How does protein affect insulin dosing for meals?

Posted on 14 December 2018

Two steaks on a wooden board with vegetables

People with type 1 diabetes need almost 50% additional insulin to keep glucose levels stable following a high-protein meal, according to a new study partly funded by JDRF.

The researchers, based in the UK and Australia, found that most of this extra insulin was required in the two hours following the meal, and that there was a lot of variation in extra insulin needs between people.

These findings may support people in managing their glucose levels after meals.

This is the first study to look at insulin needs for a high-protein compared with a low-protein meal, when carbs and fat content are kept the same.

Why did they do this research?

People with type 1 diabetes are currently encouraged to adjust their insulin doses depending on the carb content of their meal.

Recent evidence suggests however that fat and protein also affect glucose levels and so need to be taken into account when calculating insulin doses.

The researchers therefore decided to investigate the insulin requirements needed to keep blood glucose levels stable after a meal with high or low protein content.

What did they do?

11 teenagers participated in this study.

The participants ate pasta meals that contained 30g of carbs, 8g of fat, and then either 60g or 5g of protein for the high-protein and low-protein meals respectively, a week apart.

The researchers measured how much insulin the teenagers needed and when in order to keep blood glucose levels stable at around 5.5 mmol/l during and after the meals.

What did they find?

Participants needed on average 54% extra insulin, or about 3.6 additional units, when they ate the high-protein meal compared with the low-protein one.

Insulin needs did vary greatly between participants however, with requirements ranging from slightly less insulin than the low-protein meal (-1.3 units), up to 9.4 additional units.

The researchers found that the majority of the extra insulin was needed in the first two hours after the meal in order to keep glucose levels stable.

What does this mean for type 1?

These results highlight that carbs are not the only food group that affect glucose levels and insulin needs.

In their paper, the researchers explained that people might need individualised insulin-to-protein ratios:

“Large inter-individual variation in the quantity of additional insulin required for the high-protein meal was seen (–1.3 to 9.4 units), indicating the need for individual insulin to protein ratios to be calculated.”

This was a small study however with limited numbers of participants and meals tested, and so further research will be needed to get a better understanding of how protein affects insulin dosing.

The researchers stated that more work is needed before new guidelines can be recommended:

“Given that this is the first study to suggest this early increase in insulin requirements, further research is required before the development of definitive recommendations around the optimal timing of insulin delivery to manage high-protein meals.”

If you have any questions about calculating insulin requirements for meals, your healthcare team will be able to offer advice.

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