Black pepper
It is not here for the taste. Piperine opens the door for compounds your liver would otherwise break down before you use them.
Glycemic index
None. There are hardly any carbohydrates in this, and the index measures what carbohydrates do to your blood sugar.
How to use it
On anything with turmeric in it, and wherever else you like it. A pinch is enough: this is a key, not a dose.
The best version
Whole corns in a mill. Pre-ground pepper loses its volatile oil and with it its smell, and what you have left is dust with heat in it.
How to prepare it
Grind it fresh, at the end. Cooking it from the start turns it bitter.
Combine with
Turmeric
This is what pepper is here for. Piperine blocks the breakdown in the liver and gut wall, and that lifted curcumin absorption by two thousand percent.
What it does
Piperine blocks the breakdown that happens in the liver and the gut wall. In healthy volunteers, curcumin was barely detectable in the blood after 2 grams of powder; with 20 milligrams of piperine alongside it, absorption rose by 2000 percent, with no adverse effects at that dose.
Watch out
What opens the door for curcumin opens it for medicines that leave by the same route. A pinch on your food is not the problem. A piperine supplement while you are on medication is a question for your doctor and not for a website.