other diseases such as cancer, cardiovascular disease, and cognitive diseases such as as Alzheimer diseases.

As mentioned earlier, fruit is high in fibre which can help prevent constipation and can help to improve and maintain a healthy gut. Fibre can also help lower cholesterol levels.

How to eat fruit

Fruit is best eaten fresh or frozen. Tinned fruit in natural fruit is better than tinned fruit in fruit juice or syrup. When eating dried fruit, stick to the recommended portion sizes. It is best to avoid fruit juice as it is generally higher in sugar and GI and low in fibre.  

In summary

Fruit is fine to eat when you have diabetes. It is typically lower GI and lower GL than other foods containing carbohydrate. Fruit also contains flavonoids and fibre which support a healthy body and gut.