Christine Manga, a diabetes nurse educator, explains the calculation of insulin dosing for fat and protein.
We are social creatures and food plays an enormous role in our lives. Many gatherings and celebrations revolve around food, promoting socialisation and fostering a sense of belonging. These events should be fun and exciting but instead they often present as daunting and challenging if you have diabetes, especially if you need to inject insulin.
Who needs to inject insulin?
Type 1 diabetes is the absolute absence of insulin. Insulin is required to facilitate the movement of glucose from the bloodstream into the cells for energy use and storage. People with long-standing Type 2 diabetes may also have less or no insulin reserves. This will necessitate the need to inject a rapid-acting insulin before eating a meal as well as a long-acting insulin at least once a day.
Carb counting is a commonly taught skill that involves calculating the amount of insulin required to match the amount of carbohydrates eaten at a meal. Your healthcare provider will assist you in working out a carb ratio and insulin sensitivity factor (ISF). This will be used at each meal.
Meals are more than just carbs
Fats and proteins also impact blood glucose levels by delaying the digestion and absorption of carbohydrates, often causing a delayed and prolonged hyperglycaemia (high blood glucose). It can be drawn out for as long as three to five hours post-meal.
Fat causes and worsens insulin resistance which would mean more insulin would be required. A meal that contains 35% or more of it’s total calories is considered a high fat meal. This amount varies in the literature.
There are vast differences in interpersonal and intrapersonal blood glucose responses to fat and protein. There is no uniform response to a meal. These differences can be caused by, but are most definitely not limited to carb ratio, ISF, exercise, weather, duration of diabetes, order in which food is eaten as well as overall health.
To establish how fat or protein affect your glucose, it’s imperative to monitor yourself for patterns. Measurements should be taken three- and five-hours post-meal. It’s possible to monitor with manual finger pricks, but continuous glucose monitoring (CGM) is really helpful in these situations. Pattern detection is far easier.
High fat and protein meals
Examples of high fat and protein meals could include bacon and eggs, burger with avo and chips, salmon with olive oil drizzled on roast vegetables, pizza, creamy sauce pasta, pastries. The list goes on.
It’s often the case that even when carb counting is accurate, a high fat and protein content in the meal will result in under dosing of insulin and a delayed hyperglycaemia. A study using a 50g protein example: 200g cooked steak and 30g carb meal received an extra 30% insulin delivered in a combination bolus. This amount improved post-meal glucose levels without any additional risk of hypoglycaemia. When the amount of insulin was increased to 45%, there was increased hypoglycaemia whereas a 15% increased dose still resulted in post-meal hyperglycaemia.
Whittington Health, followed on the NHS guidelines, suggest counting carbs for the high fat or protein meal and adding 20% extra insulin along with a correction, if necessary. If the meal contains no carbs and more than 50g of protein, count it as 10g of “carbs” and dose according to your carb ratio. If you’re consuming alcohol with the meal, make no adjustments.
Calculating is hard work
In my practice, I tend not to teach insulin bolusing for fat and protein. Carb counting is already an additional step someone with diabetes must contend with pre-meal. Working out the carb content of food can already be challenging. Add in trying to establish the fat or protein content of the meal too and then calculate the extra insulin required. That is hard work and adds to the diabetes burden, possibly causing distress and eventual burnout.
With saying that, there are carb counting apps that make provision for fat and protein. If you choose to follow a low-carb, high-protein, with or without high-fat diet, you will need to work out with your HCP the best insulin ratios to use. There will be a lot of trial and error, but a certain amount of insulin will almost definitely be required, albeit a small amount.
If you’re fortunate enough to be on a sensor-augmented insulin pump, you’ll be better able to negate the effects of fat and protein in the meals. Depending on the pump, there are different features that will accommodate for the extra insulin requirements. Insulin can be given as a dual or square wave bolus which is a bolus given over an extended period. Auto correction from the pump will assist in compensating for the delayed rise in glucose. These are very small bolus amounts delivered by the pump without the user needing to initiate them. The pumps are also able to modulate the basal rate to regulate the blood glucose levels. If you’re manually injecting, you may need to give two boluses to compensate for high fat or protein meals.
The choice is entirely up to you, if you would like to take your diabetes management to this level. Many people who don’t bolus for high fat or protein are still extremely well-controlled with an excellent Hba1c only counting for carbs.
MEET THE EXPERT
Christine Manga (Post Grad Dip Diabetes and Msc Diabetes) is a professional nurse and a diabetes nurse educator. She has worked with Dr Angela Murphy at CDE Centre, Sunward Park since 2012.
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