A pharmacist's perspective on health and metabolic disease
One of the disadvantages to Kraft’s insulin response patterns is that there are no longitudinal studies with pattern and health outcomes over time. This means that we do not know if people with a pattern III have (for example) twice the risk of developing type 2 diabetes compared to those with a pattern I.
This paper by Hayashi and colleagues starts to answer some of these questions.
400 Japanese Americans men had an oral glucose tolerance test with insulin assays at test commencement and were then followed for about 10 years. The study aim was to see whether there were any relationships between insulin response pattern in those who developed type 2 diabetes.
Those with an insulin peak at 2 hours were three times more likely to develop type 2 diabetes over ten years compared to those with an insulin peak at 30 minutes.
On the surface, this sounds quite similar to Dr Kraft’s work, but there are some big differences. These patterns are based on the timing of the peaks and troughs only (not the actual value of the results), and the test only ran for 2 hours.
We know from looking at Dr Kraft’s work that people can have the same timing of peaks and troughs but very different patterns, and therefore, probably have different outcomes. Here we can see that two people have a peak at 30 minutes but patient 1 has a Kraft I pattern (normal), but patient 2 has a Kraft IV, or hyperinsulinaemic,pattern. According to Hayashi’s work, these patients have the same pattern and therefore, the same risk of developing type 2 diabetes.
The other challenge with Hayashi’s study is that they only excluded people with pre-existing type 2 diabetes. Those with impaired fasting glucose and/or impaired glucose tolerance were included in the study and predominantly had an insulin peak at 2 hours.
There are still a lot more questions than answers. Was it the insulin response that predicted the type 2 diabetes, or were these people at higher risk because they had impaired glucose tolerance and were already down the slippery path to diabetes. But this study is a start to giving us long-term outcomes from insulin response patterns. Now we need to try again with a better planned study. The fastest way to progress research is to get access to the raw data from these, and similar studies and re-analyse looking only at people with normal glucose tolerance and reassessing the patterns and outcomes. Maybe we could also differentiate groups based on magnitude as well as timing of the peaks and troughs.
The challenge is getting access to the raw data. Not all researchers are as open (or as generous) as Dr Kraft to the idea of collaboration or looking at their ideas in a different light. Perhaps if more were, were could make more progress.