Carbs, carbs, carbs. I’ve spent the last 25 years focused on carb counting as the be-all-and-end-all when it comes to managing my Blood Glucose Levels (BGL). But interesting new research from Australia, has led me to think twice.

Fat and protein are now on the radar.

Prof Bruce King and Megan Paterson, shed light on this topic and discuss some interesting findings from their latest research. 

Prof Bruce King is Staff Specialist in Paediatric Endocrinology at John Hunter Hospital and Conjoint Senior Lecturer at the University School of Medicine and Public Health; and Megan Paterson is a CDE and Paediatric Diabetes CNC at John Hunter Children’s Hospital and PhD student researcher at Hunter Medical Research Institute and University of Newcastle. 

Prof King and Ms Paterson: For people living with type 1 diabetes (T1D) it’s well known that taking insulin for each meal using multiple daily injections or a pump, is the best way to achieve optimal glucose levels and reduce the risk of both long and short-term complications of diabetes.

As we know, to do this properly, you have to count the amount of carbohydrates in your meal and this, along with your pre-meal BGL is used to calculate your insulin dose.

This method suggests that carbohydrate is the only macronutrient to impact blood glucose, but, many people with T1D still find it hard to manage their post-meal blood glucose levels, often despite accurate carbohydrate counting.

Recently, there’s been a focus on the glycaemic impact of fat and protein.

Our research team from Australia’s Hunter Medical Research Institute, the Australian Artificial Pancreas Program and the John Hunter Children’s Hospital, have found that fat and protein can also raise BGL.

Impact of Fat

High fat meals have been shown to initially cause low BGL, but often this is followed by delayed hyperglycaemia (high glucose) several hours after the meal.

In a study published by our research group,

… we compared the blood glucose levels of people with T1D after eating a standard meal, with the same meal that had an additional 35g of fat added (equivalent to a meal of a hamburger and chips).

A lower glucose response was seen in the first 90 minutes after the meal, followed by higher glucose levels over the next 3 hours.

Impact of Protein

Protein has also been shown to cause delayed higher glucose levels after a meal (approx. 2-5 hours later). Our team conducted various studies looking at the impact of protein, both when eaten alone and also with carbohydrate and fat.

We have shown that the addition of protein (more than 25-50g) to standard meals, causes a delayed increase in BGL after the meal.

We also showed that 75-100g of protein when consumed without carbohydrates or fat (equivalent to eating a 300g rump steak and salad) also caused elevated glucose levels 3-5 hours after the meal that was similar to the effect of eating 20g of carbs (with no insulin).

However, the timing of the response is very different (protein has a much slower effect on BGL).

From previous research, together with our findings, it seems that approximately ~1g of glucose is produced from every 5g of protein eaten. It’s important to remember though, that the response is very different in terms of timing.

If additional insulin was to be given up front for a large protein meal it may risk hypoglycaemia due to the delayed glucose response from protein.

Our studies have shown that when protein and fat are eaten independently of each other, they can impact BGL; and when they are eaten together, the effect is increased.

So what does this mean for people with T1D?

These studies show a need to consider giving additional insulin for the protein and fat content of meals.  However, adjusting insulin for fat and protein requires advanced skill and it is important that you speak to your health care team for advice before adjusting your insulin.

Calculating additional insulin for fat and protein is currently being investigated by our research group together with the Australian Artificial Pancreas researchers from the University of Newcastle.

We have studies running at the moment, where we are testing increased doses of insulin for fat and protein, both for people using pumps and for those using multiple daily injections.

We are also excited to say that our team is developing a mobile phone app (OptimAAPP) which is being tested in limited patient trials in Australia.

The app uses an algorithm to calculate insulin requirements while taking into account carbohydrates, fat and protein in a meal and the pre-meal BGL.

The app is individualised with a patient’s specific meal-to-insulin ratios and insulin sensitivity, so it can also calculate corrections and can take into account insulin which may have already been given when recommending a bolus.

OptimAAPP is currently only available for the Android platform (and not yet available to the general public until testing is complete) and an iOS version of the app will be produced in Australia once testing of the Android version is complete.

If you’re feeling overwhelmed, or if you’re not currently counting fat and protein, don’t panic.

While fat and protein have been shown to impact BGL, if you’re maintaining stable blood glucose levels, then rest easy.

We encourage you to chat with your doctor before making any changes to your insulin. 

*** Acknowledgement is given to the research team including A/Prof Bruce King, Dr Carmel Smart, Dr Prudence Lopez, Dr Adrian Medioli, Laureate prof Grahame Goodwin, Tenele Smith, research assistant Jordan Rafferty, statistician Prof Patrick McElduff, and Megan Paterson. Thank you also to all the participants and their families who were involved in this research. ***

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