GAPS diet + Instant Pot
First, I look at everything from a GAPS perspective, because that's the healing diet I lean towards. And this article contains info approved by Dr NCM. She has said no pressure cooking and only meat broth for GAPS Intro. HOWEVER, she has also said that it is perfectly fine to can meat broth. I have no idea how Australians can meat broth, but here in the USA, it involves a pressure canner. I don't know if the fact that the broth is already cooked and the bones/meat are removed before canning are critical to that distinction or not.
From the GAPS FAQ document:
Now, I also looked into the temperatures in pressure cooking. The InstantPot Smart lists the internal temp while cooking - the highest temp recorded when cooking under pressure is 237 degrees. On a stovetop, broth is usually brought to a boil and then simmered, which is around 200 degrees. Stovetop broth is usually cooked 1.5-3 hours; in the Instant Pot you can go 45-60 minutes.
For GAPS, you WANT the connective tissue to denature (it's how the connective tissue becomes gelatin). At the same time, though, the proteins in the muscle meat denature, which then loses nutrients (which arguably can be found in the broth, to some extent). It's a very fine line.
Pressure cooking was actually recommended in this study as a good way to preserve ascorbic acid and beta-carotene in spinach and amaranth leaves.
This study talks about pressure cooking meat for dialysis patients - pressure cooking reduces the phosphorus content while preserving protein content. Is that good for leaky gut patients? Protein is preserved, but phosphorus is lost - do we want that? I don't know. But is the phosphorus available in the broth and not lost? I don't know that either.
This study found the highest levels of soluble collagen content in pressure cooked goat meat (curry. Seriously. We don't have tests showing nutrient degradation and how badly protein is denatured in broth, but we know pressure cooking goat meat curry has high soluble collagen. Sheesh.). Anyway, we're after lots of soluble collagen because it becomes gelatin.
So. All of that to say this: I do cook meat broth (not bone broth) and I do (usually) cook it in the Instant Pot. We don't seem to be sensitive to bone broth, but if I'm going to be forcing them to drink broth and soup, it's going to be the most healing of the two. And I'm going to cook it in the InstantPot, because I can't tell you how many times I've walked away from the stove and steamed out broth. Or almost left the house, forgetting I have it on. I can cook chicken meat broth in the IP in 45 minutes and be done. I don't can broth if I have extra; I freeze it (I don't usually have extra, though).
Also, longer cooking times also result in increased histamine, so if histamine intolerance is an issue, shorter cooking times are a must.